- 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.
- SEASONAL EFFECTS OF HYDROPEAKING ON GROWTH, ENERGETICS AND MOVEMENT OF
JUVENILE ATLANTIC SALMON (SALMO SALAR)
- Authors: M. Puffer; O. K. Berg, A. Huusko, T. Vehanen, T. Forseth, S. Einum
Pages: n/a - n/a
Abstract: The performance and movements of juvenile Atlantic salmon Salmo salar exposed to variable water discharge (simulating hydropeaking) but with a stable water‐covered area were studied in six experimental stream channels, both during the winter and summer. Thirty fish were stocked into each channel, and the growth, body fat and movements of the fish were followed for about 2.5 months in each season. During the winter, no effect of hydropeaking was documented on performance or movement. In the summer, fish experiencing hydropeaking had lower body mass, lower body fat, and higher movement rates than the control fish. In general, effect sizes were small, and the rapid and frequent changes in water discharge and water level in the present study had small effects on the performance of juvenile Atlantic salmon. The cumulative long‐term effect at the population level is unknown, but a reduced growth rate of 10% and a reduction in body fat of 16% in the hydropeaking experiments in the summer might to some extent translate into increased smolt age and lower overwintering survival. Copyright © 2014 John Wiley & Sons, Ltd.
- RAPID CHANNEL WIDENING FOLLOWING WEIR REMOVAL DUE TO BED‐MATERIAL
WAVE DISPERSION ON THE RIVER MONNOW, WALES
- Authors: R. J. Thomas; J. A. Constantine, P. Gough, B. Fussell
Pages: n/a - n/a
Abstract: Kentchurch Weir, a low‐head weir on the river Monnow, Wales, was demolished in August 2011, releasing a sediment wave that had formed behind the structure for at least a century. We surveyed channel topography and bed‐material composition through a 1.5‐km long reach prior to weir removal and then periodically over a 2‐year period. The fill material was finer than the ambient bed material with all particles mobilized by bankfull flows. Rapid degradation of the 1460‐m3 sediment fill in the previously impounded reach occurred as bed material appeared to disperse downstream, consistent with other studies of sediment waves in gravel‐bed rivers. The riverbed profile was gradually smoothed through the study reach by degrading the elevated fill as a migrating knickpoint and aggrading the channel bed and bars immediately downstream of the former weir location. Extensive bank erosion was evident in the previously impounded reach with up to 10 m of widening following a single flow event, increasing channel width by more than 20%. Mitigation measures to enforce the riverbanks have been required as the gradual dispersion of the sediment wave continues to force flow diversion towards the riverbanks. The evolution of sediment stores behind flow obstructions follows that of sediment waves and theory available to describe wave evolution should do much to improve management efforts that seek to minimize channel widening following weir removal. Copyright © 2014 John Wiley & Sons, Ltd.
- LINKING STREAM SEDIMENT DEPOSITION AND AQUATIC HABITAT QUALITY IN PEARL
MUSSEL STREAMS: IMPLICATIONS FOR CONSERVATION
- Authors: M. Denic; J. Geist
Pages: n/a - n/a
Abstract: The introduction of fine sediments into streams is considered to have a major effect on habitat quality affecting the reproduction of sensitive species such as unionid mussels and salmonid fishes. To date, there is a lack of information on the magnitude and spatio‐temporal resolution of sediment introduction.This study aimed to quantify the spatio‐temporal deposition of fine sediments in headwater streams in relation to the status of Margaritifera margaritifera and Salmo trutta. Fine sediment deposition was linked to physicochemical conditions of the adjacent streambed.The mean observed deposition of fine sediments over the study period was 3.4 kg m−2 month−1 with a high spatio‐temporal variation ranging from
- CAN THE REGENERATION OF VEGETATION FROM RIPARIAN SEED BANKS SUPPORT
BIOGEOMORPHIC SUCCESSION AND THE GEOMORPHIC RECOVERY OF DEGRADED RIVER
- Authors: J. O'Donnell; K. Fryirs, M. R. Leishman
Pages: n/a - n/a
Abstract: For rivers degraded by erosion and channel widening, the re‐establishment of riparian vegetation is essential. We assess the potential for riparian seed banks to facilitate natural channel contraction through the regeneration of plants involved in the biogeomorphic succession of three discrete geomorphic units of increasing age and height above the channel bed: bars, benches and floodplain. Standing vegetation upon each unit type was surveyed for four river reaches in the Hunter catchment of eastern Australia. Seed bank composition was determined using seedling emergence techniques on sediment sampled from the units. We compared species richness and composition, and longevity, growth form and seed dispersal mechanisms between the standing vegetation and seed bank species. The seed bank was similar across bars, benches and floodplain, containing mostly perennial pioneer herbs, sedges and rushes, dispersed by wind and hydrochory (water transport). While bar vegetation was similar to the seed bank, bench and floodplain vegetation included later successional species such as shrubs and trees, significantly more grasses and vines (benches: χ25, N = 402 = 102.033, p
- DOWNSTREAM ECOLOGICAL IMPACTS OF CONTROLLED SEDIMENT FLUSHING IN AN ALPINE
VALLEY RIVER: A CASE STUDY
- Authors: P. Espa; G. Crosa, G. Gentili, S. Quadroni, G. Petts
Pages: n/a - n/a
Abstract: Sediment flushing may be effective to tackle the loss of reservoir storage as a result of siltation. When operationally possible, the impact of this practice on the downstream aquatic environment can be mitigated by limiting the sediment concentration of the discharged waters (controlled sediment flushing). However, this topic is poorly documented, and concerns arise when limits are discussed. We present the results of a 3‐year field investigation concerning the controlled sediment flushing of a small reservoir on the Adda River, the main tributary of Lake Como—Italy. Two limits for suspended solid concentration (SSC) were adopted: 1.5 g L−1, as average value throughout the whole working day, and 3.0 g L−1, as alert threshold to adjust the ongoing activity. These constraints were essentially fulfilled in the course of the documented operations. The first year sediment flushing was more significant than the following year: 25 000 tons of fines below 2 mm in diameter were flushed in six non‐consecutive days in summer 2010, while, one year earlier, 75 000 tons were flushed in 16 non‐consecutive days. In the third year of investigation (2011), no sediment evacuation took place. The benthic macroinvertebrate and the fish communities were surveyed a short distance below the reservoir, that is, in the potentially more affected river reach. Clear pieces of evidence of environmental quality degradation were not detected; the adopted strategies can therefore be considered to be appropriate when planning sediment flushing management in comparable contexts. Copyright © 2014 John Wiley & Sons, Ltd.
- THE INFLUENCE OF LOGJAMS ON LARGEMOUTH BASS (MICROPTERUS SALMOIDES)
CONCENTRATIONS ON THE LOWER ROANOKE RIVER, A LARGE SAND‐BED RIVER
- Authors: E. R. Schenk; J. W. McCargo, B. Moulin, C. R. Hupp, J. M. Richter
Pages: n/a - n/a
Abstract: This study examines the relation between logjams and largemouth bass (Micropterus salmoides) on the alluvial sand‐bed lower Roanoke River. Disparate data sets from previous bank erosion, fisheries, and large wood studies were used to compare the distribution of largemouth bass with logjam frequency. Logjams are related to the frequency of bank mass wasting increasing from near an upstream dam to the middle reach of the study segment and then decreasing as the river approaches sea level. The highest concentration of largemouth bass and logjams was in the middle reach (110 fish per hour and 21 jams per km). Another measure of largemouth bass distribution, fish biomass density (g h−1), had a similar trend with logjams and was a better predictor of fish distribution versus logjams (R2 = 0.6 and 0.8 and p = 0.08 and 0.02 for fish per hour and g h−1 versus logjam, respectively). We theorize that the preference for adult bass to congregate near logjams indicates the use of the jams as feeding areas. The results of a principal component analysis indicate that fish biomass concentration is much more related to logjam frequency than channel geometry (width, depth, and bank height), bed grain size, bank erosion, or turbidity. The results of this research support recent studies on in‐channel wood and fisheries: Logjams appear to be important for maintaining, or increasing, both largemouth bass numbers and total biomass of fish in large eastern North American rivers. Persistent logjams, important as habitat, exist where relatively undisturbed river reaches allow for bank erosion inputs of wood and available anchoring locations. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- COMPARISON OF CARBON SEQUESTRATION ABILITY AND EFFECT OF ELEVATION IN
FENCED WETLAND PLANT COMMUNITIES OF THE XILIN RIVER FLOODPLAINS: A MODEL
- Authors: Y. Liu; L. Wang, H. Liu, W. Wang, C. Liang, J. Yang, J. T. A. Verhoeven
Pages: n/a - n/a
Abstract: Floodplain habitats of the Xilin River in Inner Mongolia, China, were overgrazed by sheep and cattle until fencing of the floodplains was implemented in 2000. Carbon cycling of three plant communities of differing floodplain elevation after fencing showed that biomass in low‐elevation wetlands increased fastest until reaching its maximum at 20 years in the future, while a slower increase in biomass existed in high‐elevation and ‘hummock’ wetlands. Modelling and field experiments revealed differences between the three plant communities that were primarily attributed to different elevation levels and inundation periods. This study also determined the carbon sequestration capacity of the three floodplain wetland types (0.18 kg C m−2 year−1 in low‐elevation wetlands, 0.09 kg C m−2 year−1 in high‐elevation wetlands, and 0.05 kg C m−2 year−1 in hummock wetlands). Copyright © 2014 John Wiley & Sons, Ltd.
- THE EFFECTS OF DAM REMOVAL ON RIVER COLONIZATION BY SEA LAMPREY PETROMYZON
- Authors: E. Lasne; M.‐R. Sabatié, N. Jeannot, J. Cucherousset
Pages: n/a - n/a
Abstract: Habitat fragmentation is an important cause of biodiversity loss in freshwater systems, as worldwide rivers have been fragmented by dams and other hydraulic structures. To restore freshwater fish populations, some barriers have been removed, but the long‐term ecological effects of this removal have been rarely quantified. In the present study, we quantified the effects of barrier removal on river colonization by anadromous sea lamprey (Petromyzon marinus) by analyzing the spatial distribution and nest density in a small coastal river (France) from 1994 to 2011. Our results demonstrated the benefit of dam removal within few years after restoration. Indeed, the spatial distribution of nests shifted significantly upstream and was more uniform throughout the river after removal. Our results also suggest that the spatial patterns of habitat colonization were affected by the density of nests, river flow and connectivity. Finally, although the number of nests was significantly higher after removal, it was not possible to clearly identify the contribution of intrinsic versus external factors involved in this pattern. Further investigations are therefore needed to quantify the potential subsequent effects on juvenile recruitment and the overall population dynamics. Copyright © 2014 John Wiley & Sons, Ltd.
- A COMPARISON OF ELECTROFISHING AND VISUAL SURVEYING METHODS FOR ESTIMATING
FISH COMMUNITY STRUCTURE IN TEMPERATE RIVERS
- Authors: C. J. Macnaughton; S. Harvey‐Lavoie, C. Senay, G. Lanthier, G. Bourque, P. Legendre, D. Boisclair
Pages: n/a - n/a
Abstract: Studies attempting to describe fish community structure in shallow riverine environments typically rely on electrofishing and/or visual (snorkelling) surveys, but few have addressed the relative efficiencies of these two methods at estimating fish density and biomass across wide ranges of geography, taxonomy and life history stages. Multiple paired electrofishing and visual surveys were conducted in 18 temperate Canadian rivers in order to obtain community‐wide density and biomass estimates from both methods. Partial canonical multivariate analyses were applied to the paired fish community matrices comparing the results of both surveying methods at the taxonomic levels of family, genus and species, as well as size classes within families and species, to assess the particular effectiveness of each sampling method. Although electrofishing estimates of family and species richness were generally greater, snorkelling surveys tended to generate higher density and biomass estimates for different size classes of many salmonid and cyprinid species. Moreover, mean river biomass estimates derived from visual surveying matched those obtained from our best mean river biomass estimates arising from the two methods combined. This study provides empirical evidence that electrofishing and visual survey methods generate different types of information when assessing fish community structure at the family level or by size classes. Our results provide ample background information for determining the most accurate sampling method for a particular fish community assemblage, which is fundamental to fisheries management and research. Copyright © 2014 John Wiley & Sons, Ltd.
- EFFECTS OF IMPOUNDMENT ON MACROINVERTEBRATE COMMUNITY ASSEMBLAGES IN
- Authors: B. R. Gillespie; L. E. Brown, P. Kay
Pages: n/a - n/a
Abstract: Approximately 15% of the world's river flow is regulated, but evidence for the impacts of regulation on macroinvertebrate communities remains contradictory. Sound understanding of this topic is now required to meet legislative targets (e.g. EU Water Framework Directive good ecological potential). In the UK, research has either been undertaken at large (national) or small (reach) scales, and typically, researchers have made comparisons between sites classed simply as either regulated or unregulated. We present an alternative, medium (regional) scale study and contrast three methods of defining the extent to which a site is regulated (ER): (i) regulated or unregulated (ERLOW); (ii) fully‐regulated, semi‐regulated or unregulated (ERMED); and (iii) a continuous score reflecting the relative regulated and unregulated river influence on a site (ERHIGH). The potential for highlighting the impacts of regulation of two recently developed pressure‐specific biotic indices [Lotic Invertebrate index for Flow Evaluation (LIFE) and Proportion of Sediment‐sensitive Invertebrates] is also assessed. We found that (i) regulation was associated with reduced relative abundance of Coleoptera and Ephemeroptera and enhanced relative abundance of Trichoptera, Chironomidae and Oligochaeta; (ii) Potamopyrgus antipodarum and Amphinemura sulcicollis were both positively associated with regulation; this observation is novel for the UK; (iii) ERHIGH was superior to both ERLOW and MED as a means of detecting an impact; and (iv) of all indices tested, only LIFE was significantly associated with regulation. The use of LIFE and ERHIGH should be tested further to understand the extent to which they can provide clearer insights into the effects of river regulation on macroinvertebrate communities. Copyright © 2014 John Wiley & Sons, Ltd.
- FISH RESPONSE TO ANTHROPOGENIC PRESSURES IN TEMPORARY STREAMS: THE
IMPORTANCE OF ENVIRONMENTAL DRIVERS
- Authors: P. Matono; J. M. Bernardo, A. M. Costa, M. Ilhéu
Pages: n/a - n/a
Abstract: Mediterranean temporary streams show high spatial and temporal heterogeneity. Native fish species are adapted to this natural variability, but the cumulative effect of natural and anthropogenic disturbances may compromise the stability and persistence of fish assemblages. This study aimed to determine if environmental drivers affect the response of fish assemblages to anthropogenic pressures in temporary streams and identify what type of fish assemblages are particularly vulnerable to anthropogenic disturbance. Data were collected from 22 sites located in southern Portuguese temporary streams between 1996 and 2012. The temporal pattern of fish assemblages in each site was used to examine fish assemblage stability, that is, the relative constancy of species abundance over time, quantified using the Bray–Curtis similarity coefficient. Native fish assemblage stability was positively associated with altitude, annual rainfall, percentage of riffles and habitat diversity and highly negatively related to anthropogenic pressure, particularly land use intensification, riparian degradation, sediment load and organic contamination/nutrient enrichment. Results highlighted an interaction between natural environmental and anthropogenic pressure gradients; anthropogenic disturbance tends to be lower in high‐elevation headwater streams and increases in lowland streams, particularly in downstream reaches. In upstream reaches, especially in lowland streams, fish assemblage stability showed a steep decline with the increase in anthropogenic pressure. Lowland downstream reaches displayed a less steep decline of fish assemblage stability in response to degradation, despite having greater anthropogenic disturbance. The results highlight the particular vulnerability of headwater streams in lowland sectors to anthropogenic disturbance. Copyright © 2014 John Wiley & Sons, Ltd.
- THE HYDROLOGICAL STATUS CONCEPT: APPLICATION AT A TEMPORARY RIVER
- Authors: A. M. De Girolamo; A. Lo Porto, G. Pappagallo, O. Tzoraki, F. Gallart
Pages: n/a - n/a
Abstract: In achieving the final objective of the European Water Framework Directive, the evaluation of the ‘hydrological status’ of a water body in a catchment is of the utmost importance. It represents the divergence of the actual hydrological regime from its ‘natural’ condition and may thus provide crucial information about the ecological status of a river. In this paper, a new approach in evaluating the hydrological status of a temporary river was tested. The flow regime of a river has been classified through the analysis of two metrics: the permanence of flow and the predictability of no‐flow conditions that were evaluated on monthly streamflow data. This method was applied to the Candelaro river basin (Puglia, Italy) where we had to face the problem of limited data availability. The Soil and Water Assessment Tool model was used when streamflow data were not available, and a geographic information system procedure was applied to estimate potential water abstractions from the river. Four types of rivers were identified whose regimes may exert a control on aquatic life. By using the two metrics as coordinates in a plot, a graphic representation of the regime can be visualized in a point. Hydrological perturbations associated with water abstractions, point discharges and the presence of a reservoir were assessed by comparing the position of the two points representing the regime before and after the impacts. The method is intended to be used with biological metrics in order to define the ecological status of a stream, and it could also be used in planning the ‘measures’ aimed at fulfilling the Water Framework Directive goals. Copyright © 2014 John Wiley & Sons, Ltd.
- ESTIMATION OF SEDIMENT HYDRAULIC CONDUCTIVITY IN RIVER REACHES AND ITS
POTENTIAL USE TO EVALUATE STREAMBED CLOGGING
- Authors: T. Datry; N. Lamouroux, G. Thivin, S. Descloux, J. M. Baudoin
Pages: n/a - n/a
Abstract: Streambed substrates have pervasive effects on stream biodiversity and biogeochemistry. The excessive input of fine sediments in streams and the subsequent alteration of the physical characteristics of streambed substrates are considered today as a major environmental issue. The estimation of streambed hydraulic conductivity (K) may be simpler than other estimations of reach‐scale physical characteristics and could serve to quantify the alterations of streambeds across stream networks. In this study, we examined between‐reach and within‐reach variability and temporal changes of streambed K across 101 stream reaches in France, including nine reaches previously judged as clogged and nine as references (unclogged). We also examined the relationships between K and some environmental variables such as vertical hydraulic gradient, streambed grain size, flow velocity or distance to the bank. We demonstrated that 15 measurements of streambed K per reach could be used to compare streams among each other and over time. Clogged reaches displayed much lower K than reference reaches, and more generally, reach‐averaged K and the number of non‐null K values per reach allowed discriminating reaches among each other without observer bias. K was higher in upwelling compared with downwelling areas, probably because of fine sediment uplifting. With the low cost in terms of equipment (
- OUT OF POOLS: MOVEMENT PATTERNS OF MEDITERRANEAN STREAM FISH IN RELATION
TO DRY SEASON REFUGIA
- Authors: D. F. Pires; P. Beja, M. F. Magalhães
Pages: n/a - n/a
Abstract: Movement may critically influence population persistence in the face of disturbance. However, data on individual movements into and out of refugia in response to disturbance remain limited, leading to an incomplete understanding of the ecological significance of mobility. Using individually marked chubs Squalius torgalensis in a seasonally drying Mediterranean stream, we quantified the rate, direction and magnitude of movements out of dry season pools, and of movements displayed across the stream over the period of hydrological connection. Recapture rate was lower in individuals marked in dry season pools (3.3%; n = 894) than in individuals marked during hydrological connection (13.0%; n = 522). Nearly half the recaptures (46.7%; n = 30) of chubs marked in dry season pools corresponded to movements that were generally longer than 100 m, overpassing the average distance among isolated pools. The frequency and distances travelled out of dry season pools were similar in upstream and downstream directions. Only 20.6% of recaptures of individuals marked during hydrological connection corresponded to movements, with more frequent and larger movements in the upstream direction. Body size was related to movement probability only for chubs marked during hydrological connection. Our results highlight considerable individual variability in movement and underscore the importance of understanding the consequences of this variation and how it may be maintained in fish populations facing increasing fragmentation and intermittency of riverscapes. Copyright © 2014 John Wiley & Sons, Ltd.
- HABITAT RESTORATION IN THE CONTEXT OF WATERSHED PRIORITIZATION: THE
ECOLOGICAL PERFORMANCE OF URBAN STREAM RESTORATION PROJECTS IN PORTLAND,
- Authors: B. Rios‐Touma; C. Prescott, S. Axtell, G. M. Kondolf
Pages: n/a - n/a
Abstract: In Portland (Oregon, USA), restoration actions have been undertaken at the watershed scale (e.g. revegetation and stormwater management) to improve water quality and, where water quality and quantity are adequate at the reach scale, to increase habitat heterogeneity. Habitat enhancement in urban streams can be important for threatened species, but challenging, because of altered catchment hydrology and urban encroachment on floodplains and channel banks. To evaluate reach‐scale restoration projects in the Tryon Creek watershed, we sampled benthic macroinvertebrates and conducted habitat quality surveys pre‐project and over 4 years post‐project. Species sensitive to pollution and diversity of trophic groups increased after restoration. Taxonomic diversity increased after restoration but was still low compared with reference streams. We found no significant changes in trait proportions and functional diversity. Functional diversity, proportion of shredders and semivoltine invertebrates were significantly higher in reference streams than in the restored stream reaches. We hypothesized that inputs of coarse particulate organic matter and land use at watershed scale may explain the differences in biodiversity between restored and reference stream reaches. Habitat variables did not change from pre‐project to post‐project, so they could not explain community changes. This may have been partly attributable to insensitivity of the visual estimate methods used but likely also reflects the importance of watershed variables on aquatic biota—suggesting watershed actions may be more effective for the ecological recovery of streams. For future projects, we recommend multihabitat benthic sampling supported by studies of channel geomorphology to better understand stream response to restoration actions. Copyright © 2014 John Wiley & Sons, Ltd.
- PREDICTING HABITAT RESPONSE TO FLOW USING GENERALIZED HABITAT MODELS FOR
TROUT IN ROCKY MOUNTAIN STREAMS
- Authors: T. K. Wilding; B. Bledsoe, N. L. Poff, J. Sanderson
Pages: 805 - 824
Abstract: Dams and water diversions can dramatically alter the hydraulic habitats of stream ecosystems. Predicting how water depth and velocity respond to flow alteration is possible using hydraulic models, such as Physical Habitat Simulation (PHABSIM); however, such models are expensive to implement and typically describe only a short length of stream (102 m). If science is to keep pace with development, then more rapid and cost‐effective models are needed. We developed a generalized habitat model (GHM) for brown and rainbow trout that makes similar predictions to PHABSIM models but offers a demonstrated reduction in survey effort for Colorado Rocky Mountain streams. This model combines the best features of GHMs developed elsewhere, including the options of desktop (no‐survey) or rapid‐survey models. Habitat–flow curves produced by PHABSIM were simplified to just two site‐specific components: (i) Q95h (flow at 95% of maximum habitat) and (ii) Shape. The Shape component describes the habitat–flow curves made dimensionless by dividing flow increments by Q95h and dividing habitat (weighted usable area) increments by maximum habitat. Both components were predicted from desktop variables, including mean annual flow, using linear regression. The rapid‐survey GHM produced better predictions of observed habitat than the desktop GHM (rapid‐survey model explained 82–89% variance for independent validation sites; desktop 68–85%). The predictive success of these GHMs was similar to other published models, but survey effort to achieve that success was substantially reduced. Habitat predicted by the desktop GHM (using geographic information system data) was significantly correlated with the abundance of large brown trout (p
- EFCAM: A METHOD FOR ASSESSING ALTERATION OF ENVIRONMENTAL FLOW COMPONENTS
- Authors: T. W. FitzHugh
Pages: 825 - 844
Abstract: The environmental flow components (EFCs) are a set of 34 streamflow statistics computed by the Indicators of Hydrologic Alteration software, which are used for environmental flow assessments and developing environmental flow recommendations. The objective of this paper is to demonstrate a methodology for analysing and summarizing the alteration of EFCs, called the EFC assessment method (EFCAM). EFCAM uses non‐parametric rank‐sum statistical tests, sometimes in conjunction with per cent change, to produce ratings of alteration for each EFC statistic, for both central tendency and range of variability. These ratings are combined into summary indexes of alteration, by event type (extreme low flow, low flow, high‐flow pulse, small flood and large flood), flow characteristic (frequency, magnitude, duration, timing and rise/fall rates) and overall. EFCAM is demonstrated by analyzing typical patterns of EFC changes in 66 rivers across the United States where flow is altered by dams. The results reported here show that EFCAM is an effective method for efficiently summarizing flow alteration of ecologically relevant components of flows, and hence would be a useful addition to the Indicators of Hydrologic Alteration software. Results of this study show an overall trend towards compression of the hydrograph from above and below into a more limited overall range on these 66 rivers. The results shown here add to previous findings on dam impacts on river flows by separating out alteration in different segments of the hydrograph, and identify some patterns of alteration not previously reported. Although the version of EFCAM used here is believed to be appropriate for most situations, it is flexible and can be tailored to the needs of a particular project by including or excluding certain flow statistics or using a different weighting system. Copyright © 2013 John Wiley & Sons, Ltd.
- ESTIMATING ANNUAL RIVERBANK EROSION RATES—A DENDROGEOMORPHIC METHOD
- Authors: B. M. Dick; R. Hey, P. Peralta, I. Jewell, P. Simon, I. Peszlen
Pages: 845 - 856
Abstract: An accurate estimation of riverbank erosion rates is critical for the evaluation of the past, present, and future sediment regime of river systems. Understanding these relationships allows watershed managers and regulators to prioritize river restoration and contaminated site remediation projects. In this dendrogeomorphic study, changes in the anatomy of tree roots exposed between 1 and 31 years were used to estimate the average annual erosion rates of riverbank sediments on a large river in Michigan, USA. Exposed root samples from diffuse and ring‐porous hardwoods, together with buried ones as controls, were analyzed. Differences in the arrangement, size and frequency of vessels, fiber diameter, cell wall thickness, growth ring width, and scarring between the exposed and the buried samples were used to identify the first year of root exposure. Results of the regression analysis between the average annual erosion rate and the Bank Erosion Hazard Index (BEHI) indicated that the more recently exposed roots (less than 7 years in this study) explained more of the variance (R2 = 0.67) than when all samples were included (R2 = 0.38). Although the average erosion rates for long periods can be accurately determined from the dating of exposed tree roots, attempts to relate these rates using the BEHI for longer periods are less successful, as BEHI values can vary considerably over time as the riverbank erodes. Consequently, when using exposed tree roots to develop regression equations and erosion rate curves for the estimation of erosion rates based on BEHI scores, it is necessary to use roots that were recently exposed. Copyright © 2013 John Wiley & Sons, Ltd.
- IDENTIFICATION OF FLUVIAL WOOD USING GOOGLE EARTH
- Authors: J. B. Atha
Pages: 857 - 864
Abstract: Fluvial wood has long been known to enhance stream complexity by creating aquatic habitat and by increasing complexity in channel hydraulics and morphology. Although the presence and dynamics of large wood in river floodplains have been studied in a multitude of settings due to its importance in monitoring and managing ecohydrologic systems, limitations occur when studying fluvial wood on a basin scale. I postulate that with the employment of Google Earth, satellite images may be used to identify large wood and measure floodplain width across broader spatial scales previously inhibited by expensive and incomplete geospatial data. In this study, large wood was correctly identified within the floodplain of the Queets River, Washington, USA, through Google Earth; however, correct identification within the wetted channel was only possible during low flow if at least 50% was above water level. Within the study area, fluvial channel widths are measured as well. Google Earth proves to be an effective tool to discern large wood across greater spatial scales if the high‐resolution imagery is available for the study area. Results of statistical analyses derived from the downstream hydraulic geometry of the river reveal that this channel is influenced by bankfull width, the orientation of the wood to the channel, and whether it is located on a bar or within the wetted channel. In addition, wood counts analyzed in the context of the geometry of the river indicate that the fluvial wood has an influence on overall channel behavior. Copyright © 2013 John Wiley & Sons, Ltd.
- STREAM RESTORATION AND CRIBWALL PERFORMANCE: A CASE STUDY OF CRIBWALL
MONITORING IN SOUTHERN ONTARIO
- Authors: V. Krymer; A. Robert
Pages: 865 - 873
Abstract: Stream restoration focusing on adaptable natural and inert material use has been implemented through soil bioengineering designs aimed at the stabilization of urbanized streams. Within each design application materials such as large wood, sediment fill and vegetation must be suited to diverse settings. This paper discusses the application of cribwalls as soil bioengineering designs found in two Southern Ontario watersheds and the criteria that influence their performance. Field measurements of cribwall cuttings, sediment sampling, erosion pin monitoring, and computer‐generated stream power analysis are used to compare design performance at several sites. It is determined that the technical specifications of the design and site characteristics such as stream power distribution, sediment, and channel planform are equally involved in long‐term streambank stability. The results indicate that cribwalls with dense cutting growth perform well on streambanks that offer a greater amount of soil cohesion, nutrients, and infiltration in the mid and upper sections of the bank. In streams with moderate channel slopes and stream power distribution that is above the watershed mean, streams with well‐developed floodplains, sinuous channel planforms, and low bank height ratios perform better than those that are confined, straightened, and have greater bank height ratios. Throughout the comparison of several cribwall sites, the implication of this work is to demonstrate how to assess the fitness of similar soil bioengineering designs for application to diverse stream settings and to further validate their significance in stream restoration as designs that are multifunctional. Copyright © 2013 John Wiley & Sons, Ltd.
- WETLAND HABITAT PATCHES AS ECOLOGICAL COMPONENTS OF LANDSCAPE MEMORY IN A
HIGHLY MODIFIED FLOODPLAIN
- Authors: A. Ortmann‐Ajkai; D. Lóczy, P. Gyenizse, E. Pirkhoffer
Pages: 874 - 886
Abstract: Landscape memory and ecological memory are relatively new concepts developed independently in geomorphology and ecology. Eco‐geomorphology strives to enrich the concept of landscape memory with that of ecological memory, as ecosystems build inherent parts of landscapes and are controlled by geomorphological factors. This integration is illustrated by a small‐scale eco‐geomorphological case study of links between ecosystems and their hydrogeomorphological template, in the floodplain of a medium size Hungarian River. Despite that the river is channelized by 1835 and most of the study area is under intensive agricultural cultivation, the seminatural vegetation along the various reaches shows significant variations according to geomorphological background variables: detrended correspondence analysis yields results of p = 0.002 significance. Our results prove that geomorphological patterns in floodplains, defined by landscape memory, and the related vegetation patterns, as manifestations of ecological memory, jointly determine the face of floodplain landscapes. The integration of ecological memory into the definition of landscape memory may help meet the challenges of eco‐geomorphology and facilitate a holistic understanding of landscapes, and thus be instrumental for reconstructing past environments—both in theory (scientific research) and practice (rehabilitation projects). Copyright © 2013 John Wiley & Sons, Ltd.
- REVISION OF THE BIOLOGICAL MONITORING WORKING PARTY (BMWP) SCORE SYSTEM:
DERIVATION OF PRESENT‐ONLY AND ABUNDANCE‐RELATED SCORES FROM
- Authors: M. F. Paisley; D. J. Trigg, W. J. Walley
Pages: 887 - 904
Abstract: The Biological Monitoring Working Party (BMWP) score system was introduced in 1980 to provide an index of river water quality for England and Wales based on aquatic macroinvertebrates. The score allocated to each taxon was set by a group of expert river biologists on the basis of their collective experience of the taxon's sensitivity to organic pollution. This paper describes an objective reappraisal of these subjectively derived scores by the statistical analysis of a large and comprehensive database of field data. Two different methods of using biological and environmental data were evaluated as a basis for revising BMWP scores, both of which accounted for variations in site type. One method, Modified New Walley–Hawkes (MNWH), used a modified average score per taxon (MASPT) as its ranking metric and required analyses performed on separated data sets divided into three site types. The other method used the environmental quality index based on MASPT (EQIMASPT) to provide its ranking metric. Both of these methods involved the use of modified BMWP values for Oligochaeta and Chironomidae for reasons that are explained. Following evaluation, the MNWH method was chosen to derive present‐only and abundance‐related scores for the BMWP taxa, 19 additional taxa mostly from the order Diptera, and 16 extra taxa resulting from the splitting of eight BMWP composite taxa. The MNWH scores were generally in keeping with those derived in an earlier study, except for a few rare taxa that were represented by few samples in that study. The UK Regulatory Authorities intend adopting a new index based on the MNWH scores, and this is given in two appendices. Copyright © 2013 John Wiley & Sons, Ltd.
- EVALUATING SHALLOW‐WATER BATHYMETRY FROM THROUGH‐WATER
TERRESTRIAL LASER SCANNING UNDER A RANGE OF HYDRAULIC AND PHYSICAL WATER
- Authors: M.W. Smith; D. Vericat
Pages: 905 - 924
Abstract: The fine‐scale structure of the water–sediment boundary in fluvial environments is dynamic and complex, influencing near‐bed flows, sediment transport and instream ecology. However, accurate high‐resolution surveying of marginally or partially inundated areas of river channels is problematic. Previous work has shown that terrestrial laser scanning (TLS) through relatively shallow‐water columns using standard green‐wavelength equipment introduces errors of
- APPLICATION OF AERIAL DIGITAL PHOTOGRAPHY FOR MACROPHYTE COVER AND
COMPOSITION SURVEY IN SMALL RURAL STREAMS
- Authors: Y. Anker; Y. Hershkovitz, E. Ben Dor, A. Gasith
Pages: 925 - 937
Abstract: Macrophytes are a key biological component in many fluvial ecosystems. In altered streams, they can become highly dominant features, covering extensive parts of the channel with cascading effects on stream conditions and biological composition. The aim of this study is to examine the possibility of using information collected by aerial digital photography‐spectral analysis (ADP‐SA) as an alternative, cost‐effective methodology to the commonly used spectral procedure at a large (section) scale, and to the ground level visual survey (gridded frame) at a smaller (organism) scale. Cladophora glomerata and Nasturtium officinale, were selected as the targeted macrophyte species and classified at the same time (species relative cover) by using the three methodologies. Our findings show that the ADP‐SA methodology was able to detect species and relative cover in similar accuracy (≤10% differences) at the two spatial scales. ADP‐SA had a better spatial resolution than both the hyperspectral and the visual methodology (4 cm vs. 1 m and 10 cm, respectively) and was capable to differentiate submerged from emergent plants. However, on a smaller scale, ground level work is suitable and essential for detecting rarer species and is not hindered by weather, canopy cover or multi‐layered plant composition. ADP‐SA can therefore add a cost‐effective and nonsubjective practice to the existing tool kit of macrophyte surveys, particularly in small streams, which require high spatial resolution. Copyright © 2013 John Wiley & Sons, Ltd.