- AT‐A‐STATION HYDRAULIC GEOMETRY SIMULATOR
- Authors: Daniel John McParland; Brett Eaton, Jordan Rosenfeld
Pages: n/a - n/a
Abstract: Presented in this paper is a hydraulic model that combines a rational regime theory with an at‐a‐station hydraulic geometry simulator (ASHGS) to predict reach‐averaged hydraulic conditions for flows up to but not exceeding the bankfull stage. The hydraulic conditions determined by ASHGS can be paired with an empirical joint frequency distribution equation and applicable habitat suitability indices to generate weighted usable area (WUA) as a function of flow. ASHGS was tested against a 2‐dimensional hydrodynamic model (River2D) of a mid‐size channel in the Interior Region of British Columbia. By linking ASHGS to a regime model, it becomes possible to evaluate the direction and magnitude of habitat changes associated with a wide range of environmental changes. Our regime model considers flow regime, sediment supply, and riparian vegetation: these governing variables can be used to simulate responses to forest fire, flow regulation and changes in climate and land use. Practitioners can examine ‘what‐if’ scenarios that otherwise would be too expensive and time consuming to fully explore. The model boundaries of commonly used data‐intensive hydraulic habitat models (e.g. PHABSIM) are not easily adjusted and such models are not designed to estimate future morphological and hydraulic habitat conditions in rivers the undergo significant channel restructuring. The proposed model has the potential to become an accepted flow assessment tool amongst practitioners due to modest data requirements, user‐friendliness, and large spatial applicability; it can be used to conduct preliminary assessments of channel altering projects and determine if in‐depth habitat assessments are justified.
- AN ESTIMATE OF BASIN‐WIDE DENITRIFICATION BASED ON FLOODPLAIN
INUNDATION IN THE ATCHAFALAYA RIVER BASIN, LOUISIANA
- Authors: M. G. Bennett; K. A. Fritz, A. Hayden‐Lesmeister, J. P. Kozak, A. Nickolotsky
Pages: n/a - n/a
Abstract: Maximizing the reduction of nitrate to dinitrogen gas (denitrification) has been advocated as a means to decrease nitrate pollution that causes eutrophication and hypoxia in estuaries worldwide. Managing this flux in bottomland forest wetlands of the Mississippi River could potentially reduce the world's second largest hypoxic zone. We used published denitrification rates, geospatial data on habitat area and inundation frequency, water level records (1963–2011), and average monthly temperatures to estimate annual denitrification in the Atchafalaya River Basin, the principal distributary of the Mississippi River. Denitrification rates ranged from 5394 kg N year−1 (3.07 kg N km−2 year−1) in 1988 to 17 420 kg N year−1 (9.92 kg N km−2 year−1) in 1981, and rates were consistently higher in fall compared with those in spring. Total NO3− denitrified in the basin was negligible compared with total NO3− entering the Gulf of Mexico. If all N denitrified in the basin instead entered the Gulf, the hypoxic zone was predicted to increase only 5.07 km2 (0.06%). This negligible effect of the basin on N dynamics in the Gulf agrees with other mass balance and isotopic studies in the region. Copyright © 2014 John Wiley & Sons, Ltd.
- ECOSYSTEM MANAGEMENT ALONG EPHEMERAL RIVERS: TRADING OFF
SOCIO‐ECONOMIC WATER SUPPLY AND VEGETATION CONSERVATION UNDER FLOOD
- Authors: S. Arnold; S. Attinger, K. Frank, P. Baxter, H. Possingham, A. Hildebrandt
Pages: n/a - n/a
Abstract: In ecosystems driven by water availability, plant community dynamics depend on complex interactions between vegetation, hydrology, and human water resources use. Along ephemeral rivers—where water availability is erratic—vegetation and people are particularly vulnerable to changes in each other's water use. Sensible management requires that water supply be maintained for people, while preserving ecosystem health. Meeting such requirements is challenging because of the unpredictable water availability. We applied information gap decision theory to an ecohydrological system model of the Kuiseb River environment in Namibia. Our aim was to identify the robustness of ecosystem and water management strategies to uncertainties in future flood regimes along ephemeral rivers. We evaluated the trade‐offs between alternative performance criteria and their robustness to uncertainty to account for both (i) human demands for water supply and (ii) reducing the risk of species extinction caused by water mining. Increasing uncertainty of flood regime parameters reduced the performance under both objectives. Remarkably, the ecological objective (species coexistence) was more sensitive to uncertainty than the water supply objective. However, within each objective, the relative performance of different management strategies was insensitive to uncertainty. The ‘best’ management strategy was one that is tuned to the competitive species interactions in the Kuiseb environment. It regulates the biomass of the strongest competitor and, thus, at the same time decreases transpiration, thereby increasing groundwater storage and reducing pressure on less dominant species. This robust mutually acceptable strategy enables species persistence without markedly reducing the water supply for humans. This study emphasises the utility of ecohydrological models for resource management of water‐controlled ecosystems. Although trade‐offs were identified between alternative performance criteria and their robustness to uncertain future flood regimes, management strategies were identified that help to secure an ecologically sustainable water supply. Copyright © 2014 John Wiley & Sons, Ltd.
- HYDROLOGIC VARIABILITY INFLUENCES LOCAL PROBABILITY OF PALLID STURGEON
OCCURRENCE IN A MISSOURI RIVER TRIBUTARY
- Authors: M. J. Hamel; J. J. Spurgeon, M. A. Pegg, J. J. Hammen, M. L. Rugg
Pages: n/a - n/a
Abstract: A river's flow regime creates and maintains spatial variability in habitat and dictates the distribution and abundance of riverine fishes. Changes to patterns of natural hydrologic variation and disturbance create novel flow conditions and may influence distribution of native fishes. We examined local and regional‐scale factors that influenced the presence of pallid sturgeon Scaphirhynchus albus in the Platte River, a large tributary to the Missouri River in Nebraska, USA. Daily river discharge, diel flow variability, season and location in the study area were the most supported variables in logistic regression models explaining pallid sturgeon distribution. The probability of pallid sturgeon occurrence was greatest during periods of high discharge (>90th percentile flows) in the spring and fall. Pallid sturgeon occurrence was always lower when variability in diel flow patterns was high (i.e. hydropeaking). Our results indicate that pallid sturgeon use of the lower Platte River was strongly tied to the flow regime. Therefore, the lower Platte River may provide an opportunity to preserve and restore sturgeon and possibly other large‐river fishes through appropriate water management strategies. Copyright © 2014 John Wiley & Sons, Ltd.
- MONITORING OF RIVER CONTAMINATION DERIVED FROM ACID MINE DRAINAGE USING
AIRBORNE IMAGING SPECTROSCOPY (HyMap DATA, SOUTH‐WEST SPAIN)
- Authors: J. Buzzi; A. Riaza, E. García‐Meléndez, V. Carrère, S. Holzwarth
Pages: n/a - n/a
Abstract: Imaging spectroscopy is used in this work as an essential mapping tool to monitor changes in contaminated river sediments. Multidate hyperspectral image data (HyMap) are utilized to identify spatial mineral patterns, to detect temporal changes in mineralogy and to link these changes with geochemical processes and short‐term climate characteristics.
River sediments contaminated by acid mine drainage are covered by crusts with variably hydrated iron sulphate. The mineralogy of the crusts and the grain size of the underlying fluvial sediments overlap. The spectra used to build up maps from HyMap data are diagnosed mineralogically with archive spectral libraries from pyrite oxidation minerals from well‐known sequences of minerals.
The maps compiled from hyperspectral imagery display generalized oxidation shown by the coatings over river sediments following warm and dry periods with low water level. After the wet periods, the area covered by oxidized mineralogical phases recedes in favour of hydrated sulphate.
The iteration of image processing algorithms and the mineralogical and potential contamination in a geological context are described. Change detection of the mineral crusts on the river sediments by mapping using hyperspectral remote sensing data may thus enable a quantitative and qualitative environmental evaluation by the regulators. Copyright © 2014 John Wiley & Sons, Ltd.
- DO MANAGEMENT ACTIONS TO RESTORE RARE HABITAT BENEFIT NATIVE FISH
CONSERVATION? DISTRIBUTION OF JUVENILE NATIVE FISH AMONG SHORELINE
HABITATS OF THE COLORADO RIVER
- Authors: M. J. Dodrill; C. B. Yackulic, B. Gerig, W. E. Pine, J. Korman, C. Finch
Pages: n/a - n/a
Abstract: Many management actions in aquatic ecosystems are directed at restoring or improving specific habitats to benefit fish populations. In the Grand Canyon reach of the Colorado River, experimental flow operations as part of the Glen Canyon Dam Adaptive Management Program have been designed to restore sandbars and associated backwater habitats. Backwaters can have warmer water temperatures than other habitats, and native fish, including the federally endangered humpback chub Gila cypha, are frequently observed in backwaters, leading to a common perception that this habitat is critical for juvenile native fish conservation. However, it is unknown how fish densities in backwaters compare with that in other habitats or what proportion of juvenile fish populations reside in backwaters. Here, we develop and fit multi‐species hierarchical models to estimate habitat‐specific abundances and densities of juvenile humpback chub, bluehead sucker Catostomus discobolus, flannelmouth sucker Catostomus latipinnis and speckled dace Rhinichthys osculus in a portion of the Colorado River. Densities of all four native fish were greatest in backwater habitats in 2009 and 2010. However, backwaters are rare and ephemeral habitats, so they contain only a small portion of the overall population. For example, the total abundance of juvenile humpback chub in this study was much higher in talus than in backwater habitats. Moreover, when we extrapolated relative densities based on estimates of backwater prevalence directly after a controlled flood, the majority of juvenile humpback chub were still found outside of backwaters. This suggests that the role of controlled floods in influencing native fish population trends may be limited in this section of the Colorado River. Copyright © 2014 John Wiley & Sons, Ltd.
- HYDROMORPHOLOGY MEETS MAMMAL ECOLOGY: RIVER MORPHOLOGICAL QUALITY, RECENT
CHANNEL ADJUSTMENTS AND OTTER RESILIENCE
- Authors: V. Scorpio; A. Loy, M. Di Febbraro, A. Rizzo, P. Aucelli
Pages: n/a - n/a
Abstract: The need for a multidisciplinary approach for characterizing water bodies in terms of morphological, chemical and ecological quality has hastened the growth of hydromorphology as a cross‐disciplinary topic at the interface of hydrology, geomorphology and ecology. Many authors have analysed how hydroecology may affect freshwater biodiversity, although little is known about how this biodiversity might be affected by river morphological quality. We examined how well the presence of the semi‐aquatic Eurasian otter can be predicted by the rivers' morphological quality and its adjustments over the last decades. We tested the morphological quality index (MQI) methodology in 38 reaches of five rivers in southern Italy, 23 of which were positive to otter presence. In each reach, we examined 28 indicators contributing to the MQI and its 11 sub‐indices. The results showed a significant relationship between the probability of the presence of otters, MQI, and some sub‐indices. The best performing sub‐indices were related to channel adjustments and the continuity of river processes. A more detailed analysis of channel adjustments showed a detrimental effect of channel incision (>3 m) and a positive effect of narrowing, particularly where it occurred simultaneously with the development of forest in the new floodplain. The continuity of river processes has driven the migration of river banks and the development of ponds and secondary channels, likely increasing the availability of dens and resting sites and the hunting capabilities of otters. Our results stressed the importance of fluvial dynamics and sustainable adaptive river management for the habitat quality of semi‐aquatic species. Copyright © 2014 John Wiley & Sons, Ltd.
- RAPID RESPONSE OF A SAND‐DOMINATED RIVER TO INSTALLATION AND REMOVAL
OF A TEMPORARY RUN‐OF‐THE‐RIVER DAM
- Authors: K. H. Costigan; C. M. Ruffing, J. S. Perkin, M. D. Daniels
Pages: n/a - n/a
Abstract: Run‐of‐the‐river dams (RORDs) comprise the vast majority of dams on river systems and are commonly removed as a part of stream restoration strategies. Although these dams are routinely removed, few studies have documented the geomorphological responses of sand‐bed rivers to the removal of RORDs. We examined the response of a large sand‐bed river located in South‐Central Kansas, USA, to the installation and removal of a dam that is installed annually for seasonal recreational purposes. Channel adjustments were tracked using cross‐sections sampled over the course of 7 months as the dam was installed and subsequently removed. Multivariate spatiotemporal analysis revealed emergence of channel stability when the dam was in place for most cross‐sections, except for those immediately adjacent to or at great distances from the dam. Our results provide an approximation for how sand‐bed rivers respond to RORD construction and removal and are useful for guiding management decisions involving preservation or restoration of connectivity. Results of this study suggest that sand‐bed rivers are resilient and recover quickly when transient RORDs are removed. Copyright © 2014 John Wiley & Sons, Ltd.
- HEADWATER STREAMS OF FLORIDA: TYPES, DISTRIBUTION AND A FRAMEWORK FOR
- Authors: W. R. White; T. L. Crisman
Pages: n/a - n/a
Abstract: Using geographic information system and topographic maps, 5829 headwater streams in Florida were surveyed for several parameters including elevation, stream length, flow regime and surrounding geology, and vegetation. Each was assigned to one of four headwater types: wetland, seep, lake, and spring. Wetland headwaters were the most common and widespread followed by seeps, many displaying temporary flow, while springs were perennial and least numerous. Four groups of Florida rivers were identified through cluster analysis of drainage densities (number headwaters/km of river length). Group 1 consisted of six rivers with lowest drainage densities (0.30–1.39 streams/km main channel). All were coastal rivers of peninsular Florida and, with one exception, drain to the Gulf of Mexico. Seven of eight rivers (group 2) with intermediate drainage densities (1.77–3.04 streams/km main channel) were located in peninsular Florida. Only three of 12 rivers comprising the two groups (groups 3 and 4) with greatest drainage densities (5.16–9.37 and 15.49–16.96 streams/km main channel) were not located in the Florida panhandle. Stream conservation efforts should focus on both highly complex dendritic river networks of the panhandle and on the 7000 km2 area in central Florida mostly lacking headwaters that may become a significant dispersal bottleneck for aquatic biota seeking refugia farther north from projected climate change. Copyright © 2014 John Wiley & Sons, Ltd.
- ANTHROPOGENIC DISTURBANCE AND ENVIRONMENTAL ASSOCIATIONS WITH FISH
ASSEMBLAGE STRUCTURE IN TWO NONWADEABLE RIVERS
- Authors: T. P. Parks; M. C. Quist, C. L. Pierce
Pages: n/a - n/a
Abstract: Nonwadeable rivers are unique ecosystems that support high levels of aquatic biodiversity, yet they have been greatly altered by human activities. Although riverine fish assemblages have been studied in the past, we still have an incomplete understanding of how fish assemblages respond to both natural and anthropogenic influences in large rivers. The purpose of this study was to evaluate associations between fish assemblage structure and reach‐scale habitat, dam, and watershed land use characteristics. In the summers of 2011 and 2012, comprehensive fish and environmental data were collected from 33 reaches in the Iowa and Cedar rivers of eastern‐central Iowa. Canonical correspondence analysis (CCA) was used to evaluate environmental relationships with species relative abundance, functional trait abundance (e.g. catch rate of tolerant species), and functional trait composition (e.g. percentage of tolerant species). On the basis of partial CCAs, reach‐scale habitat, dam characteristics, and watershed land use features explained 25.0–81.1%, 6.2–25.1%, and 5.8–47.2% of fish assemblage variation, respectively. Although reach‐scale, dam, and land use factors contributed to overall assemblage structure, the majority of fish assemblage variation was constrained by reach‐scale habitat factors. Specifically, mean annual discharge was consistently selected in nine of the 11 CCA models and accounted for the majority of explained fish assemblage variance by reach‐scale habitat. This study provides important insight on the influence of anthropogenic disturbances across multiple spatial scales on fish assemblages in large river systems. Copyright © 2014 John Wiley & Sons, Ltd.
- IMPACTS OF PROJECTED CLIMATE CHANGES ON STREAMFLOW AND SEDIMENT TRANSPORT
FOR THREE SNOWMELT‐DOMINATED RIVERS IN THE INTERIOR PACIFIC
- Authors: S. Praskievicz
Pages: n/a - n/a
Abstract: Anthropogenic climate change is likely to have significant impacts on river systems, particularly on rivers dominated by seasonal snowmelt. In addition to altering the timing and magnitude of streamflow, climate change can affect the energy available to transport sediment, as well as the availability of sediment to be transported. These hydrologic changes are sensitive to local climate, which is largely controlled by topography, but climate models cannot resolve processes at these scales. Here, I investigate impacts of climate change on streamflow and suspended‐sediment transport for three snowmelt‐dominated rivers in the interior Pacific Northwest – the Tucannon River in Washington and the South Fork Coeur d'Alene and Red rivers in Idaho – using downscaled climate simulations from regional climate models (a range of three models plus an ensemble average) to drive a basin‐scale hydrologic model. The results indicate that climate change is likely to amplify the annual cycle of river discharge, producing higher winter discharge (increases in ensemble mean January discharge ranging from 4.1% to 34.4% for the three rivers), an earlier spring snowmelt peak (by approximately one month), and lower summer discharge (decreases in ensemble mean July discharge ranging from 5.2% to 47.2%), relative to a late 20th‐century baseline. The magnitude of the largest simulated flood under the ensemble‐average climate change scenario increases by 0.6–41.6% across the three rivers. Simulated changes in suspended‐sediment transport generally follow the changes in streamflow. These changes in discharge and sediment transport will likely produce significant impacts on the study rivers, including changes in flooding, physical habitat, and river morphology. Copyright © 2014 John Wiley & Sons, Ltd.
- SIZE‐MEDIATED EFFECTS OF WATER‐FLOW VELOCITY ON RIVERINE FISH
- Authors: A. Del Signore; H. J. R. Lenders, A. J. Hendriks, J. A. Vonk, C. Mulder, R. S. E. W. Leuven
Pages: n/a - n/a
Abstract: We applied species sensitivity distributions (SSDs), commonly used in chemical risk assessment, to quantify the impact of water‐flow velocity on the presence of fish species in a river. SSDs for water‐flow velocity were derived from observational field data (maximal velocity at which species occur, Vmax) and laboratory measurements (critical swimming velocity, Vcrit). By calculating the potentially affected fraction of the fish species of the river Rhine, effects of water‐flow velocity on different life stages and guilds were estimated. Vmax values for adults were significantly higher than those for juveniles and larvae. At water‐flow velocity of 60 cm s−1, half of the adults were affected, while half of the non‐adult life stages were affected at velocities of 25 to 29 cm s−1. There was a positive correlation between body size and fish tolerance to water‐flow. As expected, rheophilic species tolerated higher water‐flow velocities than eurytopic and limnophilic species. Maximal velocities measured in littoral zones of the Rhine were, on average, 10 cm s−1, corresponding to an affected fraction of 2%. An increase in water‐flow velocity up to 120 cm s−1 as a result of passing vessels caused an increase in affected species to 75%. For a successful ecological river management, the SSD method can be used to quantify the trait‐mediated effects of water‐flow alterations on occurring species enabling to compare and rank the effects of chemical and physical stress. Copyright © 2014 John Wiley & Sons, Ltd.
- COMBINING POPULATION GROWTH MODEL AND GENERALIZED ADDITIVE MODEL TO
DETERMINE OPTIMAL WATER LEVEL FOR WATERBIRD CONSERVATION: A CASE STUDY OF
SIBERIAN CRANE (LEUCOGERANUS LEUCOGERANUS) IN LAKE POYANG, CHINA
- Authors: Y. Jia; L. Guan, Y. Wang, G. Liu, G. Lei, L. Wen
Pages: n/a - n/a
Abstract: Siberian crane (Leucogeranus leucogeranus) is one of the most endangered species in the world. The ecological integrity of its main wintering ground at Poyang Lake in China is crucial for the future of the species because Poyang Lake accommodates 99% of its global population. With the Three Gorges Dam fully operational, science‐based adaptive strategies are urgently needed to avoid catastrophic ecological consequences.
This study quantified the link between water level variation and population growth rate of the Siberian crane in Poyang Lake using a suite of advanced statistical techniques. We first used the stochastic Gompert growth model within the state space modelling (SSM) framework to infer population growth rate, density dependence, and process variability and observation errors. We then applied generalized additive models (GAMs) to the population growth rate to quantify the effects of environmental stochasticity.
Our SSM results indicated that there was little support for density dependence, and environmental stochasticity was the main forcing for Siberian crane population variations in Poyang Lake. Although the SSM suggested that water levels in both high‐ and low‐water seasons were important factors for Siberian crane population, inference on their effects were elusive because of large confidence intervals of the estimated coefficients. Using GAM, we confirmed the non‐linear effects of water level on population growth rate. Based on the modelled response curves, we proposed the optimal water level for Siberian crane conservation: (a) maximum summer water season level should be less than 19.5 m and (b) minimum winter water level should be between 8.7–10.2 m. Our methods of integrating population dynamic model and GAM have wide relevance for regional biological conversation efforts that seek to maintain a resilient population of threatened species. Copyright © 2014 John Wiley & Sons, Ltd.
- ISCHNURA GRAELLSII (INSECTA: ODONATA) A WATER POLLUTION BIOVULNERABILITY
INDICATOR—PROBABILITY MAPPING USING SPATIAL UNCERTAINTY
- Authors: F. Campos; T. Velasco, G. Sanz, P. Casanueva, M. T. D. Albuquerque, I. M. H. R. Antunes
Pages: n/a - n/a
Abstract: Monitoring changes of anthropogenic impacts from a broad scope of species in biodiversity research require practical, easy‐to‐use and efficient assessment as well as monitoring methods. Odonates (Insecta: Odonata) are a valuable tool for assessing freshwater systems' quality and have been used as bioindicators of environmental variety.
The Águeda watershed, located in the central west of the Iberian Peninsula, shows an exponential increase in the last 60 years of natural resource exploitation coupled with alterations in consumer habits, causing significant environmental changes and deferred direct effects on the natural habitats.
Fourteen river sites, selected a priori, were sampled. Adult odonates were collected using standardized methods. Selected environmental variables and water quality parameters were evaluated in situ. Precipitation and altitude were the most important physical, environmental variables in explaining the assemblage structure. Meaningful abiotic–biotic as well as biotic–biotic relationships were set up. Furthermore, situations in the urbanized watershed area showed to be highly impacted and closely related with damselfly Ischnura graellsii, which should be targeted as a possible vulnerability indicator for polluted fresh waters.
A probability map for Ischnura graellsii distribution was performed using indicator kriging with external drift and spatial uncertainty obtain through the calculation of two categorical maps (binary), corresponding to the mean (0.485) and the trimmed mean by discharging the 10% lower distribution tail (0.533). The subsequent overlapping of both categorical maps (binary) allowed the definition of the higher spatial uncertainty map for surface water contamination. Copyright © 2014 John Wiley & Sons, Ltd.
- AN EVALUATION OF THE STREAM SIMULATION CULVERT DESIGN METHOD IN WASHINGTON
- Authors: R. J. Barnard; S. Yokers, A. Nagygyor, T. Quinn
Pages: n/a - n/a
Abstract: Stream simulation has become an increasingly common culvert design method around the world. It is based on the assumption that geologic and hydraulic conditions in natural channels define passage characteristics for migrating fish and that water crossing structures that imitate these conditions can then achieve those same passage characteristics. This study expands on an initial evaluation of 19 culverts in 2003 to 50 culverts and includes methods and analyses comparing hydraulic characteristics based on cross sections, profile variation, and bed texture between each culvert and its paired reference reach situated in an adjacent section of the natural channel of each stream. Taken as a group, these culverts simulate bed texture, 100‐year recurrence interval flood velocity and 2‐year flood width but did not simulate thalweg complexity or other hydraulic metrics. Culvert span, relative to the bankfull width of the stream, does not by itself determine whether the culvert simulates the reference reach. Of the 50 culverts, many of which experienced record floods, only one showed significant bed degradation. Copyright © 2014 John Wiley & Sons, Ltd.
- INVASIBILITY DRIVES RESTORATION OF A FLOODPLAIN PLANT COMMUNITY
- Authors: L. A. Toth
Pages: n/a - n/a
Abstract: An understanding of the processes that determine plant community structure is a requisite for the planning and evaluation of restoration efforts on river floodplains. Variable disturbance regimes derived from flood pulses increase the susceptibility of river floodplains to colonizations by new species and establish invasibility as a potentially important factor in plant community assembly and dynamics. The role of invasibility in the restoration of a wet prairie community on the Kissimmee River floodplain in central Florida was evaluated by quantifying temporal species turnover rates during wet and dry season sampling over a 12‐year pre‐restoration and post‐restoration period. Turnover rates increased with reestablishment of annual inundation regimes and were significantly greater on the reflooded floodplain than on the drained, channelized floodplain. Recurrent periods of increased invasibility were associated with repeated high‐amplitude flood pulses and accompanied by increased diversity of plant communities within the wet prairie landscape. Neither invasibility nor beta diversity was strongly related to the variable hydroperiods or depths provided by local topography and restoration of seasonal hydrologic regimes. Results suggest that invasibility is a functional process by which the restored flood pulse has reestablished the structure and diversity of the wet prairie. Copyright © 2014 John Wiley & Sons, Ltd.
- AN EVALUATION OF THE RELATIONS BETWEEN FLOW REGIME COMPONENTS, STREAM
CHARACTERISTICS, SPECIES TRAITS, AND META‐DEMOGRAPHIC RATES OF
WARM‐WATER‐STREAM FISHES: IMPLICATIONS FOR AQUATIC RESOURCE
- Authors: J. T. Peterson; C. P. Shea
Pages: n/a - n/a
Abstract: Fishery biologists are increasingly recognizing the importance of considering the dynamic nature of streams when developing streamflow policies. Such approaches require information on how flow regimes influence the physical environment and how those factors, in turn, affect species‐specific demographic rates. A more cost‐effective alternative could be the use of dynamic occupancy models to predict how species are likely to respond to changes in flow. To appraise the efficacy of this approach, we evaluated relative support for hypothesized effects of seasonal streamflow components, stream channel characteristics, and fish species traits on local extinction, colonization, and recruitment (meta‐demographic rates) of stream fishes. We used 4 years of seasonal fish collection data from 23 streams to fit multistate, multiseason occupancy models for 42 fish species in the lower Flint River Basin, Georgia. Modelling results suggested that meta‐demographic rates were influenced by streamflows, particularly short‐term (10‐day) flows. Flow effects on meta‐demographic rates also varied with stream size, channel morphology, and fish species traits. Small‐bodied species with generalized life‐history characteristics were more resilient to flow variability than large‐bodied species with specialized life‐history characteristics. Using this approach, we simplified the modelling framework, thereby facilitating the development of dynamic, spatially explicit evaluations of the ecological consequences of water resource development activities over broad geographic areas. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- DIVERSITY AND COMMUNITY STRUCTURE OF FISHES IN THE REGULATED VERSUS
UNREGULATED TRIBUTARIES OF THE MEKONG RIVER
- Authors: P. Phomikong; M. Fukushima, B. Sricharoendham, S. Nohara, T. Jutagate
Pages: n/a - n/a
Abstract: Diversity and community structure of fishes were studied in three neighbouring tributaries of the Mekong River in Thailand, namely the Mun, Songkhram and Gam Rivers. The rivers are located in the same ecoregion but have contrasting levels of both hydrological regulations and mitigation measures; the Mun River has a hydropower dam with a fish ladder and sluice gates that are opened during the wet season each year, the Gam River has several irrigation dams with a fish ladder at each dam site, and the Songkhram River has no dams along its river course. A total of 124 freshwater fish species were sampled in these rivers from August 2009 to June 2010. Overall species richness was highest in the Songkhram River (112), followed by the Mun (97) and Gam (54) Rivers. Average per site species richness was also significantly different among rivers but not among sampling months. Abundance–biomass comparison plots revealed considerably overlapping distributions of these two metrics from the dry to early rainy seasons in the Songkhram River and, to a lesser extent, in the Mun River. Fish assemblage data were classified into six clusters with similar community structure. Fish assemblages in the Gam River constituted a single cluster, while those in the other two rivers formed multiple clusters depending on the sampling season. The results of the cluster analysis are discussed in relation to the dominance of the three migration guilds (white, black, and grey fishes) of the Mekong River fishes. The effectiveness of the mitigation measures was determined to be limited in alleviating adverse impacts of dams in these tributaries of the Mekong River. Copyright © 2014 John Wiley & Sons, Ltd.
- GLOBAL WARMING EFFECTS ON FAECAL COLIFORM BACTERIUM WATERSHED IMPAIRMENTS
- Authors: A. Fonseca; C. Botelho, R. A. R. Boaventura, V. J. P. Vilar
Pages: n/a - n/a
Abstract: Impairment of surface water quality by faecal coliform bacteria is an issue of great importance across the globe. A water quality model, Hydrological Simulation Program FORTRAN, was used to predict the impacts of farming and climate change on faecal coliform loads and concentrations in streams of the Lis River watershed, in the Leiria region, Portugal. The calibrated faecal coliform model simulated well the patterns and range of observed faecal coliform concentrations. The accuracy of the model was evaluated by the per cent bias coefficient and the coefficient of determination. The results indicate a general deterioration of the water quality regarding faecal contamination in Lis River. Maximum daily loads were calculated for each of the impaired streams; an average of 77% reduction in the current faecal coliform load from the watershed is necessary to achieve the established water quality goals by the Council Directive 75/440/EEC (). Climate change scenarios (increments on temperature and precipitation) were assumed to predict the behaviour of faecal coliform bacteria in the watershed. The simulated results showed that an increase of 1°C in air daily temperature results in an increase of water temperature of 1.1°C and a 1.5% decrease on faecal coliform bacteria in stream concentration. The combined effect of air temperature (+1°C) and precipitation (+7%) increment leads to an increase of ~2% in bacteria inflow to the basin. Copyright © 2014 John Wiley & Sons, Ltd.
- FLOODING AND SURFACE CONNECTIVITY OF TAXODIUM‐NYSSA STANDS IN A
SOUTHERN FLOODPLAIN FOREST ECOSYSTEM
- Authors: J. A. Kupfer; K. M. Meitzen, P. Gao
Pages: n/a - n/a
Abstract: An understanding of the factors controlling the permanent and episodic links between the main stem of a river and the ecosystems of its alluvial floodplain is necessary for evaluating the influence of modern river processes on floodplain ecology and habitat diversity and for the successful implementation of flow regimes that meet human needs for water in a manner that sustains the ecological integrity of affected systems. In this study, we examined relationships between river hydrology and lateral hydrological connectivity, which is crucial to directing fluxes of water, material, and organisms into and across a floodplain. We did so by translating measures of river discharge for the Congaree River into high resolution maps of flood conditions for the floodplain at Congaree National Park using a 2D flood inundation model. Utilizing a graph network approach, we then analyzed the connectivity of a key wetland ecosystem, Taxodium‐Nyssa forested swamps, to the main stem river and to each other under different flows. Our results underscore that floodplain connectivity is initiated at sub‐bankfull discharges and does not depend on levee overtopping, while also clarifying that various sources of connectivity are triggered at different flow levels in specific reaches. Further, our findings demonstrate the sensitive and non‐linear response of floodplain connectivity to river flows and provide useful information to facilitate the management of flood processes in the Congaree River watershed. Copyright © 2014 John Wiley & Sons, Ltd.
- FATE, TRANSPORT AND EFFECTS OF POLLUTANTS ORIGINATING FROM ACID MINE
DRAINAGE IN THE OLIFANTS RIVER, SOUTH AFRICA
- Authors: J. M. Dabrowski; J. Dabrowski, L. Hill, P. MacMillan, P. J. Oberholster
Pages: n/a - n/a
Abstract: Concentrations of pollutants were measured in water, sediment and algal samples collected along a longitudinal gradient from a stretch of the Olifants River, South Africa, that receives acid mine drainage (AMD) from the Klipspruit River. The effects of AMD were determined through macroinvertebrate biotic indices (SASS5) and multivariate analysis of macroinvertebrate communities. The acidic Klipspruit River caused increased concentrations of total Al, Fe and Mn in the Olifants River. Upon mixing of the Klipspruit with that from the alkaline Olifants River, Al and Fe precipitate rapidly, leading to lower concentrations in the dissolved phase and higher concentrations in the suspended phase and in sediment at sites in close proximity to the confluence. Similarly, filamentous algae accumulated high concentrations of Al, Fe and Zn immediately after the confluence. Mn remains in the dissolved phase, and sediment and algal concentrations increase with increasing distance downstream. Metal speciation analysis indicate that Al is rapidly converted from more toxic forms (e.g. Al3+ and Al(OH)2+) to less toxic forms (e.g. Al(OH)3(aq) and Al(OH)4−). In contrast, Mn remains in the soluble Mn2+ form. Macroinvertebrate metrics and community structure showed clear signs of deterioration in water quality in the Olifants River downstream of the point of AMD input. While total TDS concentrations at all sites fall within ranges likely to affect macroinvertebrates, the relative composition of major ions changes as a result of AMD input, which may also account for the observed changes in macroinvertebrate communities. Further downstream, the Wilge River discharges into the Olifants River and significantly improves water quality downstream of the confluence. Future mining and development activities in the Wilge catchment should be carefully managed and monitored so as to ensure sufficient flows of acceptable quality to prevent further deterioration of water quality in the Olifants River and downstream reservoirs. Copyright © 2014 John Wiley & Sons, Ltd.
- LIFE‐HISTORY PLASTICITY OF RIPARIAN ANNUAL PLANTS ADAPTED TO EXTREME
VARIATIONS IN WATER LEVEL: MESOCOSM EXPERIMENTS
- Authors: Y. Song; X. Ke, W. Liu, A. J. Davy, G. Liu
Pages: n/a - n/a
Abstract: The riparian zones of reservoirs associated with regulated rivers in China experience annual fluctuations in water level of up to 30 m that may vary in timing from year to year. Few plant species can tolerate such hydrological perturbation, but short‐lived riparian annuals might be evolutionarily pre‐adapted to such conditions. This study investigated plasticity of life history in four annual species: one typically associated with free‐flowing rivers (Panicum bisulcatum) and three that colonize reservoir margins (Cyperus michelianus, Fimbristylis miliacea and Eclipta prostrata). We found that all four species produced non‐dormant seeds that survived prolonged submergence; germination percentage was independent of the time of exposure by receding waters. Although growth was reduced as a result of shorter growing seasons, all four species completed their life cycles and produced seeds before winter. In addition, P. bisulcatum and C. michelianus allocated biomass to seed production, at the expense of roots and stems, in response to later establishment. All species responded to later establishment with a reduced vegetative growth period before seed production. C. michelianus, F. miliacea and E. prostrate could also delay the onset of flowering time by up to 2 months. P. bisulcatum, a plant that can flower only after exposure to short days, consequently had a fixed flowering time and could accommodate delayed establishment only with a progressively shorter period of vegetative growth. This lower flexibility might explain its absence from reservoir margins. The conceptual framework presented here offers a tool to predict the establishment of vegetation under hydrological disturbance in riparian environments and thereby provides insights into improved restoration practice. Copyright © 2014 John Wiley & Sons, Ltd.
- A GENERAL APPROACH TO PREDICTING ECOLOGICAL RESPONSES TO ENVIRONMENTAL
FLOWS: MAKING BEST USE OF THE LITERATURE, EXPERT KNOWLEDGE, AND MONITORING
- Authors: J. A. Webb; S. C. Little, K. A. Miller, M. J. Stewardson, I. D. Rutherfurd, A. K. Sharpe, L. Patulny, N. L. Poff
Pages: n/a - n/a
Abstract: Around the world, governments are making huge investments in environmental flows. However, much of the rationale for these releases is based on expert opinion and is thus open to challenge. Empirical studies that relate ecological responses to flow restoration are mostly case studies of limited generality. Radically, different approaches are required to inform the development of general models that will allow us to predict the effects of environmental flows. Here, we describe the modelling framework being used in a major study of environmental flows in the Australian state of Victoria. The framework attempts to make best use of all the information available from the literature, experts, and monitoring data, to inform the development of general quantitative response models. It uses systematic review of the literature to develop evidence‐based conceptual models, formal expert elicitation to provide an initial quantification of model links, and data derived from purpose‐designed monitoring programs over large spatial scales. These elements come together in a Bayesian hierarchical model that quantifies the relationship between flow variation and ecological response and hence can be used to predict ecological responses to flow restoration. We illustrate the framework using the example of terrestrial vegetation encroachment into regulated river channels. Our modelling framework aims to develop general flow‐response models and can immediately be used to demonstrate the ecological return on investment from environmental flow programs. However, the framework also has the potential to be incorporated into planning and decision‐making processes, helping to drive a transformation in evidence‐based practice for environmental flow management. © 2014 The
Authors . River Research and Applications published by John Wiley & Sons, Ltd.
- TEMPORARY RIVERS: LINKING ECOHYDROLOGY, ECOLOGICAL QUALITY AND
- Authors: A. H. Arthington; J. M. Bernardo, M. Ilhéu
Pages: n/a - n/a
Abstract: Temporary streams and rivers, also referred to as intermittent, are defined as waterways that cease to flow at some points in space and time along their course. They are shaped by alternating wet and dry periods over annual and inter‐annual cycles, making them one of the most dynamic freshwater ecosystems. These distinctive systems represent a substantial proportion of the total number, length and discharge of the global river network and are expected to become more widespread and face increasing pressures in many regions as a result of human activities and climate change. This collection of papers arose from the Conference on ‘Ecohydrology and Ecological Quality in Temporary Rivers’ held at the University of Evora, Portugal, 12–14 September 2012. The primary objectives of the meeting were to bring together researchers and expertise from a range of temporary ecosystems, from small temporary Mediterranean and Californian streams to intermittent rivers from semi‐arid and arid zones. A common thread through the discussions was the assessment of ecological conditions within these dynamic ecosystems. To undertake a ’condition assessment’ is challenging because of the need to differentiate between biotic responses to anthropogenic pressures and natural variability associated with the hydro‐climatology and disturbance regime typical of these systems, that is, drought, drying and flooding. The management of degraded intermittent streams and rivers presents many new challenges, not least how to reconcile ecological and societal goals for emerging ‘novel’ ecosystems. Reconciliation ecology presents a realistic way of managing novel ecosystems given their value and desirable ecological services to society, rather than trying to restore to an original ecological state that may not be sustainable or economically possible. Copyright © 2014 John Wiley & Sons, Ltd.
- EFFECTS OF WATER TEMPERATURE ON BREEDING PHENOLOGY, GROWTH, AND
METAMORPHOSIS OF FOOTHILL YELLOW‐LEGGED FROGS (Rana boylii): A CASE
STUDY OF THE REGULATED MAINSTEM AND UNREGULATED TRIBUTARIES OF
CALIFORNIA'S TRINITY RIVER
- Authors: C. A. Wheeler; J. B. Bettaso, D. T. Ashton, H. H. Welsh
Pages: n/a - n/a
Abstract: Many riverine organisms are well adapted to seasonally dynamic environments, but extreme changes in flow and thermal regimes can threaten sustainability of their populations in regulated rivers. Altered thermal regimes may limit recruitment to populations by shifting the timing of breeding activities and affecting the growth and development of early life stages. Stream‐dwelling anurans such as the foothill yellow‐legged frog (Rana boylii) in the Trinity River of northern California are model subjects for examining associations between water temperature and the timing of oviposition, hatching, and metamorphosis, and body condition and size of tadpoles and metamorphs. Breeding activity, hatching success, and metamorphosis occurred later, and metamorphs were smaller and leaner along the regulated and colder mainstem relative to six unregulated tributaries of the Trinity River. Persistently depressed summer water temperatures appear to play a seminal role in inhibited tadpole growth on the regulated mainstem and may be a causative factor in the pronounced decline of this population. Environmental flow assessments should account for the influence of the thermal regime on the development of vulnerable embryonic and larval life stages to improve outcomes for declining amphibian populations. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- DYNAMIC MODELLING OF SOIL NITROGEN BUDGET AND VEGETATION COLONIZATION IN
SEDIMENT BARS OF A REGULATED RIVER
- Authors: T. Asaeda; M. H. Rashid, R. Abu Bakar
Pages: n/a - n/a
Abstract: Intensive forestation widely occurs in East Asian rivers. It deteriorates the ecosystem of gravelly or sandy bars, affects flood protection, and changes the landscape of the river. For the regulation of forestation and vegetative succession on the bars, a suitable tool, through either a numerical simulation model or through empirical knowledge that will predict the future process after treatment, is required. With this background, a dynamic model is developed based on the empirical knowledge obtained by field observations in order to simulate the vegetative growth process on the bars. Observations were conducted at several Japanese rivers in order to better understand tree growth and biomass, herbaceous plant biomass, and soil nitrogen content. The model is composed of four modules: a hydrological module, which provides for flood inundation, flushing and sedimentation processes, a tree module, which describes the recruitment, growth and thinning of tree densities, and a herbaceous plant module, which describes the biomass of herbs as a function of environmental conditions. Finally, there is a soil module, which mostly describes nitrogen budgets. The model was successfully applied to the Arakawa River in central Japan in order to simulate a 30‐year process after a major flood. Simulations were conducted for several cases related to the processes of two tree species: Robinia pseudoacacia and Salix spp. The model was then applied in order to elucidate the forestation mechanism of the bar, which indicated a possible reason for the effect of decreasing the supply of coarse sediment. The impact of the tree and herbaceous plants by different hydrological processes is also discussed. Copyright © 2014 John Wiley & Sons, Ltd.
- RIPARIAN VEGETATION COMMUNITIES OF THE AMERICAN PACIFIC NORTHWEST ARE TIED
TO MULTI‐SCALE ENVIRONMENTAL FILTERS
- Authors: N. Hough‐Snee; B. B. Roper, J. M. Wheaton, R. L. Lokteff
Pages: n/a - n/a
Abstract: Riparia surrounding low‐order streams are dynamic environments that often support distinct biodiversity. Because of their connection to nearby uplands, riparian vegetation communities at these streams respond to many environmental filters—climatic, physical, chemical or biotic factors—that restrict what species can occur at a given location from within larger regional species pools. In this study, we examined how environmental filters originating at the landscape, watershed and reach scales correspond to riparian plant community composition across the interior Columbia and upper Missouri River basins, USA. We correlated riparian vegetation to environmental filters, identified unique communities and partitioned the variance within riparian vegetation data among filters originating at different scales. Riparian vegetation composition was strongly correlated to landscape‐scale filters including elevation, precipitation and temperature. Watershed‐scale filters such as grazing and reach filters indicative of fluvial setting were also correlated to vegetation composition, often differentiating communities with similar landscape settings. We identified 10 distinct vegetation communities. Forested communities occurred at higher elevation, moderate gradient reaches with high mean annual precipitation. Shrub–forb systems corresponded to fluvial and watershed disturbances and occurred within climates that could preclude forest establishment. Meadows corresponded to high water tables and/or high grazing activity. Variance partitioning showed that landscape‐scale filters explained the most variance within vegetation communities. Global change will alter many of the environmental filters that drive vegetation. Vegetation change may occur rapidly if local filters (e.g. fluvial process) change rapidly or may occur more slowly if larger‐order filters (e.g. climate) change slowly and without influencing local hydrogeomorphic filters. By identifying filter–vegetation relationships at large spatial scales, hypotheses can be constructed on how riparian vegetation communities may change under future environmental conditions. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- DOWNSTREAM EFFECTS OF RECENT RESERVOIR DEVELOPMENT ON THE MORPHODYNAMICS
OF A MEANDERING CHANNEL: SAVERY CREEK, WYOMING, USA
- Authors: C. J. Legleiter
Pages: n/a - n/a
Abstract: Recent reservoir construction on Savery Creek provided an opportunity to examine the downstream effects of a dam on a small, meandering channel. The new dam, completed in 2005, modified the flow regime by reducing the magnitude of spring peaks and increasing baseflows, including a second period of high discharge in the fall. A time series of remotely sensed data spanning 1980–2011 was used to measure lateral migration rates, quantify areas of erosion and deposition, and map spatial patterns of channel change. Both migration rates, and gross erosion and deposition increased during the post‐dam era, although 2 years of exceptionally large snowmelt runoff also occurred during this time. Net sediment flux inferred from the image time series was negative for both the upper and lower reaches for the first photo pair after the dam's completion but became positive for the most recent photos. Detailed topographic surveys of five individual meander bends were used to produce digital elevation models of difference and infer bed material transport rates. For three sites located in the upper reach, downstream increases in transport rate implied a sediment deficit satisfied through channel incision and/or bank erosion. For two sites in the lower reach where sediment supply was greater, larger values of gross erosion were balanced by enhanced deposition and transport rates stabilized or increased along each bend. Together, these results suggest that Savery Creek has entered a period of adjustment as the channel adapts to altered, dam‐regulated supplies of water and sediment. Copyright © 2014 John Wiley & Sons, Ltd.
- CLIMATE‐INDUCED FLOW REGIME ALTERATIONS AND THEIR IMPLICATIONS FOR
THE LANCANG RIVER, CHINA
- Authors: J. Tang; X. A. Yin, P. Yang, Z. F. Yang
Pages: n/a - n/a
Abstract: Most studies of the Lancang River have focussed on the influence of hydropower generation on the riverine ecosystem. Few studies have explored climate‐induced flow regime alterations and their implications for the riverine ecosystem. There is a pressing need for improved understanding of the implications of such climate‐induced flow regime alterations in the Lancang River Basin. Future streamflow under the A2 and B2 scenarios of Hadley Centre coupled model version 3 (HadCM3) are predicted using a back propagation artificial neural network. Potential effects of flow regime alterations are tested by amended annual proportional flow deviation (AAPFD). Projected streamflow will decrease in wet season months and will increase in dry season months. Monthly streamflow at Jiuzhou station was projected to range from a 27.9% decrease to a 158.4% increase. For Gajiu station, the percent increase was projected to range from 1.4% to 70.4%, while the decrease ranged from 0.2% to 16.9%. Changes in streamflow at Yunjinghong station ranged from a 46.5% decrease to a 135.3% increase. Projected streamflow changes during high and low flow periods will have important implications for the ecological processes of the Lancang River Basin. AAPFD indicates that these changes will have serious effects on the Lancang River Basin ecosystem. Projected climate‐induced flow regime alterations during the period of 2071–2095 will have particularly serious effects on riverine ecosystem, especially in the upstream and downstream sections of the Lancang River. The A2 scenario will pose a more serious threat to riverine ecosystem health. Copyright © 2014 John Wiley & Sons, Ltd.
- THE SURVIVAL OF ATLANTIC SALMON (Salmo salar) EGGS DURING DEWATERING IN A
RIVER SUBJECTED TO HYDROPEAKING
- Authors: R. Casas‐Mulet; S. J. Saltveit, K. Alfredsen
Pages: n/a - n/a
Abstract: Hydropeaking in regulated rivers is likely to become more frequent with increasing demands for renewable energy. Sudden fluctuations affect surface and subsurface flow regimes and change hydrological interactions occurring in the hyporheic zone. The hyporheic zone plays an important role for salmon embryonic development, and groundwater influx may create refuges for egg survival during low flow in hydropeaking regulated rivers. The links between salmon embryo survival and hyporheic hydrological processes during hydropeaking have hardly been investigated.
A field experiment was undertaken in a 5 × 20 m side gravel bar subject to dewatering due to hydropeaking. Eleven cylindrical boxes composed of eight compartments were placed in the permanently wet area and the ramping zone. Sixty eggs were placed in two compartments (at 10 and 30 cm depth) in each box. Surface and interstitial water levels and temperatures were monitored at 2 min resolution. Data were collected for a period of 3 months, coinciding with early stages of salmonid egg development in this catchment. Egg compartments were checked on six occasions for survival after different hydropeaking events. Dead eggs were counted and removed. Survival rates were lower in the top compartments in the ramping zone (78%) compared with the boxes in the permanently wet area and the lowermost compartments in the ramping (survival rates >99%). With no water quality issues in the catchment and very low inputs of fine sediments in the egg compartments, exposure to dry conditions and subzero temperatures were the main factors explaining egg mortality in the top compartments of the ramping zone. The rate of survival will thus depend on the surface water and groundwater interactions. Site‐specific hydrological interactions occurring in the hyporheic zone should be actively considered when managing fish populations in rivers with hydropeaking. Copyright © 2014 John Wiley & Sons, Ltd.
- BIOFILM RESPONSES TO FLOW REGULATION BY DAMS IN MEDITERRANEAN RIVERS
- Authors: L. Ponsatí; V. Acuña, I. Aristi, M. Arroita, E. García‐Berthou, D. Schiller, A. Elosegi, S. Sabater
Pages: n/a - n/a
Abstract: Dams regulate downstream hydrology and modify water quality, which in turn can impinge on the biota, especially in rivers naturally subject to large hydrological variability, such as those under Mediterranean climate. The effect of dams on biofilms was analysed in three tributaries (Cinca, Siurana and Montsant) of the Ebro River (NE Spain). We hypothesized that flow regulation would lead to lower spatial variability of biofilms on the streambed and to a decrease in their metabolic rate per unit biomass, especially during low flow periods. Biofilm characteristics were studied in five transects evenly spaced along river reaches upstream (control) and downstream (impact) of dams in each river, along with riverbed granulometry, hydraulics and water chemistry. Chlorophyll‐a, respiratory activity, photosynthetic capacity and efficiency, and extracellular enzymatic activities (β‐d‐glucosidase, alkaline phosphatase and leucine‐amino‐peptidase) of epilithic biofilms were measured in different seasons. Spatial variability of chemical and biological variables was reduced downstream of the dams. Chlorophyll‐a concentration, photosynthetic efficiency and respiration capacity were higher in impact than in control reaches, but generally, low inorganic phosphorus concentrations resulted in comparable phosphatase activities downstream and upstream of dams. On the other hand, β‐d‐glucosidase and leucine‐amino‐peptidase activities were higher at impact reaches. Biofilms were thicker and metabolically more active at the impact reaches, with higher ability to transform dissolved organic matter. Overall, results from this study provide evidence that dams can largely affect the structure and activity of river biofilms, with foreseeable important consequences for river ecosystem functioning. Copyright © 2014 John Wiley & Sons, Ltd.
- LOG‐VANE SCOUR IN CLEAR WATER CONDITION
- Authors: S. Pagliara; L. Sagvand Hassanabadi, S. Mahmoudi Kurdistani
Pages: n/a - n/a
Abstract: Log‐Vane is a grade‐control structure of common use to stabilize river bed and river banks. The purpose of this paper is to study the scour phenomena downstream of Log‐Vanes in straight rivers. The main goal is to obtain design equations to determine the main scour parameters and the scour morphology. All the experiments have been carried out in a horizontal channel and in clear water conditions. Log‐Vanes made of wood, with different heights and vane angles, were tested. Different hydraulic conditions including densimetric Froude numbers, water drops and tail water values were tested. Results show that the tail water depth is an important variable to determine the maximum scour depth. The vane angle results to be an important parameter to predict the scour parameters. Dimensional analysis allows to derive design equations useful to estimate the maximum scour depth, maximum length of the scour and maximum height and length of the dune. Copyright © 2014 John Wiley & Sons, Ltd.
- OPTIMIZING A STANDARDIZED ELECTROFISHING SAMPLING PROTOCOL FOR WARMWATER
RESIDENT SPORTFISH IN THE TALLAPOOSA RIVER, ALABAMA, USA
- Authors: S. M. Sammons
Pages: n/a - n/a
Abstract: A two‐year electrofishing study was initiated in the Tallapoosa River, Alabama, to identify an optimal standardized sampling program for three principal resident sportfish: Alabama bass Micropterus henshalli, redbreast sunfish Lepomis auritus, and redeye bass Micropterus coosae. Samples were conducted in spring (May), summer (July), and fall (October) in 2010 and 2011 from seven 1‐h transects. Spring samples of Alabama bass had lower catch per effort (CPE) and were more skewed towards fish between 200 and 300 mm total length (TL) than samples in other seasons; whereas, fall samples collected more redeye bass >200 mm TL but CPE was similar among seasons. Fewer, but larger, redbreast sunfish were sampled during fall compared with other seasons. Mean CPE of all three species was independent of transect duration. The total time spent electrofishing and processing fish in order to estimate a mean CPE with a specified precision was a function of transect duration and CPE. More effort was needed as CPE decreased for most species, but the relations between transect duration and total effort were parabolic. A precision of within 10% of the mean CPE was unattainable for most species as a result of logistic considerations. Based on the results of this study, it appears that fall is the optimal sampling time for these species in the Tallapoosa River and the optimal transect duration is likely 10 min. At a precision level of 20% of the mean, the number of 10‐min transects required ranged from 5 to 40, with a total sample time for each individual species of 0.82–7.16 h. Copyright © 2014 John Wiley & Sons, Ltd.
- TEMPORAL VARIABILITY AND POTENTIAL PREDICTABILITY OF THE STREAMFLOW
REGIMES IN THE NORTH‐EASTERN IBERIAN PENINSULA
- Authors: M. Hernández‐Martínez; J. M. Hidalgo‐Muñoz, S. R. Gámiz‐Fortis, Y. Castro‐Díez, M. J. Esteban‐Parra
Pages: n/a - n/a
Abstract: This paper investigates the temporal variability and potential predictability of streamflow regimes in the north‐eastern Spain for the 1970–2010 period. Two different regimes are found, those characterized for having peak flows in the winter and those where this maximum appears in the spring. The main characteristic time scales of streamflows in each area are studied by singular spectral analysis (SSA). While winter streamflow regime only shows interannual variability (quasi‐oscillatory modes around 5.5 and 2.3 years), spring streamflow (2.6 and 6.6 years) also presents a decadal variability component. Based on this result, a modelling process is conducted using autoregressive moving average (ARMA) models, for interannual variability modelling, and stable teleconnections between global oceanic sea surface temperature (SST) anomalies and river flow, for decadal variability modelling. Finally, a one‐step‐ahead prediction experiment is computed to obtain forecasted streamflows.
The results for winter streamflow regime modelling show a phase concordance between the raw and the forecasted streamflow time series of around 70% and a correlation around 0.7, for the validation period (2001–2010). For spring streamflow, additionally to the ARMA modelling for the interannual component, a model based on the SST has been established that involves some oceanic regions from previous seasons located, fundamentally, not only in the North Atlantic but also in the Indian Ocean. The combined model (SST + ARMA) significantly improves the prediction based on the ARMA model alone, showing a phase concordance and a correlation around 90% and 0.7 respectively.
This modelling scheme provides predictability skills of the rivers from the Inland Catalan Basins at different time scales, representing an added value for water planning. Copyright © 2014 John Wiley & Sons, Ltd.
- WHY DO FISH STRAND? AN ANALYSIS OF TEN YEARS OF FLOW REDUCTION
MONITORING DATA FROM THE COLUMBIA AND KOOTENAY RIVERS, CANADA
- Authors: R. L. Irvine; J. L. Thorley, R. Westcott, D. Schmidt, D. DeRosa
Pages: n/a - n/a
Abstract: Stranding of fish due to flow reductions has been documented in the near shore of the Columbia and Kootenay Rivers, Canada, and can result in sub‐lethal or lethal effects on fish. Ten years (1999–2009) of monitoring data have been collected at sites below two hydro‐electric dams (Hugh‐L‐Keenleyside and Brilliant Dam) following flow reductions. A generalized linear mixed effects model analysed the probability of a stranding event in relation to environmental and operational variables including the rate of change in the water levels, the duration of shoreline inundation prior to a reduction (wetted history), the river stage, the magnitude of the reduction, distance downstream from the dam, time of day, day of year (season) and whether a site had been physically altered to mitigate stranding. The results demonstrated statistically significant effects on stranding risk from minimum river stage, day of the year and whether a site had been physically re‐contoured. The combination of investigated factors giving the highest probability of stranding was a large magnitude reduction completed in the afternoon in midsummer, at low water levels when the near shore had been inundated for a long period. This research is significant in its approach to assessing years of ecosystem scale monitoring data and using the modelling results to determine ways for these findings to be applied in regulated river management to minimize fish stranding. It also highlighted data gaps that require addressing and provides ecosystem scale results to compare with stranding studies carried out in mesocosms. Copyright © 2014 John Wiley & Sons, Ltd.
- DIATOMS OF TEMPORARY AND PERMANENT WATERCOURSES IN SOUTHERN EUROPE
- Authors: M. H. Novais; M. M. Morais, J. Rosado, L. S. Dias, L. Hoffmann, L. Ector
Pages: n/a - n/a
Abstract: The potential importance of benthic diatoms in Mediterranean watercourses has received limited academic attention historically. This study sought to provide baseline information for this poorly studied group. Temporary and permanent watercourses in Portugal differ in catchment characteristics, climatic variables and water chemistry. The benthic diatom communities were characterized in terms of ecological preferences and conservation status for taxa with relative abundance above 1% in at least one site covering 39 temporary sites (109 taxa) and 53 permanent sites (130 taxa). The low‐profile guild dominated both temporary and permanent watercourses, followed by the high‐profile and motile guilds. Indicator value analysis indicated that Amphora copulata, Cocconeis placentula, Diploneis separanda, Encyonopsis subminuta, Fragilaria radians, Gomphonema olivaceum, Gomphonema truncatum, Halamphora veneta, Navicula radiosa, Navicula veneta, Sellaphora seminulum and Ulnaria acus were indicators of temporary watercourses, whereas Encyonema minutum, Eunotia minor, Fragilaria rumpens, Fragilaria cf. socia and Navicula rhynchocephala were characteristic of permanent watercourses. Ecological preferences of indicator taxa were inferred on the basis of environmental variables that differed significantly between temporary and permanent watercourses. The importance of temporary watercourses for the maintenance of diatom biodiversity is discussed and explored. Copyright © 2014 John Wiley & Sons, Ltd.
- CONCEPTUAL MODELLING TO ASSESS HYDROLOGICAL IMPACTS AND EVALUATE
ENVIRONMENTAL FLOW SCENARIOS IN MONTANE RIVER SYSTEMS REGULATED FOR
- Authors: J. Geris; D. Tetzlaff, J. Seibert, M. Vis, C. Soulsby
Pages: n/a - n/a
Abstract: To improve understanding of natural and managed flow regimes in data‐sparse regulated river systems in montane areas, the commonly used Hydrologiska Byråns Vattenbalansavdelning (HBV) conceptual run‐off model was adapted to incorporate water regulation components. The extended model was then applied to the heavily regulated river Lyon (391 km2) in Scotland to reconstruct the natural flow regime and to assess the impacts of regulation at increasing spatial scales. Multi‐criteria model evaluation demonstrated that the model performed well in capturing the dominant catchment processes and regulation effects, especially at the timescales at which operation rules apply. The main change as a result of regulation in the river Lyon is a decrease in inter‐annual and intra‐annual variability of all elements of the flow regime, in terms of magnitude, frequency, and duration. Although these impacts are most pronounced directly downstream of the impoundments, the regulation effects propagate throughout the river system. The modelling approach is flexible and widely applicable and only limited amounts of data are required. Moreover, results are easily communicated to stakeholders. It has the potential to contribute to the development of flow regimes that may be more beneficial to the ecological status of rivers. In the case of the river Lyon, it is likely that this involves a more variable release regime. The approach developed here provides a tool for assessing impacts on flow regimes and informing environmental flows in other data‐sparse regions with heavily regulated montane river systems. Copyright © 2014 John Wiley & Sons, Ltd.
- ABIOTIC ATTRIBUTES SURROUNDING ALLUVIAL ISLANDS GENERATE CRITICAL FISH
- Authors: W. D. Hintz; A. P. Porreca, J. E. Garvey, Q. E. Phelps, S. J. Tripp, R. A. Hrabik, D. P. Herzog
Pages: n/a - n/a
Abstract: Identifying the appropriate scale at which habitat is biologically relevant to riverine fishes in large, sand‐dominated rivers is a challenge. Alluvial islands are important to several of these fishes throughout the central USA, but there is a paucity of information on island habitat features that restoration efforts should try to replicate. We determined the physical characteristics of two island complexes in the middle Mississippi River that facilitate the settlement and survival of age‐0 shovelnose sturgeon Scaphirhynchus platorynchus at relatively large (mean 39,000 m2) and small (mean 320 m2) scales. Depth (m), flow rate (m s−1), substrate (sand, rock, silt) and vegetation were quantified at these two scales using hydroacoustic techniques (split‐beam sonar and acoustic Doppler current profiler). Abiotic attributes in the surrounding littoral zone of the island complexes were highly correlated but differed depending on location. At the coarse spatial scale, vegetation was positively related to shovelnose sturgeon abundance. At the fine spatial scale, age‐0 shovelnose sturgeon were restricted to flow rates
- USE OF STABLE ISOTOPES TO TRACE MUNICIPAL WASTEWATER EFFLUENTS INTO FOOD
WEBS WITHIN A HIGHLY DEVELOPED RIVER SYSTEM
- Authors: H. A. Loomer; K. D. Oakes, S. L. Schiff, W. D. Taylor, M. R. Servos
Pages: n/a - n/a
Abstract: Many anthropogenic inputs, such as municipal wastewater effluents (MWWEs), affect stable isotope signatures (δ13C and δ15N) at the base of exposed food webs creating spatial patterns reflecting their incorporation into aquatic food webs. The Grand River in southern Ontario, Canada, is a heavily modified, rapidly urbanizing river that assimilates wastewater from 30 municipal wastewater treatment plants. Stable isotope analysis was applied to resident aquatic invertebrates and fish influenced by three different wastewater outfalls in early, middle, and late summer to determine how values shifted seasonally and with differing effluent quality. There was a slight increase in δ13C in both invertebrates and fish in late summer downstream from the three outfalls, but it is difficult to separate effects of the effluents from downstream gradients. Downstream of two of the three outfalls, the δ15N tended to increase relative to upstream, while the remaining effluent, of the poorest quality, decreased δ15N values of both invertebrates and fish. Spatial trends in stable isotopes became more pronounced as the summer progressed with the greatest between‐site differences occurring in late summer. This study reflects the complex nutrient dynamics associated with MWWE inputs to rivers and contributes to our understanding and application of stable isotope analysis in impacted lotic ecosystems. Copyright © 2014 John Wiley & Sons, Ltd.
- EFFECTS OF ROAD CROSSINGS ON HABITAT CONNECTIVITY FOR
- Authors: M. W. Diebel; M. Fedora, S. Cogswell, J. R. O'Hanley
Pages: n/a - n/a
Abstract: Road crossings can act as barriers to the movement of stream fishes, resulting in habitat fragmentation, reduced population resilience to environmental disturbance and higher risks of extinction. Strategic barrier removal has the potential to improve connectivity in stream networks, but managers lack a consistent framework for determining which projects will most benefit target species. The objective of this study is to develop a method for identifying and prioritizing action on road crossings in order to restore stream network connectivity. We demonstrate the method using a case study from the Pine‐Popple watershed in Wisconsin. First, we propose a new metric for quantifying stream connectivity status for stream‐resident fish. The metric quantifies the individual and cumulative effects of barriers on reach and watershed level connectivity, while accounting for natural barriers, distance‐based dispersal limitations and variation in habitat type and quality. We conducted a comprehensive field survey of road crossings in the watershed to identify barriers and estimate replacement costs. Of the 190 surveyed road crossings, 74% were determined to be barriers to the movement of at least one species or life stage of fish, primarily due to high water velocity, low water depth or outlet drops. The results of the barrier removal prioritization show that initial projects targeted for mitigation create much greater improvements in connectivity per unit cost than later projects. Benefit–cost curves from this type of analysis can be used to evaluate potential projects within and among watersheds and minimize overall expenditures for specified restoration targets. Copyright © 2014 John Wiley & Sons, Ltd.
- A NEW METHOD TO ASSESS THE FLOW REGIME ALTERATIONS IN RIVERINE ECOSYSTEMS
- Authors: X. A. Yin; Z. F. Yang, G. E. Petts
Pages: n/a - n/a
Abstract: Assessing alterations of a river's flow regime provides the basis for river protection and restoration planning. The range of variation approach (RVA) is a commonly used method to evaluate alterations in a river's flow regime. However, RVA underestimates the degree of flow regime alteration potentially, because it only considers the difference in frequency between the pre‐impact and post‐impact hydrologic indicator values within certain target ranges and does not consider alteration of the order of hydrologic year types (HYTs; i.e. wet, average and dry years). The HYT order is an important holistic feature of the flow regime. The human‐induced change of HYTs, such as from a dry year to a wet year or from an average year to a dry year, can be a major cause of ecosystem alteration. For some species, the order of the HYTs was more important than single‐year events (such as the flood magnitude during a given year). To address this problem with the RVA, we proposed a modification of this method that accounts for alteration of the order of HYTs. We developed a metric for assessing the alteration of the HYT order based on Euclidean distance and then combined this metric with the RVA. We applied the revised method to a case study of the Sha River in northern China to test its effectiveness. The results demonstrated that the new method solved RVA's problem of potentially underestimating the degree of flow regime alteration and enabled a more comprehensive analysis of the alteration of the flow regime. Copyright © 2014 John Wiley & Sons, Ltd.
- IMPACT OF DROUGHT ON DIATOM COMMUNITIES AND THE CONSEQUENCES FOR THE USE
OF DIATOM INDEX VALUES IN THE RIVER MAUREILLAS
- Authors: A. Barthès; J. Leflaive, S. Coulon, F. Peres, J.‐L. Rols, L. Ten‐Hage
Pages: n/a - n/a
Abstract: In the context of climate change, with an increase in the incidence of seasonally dry streambeds, we examined the impact of drought, and its duration, on the structure of diatom communities and the consequences of this on diatom index values (Biological Diatom Index; Specific Polluosensitivity Index) in the Mediterranean river Maureillas. The effects of several durations of droughts or low flow events (1, 2 and 4 weeks) on diatom‐dominated biofilms were studied by removing pebbles from the river and comparing the growing communities after rewetting with those of control biofilms (pebbles left in the streambed) and with those of newly formed biofilms (cleaned‐up pebbles). Sampling was performed six times during the 28‐day rewetting phase. We determined the specific composition of diatom communities, the mortality rate after rewetting, and the Biological Diatom Index and Specific Polluosensitivity Index scores for each sample, distinguishing between potentially living diatoms (full frustules with chloroplasts) and dead diatoms (empty frustules). Our results showed a notable and durable impact of even short drought on diatom communities. The different trajectories of biofilm communities observed between the types of pebbles showed the importance of the biofilm history for the community structure. This should be taken into account to improve the sampling practices used for monitoring. We also observed a stable mortality rate whatever the drought duration was. Diatom index values were stable despite the observed impact of treatment on diatom communities. These results emphasize the reliability of the diatom index to evaluate biological quality according to European requirements. In addition, the distinction of empty and full frustules did not induce significant differences, but it may reduce biases in interpretation. Copyright © 2014 John Wiley & Sons, Ltd.
- MASS DISPERSAL OF TERRESTRIAL ORGANISMS DURING FIRST FLUSH EVENTS IN A
- Authors: J. Rosado; M. Morais, K. Tockner
Pages: n/a - n/a
Abstract: Temporary streams expand and contract seasonally, forming a complex mosaic of aquatic, amphibic and terrestrial habitats. We studied the terrestrial arthropod fauna at the surface of the dry river bed as well as the fauna of Coarse Particulate Organic Matter (CPOM) deposits 0, 5 and 10 days after first flush events (years 2004–2006) along the Pardiela stream (SE Portugal). During the dry period, large amounts of organic material accumulated at the surface of the dry bed, colonized by abundant terrestrial arthropods (mean density: 13.3 ± 15.29 Ind g DM (Dry Mass of CPOM)). Arthropod density peaked in fresh flood deposits (mean density: 35.8 ± 33.4 Ind g DM), and subsequently decreased within time. Concurrently, the relative composition of the arthropod community changed from Day 0 to Day 10. The present results demonstrated that the dry bed of temporary streams served as a major habitat for terrestrial arthropods. During the first flush events, a mass dispersal of terrestrial arthropods, rafting on floating CPOM, occurred, subsequently forming distinct deposits along the channel margin. These deposits may constitute critical habitats, refugia and food resources for local and regional terrestrial arthropod assemblages. Copyright © 2014 John Wiley & Sons, Ltd.
- USING GOOGLE EARTH, A VIRTUAL‐GLOBE IMAGING PLATFORM, FOR ECOSYSTEM
SERVICES‐BASED RIVER ASSESSMENT
- Authors: A. R. G. Large; D. J. Gilvear
Pages: n/a - n/a
Abstract: A methodology for reach‐based river ecosystem service assessment of eight ecosystem functions using remote sensing via Google Earth is presented. The number of publications addressing Google Earth and ecosystem services has grown significantly since 2005, yet this powerful remote sensing platform remains under‐used in river science. Theoretical linkages between 18 riverscape fluvial features, attributes and land cover types, observable and measurable on Google Earth, and resultant river ecosystem service delivery are central to the methodology. Using this framework, we build on earlier ecosystem service conceptual models to develop a rules‐based scoring approach and apply it to three rivers of differing size and character from source to mouth. The aim was to devise a robust ecosystem service assessment tool applicable to any ecoregion and to rivers of any size, degree of human modification and character. Reach or sector scales are river length dependent. The minimum reach scale recommended is 500 m, and a 10 km sector length was used on the longest of our three rivers. Two key metrics, the individual ecosystem service score and the total ecosystems service score, are derived at the river reach scale from source to mouth. Scoring is on a 0–3 scale with 0 representing an absent or virtually no ecosystem service value and 3 an optimal or maximum value. Output is best expressed in score per kilometre of river length. The exercise showed the tool to be applicable across two ecoregions and to rivers of varying size, level of human modification and character. While requiring further refinement, the approach shows that ecosystem service assessments based on virtual globes can be universally applied providing valuable information on riverscape ecosystem service delivery. Copyright © 2014 John Wiley & Sons, Ltd.
- RESPONSE OF FISH COMMUNITIES TO HYDROLOGICAL AND MORPHOLOGICAL ALTERATIONS
IN HYDROPEAKING RIVERS OF AUSTRIA
- Authors: S. Schmutz; T. H. Bakken, T. Friedrich, F. Greimel, A. Harby, M. Jungwirth, A. Melcher, G. Unfer, B. Zeiringer
Pages: n/a - n/a
Abstract: Climate change asks for the reduction in the consumption of fossil‐based fuels and an increased share of non‐regulated renewable energy sources, such as solar and wind power. In order to back up a larger share of these intermittent sources, ‘battery services’ are needed, currently provided only in large scale by hydropower, leading to more rapid and frequent changes in flows (hydropeaking) in the downstream rivers. Increased knowledge about the ecosystem response to such operations and design of cost‐effective measures is needed.
We analysed the response of fish communities to hydropeaking (frequency, magnitude, ramping rate and timing) and the interaction with the habitat conditions in Austrian rivers. An index of biotic integrity (Fish Index Austria) was used to compare river sections with varying degrees of flow fluctuations under near‐natural and channelized habitat conditions. The results showed that habitat conditions, peak frequency (number of peaks per year), ramping rate (water level variation) and interaction between habitat and ramping rate explained most of the variation of the Fish Index Austria. In addition, peaking during the night seems to harm fish more than peaking during the day. Fish communities in hyporhithral and epipotamal types of rivers are more affected by hydropeaking than those in metarhithral type of rivers. The results support the findings of other studies that fish stranding caused by ramping rates >15 cm h−1 are likely to be the main cause of fish community degradation when occurring more often than 20 times a year. While the ecological status degrades with increasing ramping rate in nature‐like rivers, fish communities are heavily degraded in channelized rivers regardless of the ramping rate. The mitigation of hydropeaking, therefore, requires an integrative approach considering the combined effects of hydrological and morphological alterations on fish. © 2014 The
Authors . River Research and Applications published by John Wiley & Sons, Ltd.
- A COMPARISON OF THE TEMPERATURE REGIME OF SHORT STREAM SEGMENTS UNDER
FORESTED AND NON‐FORESTED RIPARIAN ZONES AT ELEVEN SITES ACROSS
- Authors: J. A. Simmons; M. Anderson, W. Dress, C. Hanna, D. J. Hornbach, A. Janmaat, F. Kuserk, J. G. March, T. Murray, J. Niedzwiecki, D. Panvini, B. Pohlad, C. Thomas, L. Vasseur
Pages: n/a - n/a
Abstract: When forested riparian zones are cleared for agriculture or development, major changes can occur in the stream temperature regime and consequently in ecosystem structure and function. Our main objective was to compare the summer temperature regimes of streams with and without forest canopy cover at multiple sites. The secondary objective was to identify the components of the stream heat budget that had the greatest influence on the stream temperature regime. Paired stream reaches (one forested and one non‐forested or ‘open’) were identified at 11 sites distributed across the USA and Canada. Stream temperature was monitored at the upstream and downstream ends of 80 to 130‐m‐long reaches during summer, and five variables were calculated to describe the stream temperature regime. Overall, compared with forested reaches, open reaches tended to have significantly higher daily mean (mean difference = 0.33 ± 1.1°C) and daily maximum (mean difference = 1.0 ± 1.7°C) temperatures and wider daily ranges (mean difference = 1.1 ± 1.7°C). Mean and maximum daily net heat fluxes in open reaches tended to be greater (or less negative) than those in forested reaches. However, certain sites showed the opposite trends in some variables because of the following: (i) Daily mean and maximum temperatures were biased by differences in inflow temperature between paired reaches and (ii) inputs of cold groundwater exerted a strong influence on temperature. Modelling and regression results suggested that within sites, differences in direct solar radiation were mainly responsible for the observed differences in stream temperature variables at the daily scale. © 2014 The
Authors . River Research and Applications published by John Wiley & Sons, Ltd.
- FISH BODY CONDITION AND RECRUITMENT RESPONSES TO ANTECEDENT FLOWS IN
DRYLAND RIVERS ARE SPECIES AND RIVER SPECIFIC
- Authors: S. R. Balcombe; A. H. Arthington, D. Sternberg
Pages: n/a - n/a
Abstract: Dryland rivers in arid and semi‐arid regions drain approximately one‐third of the Earth's land area, yet basic aspects of their ecology are poorly documented and many are threatened by excessive water use leading to alterations of the flow regime. Management of dryland rivers imperilled by changes to the flow regime requires quantitative hydro‐ecological relationships and models to support environmental flow restoration strategies and to define ecological response indicators for assessment of trends in ecological health. Fish living in dryland rivers experience highly variable levels of food resources associated with ‘boom and bust’ productivity patterns driven by highly irregular episodes of rainfall, runoff and floodplain inundation followed by busts associated with drying of remnant aquatic habitats. To cope with variable food resource levels, fish store energy as fat during productivity booms, enabling them to breed later or to survive through extended periods of limited food resources. This study tracked temporal patterns of body condition and recruitment success of the four most abundant fish species in two Australian dryland river systems with contrasting patterns of flow variability, Cooper Creek and the Moonie River. We found consistent responses to flow magnitude and timing for body condition and/or recruitment success in Cooper Creek but fewer responses in the Moonie River. Results suggest that the fish metrics and relationships to flow established for Cooper Creek may apply in similar dryland rivers exhibiting clear boom and bust patterns, whereas the Moonie River results could be applicable to rivers with less variable flow patterns and fewer spells of zero flows. Our study demonstrates that simple, non‐destructive methods based on fish length and weight provide useful biological indicators of response to flow variability provided that care is taken with species selection and that hydro‐ecological relationships are calibrated for each contrasting type of hydrologic regime. Copyright © 2014 John Wiley & Sons, Ltd.
- INVESTIGATION OF STREAM TEMPERATURE RESPONSE TO NON‐UNIFORM
GROUNDWATER DISCHARGE IN A DANISH LOWLAND STREAM
- Authors: K. Matheswaran; M. Blemmer, P. Thorn, D. Rosbjerg, E. Boegh
Pages: n/a - n/a
Abstract: Non‐uniform groundwater discharge into streams influences temperature, a vital stream physical property recognized for its dominant controls on biological processes in lotic habitats at multiple scales. Understanding such spatially heterogeneous processes and their effects is difficult on the basis of stream temperature models often calibrated with discrete temperature measurements. This study focused on examining the effect of groundwater discharge on stream temperature using a physically based stream temperature model calibrated on spatially rich high‐resolution temperature measurements. A distributed temperature sensing (DTS) system with a 1.8‐km fibre optic cable was used to collect temperature measurements for every 1 m of the reach length at 3‐min temporal resolution in the stream Elverdamsåen. The groundwater inflow locations identified using DTS data and 24‐h temperature measurements (14:00 h 6 May 2011 to 14:00 h 7 May 2011) were used for further calibration of the stream temperature model. With 19 inflow locations, the model simulated temperature trends closely mirroring the observed DTS profile with a root mean square error of 0.85 °C. The aggregation of inflows at specific locations forced the model to simulate stepwise inflow signals and small change in downstream temperature. In turn, the DTS data exemplified spiked signals with no change in downstream temperature, a typical characteristic of lowland streams. In spite of the difference in modelled and measured inflow signals, the results indicate that the represented groundwater inflows imperatively controlled the spatial variations of temperature within the study reach, creating three unique thermal zones. Copyright © 2014 John Wiley & Sons, Ltd.
- MODELLING EVALUATION OF DAM REMOVAL IN THE CONTEXT OF RIVER ECOSYSTEM
- Authors: Y. Wan; D. Sun, J. Labadie
Pages: n/a - n/a
Abstract: Applications of environmental models may provide imperative information to enable informed decision‐making of river management actions, which are often made in the face of high system complexity and uncertainty. We applied Hydrologic Engineering Centers River Analysis System(HEC‐RAS) and Curvilinear Hydrodynamics Three‐Dimensional (CH3D) models to aid in the decision‐making of the proposed removal of the Masten Dam, a small, ‘run‐of‐the‐river’ dam on the Loxahatchee River, a federally designated ‘Wild and Scenic River’ in south‐east coast of Florida (USA). Anthropogenic alteration of the system has led to changing hydroperiods and salinity regimes in the floodplain. Both models are calibrated against measured data taken at varying temporal and spatial scales. The HEC‐RAS modelling results show that removal of the Masten Dam would lower water levels in the upstream riverine reach, leading to reduced soil moisture or inundation in the floodplain. The CH3D modelling results indicate that dam removal would increase river salinity during the dry season in the tidal reach where salinity compliance for environmental flow regulation is measured. These environmental changes would exert additional stress on freshwater vegetation communities in the floodplain. Given the scarcity of water resources in the region, removal of the Masten Dam would not offer an effective restoration strategy. This study demonstrates not only the need for evaluation of dam removal on a case‐by‐case basis but also the usefulness of environmental models in providing the technical basis for such management decisions. Copyright © 2014 John Wiley & Sons, Ltd.
- ENVIRONMENTAL FLOWS IN A HUMAN‐DOMINATED SYSTEM: INTEGRATED WATER
MANAGEMENT STRATEGIES FOR THE RIO GRANDE/BRAVO BASIN
- Authors: B. A. Lane; S. Sandoval‐Solis, E. C. Porse
Pages: n/a - n/a
Abstract: Water management in the transboundary Rio Grande/Bravo (RGB) Basin, shared by the US and Mexico, is complicated by extreme hydrologic variability, overallocation, and international treaty obligations. Heavy regulation of the RGB has degraded binationally protected ecosystems along the Big Bend Reach of the RGB. This study addresses the need for integrated water management in Big Bend by developing an alternative reservoir operation policy to provide environmental flows while reducing water management trade‐offs. A reach‐scale water planning model was used to represent historical hydrology (1955–2009), water allocation, and reservoir operations, and key human water management objectives (water supply, flood control, and binational treaty obligations) were quantified. Spatially distributed environmental flow objectives and an alternative reservoir rule curve were developed. We simulated current and alternative water management policies and used an iterative simulation–evaluation process to evaluate alternative policies based on water system performance criteria with respect to specified objectives. A single optimal policy was identified that maximized environmental flows while maintaining specified human objectives. By changing the timing but not the volume of releases, the proposed reservoir re‐operation policy has the potential to sustain key ecological and geomorphic functions in Big Bend without significantly impacting current water management objectives. The proposed policy also improved water supply provisions, reduced average annual flood risk, and maintained historical treaty provisions. Copyright © 2014 John Wiley & Sons, Ltd.
- HABITAT‐ORIENTED SAMPLING OF MACROINVERTEBRATES AFFECTS THE
DETERMINATION OF ECOLOGICAL STATUS IN TEMPORARY MEDITERRANEAN RIVER
- Authors: F. Leitão; S. J. Hughes, I. Máximo, N. Atanasova, A. Furtado, L. Chicharo
Pages: n/a - n/a
Abstract: Inter‐annual and annual variation in precipitation levels in Mediterranean temporary river systems strongly influence riverine flow regimes and as a result habitat' availability for biological assemblages. Under‐sampling of less well‐presented microhabitats in such changeable, dynamic systems can result in information loss leading to misclassification of Water Framework Directive (WFD) compliant ecological status, with serious consequences for Programmes of Measures in River Basin Management Plans. This paper compares two benthic macroinvertebrate sampling protocols tested in intermittent Mediterranean streams (n = 40) in the Algarve region of southern Portugal. The officially adopted WFD compliant European assessment system for the ecological quality of rivers using benthic macroinvertebrates, a composite sampling protocol, focuses sampling a greater area of the most representative microhabitats at a given sampling site (proportional habitat sampling). A non‐proportional habitat sampling protocol was applied to test the assumption that taxa may have preference for different microhabitats and that this could influence classification of ecological status. Variation was detected in the levels of similarity in the structure and the composition of the benthic macroinvertebrate community within sampling sites and rivers, based on material collected using the two collection methods. Ecological index scores and biotic metrics were higher when the non‐proportional oriented sampling protocol was utilized resulting in a ‘good ecological status’ classification at sites that had been classified as ‘Bad’ using the official WFD, Decision tree analysis results indicated that changes in the area of individual microhabitats sampled among protocols was the principal driver behind differences in ecological status derived. The results indicate that more realistic classifications could be achieved in intermittent Mediterranean rivers when considering and sampling less well‐represented microhabitat types (non‐proportional sampling) rather than distributing sampling effort by the proportion of the dominant habitat present as currently used for the WFD protocol. The application of the non‐proportional microhabitat‐based approach, which accounts for selective preferences of some benthic macroinvertebrate taxa, would ensure that a greater proportion of a given site community contributes to the assessment. Copyright © 2014 John Wiley & Sons, Ltd.
- ASSESSMENT OF THE EFFECTS OF HIGH SUMMER WATER TEMPERATURES ON SHOVELNOSE
STURGEON AND POTENTIAL IMPLICATIONS OF CLIMATE CHANGE
- Authors: R. N. Hupfeld; Q. E. Phelps, M. K. Flammang, G. W. Whitledge
Pages: n/a - n/a
Abstract: Rivers worldwide have experienced changes through habitat modifications and are likely further exacerbated with the onset of climate change. The coupling of these anthropogenic disturbances has reduced the ability of river ecosystems and associated biota to adjust. The aforementioned human‐induced habitat perturbations coupled with high summer river temperatures have been associated with an increased frequency of fish kills. Recently, shovelnose sturgeon Scaphirhynchus platorynchus have experienced numerous events of excessive summer mortality in rivers across the USA. During the summer of 2012, multiple fish kills occurred on the lower Des Moines River. During one of these events, we collected numerous dead or dying shovelnose sturgeon (N = 132) to explore factors causing mortality. Water temperatures were exceedingly high (29–35°C), while dissolved oxygen levels varied between 4 and 10 mg L−1. Based on population simulation modelling, only ~14% mortality would need to occur to reduce the reproductive potential below sustainable levels, which was likely exceeded. The results of our controlled experiment demonstrate that the high temperature in the Des Moines River was likely the mechanism initiating mortality. Future climate projections indicate that increases in temperature on the Des Moines River are possible; thus, the population may be at risk in the future. Through our microchemistry investigation, immigration from the Upper Mississippi River appears to be common and may be a source population to the Des Moines River. Despite immigration, the influence that these mortality events have on the Upper Mississippi River is unknown. Thus, proactive management efforts are needed to ensure sustainability of this population. Copyright © 2014 John Wiley & Sons, Ltd.
- THE IMPACT OF LOW FLOW ON RIVERINE FOOD WEBS IN SOUTH‐CENTRAL
- Authors: J. M. Brush; M. Power, K. D. Clarke, C. J. Pennell
Pages: n/a - n/a
Abstract: Low‐flow events can reduce food availability and decrease the feeding niche of consumers within rivers. Stable carbon (δ13C) and nitrogen (δ15N) isotope and stomach content analyses were employed to evaluate resource use and overlap between fish species in a natural and regulated river in normal and low‐flow years, with the use of multiple methodological approaches providing the best means of understanding short‐term and long‐term observations on fish feeding and resource overlap under changing flow conditions. Diet analyses generally indicated significant inter‐specific differences in the diets of key fish species within rivers and similarities in resource use between rivers. In comparison with fish from the natural river, fish from the regulated river had lower and less inter‐annually variable δ13C values. In the natural river, there was a significant reduction and increase, respectively, in δ13C and δ15N variation in the low‐flow year. Intra‐annual or inter‐annual differences in trophic niche area were not apparent in the regulated river, whereas within the natural river, intra‐annual and inter‐annual differences in trophic niche were found. Resource overlap between key fish species was also higher in the low‐flow year and lower in the spring and higher in the summer as a result of differences in flow. Resource overlap was also higher between rivers in the low‐flow year. High resource overlap between rivers during decreased summer flow indicates a strong effect of flow on river organisms, where both fish and their invertebrate prey resources are concerned. Copyright © 2014 John Wiley & Sons, Ltd.
- HYDRAULIC INTERACTION BETWEEN ROCK CROSS VANE STREAM RESTORATION
STRUCTURES AND A BRIDGE CROSSING
- Authors: J. T. Newlin; B. P. Schultz
Pages: n/a - n/a
Abstract: The performance of a stream restoration project that incorporates a bridge crossing is evaluated within a 3‐year monitoring period. A goal of the project was to alleviate and prevent future sediment aggradation within the waterway of a low‐clearance bridge crossing. The stream restoration project included two rock cross vanes and stepped riprap and vegetation bank stabilization. Monitoring of the project involved the collection of channel survey data, pebble counts, and general observations of instream structure condition and sediment movement. The evaluated performance of the restoration structures is related to the general hydrologic conditions, the historical changes in the watershed and channel, and the hydraulic conditions created by the low‐clearance bridge crossing. Backwater effects created by the bridge crossing are found to be a substantial cause of the failure of the stream restoration project to meet its goals. The low‐clearance bridge hydraulics are preventing a rock cross vane located upstream of the bridge from creating a scour hole in the centre of the channel; instead, aggradation is occurring in this portion of the channel. However, degradation is occurring downstream of the bridge causing the failure of the second rock cross vane and of the riprap and vegetation bank. Although the hydraulic conditions may stem from the initial design of the bridge crossing, any restoration structure should be designed according to the current site hydraulics. In addition to providing insight into the design and construction of stream restoration structures, the results have implications for the design and management of bridge crossings. Copyright © 2014 John Wiley & Sons, Ltd.
- EFFECTS OF RIGID UNSUBMERGED VEGETATION ON FLOW FIELD STRUCTURE AND
TURBULENT KINETIC ENERGY OF GRADUALLY VARIED FLOW
- Authors: H. Y. Zhang; Z. Y. Wang, W. G. Xu, L. M. Dai
Pages: n/a - n/a
Abstract: The influence of rigid unsubmerged vegetation on flow structure and turbulent kinetic energy of gradually varied flow are experimentally investigated in this research. Natural reed stems of different densities are employed to examine the effects of the rigid unsubmerged vegetation on the flow in rivers. The results reveal that the vegetation existence significantly changes the gradually varied flow state from type M1 to type M2 in the vegetation section. The traditional power law describing the vertical flow velocity profile is evidently invalid when the vegetation density becomes high. With the irregularity index proposed in the research, the irregularity of vertical flow velocity profile in vegetated reach can be exponentially described in relation to the vegetation density. Furthermore, the turbulent kinetic energy is found to increase and reach a maximum value near the end of the vegetation section that is a potential localized erosion area. The results of the research have significances in river ecological restoration applications utilizing aquatic vegetation. Copyright © 2014 John Wiley & Sons, Ltd.
- REMOVAL OF THE INVASIVE SHRUB, LONICERA MAACKII, FROM RIPARIAN FORESTS
INFLUENCES HEADWATER STREAM BIOTA AND ECOSYSTEM FUNCTION
- Authors: R. E. McNeish; E. M. Moore, M. E. Benbow, R. W. McEwan
Pages: n/a - n/a
Abstract: Riparian forests and streams are interlinked by cross‐system subsidies and alterations of the terrestrial environment can have substantial effects on aquatic biota and ecosystem function. In the Midwestern USA, the exotic shrub Lonicera maackii (Amur honeysuckle) has successfully invaded many riparian habitats, creating near‐monocultures in some locations. This terrestrial invasion has strong potential to modify cross‐system subsidies and impact stream ecosystems. We removed L. maackii from a riparian forest to assess impacts on the aquatic environment. In August 2010, removal occurred along a 150 m stream reach, 10 m downstream of a non‐removal reach, before natural leaf senescence. Over 74 days, in‐stream leaf litter [organic matter (OM)] was collected weekly from plots located in riffles (five/reach). Benthic algal biomass, above stream canopy cover, and macroinvertebrate density were measured for 18 months. L. maackii removal was associated with decreased canopy cover and a significant increase in total in‐stream leaf OM in early autumn (P
- INFLUENCE OF RIPARIAN AND WATERSHED ALTERATIONS ON SANDBARS IN A GREAT
- Authors: J. Fischer; C. Paukert, M. Daniels
Pages: n/a - n/a
Abstract: Anthropogenic alterations have caused sandbar habitats in rivers and the biota dependent on them to decline. Restoring large river sandbars may be needed as these habitats are important components of river ecosystems and provide essential habitat to terrestrial and aquatic organisms. We quantified factors within the riparian zone of the Kansas River, USA, and within its tributaries that influenced sandbar size and density using aerial photographs and land use/land cover (LULC) data. We developed, a priori, 16 linear regression models focused on LULC at the local, adjacent upstream river bend, and the segment (18–44 km upstream) scales and used an information theoretic approach to determine what alterations best predicted the size and density of sandbars. Variation in sandbar density was best explained by the LULC within contributing tributaries at the segment scale, which indicated reduced sandbar density with increased forest cover within tributary watersheds. Similarly, LULC within contributing tributary watersheds at the segment scale best explained variation in sandbar size. These models indicated that sandbar size increased with agriculture and forest and decreased with urban cover within tributary watersheds. Our findings suggest that sediment supply and delivery from upstream tributary watersheds may be influential on sandbars within the Kansas River and that preserving natural grassland and reducing woody encroachment within tributary watersheds in Great Plains rivers may help improve sediment delivery to help restore natural river function. Copyright © 2014 John Wiley & Sons, Ltd.
- ENVIRONMENTAL INFLUENCES ON FISH MIGRATION IN A HYDROPEAKING RIVER
- Authors: N. E. Jones; I. C. Petreman
Pages: n/a - n/a
Abstract: Fish have evolved traits and life history characteristics that enable them to survive, exploit and depend on the flow regime of rivers, particularly the timing and predictability of flows for spawning and rearing their young. It is unclear to what degree pulsed flows from hydropower facilities and other environmental variables influence migratory behaviours. We used Dual Frequency Identification Sonar in the Michipicoten River, Canada, to address the relationship between fish migration and environmental factors with a focus on flow magnitude and fluctuation. In both 2007 and 2009, the peak of the Chinook (Oncorhynchus tshawytscha) and pink salmon (Oncorhynchus gorbuscha) migration occurred on 8 September. Mean water temperature on this date was 18 °C and precipitously dropped afterwards. The photoperiod was roughly 12‐h long with sunrise at 700 h and sunset at 2000 h. Most fishes moved upstream during the hours of darkness between 2000 and 600 h. The lowest counts of fish occurred from noon to just before sunset, whereas highest counts commonly occurred from 1 to 2 h after sunset. Fish moved upstream during all magnitudes of flow; however, there was a slight preference for larger flows in 2007 but not in 2009. Changes in flow magnitude occurred both during the day and night, with flows typically increasing during the day to meet electrical demand and decreasing at night. Most fishes moved upstream during periods of little to no change in flow. High flows and changing flows may deter salmon from moving up the Michipicoten River but not likely in a significant manner to cause energetic stress or harm. Other adverse effects of pulsed flows, however, must still be considered for spawning, hatching and rearing success. Copyright © 2014 John Wiley & Sons, Ltd.
- EVALUATION OF THE EFFECTIVENESS OF A LIVING SHORELINE IN A CONFINED,
NON‐TIDAL WATERWAY SUBJECT TO HEAVY SHIPPING TRAFFIC
- Authors: S. De Roo; P. Troch
Pages: n/a - n/a
Abstract: River bank erosion is a point of concern along navigable waterways because it increases the likelihood of bank failure. In non‐tidal and restricted fetch waterways, bank failure is mainly the result of extreme weather events and ship wave action. To counteract progressive bank erosion, nature‐friendly bank protection (a ‘living’ shoreline) has been installed in a stretch of the Lys (Belgium). It consists of off‐bank timber piling, which separates the fairway from the shallow water riverine environment, and a reed belt, planted at the base of the vertical cut bank. To evaluate its effectiveness, short‐term and long‐term field studies were carried out. The long‐term topographic survey did not reveal a clear difference in bank erosion rates between the surveyed nature‐friendly protected and naturally eroding embayments. Horizontal bank retreat could however not be linked directly to occasional flooding events and frequent ship wave action, although the latter's influence was inferred qualitatively. Based on velocity and turbidity measurements, the short‐term study pointed out the importance of an individual ship's wave action on bed and bank erosion behind the off‐bank timber piling. All ships were able to resuspend sandy bed sediments; yet, only a significant higher sediment volume was transported because of shipping traffic of the European Conference of Ministers of Transport (ECMT) classes IV and Va. If ship wave energy exceeded 45 Jm−2, silty bank particles were dislodged from the river bank. Although validation of the results by longer term assessments may complete the physical insight in river bank erosion, the study indicated that this particular bank protecting configuration does not provide sufficient protection against ship wave action and does not adequately prevent further bank erosion. Copyright © 2014 John Wiley & Sons, Ltd.
- MACROINVERTEBRATE COMMUNITY RESPONSES TO ANNUAL FLOW VARIATION FROM RIVER
REGULATION: AN 11‐YEAR STUDY
- Authors: C. R. Holt; D. Pfitzer, C. Scalley, B. A. Caldwell, D. P. Batzer
Pages: n/a - n/a
Abstract: The majority of the world's large river systems is affected by dams. The influences of unnatural regimes induced by flow management are wide‐ranging from both biotic and abiotic standpoints. However, many of these effects are not evident over short (1–2 years) periods (e.g. impacts of annual flow variation). This study examines the long‐term effects of annual flow variation on the macroinvertebrate community in the Chattahoochee River (GA) in the reaches below Buford Dam, the major water control structure on the river. Quarterly, macroinvertebrate samples were taken from 2001 to 2011 using Surber and Hester–Dendy plate samplers at six locations spread across 65 km below the dam. Data were analysed via analysis of similarities to determine differences in community composition between high‐flow (mean discharge = 58.27 m3/s) and low‐flow (mean discharge = 26.53 m3/s) years. Taxa that contributed most to community differences were determined via similarity percentages analyses and subsequent t‐tests. Several insect taxa (e.g. Cheumatopsyche and Ceratopsyche caddisfly larvae, Maccaffertium mayfly nymphs and Taeniopteryx stonefly nymphs) were more prevalent under the high‐flow regime. Non‐insect macroinvertebrates (e.g. Crangonyx amphipods, Tricladida flatworms and Caecidotea isopods) were more abundant under low‐flow conditions. In terms of taxon richness, no significant effects of flow regime were detected. Implications of macroinvertebrate patterns for the fishery and ecological health of the river are discussed. Copyright © 2014 John Wiley & Sons, Ltd.
- IMPACT OF CHANGING HYDROLOGY ON NUTRIENT UPTAKE IN HIGH ARCTIC RIVERS
- Authors: P. J. Blaen; A. M. Milner, D. M. Hannah, J. E. Brittain, L. E. Brown
Pages: 1073 - 1083
Abstract: Despite the importance of river nutrient retention in regulating downstream water quality and the potential alterations to nutrient fluxes associated with climate‐induced changes in Arctic hydrology, current understanding of nutrient cycling in Arctic river systems is limited. This study adopted an experimental approach to quantify conceptual water source contributions (meltwater, groundwater), environmental conditions and uptake of NO3−, NH4+, PO43− and acetate at 12 headwater rivers in Svalbard and so determine the role of changing hydrology on nutrient uptake in these Arctic river systems. Most rivers exhibited low demand for NO3− and PO43−, but demand for NH4+ and acetate was more variable and in several rivers comparable with that measured in sub‐Arctic regions. The proportion of meltwater contributing to river flow was not significantly related to nutrient uptake. However, NH4+ uptake was associated positively with algal biomass, water temperature and transient storage area, whereas acetate uptake was associated positively with more stable river channels. Mean demand for NH4+ increased when added with acetate, suggesting NH4+ retention may be facilitated by labile dissolved organic carbon availability in these rivers. Consequently, nutrient export from Arctic river systems could be influenced in future by changes in hydrological and environmental process interactions associated with forecasted climate warming. Copyright © 2013 John Wiley & Sons, Ltd.
- ABANDONED FLOODPLAIN PLANT COMMUNITIES ALONG A REGULATED DRYLAND RIVER
- Authors: L. V. Reynolds; P. B. Shafroth, P. K. House
Pages: 1084 - 1098
Abstract: Rivers and their floodplains worldwide have changed dramatically over the last century because of regulation by dams, flow diversions and channel stabilization. Floodplains no longer inundated by river flows following dam‐induced flood reduction comprise large areas of bottomland habitat, but the effects of abandonment on plant communities are not well understood. Using a hydraulic flow model, geomorphic mapping and field surveys, we addressed the following questions along the Bill Williams River, Arizona: (i) What per cent of the bottomland do abandoned floodplains comprise? and (ii) Are abandoned floodplains quantitatively different from adjacent xeric and riparian surfaces in terms of vegetation composition and surface sediment? We found that nearly 70% of active channel and floodplain area was abandoned following dam installation. Abandoned floodplains along the Bill Williams River tend to be similar to each other yet distinct from neighbouring habitats: they have been altered physically from their historic state, leading to distinct combinations of surface sediments, hydrology and plant communities. Abandoned floodplains may transition to xeric communities over time but are likely to retain some riparian qualities as long as there is access to relatively shallow ground water. With expected increases in water demand and drying climatic conditions in many regions, these surfaces and associated vegetation will continue to be extensive in riparian landscapes worldwide. Copyright © 2013 John Wiley & Sons, Ltd.
- SPATIAL VARIABILITY IN SPAWNING HABITAT SELECTION BY CHINOOK SALMON
(ONCORHYNCHUS TSHAWYTSCHA) IN A WILDERNESS RIVER
- Authors: E. J. Hamann; B. P. Kennedy, D. C. Whited, J. A. Stanford
Pages: 1099 - 1109
Abstract: Chinook salmon (Oncorhynchus tshawytscha) survival during early life stages depends largely on spawning habitat selection by adults, which has been linked to biophysical stream variables (e.g. stream flow, velocity and substrate composition) as well as hyporheic exchange associated with riffle/pool and run/pool transitions. To examine how physical habitat variables influenced spawning habitat choice in one central Idaho (USA) wilderness stream, we used remote sensing techniques to classify and quantify the total amount of each aquatic habitat type present to assess how habitat quantity changed as stream order increased. Additionally, we measured physical habitat variables at each redd throughout the entire stream length for one spawning season to assess whether Chinook salmon selected for the same habitat parameters at varying spatial scales. Run, riffle and pool habitat types contributed similar proportions to the total area in both the upper and lower basins. However, ‘transitional zones’ (i.e. pool‐riffle and pool‐run transitions) accounted for 16% of the total area in the upper basin and only 4% in the lower. Redds were built in multiple habitat types in each of the three primary spawning locations, but transitional zones were chosen most frequently only in the upper basin. Significant differences in habitat variables were seen between spawning groups, with stream wetted width and velocity accounting for the majority of the variation. The techniques described here could be used to locate features that serve as indicators of potential spawning habitat, although caution should be exercised when extrapolating spawning habitat needs over large spatial extents. Copyright © 2013 John Wiley & Sons, Ltd.
- TIMING OF REDD CONSTRUCTION BY FALL CHINOOK SALMON IN THE HANFORD REACH OF
THE COLUMBIA RIVER
- Authors: D. B. Hayes; B. J. Bellgraph, B. M. Roth, D. D. Dauble, R. P. Mueller
Pages: 1110 - 1119
Abstract: Spawning habits of fall Chinook salmon in the Hanford Reach of the Columbia River have been documented with annual aerial surveys since 1948. We developed a series of models analysing these data, exploring the influence of environmental factors on the timing of redd construction. These models included a logistic regression and a dynamic modelling approach, with combinations of day of year (as a surrogate for environmental cues such as day length), water temperature and discharge as potential explanatory factors. Results of these analyses indicate that day of year was the strongest predictor of the timing of redd construction, but with significant modifying effects of water temperature and discharge. The dynamic modelling approach provides substantial advantages over a traditional logistic regression, including (1) the ability to treat data collected at non‐synchronous time intervals in a consistent fashion and (2) the ability to easily implement complex functions (e.g., threshold responses) relating behaviour to environmental cues. Evaluation of the series as a whole indicates that the median date of redd construction has increased over time, from approximately day 299 in 1950 to day 307 in 2010, as has the temperature on Oct 1 (16.3 °C–18.1 °C). The degree to which these changes are caused by climate change or dam operations is uncertain, however. Copyright © 2013 John Wiley & Sons, Ltd.
- POPULATION STRUCTURE IN THREE SPECIES OF CO‐DISTRIBUTED SALMONID
FISHES IN THE PEACE RIVER AND TRIBUTARIES NEAR A MAJOR PROPOSED
HYDROELECTRIC DEVELOPMENT IN NORTHEASTERN BRITISH COLUMBIA, CANADA
- Authors: E. B. Taylor; M. M. Yau, A. B. Mattock
Pages: 1120 - 1133
Abstract: Dam construction and reservoir formation represent profound anthropogenic alterations to natural riverscapes, especially in terms of connectivity in migratory fishes. The Peace River in northeastern British Columbia (BC), Canada, is the largest river system in BC, home to 39 native fishes and currently has two major hydroelectric projects, and a third one (‘Site C’) is proposed. Three co‐distributed and migratory fishes, the bull trout (Salvelinus confluentus), Arctic grayling (Thymallus arcticus) and the mountain whitefish (Prosopium williamsoni) are key species in the Peace River ecologically and in terms of recreational fisheries. We examined microsatellite DNA variation in these species to assess genetic diversity, levels of population subdivision and connectivity to better understand potential impacts and to provide baseline information for subsequent monitoring. Expected heterozygosity and number of alleles averaged 0.65 and 7.7, 0.73 and 11.9, and 0.72 and 10.8 for bull trout (nine loci), Arctic grayling (10 loci) and mountain whitefish (10 loci), respectively. Estimates of the effective number of breeders (Nb) ranged from 35 to 255 for bull trout to over 3700 for Arctic grayling. Population subdivision (FST, θ) was 0.040, 0.063 and 0.023 in bull trout, Arctic grayling and mountain whitefish, respectively (all p < 0.001). Temporal differences within localities for all species accounted for <1% of total variation in allele frequencies. An estimated 6.2% (mountain whitefish), 4.6% (bull trout) and 8.8% (Arctic grayling) of fish samples were inferred (p < 0.05) to be immigrants to one locality from another locality. Our results suggest that connectivity amongst localities is important to successful completion of the life history of each species, the potential disruption of which will be a critical aspect of post‐development monitoring. Copyright © 2013 John Wiley & Sons, Ltd.
- USE OF NATIVE AND NONNATIVE NEST PLANTS BY RIPARIAN‐NESTING BIRDS
ALONG TWO STREAMS IN NEW MEXICO
- Authors: D. M. Smith; D. M. Finch
Pages: 1134 - 1145
Abstract: Nonnative plant invasions are a management concern, particularly in riparian forests, but little is known about mechanisms through which they influence vertebrate communities. In the American Southwest, native trees such as cottonwood (Populus spp.) are thought to provide better habitat for breeding birds than nonnative plants, which are more tolerant of human‐altered conditions. To evaluate effects of riparian forest composition on riparian‐nesting birds, we examined nest plant use along two rivers in New Mexico that differed in abundance of nonnative vegetation. Of the nests we observed, 49% along the Middle Rio Grande were constructed in nonnative plants, compared with 4% along the Gila River. Birds in the canopy and cavity‐nesting guilds constructed less than 5% of their nests in nonnative plants along either river. At the Middle Rio Grande, birds in the subcanopy/shrub guild constructed 67% of their nests in nonnative plants. Despite the relatively low availability of cottonwoods, they were used by greater numbers of species than any other woody plant at either river. Riparian obligates and species of conservation concern in the canopy and cavity guilds were especially dependent on cottonwood and Arizona sycamore (Platanus wrightii). Our results show that, although nonnative trees and shrubs support large numbers of nests for certain birds, cottonwoods and other large native trees are disproportionately important to riparian bird communities. Copyright © 2013 John Wiley & Sons, Ltd.
- GUIDING OUT‐MIGRATING JUVENILE SEA LAMPREY (PETROMYZON MARINUS) WITH
PULSED DIRECT CURRENT
- Authors: N. S. Johnson; S. Miehls
Pages: 1146 - 1156
Abstract: Non‐physical stimuli can deter or guide fish without affecting water flow or navigation and therefore have been investigated to improve fish passage at anthropogenic barriers and to control movement of invasive fish. Upstream fish migration can be blocked or guided without physical structure by electrifying the water, but directional downstream fish guidance with electricity has received little attention. We tested two non‐uniform pulsed direct current electric systems, each having different electrode orientations (vertical versus horizontal), to determine their ability to guide out‐migrating juvenile sea lamprey (Petromyzon marinus) and rainbow trout (Oncorhynchus mykiss). Both systems guided significantly more juvenile sea lamprey to a specific location in our experimental raceway when activated than when deactivated, but guidance efficiency decreased at the highest water velocities tested. At the electric field setting that effectively guided sea lamprey, rainbow trout were guided by the vertical electrode system, but most were blocked by the horizontal electrode system. Additional research should characterize the response of other species to non‐uniform fields of pulsed DC and develop electrode configurations that guide fish over a range of water velocity. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
- COMBINING MULTIPLE MACHINE LEARNING ALGORITHMS TO PREDICT TAXA UNDER
REFERENCE CONDITIONS FOR STREAMS BIOASSESSMENT
- Authors: M. J. Feio; C. Viana‐Ferreira, C. Costa
Pages: 1157 - 1165
Abstract: In the present study, we tested the potential of combining three machine learning techniques in a bioassessment tool to more accurately predict the pool of expected taxa at a site. This tool, the Hydra, uses the best performing technique from Support Vector Machines (SVM), Multi‐layer Perceptron and K‐Nearest Neighbour (KNN), to predict the taxa expected at a stream site, and further evaluates the quality of a site, though a classification system based on observed/expected values, similar to that used in River Invertebrate Prediction and Classification System (RIVPACS) models. To test the procedure, we used a dataset composed of 137 training sites, 15 validation sites and 174 test sites (potentially disturbed) from Portuguese streams. The combined use of three machine learning techniques was more effective in the prediction of invertebrate taxa at a site than their individual use. The three methods were always tested for all invertebrate taxa, but from the three techniques tested, SVM and KNN were most often the best performing techniques (the most accurate among the three for a higher number of taxa) in the prediction of invertebrate taxa with the present dataset. The combination of all algorithms implemented in Hydra resulted in good models for stream bioassessment (e.g. SD OE50 0.6, Spearman correlations with global degradation >0.7). We also found no advantage in removing rare taxa from the training dataset, and 50% accuracy is the most adequate accuracy level for calculation of OE ratios through Hydra. Future work should consist of comparing the performance of this technique with others, such as the RIVPACS models, using the same datasets. Considering the flexibility of this technique, self‐adjustment and easy implementation through a website (aquaweb.uc.pt), we expect it to be also useful in the prediction of other aquatic elements such as fishes and algae. Copyright © 2013 John Wiley & Sons, Ltd.
- AN OBJECTIVE AND PARSIMONIOUS APPROACH FOR CLASSIFYING NATURAL FLOW
REGIMES AT A CONTINENTAL SCALE
- Authors: S. A. Archfield; J. G. Kennen, D. M. Carlisle, D. M. Wolock
Pages: 1166 - 1183
Abstract: Hydro‐ecological stream classification—the process of grouping streams by similar hydrologic responses and, by extension, similar aquatic habitat—has been widely accepted and is considered by some to be one of the first steps towards developing ecological flow targets. A new classification of 1543 streamgauges in the contiguous USA is presented by use of a novel and parsimonious approach to understand similarity in ecological streamflow response. This novel classification approach uses seven fundamental daily streamflow statistics (FDSS) rather than winnowing down an uncorrelated subset from 200 or more ecologically relevant streamflow statistics (ERSS) commonly used in hydro‐ecological classification studies. The results of this investigation demonstrate that the distributions of 33 tested ERSS are consistently different among the classification groups derived from the seven FDSS. It is further shown that classification based solely on the 33 ERSS generally does a poorer job in grouping similar streamgauges than the classification based on the seven FDSS. This new classification approach has the additional advantages of overcoming some of the subjectivity associated with the selection of the classification variables and provides a set of robust continental‐scale classes of US streamgauges. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
- ENVIRONMENTAL STRESSORS AFFLICTING TAILWATER STREAM REACHES ACROSS THE
- Authors: L. E. Miranda; R. M. Krogman
Pages: 1184 - 1194
Abstract: The tailwater is the reach of a stream immediately below an impoundment that is hydrologically, physicochemically and biologically altered by the presence and operation of a dam. The overall goal of this study was to gain a nationwide awareness of the issues afflicting tailwater reaches in the United States. Specific objectives included the following: (i) estimate the percentage of reservoirs that support tailwater reaches with environmental conditions suitable for fish assemblages throughout the year, (ii) identify and quantify major sources of environmental stress in those tailwaters that do support fish assemblages and (iii) identify environmental features of tailwater reaches that determine prevalence of key fish taxa. Data were collected through an online survey of fishery managers. Relative to objective 1, 42% of the 1306 reservoirs included in this study had tailwater reaches with sufficient flow to support a fish assemblage throughout the year. The surface area of the reservoir and catchment most strongly delineated reservoirs maintaining tailwater reaches with or without sufficient flow to support a fish assemblage throughout the year. Relative to objective 2, major sources of environmental stress generally reflected flow variables, followed by water quality variables. Relative to objective 3, zoogeography was the primary factor discriminating fish taxa in tailwaters, followed by a wide range of flow and water quality variables. Results for objectives 1–3 varied greatly among nine geographic regions distributed throughout the continental United States. Our results provide a large‐scale view of the effects of reservoirs on tailwater reaches and may help guide research and management needs. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
- SMALL IS BEAUTIFUL? STATE OF THE DAMS AND MANAGEMENT IMPLICATIONS FOR
- Authors: S. Vedachalam; S. J. Riha
Pages: 1195 - 1205
Abstract: Dams are a critical component of water infrastructure, providing services such as water supplies, recreational opportunities and flood control. At the same time, dams alter the flow regime of rivers and the biota that inhabit them. Large dams have been the subject of many studies because of their potentially significant impacts on stream hydrology and ecosystems. However, most dams are not large and consequently have received far less attention. Data for more than 5700 dams in New York State, USA located in 17 watersheds were used to develop watershed level metrics that relate the characteristics of the dams to the hydrology and demographics of each watershed. Metrics presented, stratified by watershed, include median structure age, density, dams per stream length, persons per dam, storage per drainage area, storage per person and percent high impact dams (high hazard and large). These metrics were used to perform a simple characterization of the 17 watersheds. Considerable regional differences in these parameters suggest varying management strategies in each watershed. A new era of river management has resulted in the removal of many dams, which is driven by the high cost of maintenance and state regulations. Copyright © 2013 John Wiley & Sons, Ltd.