- Effect of Proposed Large Dams on Water Flows and Hydropower Production in
the Sekong, Sesan and Srepok Rivers of the Mekong Basin
- Authors: T. Piman; T. A. Cochrane, M. E. Arias
Abstract: Water flow patterns in the Mekong are changing because of on‐going rapid hydropower development triggered by economic growth. Of immediate concern are the current and proposed hydropower dams in the transboundary Srepok, Sesan and Srekong (3S) Rivers, which contribute up to 20% of the Mekong's annual flows, have a large potential for energy production and provide critical ecosystem services to the downstream Tonle Sap Lake and Mekong Delta. The objective of this paper is to determine how the operation of the proposed largest individual dams and cascade dam schemes in the 3S Rivers will affect flow regimes and energy production. Daily flows were simulated over 20 years using the Soil and Water Assessment Tool and HEC‐ResSim models for a range of dam development and operations scenarios. The development of all dams in the 3S basin under an operation scheme to maximize individual electricity production results in an average 98% increase in dry season flows at the 3S outlet. Over 55% of dry season flows changes are caused by seven proposed large dams, with the Lower Srepok 3 project causing the highest impact. The seven large dams will generate 33.0 GWh/day with a water volume of 17 679 x 106 m3, compared with the current and definite future dams generating 73.2 GWh/day with a much lower volume of 6616 x 106 m3. When a cascade of dams are operational, downstream dams with small reservoirs will produce more energy. However, the marginal increase in energy production from the development of additional dams in the 3S basin will decline rapidly relative to the required water storage increase,. Strategic decision‐making on the future of each large proposed dam in the 3S basin needs to be considered by local governments after understanding cumulative operation effects and with further consideration to the potential impact on downstream ecosystem productivity and livelihoods. Copyright © 2016 John Wiley & Sons, Ltd.
- Effects of Oil Palm Plantations on the Habitat Structure and Biota of
Streams in Eastern Amazon
- Abstract: Oil palm plantations have expanded around the world, increasing concern about its pressure on deforestation rates and the homogenization of the landscape. In this context, the present study aimed to evaluate the impact of oil palm plantations on the physical characteristics of streams in Amazonia and their effects on Heteroptera, Odonata and Fish assemblages. A total of 23 streams were sampled, eight within fragments of primary forest, while 15 were in oil palm plantations. Data were collected on characteristics of the channel morphology, substrate, hydraulics, instream cover for aquatic organisms, riparian vegetation, human impacts and woody debris. Instream cover and proximity of human impacts were the variables that had the greatest effects on the physical structure of the streams, showing variation between streams of forest in pristine areas and oil palm plantations. Of the analyzed parameters, substrate, instream cover and woody debris influence the richness of Heteroptera, Odonata and Fish. The impact of oil palm plantations on local streams depended on the size of the plantations, and they cannot be considered an adequate substitute for lost habitats in efforts to preserve the physical habitat of Amazonian streams. Any type of conversion of the natural forest can have direct or indirect impacts on the dynamics and structure of these environments, with potentially negative consequences for their biodiversity. The maintenance of an adequate buffer zone of native riparian vegetation adjacent to the streams that flow through the plantations recommended, because this appears to be the principal factor determining the physical conditions of these streams. Copyright © 2016 John Wiley & Sons, Ltd.
- Understanding the Thermal Regime of Rivers Influenced by Small and Medium
Size Dams in Eastern Canada
- Abstract: Although small and medium‐size dams are prevalent in North America, few studies have described their year‐round impacts on the thermal regime of rivers. The objective of this study was to quantify the impacts of two types of dams (run‐of‐river, storage with shallow reservoirs) on the thermal regime of rivers in eastern Canada. Thermal impacts of dams were assessed (i) for the open water period by evaluating their influence on the annual cycle in daily mean water temperature and residual variability and (ii) for the ice‐covered winter period by evaluating their influence on water temperature duration curves. Overall, results showed that the run‐of‐river dam (with limited storage capacity) did not have a significant effect on the thermal regime of the regulated river. At the two rivers regulated by storage dams with shallow reservoirs (mean depth
- Modelling Temperature, Body Size, Prey Density, and Stream Gradient
Impacts on Longitudinal Patterns of Potential Production of
- Authors: J. J. Laliberte; J.R. Post, J.S. Rosenfeld, J.A. Mee
Abstract: In this study, we modelled idealized stream reaches using empirical hydrodynamic and bioenergetic parameters to predict how rainbow trout production depends on physical and biological variations across a downstream gradient, and we compared these downstream effects in a low and high‐gradient stream reach. We found that longitudinal production potential (i.e. net rate of energetic intake per 100 m of stream length) generally increased with increasing stream size when stream gradient was low. This was not the case, however, for high‐gradient streams, wherein maximum longitudinal production potential was associated with middle or low stream size (QMAD = 2.5 to 25 m3 s−1). Areal production potential (net rate of energetic intake per m2 of wetted stream bed) reached a maximum at low stream size (QMAD = 2.5 m3 s−1) with both high and low gradients. We also showed that high stream temperature and low drift density could potentially cause adult rainbow trout to be excluded from stream reaches with high flow. The models presented here have a stronger mechanistic basis for predicting fish production across heterogeneous stream environments and provide more nuanced predictions in response to variation in environmental features than their physical habitat‐based predecessors. Copyright © 2016 John Wiley & Sons, Ltd.
- Effects of Passive and Structural Stream Restoration Approaches on
Transient Storage and Nitrate Uptake
- Authors: J. S. Mueller Price; D. W. Baker, B. P. Bledsoe
Abstract: Understanding nitrogen dynamics in headwater streams is important for ascertaining how they influence downstream nutrient loads and identifying strategies for reducing loading through stream restoration. We compare nitrate uptake associated with two restoration approaches in headwater streams, Sheep Creek and Nunn Creek, of northern Colorado, USA. Segments of Sheep Creek were exclosed (fenced off) from open rangeland cattle grazing in the 1950s, allowing riparian corridors of these segments to naturally revegetate (passive approach), while other segments have been continually grazed. In 2003, restoration structures including cross vanes, J‐hook vanes, rootwads, log vanes, and bank riprap (structural approach) were installed along portions of Nunn Creek for trout habitat enhancement and local bank stabilization. We performed detailed physical characterizations and multiple nutrient injections of Br− and NO3− to estimate transient storage and nitrate uptake in four reaches along Sheep Creek (two reaches exclosed from grazing and two grazed reaches) and two reaches along Nunn Creek (one with restoration structures and one without structures). Parameters of transient storage and nitrate uptake were estimated with the one‐dimensional transport with inflow and storage model run through universal inverse modelling code for optimization. Responses of transient storage and nitrate uptake to restoration techniques depended upon the type and extent of restoration implemented, as well the context and physical setting of each study reach. For example, in the higher‐gradient pair of Sheep Creek reaches, the restored reach showed greater nitrate uptake, while in the lower‐gradient pair of reaches, the non‐restored reach had greater uptake. At Nunn Creek, the reach with instream wood but without restoration structures exhibited more transient storage and nitrate uptake when compared with the reach with extensive J‐hook vane structures. Copyright © 2016 John Wiley & Sons, Ltd.
- Stream Temperature Impacts Because of Changes in Air Temperature, Land
Cover and Stream Discharge: Navarro River Watershed, California, USA
- Authors: C. J. Woltemade; T. W. Hawkins
Abstract: Stream temperatures are critically important to aquatic ecology, especially cold‐water fish such as salmonids. Stream temperatures are influenced by multiple factors, including local climate, solar radiation on the stream channel, stream discharge volume and groundwater contributions. The Heat Source hydrodynamic and thermodynamic numerical model was used to evaluate temperatures in three stream reaches in the Navarro River watershed, California, USA. The model was calibrated and validated for summer 2015 conditions and then applied to scenarios that address changes in air temperatures, riparian forest cover and stream discharge. Modelling results indicate that stream temperatures are sensitive to changes in air temperatures and riparian forest cover and that higher discharge volume mitigates those impacts. Modelled stream maximum weekly average temperatures (MWAT) increased by 1.5–2.3°C in response to an air temperature increases of 3.5°C under low flow conditions (drought) but by only 0.9–2.0°C under moderate flow. Complete removal of riparian forest in a large‐scale forest fire would increase MWAT by 2.2–5.9°C in low discharges and by 1.0–4.4°C under moderate discharge. Riparian zone reforestation would decrease MWATs by less than 0.8°C, a modest change reflecting high existing shade on the modelled stream reaches. Comparison of identical climate and land cover change scenarios under low and moderate discharge conditions reveals that efforts to conserve stream discharge volume could be an effective mechanism to mitigate stream temperature increases. Copyright © 2016 John Wiley & Sons, Ltd.
- City Channel Chironomids—Benthic Diversity in Urban Conditions
- Abstract: The study focuses on the diversity of urban channel chironomids (the Aa River, the City of Münster, North‐western Germany), initially intended as a proxy of habitat structure. Three ecological key points marked the study:
The channel is the discharge effluent of a eutrophic lake.
It includes lotic and lentic sections.
Runoff variability is high (0.02 to 4 m3 s−2).
Chironomid pupal exuviae were sampled from the surface drift. Simultaneously, variable abiotic parameters (runoff, suspensoid contents and weather) were recorded. Samples were taken from September 2011 to April 2012. Communities' diversity (>64 spp.) was relatively high. Data analyses revealed that the most significant drivers of species diversity and abundance were water temperature, suspension, flow velocity, nature nearness, water depth and weather. In addition, the increase of diversity ranged significantly with the quality of suspensoids along the channel course. Considering the great complexity of ecological interrelations found on a limited physical scale, the potential of chironomids as sentinel organisms shall be discussed critically. Ongoing analyses focus on the specification of fine particulate organic matter, microhabitat structure and microhydraulics for the development of chironomid communities.
- Downstream Regime Relations for Single‐Thread Channels
- Authors: J. B. Thayer
Abstract: New empirically derived downstream hydraulic geometry relations are developed for single‐thread gravel/cobble‐bed and sand‐bed channels using the independent variables bankfull discharge, channel slope, and median bed grain size. Differences in channel response to the controlling variables are observed between gravel/cobble‐bed and sand‐bed channels. It is found that the inclusion of channel slope into regime relations is necessary for accurate channel geometry predictions and that bed grain size becomes an unnecessary variable. Accuracy of predictions is superior to many existing relations and comparable with those that already include slope as an independent variable. Variability of prediction errors is comparable with existing relations. Applications and implications of the new relations are discussed. Copyright © 2016 John Wiley & Sons, Ltd.
- Temporal and Spatial Variation in Riparian Vegetation and Floodplain
Aquifers on the Regulated Dolores River, Southwest Colorado, USA
- Authors: C. E. Dott; G. L. Gianniny, M. J. Clutter, C. Aanes
Abstract: The importance of flow variability and floodplain water table recharge for the establishment and long‐term survival of riparian vegetation has been well‐documented. However, temporal and spatial variation in floodplain aquifers has received less attention, although native species can have narrow tolerances for groundwater decline. Our observations of decreased cottonwood cover on floodplains and increased willow cover on river banks since dam completion on the Dolores River led to comparisons between three long‐term study sites above and below McPhee Dam. We summarize 5 years (2010–2014) of shallow groundwater well data from transects of three wells per site. Vegetation cover data were collected from quadrats and line‐intercept transects. In the willow zone, groundwater well levels mirror in‐channel flows and rarely drop below 0.6 m from ground surface. Willow cover and stem counts on point bars are higher at dammed sites. Wells in the cottonwood zone indicate that alluvial recharge happens only during prolonged peak discharge during spring snowmelt or dam release. Years with no dam spill reduced connectivity between surface flows and groundwater, and groundwater depth dropped to between 2 and >2.5 m. Long‐term data below the dam indicate that canopy cover of the dominant cottonwoods has declined over time (48% in 1995, 19% in 2003), especially in the wake of severe drought. Mature cottonwood cover is significantly higher at the undammed site (p = 0.025). Our results indicate that floodplain habitats below dams exist under artificially extreme drought and inform how biologically diverse riparian systems will be impacted by a drying climate. Copyright © 2016 John Wiley & Sons, Ltd.
- Hydraulic and Physical Structure of Runs and Glides Following Stream
- Abstract: Hydraulic units are often linked to ecological habitat through geomorphic structure, and a better understanding of the turbulent characteristics of the units is needed. Our work examined the near‐bed turbulent structure of runs and glides in a restored river and investigated the physical characteristics that influenced the near‐bed hydraulics in these units. The research was completed in three restored reaches and one reference reach at the Virginia Tech Stream Research, Education, and Management Laboratory. The laboratory is unique because three different restoration treatments were applied contiguously along a stream, and the restoration practices ranged from passive to active. The passive reach included cattle exclusion, while the active reaches included cattle exclusion as well as vegetation plantings, bank sloping and the construction of inset floodplains. Three‐dimensional velocities were measured near the channel bed in run and glide biotopes within the three restored reaches, as well as an upstream reference reach. The velocities were utilized to analyse and compare near‐bed turbulent structure across the reaches. While the restoration activities did not address the channel bed directly, differences in physical structure of the two physical biotopes were observed among restoration treatments, likely because of changes in bank shape and roughness due to vegetation differences. Differences between reference and restored reaches were still evident approximately 3 years after cattle exclusion and construction activities. Few differences were observed in the hydraulic structure between runs and glides, and the near‐bed flow structure in both runs and glides was related to local roughness. Copyright © 2016 John Wiley & Sons, Ltd.
- Multi‐scale Approach to Hydrological Classification Provides Insight
to Flow Structure in Altered River System
- Authors: J. J. Spurgeon; M. A. Pegg, M. J. Hamel
Abstract: Rivers are hierarchical systems exhibiting processes and patterns across spatial and temporal scales principally driven by changes in flow. Hydrological indices estimated with mean or median daily flow data (i.e. daily scale) may be insensitive to anthropogenic alteration that imparts sub‐daily variation to flow. Therefore, indices developed at multiple temporal resolutions may provide additional insight into the presence of flow patterns masked by traditional techniques. We characterized the flow regime along the longitudinal gradient of the Platte River, a large Great Plains USA river, using hydrological indices derived with mean daily and sub‐daily flow data and a combination of multivariate statistical techniques. Three unique flow units were evident using daily scale flow data, whereas six unique flow units were evident at the sub‐daily scale. Flow units at both scales were not static, but rather the presence and extent of flow units across the riverscape depended on climate, tributary inflows and human influence. Anthropogenic alteration including hydropeaking was evident at the sub‐daily scale but not at the daily scale. The full complement of flow structure within regulated rivers, therefore, may not be captured using mean or median daily discharge values alone. Inductive river classification studies may benefit from assessing hydrological indices at multiple scales, particularly when investigating river systems with anthropogenic modification such as hydropeaking. Copyright © 2016 John Wiley & Sons, Ltd.
- Coupled Hydrological/Hydraulic Modelling of River Restoration Impacts and
- Authors: H. M. Clilverd; J. R. Thompson, C. M. Heppell, C. D. Sayer, J. C. Axmacher
Abstract: Channelization and embankment of rivers has led to major ecological degradation of aquatic habitats worldwide. River restoration can be used to restore favourable hydrological conditions for target species or processes. However, the effects of river restoration on hydraulic and hydrological processes are complex and are often difficult to determine because of the long‐term monitoring required before and after restoration works. Our study is based on rarely available, detailed pre‐restoration and post‐restoration hydrological data collected from a wet grassland meadow in Norfolk, UK, and provides important insights into the hydrological effects of river restoration. Groundwater hydrology and climate were monitored from 2007 to 2010. Based on our data, we developed coupled hydrological/hydraulic models of pre‐embankment and post‐embankment conditions using the MIKE‐SHE/MIKE 11 system. Simulated groundwater levels compared well with observed groundwater. Removal of the river embankments resulted in widespread floodplain inundation at high river flows (>1.7 m3 s−1) and frequent localized flooding at the river edge during smaller events (>0.6 m3 s−1). Subsequently, groundwater levels were higher and subsurface storage was greater. The restoration had a moderate effect on flood peak attenuation and improved free drainage to the river. Our results suggest that embankment removal can increase river–floodplain hydrological connectivity to form a more natural wetland ecotone, driven by frequent localized flood disturbance. This has important implications for the planning and management of river restoration projects that aim to enhance floodwater storage, floodplain species composition and biogeochemical cycling of nutrients. © 2016 The
Authors . River Research and Applications Published by John Wiley & Sons Ltd.
- Hydropower Development, Riverine Connectivity, and Non‐sport Fish
Species: criteria for Hydraulic Design of Fishways
- Abstract: Hydropower barriers are among the most conspicuous anthropogenic alterations to natural riverine connectivity, resulting in species‐specific effects linked to dispersal abilities, especially swimming performance. They may present a particular problem for small‐bodied ‘non‐sport fish’, such as those that characterize the freshwater communities of temperate regions in the Southern Hemisphere. Recent studies have suggested that nature‐like fishways could ensure passage of diverse fish assemblages through hydropower barriers. Through experiments performed in a swim tunnel, we present, for the first time, fishway design criteria for two non‐sport species endemic to Chile, a country experiencing rapid hydropower development. In`cremental velocity tests showed that Cheirodon galusdae and juveniles of Basilichthys microlepidotus were capable of very similar standardized critical swimming speeds of 69.7 and 69.6 cm s−1, respectively. When expressed in units of body lengths, C. galusdae was capable of very high critical speeds of 16.2 bl s−1, whereas for B. microlepidotus, this was 7.6 bl s−1. However, fixed velocity tests revealed that the swimming endurance of the latter species was slightly higher. Dimensionless analysis showed a clear relationship between fatigue time and fish Froude number, similar to that already described for subcarangiforms. Based on these results, we present fishway design curves indicating a transition from sustained to prolonged swimming at a fishway length of 15 m. Our results show that the swimming capacity of these species is well‐suited to the mean flow velocity field described for nature‐like fishways. However, more work is required to understand the effects of turbulence on the passage of non‐sport species. Copyright © 2016 John Wiley & Sons, Ltd.
- Abiotic Characterization of Brown Trout (Salmo trutta f. fario) and
Rainbow Trout (Oncorhynchus mykiss) Spawning Redds Affected by Small
Hydropower Plants — Case Studies from Austria
- Authors: W. Obruca; C. Hauer
Abstract: Salmonid rivers in Austria are considerably regulated by small hydropower facilities, resulting in potential declines of the spawning habitats of salmonids. To assess the restrictions and possible quality of hydropower‐influenced river sections for salmonid, spawning redd densities of brown trout and rainbow trout were monitored in two rivers in 2014 and 2015. The results showed spawning close to small hydropower facilities for both investigated species — with similarities in redd characteristics like pit and tail length. Differences occurred concerning the distance of redd construction to the next shore. Brown trout spawn close to the banks in comparison to rainbow trout which use the entire active channel width. In addition to the preference of brown trout for certain cover types, it turned out that the presence of high quality spawning gravel in the river is the dictating abiotic variable (probably bottleneck) in the control of salmonid populations even for river reaches impacted by small hydropower plants. Moreover, the assessments of spawning redd densities enabled a discussion of different opportunities for spawning habitat enhancement of salmonids in river sections regulated by small hydropower facilities. Here, in conclusion, it was found that the fill‐up of the backwater sites by transported sediments or the structural modification (e.g. boulder placement) in the tail of the backwater could improve the spawning situation in a sustainable way. Copyright © 2016 John Wiley & Sons, Ltd.
- Future Water Supply and Demand Management Options in the Athabasca Oil
- Authors: D. Leong; S. Donner
Abstract: The Athabasca River Basin, home to Canada's growing oil sands mining industry, faces challenging trade‐offs between energy production and water security. Water demand from the oil sands mining industry is projected to increase as climate change is projected to alter the seasonal freshwater supply. In this study, a range of water management options are developed to investigate the potential trade‐offs between the scale of bitumen production and industry growth, water storage requirements, and environmental protection for the aquatic ecosystems, under projections of mid‐century climate change. It is projected that water storage will be required to supplement river withdrawals to maintain continuous bitumen production under the impacts of future climate warming. If high growth in future bitumen production and water demand is the priority, then building sufficient water storage capacity to meet industry demand will be comparable to a week of lost revenue because of interrupted production. If environmental protection is prioritized instead, it will require over nine times the water storage costs to maintain water demand under a high industry growth trajectory. Future water use decisions will need to first, determine the scale of industry and environmental protection, and second, balance the costs of water storage against lost revenue because of water shortages that limit bitumen production. This physically based assessment of future water trade‐offs can inform water policy, water management decisions, and climate change adaptation plans, with applicability to other regions facing trade‐offs between industrial development and ecosystem water needs. Copyright © 2016 John Wiley & Sons, Ltd.
- Assessment of the Entering Stock, Migration Dynamics and Fish Pass
Fidelity of European Eel in the Belgian Meuse River
- Authors: B. Nzau Matondo; J. P. Benitez, A. Dierckx, J. C. Philippart, M. Ovidio
Abstract: Migration dynamics of incoming eels in Belgium via Lixhe in the Meuse River were investigated using two fish passes with different configurations—net traps and automatic detection stations—as tools to distinguish resident and migrating eels. From April to September 2013, 435 eels (P50 length, 403 mm; range, 196–836 mm) were caught (daily maxima catch, 90 eels per day), 90% between 13 June and 1 August (50 days) and P50 on 19 July. Eels migrated mostly at 19–26 °C (P50, 24.4 °C), river discharge 65–314 m3 s−1 (P50, 84 m3 s−1), during the dark at 00:00–05:00 h and during both the waxing and waning phases of moonlight. From 396 eels tagged and released 0.3 km downstream of the Lixhe dam, 6.8% of them were recaptured, and 37.4% were detected. Migration flux was estimated at 7184 eels (0.863 t) using the mark‐recapture method and decreased to 1156 eels (0.139 t) using automatic transponder detection. Most eels probably migrated through a sluice located downstream of Lixhe to reach the upper Meuse via the Albert Canal. Eels moved almost independently to the configuration of the fish passes and their location, but most eels displayed fidelity to the fish pass where they were captured. Migrant eels showed a wide range of size and life stages, with a higher proportion of eels (80%) belonging to the yellow eel stage. A lower proportion of eels (6%) had a larger size and presented an advanced continental silvering process corresponding to the migrating stage before their transatlantic migration. Copyright © 2016 John Wiley & Sons, Ltd.
- Historical Changes of Hydrological Connectivity of Selected Polish
- Authors: J. Dawidek; B. Ferencz
Abstract: The main ecological and hydrological features of floodplain lakes (FPL) depend on the flood pulse. Temporal variations of connectivity result from natural fluctuations in a parent river water levels. The study area was a fragment of left fraction of the Bug River valley, within a gorge‐like section between Dorohusk and Włodawa. The aim of the study was to define a duration and frequency of potamophases and limnophases of 20 FPLs, during the period 1952–2013. A large variation of limnophase frequency was observed. The most frequently occurs short (8–30 days) and medium‐length (183–365 days) limnophases. In case of potamophases the most frequent were short episodes (8–30 days). In most water bodies, a general similarity of the duration of functional periods was observed. The average ratio of the duration of both phases showed prevalence of limnophases. Generally, two factors were observed that shape variability of functional periods in the study area: quantity of water input and FPL morphometry. The lower lake volume and less stable water input, the higher variability of hydrological connectivity. Copyright © 2016 John Wiley & Sons, Ltd.
- Lethal Thermal Maxima for Age‐0 Pallid and Shovelnose Sturgeon:
Implications for Shallow Water Habitat Restoration
- Authors: D. Deslauriers; L. Heironimus, S. R. Chipps
Abstract: We evaluated temperature tolerance in age‐0 pallid and shovelnose sturgeon (Scaphirhynchus albus and Scaphirhynchus platorynchus), two species that occur sympatrically in the Missouri and Mississippi Rivers. Fish (0.04–18 g) were acclimated to water temperatures of 13, 18 or 24 °C to quantify temperatures associated with lethal thermal maxima (LTM). The results show that no difference in thermal tolerance existed between the two sturgeon species, but that LTM was significantly related to body mass and acclimation temperature. Multiple linear regression analysis was used to estimate LTM, and outputs from the model were compared with water temperatures measured in the shallow water habitat (SWH) of the Missouri River. Observed SWH temperatures were not found to yield LTM conditions. The model developed here is to serve as a general guideline in the development of future SWH. Copyright © 2016 John Wiley & Sons, Ltd.
- Potential Effects of Climate Change on Ecologically Relevant Streamflow
- Authors: S. Dhungel; D. G. Tarboton, J. Jin, C. P. Hawkins
Abstract: We assessed the climate‐driven changes in ecologically relevant flow regimes expected to occur by the year 2100 in streams across the conterminous United States. We used long‐term daily flow measurements from 601 gauged streams whose watersheds were in relatively natural condition to characterize spatial variation in 16 flow regime variables selected for their ecological importance. Principal component analysis of these 16 variables produced five uncorrelated factors that described patterns of spatial covariation in flow regimes. These five factors were associated with low flow, magnitude, flashiness, timing, and constancy characteristics of the daily flow regime. We applied hierarchical clustering to the five flow factors to classify the 601 streams into three coarses and eight more finely resolved flow regime classes. We then developed a random forest model that used watershed and climate attributes to predict the probabilities that streams belonged to each of the eight finely resolved flow regime classes. The model had a prediction accuracy (per cent correct classification) of 75%. We used the random forest model with downscaled climate (precipitation and temperature) projections to predict site‐specific changes in flow regime classes expected by 2100. Thirty‐three per cent of the 601 sites were predicted to change to a different flow regime class by 2100. Snow‐fed streams in the western USA were predicted to be less likely to change regimes, whereas both small, perennial, rain‐fed streams and intermittent streams in the central and eastern USA were predicted to be most likely to change regime. Copyright © 2016 John Wiley & Sons, Ltd.
- Effects of Moderate and Extreme Flow Regulation on Populus Growth along
the Green and Yampa Rivers, Colorado and Utah
- Authors: D. M. Schook; E. A. Carlson, J. S. Sholtes, D. J. Cooper
Abstract: River regulation induces immediate and chronic changes to floodplain ecosystems. We analysed both short‐term and prolonged effects of river regulation on the growth patterns of the keystone riparian tree species Fremont cottonwood (Populus deltoides ssp. wislizenii) at three upper Colorado River Basin rivers having different magnitudes of flow regulation. We compared cottonwood basal area increment on (i) the regulated Upper Green River below Flaming Gorge Dam; (ii) the adjacent free‐flowing Yampa River; and (iii) the partially regulated Lower Green River below their confluence. Our goal was to identify the hydrologic and climatic variables most influential to tree growth under different flow regimes. A dendrochronological analysis of 182 trees revealed a long‐term (37 years) trend of declining growth during the post‐dam period on the Upper Green, but trees on the partially regulated Lower Green maintained growth rates similar to those on the reference Yampa River. Mean annual, mean growing season, and peak annual discharges were the multicollinear flow variables most correlated to growth during both pre‐dam and post‐dam periods at all sites. Annual precipitation was also highly correlated with tree growth, but precipitation occurring during the growing season was poorly correlated with tree growth, even under full river regulation conditions. This indicates that cottonwoods rely primarily on groundwater recharged by river flows. Our results illustrate the complex and prolonged effects of flow regulation on floodplain forests, and suggest that flow regulation designed to simulate specific aspects of flow regimes, particularly peak flows, may promote the persistence of these ecosystems. Copyright © 2016 John Wiley & Sons, Ltd.
- Effects of Land Use on the Composition and Structure of Aquatic
Invertebrate Community and Leaf Breakdown Process in Neotropical Streams
- Abstract: Different land uses directly affect the characteristics of a river basin and influence the aquatic biota and ecosystem processes. This study aimed to analyse the community structure and composition of aquatic invertebrates and the role of these organisms in the process of leaf litter breakdown in streams with different land uses. The study was conducted from September to December 2013 in five streams in the Neotropical region. At each stream, we placed 18 bags containing litter for colonization by aquatic invertebrates, and the bags were collected at different exposure times (5, 30, 45, 60, 75 and 90 days). We registered spatial differences in the aquatic invertebrate community structure and composition. There were no significant differences in the activity of invertebrates in the leaf litter breakdown process among streams with different land uses. However, the variability in mass decay rate was lower for the reference stream. This result may have been influenced by habitat quality, availability of organic matter and the structure and composition of benthic community present in the reference stream, which differs significantly among locations with different types of land use. The results of this study shows that human activities, particularly agriculture and urbanization, modify the structure and composition of the benthic community and acts on ecosystem processes, especially in the variability of the processing of allochthonous material invertebrates. However, we reject the hypothesis that land use negatively influences the decomposition of litter, measured by weight loss. Copyright © 2016 John Wiley & Sons, Ltd.
- Fluvial Corridor Changes Over Time in Regulated and Non‐Regulated
Rivers (Upper Esla River, NW Spain)
- Abstract: Over the last decades, rivers and fluvial corridors have been noticeably modified from their natural conditions. In general, damming and other in‐channel human interventions have been traditionally considered as the main drivers of change. However, recent studies highlight the influence of climate, hillslope and floodplain cover changes over fluvial corridor dynamics. The present study illustrates the channel morphology and riparian vegetation responses observed in three gravel bed rivers located in the Upper Esla River, north‐west of Spain. The entire study catchment was exposed to afforestation changes and farmland abandonment during the last decades, and two of the rivers are regulated by large dams. Analysis of historical orthophotos at different periods between 1956 and 2011 allowed quantifying channel narrowing, reduction of braiding index and vegetation encroachment along the three rivers. Field reconnaissance of landforms and vegetation structure along transects showed significant differences in species composition and age structure between the non‐regulated reach, where recruitment of Salicacea pioneer species existed, and the regulated reaches where mature and late‐seral species were much more abundant. These responses were consistent with reductions in mean annual discharge in all rivers and with flood disturbance decrease and summer minimum flow increase that were observed in the regulated rivers. Copyright © 2016 John Wiley & Sons, Ltd.
- Longitudinal Variability in Hydrochemistry and Zooplankton Community of a
Large River: A Lagrangian‐Based Approach
- Authors: I. Bertani; M. Del Longo, S. Pecora, G. Rossetti
Abstract: The variability in water quality and zooplankton community structure during downstream transport was investigated in the Po river (Italy) using for the first time a Lagrangian sampling approach. Two surveys were conducted, one in spring under relatively high discharge levels, and one at low flows in summer. Twelve stations along a 332‐km stretch of the river's lowland reach and four major tributaries were sampled. A hydrodynamic modelling system was used to determine water transport time along the river, with a satisfying fit between simulated and observed discharge values. No clear downstream trend in phosphorus and nitrogen concentrations was found. Conversely, a marked longitudinal decrease in dissolved silica supports the hypothesis of increasing downstream silica limitation during the phytoplankton growing season.
In spring, at low residence time, no apparent plankton growth was observed during downstream transport. In summer, higher temperatures and lower turbulence and turbidity associated with longer residence time stimulated algal growth and in‐stream reproduction of fast‐growing rotifer taxa, with the gradual downstream development of a truly potamal assemblage and the increase of the ratio of euplanktonic to littoral/epibenthic rotifer taxa. Crustacean zooplankton density was generally low. The importance of biotic interactions within the zooplankton in driving community abundance and composition appeared to increase in the downstream direction, paralleled by a decrease in the influence of physical forcing. Tributary influence was especially evident where severe anthropogenic alterations of river hydrology and trophic status resulted in enhanced plankton growth, ultimately affecting zooplankton structure in the main river. Copyright © 2016 John Wiley & Sons, Ltd.
- Impact of Incision of Gravel‐bed Rivers on Ground Beetle Assemblages
- Abstract: The impact of river incision induced by channelization and gravel mining on the structure of ground beetle assemblages in riparian habitats was investigated on three montane rivers in southern Poland. Ground beetles were collected on three benches of different elevation in 11 incised and 14 vertically stable cross sections of the rivers. In total, 5821 individuals representing 106 species were collected. The effect of river incision on the diversity and abundance of ground beetles depended on bench height. Only on the lowest bench, inundated about once per year on average, species richness of the assemblages was significantly reduced in incised river cross sections. On this bench, the abundance of the specialists of exposed riverine sediments, i.e. small and medium‐sized predators with high dispersal power and spring breeding strategy, was highly negatively affected by river incision. On the highest bench, large, brachypterous species with spring and autumn breeding strategy, typical of undisturbed habitats, were more abundant in incised cross sections. As this bench is practically not subjected to flooding even in vertically stable cross sections, these species probably benefited from the occurrence of riparian forest along most incised river sections, whereas the riparian areas along vertically stable sections are subjected to higher agricultural pressure. This study shows that in the mountain region where high precipitation helps to maintain moisture of the riparian habitats, river incision has a negative impact only on the specialists of exposed riverine sediments. Copyright © 2016 John Wiley & Sons, Ltd.
- Downstream Passage of Fish Larvae at the Salto Grande Dam on the Uruguay
- Abstract: We evaluated the passage of early‐stage fishes through the Salto Grande Dam using high‐frequency downstream ichthyoplankton monitoring and five surveys involving samples taken upstream and downstream of the dam. Eggs and larvae of migratory fishes were captured downstream of the dam, usually during high discharges. Upstream and downstream larvae were frequently unyolked, which corresponds to individuals aged 4+ days, and represents a time significantly longer than that required for the displacement of the water mass from the dam to the sampling location. In low flow rate surveys, fish larvae of the same species and degree of development were captured immediately upstream and at 1, 10, 24 and 40 km downstream of the dam. The densities and percentage of Pimelodinae larvae captured alive by short time and low speed tows were similar upstream and downstream of the dam, indicating that larval mortality was a result of sampling and not to the passage through the turbines. The results show that the larvae of fish that spawn in the middle section are partly transported to the lower section, and suggest that both spillway and turbine discharge should be considered part of the passage. We also found evidence that the passage of small and fragile Pimelodinae larvae through the Salto Grande Kaplan turbines does not significantly affect survival rates. Copyright © 2016 John Wiley & Sons, Ltd.
- Patchiness in a Large Floodplain River: Associations Among Hydrology,
Nutrients, and Fish Communities
- Authors: N. R. De Jager; J. N. Houser
Abstract: Large floodplain rivers have internal structures shaped by directions and rates of water movement. In a previous study, we showed that spatial variation in local current velocities and degrees of hydrological exchange creates a patch‐work mosaic of nitrogen and phosphorus concentrations and ratios in the Upper Mississippi River. Here, we used long‐term fish and limnological data sets to test the hypothesis that fish communities differ between the previously identified patches defined by high or low nitrogen to phosphorus ratios (TN:TP) and to determine the extent to which select limnological covariates might explain those differences. Species considered as habitat generalists were common in both patch types but were at least 2 times as abundant in low TN:TP patches. Dominance by these species resulted in lower diversity in low TN:TP patches, whereas an increased relative abundance of a number of rheophilic (flow‐dependent) species resulted in higher diversity and a more even species distribution in high TN:TP patches. Of the limnological variables considered, the strongest predictor of fish species assemblage and diversity was water flow velocity, indicating that spatial patterns in water‐mediated connectivity may act as the main driver of both local nutrient concentrations and fish community composition in these reaches. The coupling among hydrology, biogeochemistry, and biodiversity in these river reaches suggests that landscape‐scale restoration projects that manipulate hydrogeomorphic patterns may also modify the spatial mosaic of nutrients and fish communities. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.
- Drivers of Plant Invasion at Broad and Fine Scale in Short Temperate
- Abstract: Riparian ecosystems have been described as highly prone to alien plant invasions; thus, disentangling the contributing factors of the invasion process is of utmost importance to conserving and managing these valuable ecosystems. In this study we examined the drivers of riparian plant invasion in 16 Cantabrian river basins (northern Spain) ranging from 100 to ca. 1050 km2. A complete flora was determined for five randomly selected sites within those basins. One hundred and thirty alien plant species were found across the 80 sampling sites, representing 21% of the recorded total flora. At site scale, the level of plant invasion, measured as alien richness (AR) and relative alien richness (RAR), was assessed in relation to a set of explanatory variables by means of Generalised Linear Mixed Models. This level of invasion was influenced by environmental variables such as the thermicity index, the average riverbed width and the number of plant communities and by human‐related variables such as the distance to the nearest town and the proportion of surrounding urban land. At basin scale, industrialised river basins were more heavily invaded than non‐industrialised basins, and they both differed in their alien plant composition. Given that some of the alien species occurring in Cantabrian streams are specially abundant (Crocosmia x crocosmiiflora) and/or form very dense stands (Fallopia japonica, Paspalum distichum), future research should focus on the drivers that influence the presence and distribution of these species of special concern. Copyright © 2016 John Wiley & Sons, Ltd.
- Evaluating Methods to Establish Habitat Suitability Criteria: A Case Study
in the Upper Delaware River Basin, USA
- Authors: H. S. Galbraith; C. J. Blakeslee, J. C. Cole, C. A. Talbert, K. O. Maloney
Abstract: Defining habitat suitability criteria (HSC) of aquatic biota can be a key component to environmental flow science. HSC can be developed through numerous methods; however, few studies have evaluated the consistency of HSC developed by different methodologies. We directly compared HSC for depth and velocity developed by the Delphi method (expert opinion) and by two primary literature meta‐analyses (literature‐derived range and interquartile range) to assess whether these independent methods produce analogous criteria for multiple species (rainbow trout, brown trout, American shad, and shallow fast guild) and life stages. We further evaluated how these two independently developed HSC affect calculations of habitat availability under three alternative reservoir management scenarios in the upper Delaware River at a mesohabitat (main channel, stream margins, and flood plain), reach, and basin scale. In general, literature‐derived HSC fell within the range of the Delphi HSC, with highest congruence for velocity habitat. Habitat area predicted using the Delphi HSC fell between the habitat area predicted using two literature‐derived HSC, both at the basin and the site scale. Predicted habitat increased in shallow regions (stream margins and flood plain) using literature‐derived HSC while Delphi‐derived HSC predicted increased channel habitat. HSC generally favoured the same reservoir management scenario; however, no favoured reservoir management scenario was the most common outcome when applying the literature range HSC. The differences found in this study lend insight into how different methodologies can shape HSC and their consequences for predicted habitat and water management decisions. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.
- Angler Harvest, Hatchery Return, and Tributary Stray Rates of Recycled
Adult Summer Steelhead Oncorhynchus mykiss in the Cowlitz River,
- Authors: T. J. Kock; R. W. Perry, C. Gleizes, W. Dammers, T. L. Liedtke
Abstract: Hatchery ‘recycling’ programs have been used to increase angling opportunities by re‐releasing fish into a river after they returned to a hatchery or fish trap. Recycling is intended to increase opportunities for fishermen, but this strategy could affect wild fish populations if some recycled fish remain in the river and interact with wild fish populations. To quantify hatchery return and angler harvest rates of recycled steelhead, we conducted a 2‐year study on the Cowlitz River, Washington. A total of 1051 steelhead were recycled, including 218 fish that were radio‐tagged. Fates of recycled steelhead were similar between years: 48.4% returned to the hatchery, 19.2% were reported captured by anglers, and 32.4% remained in the river. A multistate model quantified the effects of covariates on hatchery return and angler harvest rates, which were positively affected by river discharge and negatively affected by time since release. However, hatchery return rates increased and angler harvest rates decreased during periods of increasing discharge. A total of 21.1% (46 fish) of the radio‐tagged steelhead failed to return to the hatchery or be reported by anglers, but nearly half of those fish (20 fish) appeared to be harvested and not reported. The remaining tagged fish (11.9% of the radio‐tagged population) were monitored into the spawning period, but only five fish (2.3% of the radio‐tagged population) entered tributaries where wild steelhead spawning occurs. Future research focused on straying behaviour, and spawning success of recycled steelhead may further advance the understanding of the effects of recycling as a management strategy. Copyright © 2016 John Wiley & Sons, Ltd.
- A Synthesis of Stream Restoration Efforts in Florida (USA)
- Authors: D. Castillo; D. Kaplan, J. Mossa
Abstract: Studies summarizing stream restoration projects in the US are outdated and omit the majority of restoration projects in Florida. To address this gap, we compiled stream restoration data from diverse sources to create a Florida Stream Restoration Database (FSRD, available at http://www.watershedecology.org/databases.html) containing information on project type, location, completion date, and costs. The FSRD contains 178 projects categorized by restoration type, including riparian management (23%), stream reclamation (19%), flow modification (13%), bank stabilization (12%), channel reconfiguration (11%), in‐stream habitat improvements (11%), floodplain reconnection (6%), invasive species removal (4%), and dam removal (1%). Projects were spatially clustered into three geographic regions, providing insight on the diversity of initiatives, needs, and funding sources of land management agencies and private landowners that motivated restoration efforts. Projects in the Florida panhandle emphasized in‐stream habitat restoration, while peninsular projects were dominated by flow modification, and projects in the west central region focused on stream reclamation to mitigate surface mining practices and water quality and habitat improvements in tidal streams. Results suggest that Florida is spending much more on stream restoration than previously documented. Between 1979 and 2015, the mean and median stream restoration project costs in Florida were $15.4 million and $180 000, respectively, indicating a strongly skewed distribution because of the large Kissimmee River restoration project in central Florida. This work highlights the need for, and utility of, statewide and national restoration databases to improve restoration tracking. This need will become increasingly critical as more stringent water quality and habitat mitigation rules are implemented across the country. Copyright © 2016 John Wiley & Sons, Ltd.
- Informing Watershed Connectivity Barrier Prioritization Decisions: A
- Authors: S. K. McKay; A. R. Cooper, M. W. Diebel, D. Elkins, G. Oldford, C. Roghair, D. Wieferich
Abstract: Water resources and transportation infrastructure such as dams and culverts provide countless socio‐economic benefits; however, this infrastructure can also disconnect the movement of organisms, sediment, and water through river ecosystems. Trade‐offs associated with these competing costs and benefits occur globally, with applications in barrier addition (e.g. dam and road construction), reengineering (e.g. culvert repair), and removal (e.g. dam removal and aging infrastructure). Barrier prioritization provides a unique opportunity to: (i) restore and reconnect potentially large habitat patches quickly and effectively and (ii) avoid impacts prior to occurrence in line with the mitigation hierarchy (i.e. avoid then minimize then mitigate). This paper synthesizes 46 watershed‐scale barrier planning studies and presents a procedure to guide barrier prioritization associated with connectivity for aquatic organisms. We focus on practical issues informing prioritization studies such as available data sets, methods, techniques, and tools. We conclude with a discussion of emerging trends and issues in barrier prioritization and key opportunities for enhancing the body of knowledge. Copyright © 2016 John Wiley & Sons, Ltd.
- A Multi‐scale, Hierarchical Model to Map Riparian Zones
- Authors: J. A. Salo; D. M. Theobald
Abstract: Riparian zones are important for their contribution to biodiversity and ecosystem services, especially in the western USA where riparian zones occupy a small proportion of the landscape but support a majority of the biodiversity. However, few accurate datasets of riparian zone locations are available over broad spatial extents, and cost efficient methods to map riparian zones at fine spatial resolutions do not currently exist. We created a multi‐scale, hierarchical, and process‐guided method to map the location of riparian zones using readily available, national datasets. We demonstrate the applicably of this straightforward method in the Southern Rockies Ecoregion, where we mapped both current riparian zones (the riparian zone that is not strongly modified by human land uses and is assumed to support natural riparian vegetation) and potential riparian zones (the area that would likely support natural riparian vegetation in the absence of human activity). The overall accuracy of our method for potential and current riparian zones was 92%. The Southern Rockies Ecoregion is composed of 3.1% (±0.3%) potential and 2.5 (±0.2%) current riparian zones, indicating that roughly 21.0% (±0.5%) of riparian zones have been removed by human activities. This modelling approach can be used to create detailed maps of riparian zones to inform regional conservation and management decision‐making, and the methods can be applied to different regions at multiple scales from small watersheds to a national analysis. Copyright © 2016 John Wiley & Sons, Ltd.
- Fish and Benthic Macroinvertebrate Assemblage Response to Removal of a
Partially Breached Lowhead Dam
- Authors: D. P. Gillette; K. Daniel, C. Redd
Abstract: Dam removal is an increasingly common restoration technique in lotic ecosystems. Potential dam removal benefits include improved aquatic organism passage, restoration of natural flow dynamics and a general improvement in habitat for native species. However, understanding potential dam removal outcomes requires data on ecosystem response in a wide variety of settings. We evaluated fish and benthic macroinvertebrate response to removal of the Spruce Pine dam in western North Carolina, USA. This dam was partially breached prior to removal, and impounded a coolwater river, both scenarios under which dam removal has been under‐studied. Post‐removal shifts in fish and benthic macroinvertebrate assemblages did not occur, suggesting that previously documented patterns of assemblage change in response to dam removal, particularly in the area upstream from the dam, are not universal, and may depend upon factors such as river gradient and water temperature, and the available species pool. Such information can aid managers in identifying conditions under which an expectation of significant instream habitat improvement in response to dam removal may not be warranted. Copyright © 2016 John Wiley & Sons, Ltd.
- Recruitment Sources of Channel and Blue Catfishes Inhabiting the Middle
- Authors: T. W. Laughlin; G. W. Whitledge, D. C. Oliver, N. P. Rude
Abstract: Insight into environments that contribute recruits to adult fish stocks in riverine systems is vital for effective population management and conservation. Catfishes are an important recreational species in the Mississippi River and are commercially harvested. However, contributions of main channel and tributary habitats to catfish recruitment in large rivers are unknown. Stable isotope and trace elemental signatures in otoliths are useful for determining environmental history of fishes in a variety of aquatic systems, including the Mississippi River. The objectives of this study were to identify the principal natal environments of channel catfish Ictalurus punctatus and blue catfish Ictalurus furcatus in the Middle Mississippi River (MMR) using otolith stable oxygen isotopic composition (δ18O) and strontium : calcium ratios (Sr : Ca). Catfishes were sampled during July–October 2013–2014, and lapilli otoliths were analysed for δ18O and Sr : Ca. Water samples from the MMR and tributaries were collected seasonally from 2006 to 2014 to characterize site‐specific signatures. Persistent differences in water δ18O and Sr : Ca among the MMR and tributaries (including the upper Mississippi, Illinois, and Missouri rivers as well as smaller tributaries) were evident, enabling identification of natal environment for individual fish. Blue and channel catfish stocks in the MMR were primarily recruited from the large rivers (Missouri and Mississippi) in our study area, with minimal contributions from smaller tributaries. Recruitment and year class strength investigations and efforts to enhance spawning and nursery habitats should be focused on in large rivers with less emphasis on smaller tributaries. Copyright © 2016 John Wiley & Sons, Ltd.
- The Migratory Behaviour and Fallback Rate of Landlocked Atlantic Salmon
(Salmo salar) in a Regulated River: does Timing Matter?
- Authors: A. Hagelin; O. Calles, L. Greenberg, D. Nyqvist, E. Bergman
Abstract: The behavior of early (June–July) and late (August–September) migrating, adult Atlantic salmon, in The River Klarälven, Sweden, was analyzed using radio telemetry. River Klarälven is a regulated river without functioning fishways, instead upstream migrating salmon are trapped and trucked past eight hydropower plants before released back to the river. We distinguished two parts of the spawning migration, that is, one part being the migration from the place where the fish was released to the spawning grounds. The other part was a holding phase on the spawning grounds with little or no movements before spawning. The late salmon spent less of their total time on holding, 36.2%, and more on migration, 63.8%, compared with early migrating salmon, which distributed their time rather evenly between migration, 47.5%, and holding, 52.5%. In total, early salmon used 30% more time migrating and 156% more time holding than late salmon. Some Atlantic salmon (Salmo salar) fell back over the hydropower plant after release and got excluded from spawning. The fallback rates of transported, tagged spawners were higher in the early than in the late group in both years. The fallback rate in 2012 was 42.8% of the early group and 15.1% in the late. In 2013, there were 51.7 % fallbacks in the early group and 3.4% in the late. The salmon fell back on average 9 days after being released in 2012 and 16 days in 2013. A high mean daily discharge on the day of release increased the probability of becoming a fallback. Copyright © 2016 John Wiley & Sons, Ltd.
- Increasing River Flow Expands Riparian Habitat: Influences of Flow
Augmentation on Channel Form, Riparian Vegetation and Birds Along the
Little Bow River, Alberta
- Authors: E. J. Hillman; S. G. Bigelow, G. M. Samuelson, P. W. Herzog, T. A. Hurly, S. B. Rood
Abstract: With river regulation, water withdrawal is common, reducing instream flows. The opposite alteration, flow augmentation, is less common and could reveal a mechanistic coordination between flow regime, channel form, and riparian ecosystems. The Little Bow River, a naturally intermittent prairie stream in Southern Alberta, has experienced flow augmentation since the late 1890s, and the Little Bow/Highwood Project of 2004 enabled a tripling of diversion flows from 2.9 to 8.5 m3/s. We investigated the subsequent responses by assessing the channel form and riparian vegetation based on aerial photographs taken in 2000 versus 2010, and riparian birds were assessed between 2005 and 2013 to investigate associations with riparian vegetation. Following recent flow augmentation, the mean channel width increased from 12.2 to 13.5 m, while sinuosity was relatively unchanged. Streamside zones with true willows (especially Salix exigua and Salix bebbiana) increased from 7 to 11% of the river corridor, and the facultative riparian wolf willow (Elaeagnus commutata) zones increased from 16 to 20%, while grassy zones decreased from 64 to 52%. Avian species richness and Shannon–Wiener index increased, while species evenness was relatively unaltered, suggesting an increase of rarer bird species in response to the increased habitat structure and diversity following the expansion of riparian shrubs and woodland. This study revealed responses to the recent flow augmentation over the first decade of implementation, and alterations following flow augmentation would likely continue for decades until the river and riparian zones adjust to the new flow regime. Copyright © 2016 John Wiley & Sons, Ltd.
- An Approach to Simulate Interstitial Habitat Conditions During the
Incubation Phase of Gravel‐Spawning Fish
- Authors: M. Noack; J. Ortlepp, S. Wieprecht
Abstract: The incubation period represents an important development phase for successful reproduction of gravel‐spawning fish, whereby colmation processes can affect the quality of the interstitial habitat. From a sedimentary perspective, the infiltration and accumulation of fine sediments can result in a reduction of the pore space and limit the transport of oxygen‐rich surface water in the interstitials of riverbeds. From a biogeochemical perspective, the increased surface area for microbial growth can lead to an increase of respiration rates, which additionally limits the oxygen supply. The assessment and prediction of such processes on interstitial habitat quality represents a challenging task given their complex dynamic interacting processes and their high spatio‐temporal variability. This study presents a new habitat‐based modelling approach, which simulates interstitial habitat suitability (IHS) to evaluate dynamically the quality of interstitial habitat conditions during incubation. For this purpose, three key parameters (hydraulic conductivity, interstitial temperature and hyporheic respiration) are linked to the habitat requirements of different developmental stages during the incubation period (egg, hatching, larvae) via a multivariate fuzzy approach. The proposed modelling concept has been developed on the River Spoel in Switzerland, whereby results of a numerical 3D sediment transport model, together with supplementary measurements, deliver the spatio‐temporal variations of the required input data. The fuzzy approach provides results in form of maps and time series of IHS values to allow for an identification of abiotic bottlenecks during the incubation period. Hence, this approach represents a significant contribution for the restoration of reproduction areas of gravel‐spawning fish. Copyright © 2016 John Wiley & Sons, Ltd.
- Assessing the Distribution and Changes of Instream Woody Habitat in
South‐Eastern Australian Rivers
- Authors: Z. Tonkin; A. Kitchingman, R. M. Ayres, J. Lyon, I. D. Rutherfurd, J. C. Stout, P. Wilson
Abstract: Managers and communities are now artificially reintroducing instream woody habitat (IWH) to rivers following historic large‐scale removal. Riverscape‐scale datasets that quantify existing habitat conditions are fundamental to setting the priorities and allocating resources for such programs. Unfortunately, such datasets are rare, primarily because existing assessment approaches are limited in their accuracy (remote sensing) or are costly and labour intensive (field assessments). This study used both field assessments and aerial data to improve the accuracy of remotely sensed measures of IWH and estimate current IWH volumes and subsequent condition (compared with reference levels) across approximately 28 000 km of stream in the south‐eastern Australian state of Victoria.
We found that aerial measures, when used in conjunction with measures of stream size and riparian overhang, produced significantly better estimates of IWH loads than using aerial data alone. The statewide assessment indicated that streams currently have IWH volumes, on average, 41% lower than reference levels that represented an average reduction of 0.0207 m3 m−2. The degree of IWH condition was highly variable across regions (20–95% reductions from reference levels), a likely reflection of regional variation in land use practices and past river work activities.
This scale of IWH reduction may pose major negative impacts on the ecological integrity of these streams. Whilst the approach used during this study has temporal and spatial limitations, it was designed as a generalised, rapid and relatively inexpensive method to measure stream condition and assist with priority setting at state and regional levels. Copyright © 2016 John Wiley & Sons, Ltd.
- Riverine Landscape Patches Influence Trophic Dynamics of Riparian Ants
- Authors: P. Tagwireyi; S. M. P. Sullivan
Abstract: Food webs in riparian corridors are increasingly viewed as embedded in complex riverine landscapes characterized by an amalgam of aquatic, semi‐aquatic, and terrestrial habitats. However, the influence of riverine landscape pattern on trophic dynamics of riparian consumers remains largely unknown. We used naturally abundant stable isotope ratios (δ15N) to compare trophic structure of ants (Formica subsericea) among riparian patch types (crop, grass/herbaceous, gravel bar, lawn, mudflat, shrub, swamp, and woody vegetation) at 12 riverine landscapes distributed along an urban‐rural landscape gradient of the Scioto River, Ohio, USA. We expected that the diet of F. subsericea, a common generalist consumer, would reflect local prey availability and thus differences in trophic dynamics among patch types. Mean ant δ15N was higher in crop patches than in any other patch type, and was lowest in grass/herbaceous, lawn, shrub, and woody vegetation patches, suggesting that patch type was associated with trophic position of F. subsericea. We also found that the range of δ15N, and thus trophic breadth, was significantly different by patch type, with woody vegetation exhibiting the greatest spread. Variability in canopy, tree and shrub cover, and the degree of urban development was positively correlated with δ15N range (R2 = 0.78), pointing to the role of habitat structure in mediating trophic breadth of riparian ants. These findings provide evidence that riverine landscape pattern can strongly influence trophic dynamics of riparian arthropods. Copyright © 2016 John Wiley & Sons, Ltd.
- Growth and Smoltification of Three Norwegian Strains of Atlantic Salmon
Salmo salar Reared under Different Thermal Regimes
- Authors: A. K. Imsland; K. Pettersen, S. O. Stefansson
Abstract: A comparative study was performed with juvenile Atlantic salmon Salmo salar from three stocks in Western Norway that differ in their natural conditions. One is from warm, lowland river conditions (Årdal), one is from cold glacial river conditions (Stryn) and the last one (Suldalslågen) is from a hydropower‐regulated river. The salmon parr were tagged and reared at 4, 5.5 and 7 °C and simulated natural water temperature (SNT) for river Suldalslågen. Size distribution was unimodal at 4 °C, with a change to a bimodal distribution, representing potential 1+ and 2+ smolts, at the other temperature regimes. The relative biomass of 1+ smolts varied between the stocks as Stryn (cold glacial river) stock had the highest number of smolts at 7 °C and the Suldalsågen stock (hydropower‐regulated river) displaying the highest number at the SNT regime. Overall, the Stryn stock, originating from cold river conditions, seemed to be well adapted to growth and smoltification at cold temperatures, whereas salmon parr from river Suldalslågen seem to be better adapted to the natural temperature regime (SNT) of this river than the other two stocks. This was reflected in the gill Na+,K+‐ATPase as the Suldalslågen stock showed increasing activity from 16 April (4.2 µmol ADP mg protein−1 h−1) to 10 May (9.2 µmol ADP mg protein−1 h−1), and at the end of the experiment, enzyme activity in Suldalslågen stock was significantly higher than both Stryn (5.7) and Årdal (5.9 µmol ADP mg protein−1 h−1) stock. In contrast, the warm lowland stock, Årdal, fish had low Na+,K+‐ATPase activity with no distinct peak at any of the sampled dates from March through May. Copyright © 2016 John Wiley & Sons, Ltd.
- Influence of Hydrological Connectivity on Plankton Communities in Natural
and Reconstructed Side‐Arms of a Large New Zealand River
- Authors: M. A. Ginders; K. J. Collier, I. C. Duggan, D. P. Hamilton
Abstract: We sampled natural and reconstructed side‐arms during different stages of hydrological connectivity with a large floodplain river in northern New Zealand, to determine whether re‐establishment of connectivity would be an effective strategy for restoring plankton communities in former side‐arms. Connectivity between side‐arms and the river was moderated by water level and influenced flow rates and closure of inlets and outlets. Physicochemical conditions were more strongly related to the connectivity phase than to habitat type (river, natural or reconstructed side‐arm), except during low connectivity when natural side‐arms in particular were characterised by higher ammonium (NH4‐N) and total phosphorus (P) concentrations, as well as specific conductivity. Dissolved reactive phosphorus (PO4‐P), water temperature, conductivity and dissolved oxygen were identified as explanatory variables of phytoplankton and zooplankton community composition, which along with total nitrogen (phytoplankton) or total suspended solids (zooplankton) explained 44–52% of variation. Phytoplankton community composition and the abundance of several dominant or discriminatory taxa were affected by connectivity but not habitat type, whereas habitat and connectivity both had significant effects on zooplankton communities and abundances of the cladoceran Bosmina meridionalis. Significant interactions between connectivity and paired habitat types occurred for abundances of the diatom Asterionella, the cryptophyte Cryptomonas, the rotifer Synchaeta oblonga and cyclopoid copepods, reflecting differential responses to connectivity among habitats by these taxa. Overall, these results underscore the importance of hydrological connectivity between side‐arms and rivers in moderating plankton community composition, and highlight unpredictable trajectories of community development and alternative transient states that can occur soon after side‐arm reconnection. Copyright © 2016 John Wiley & Sons, Ltd.
- Regional Statistical and Precipitation–Runoff Modelling for
Ecological Applications: Prediction of Hourly Streamflow in Regulated
Rivers and Ungauged Basins
- Authors: Teklu T. Hailegeorgis; K. Alfredsen
Abstract: Prediction of natural streamflow in regulated rivers for derivation of ecologically relevant streamflow metrics (ERSFMs) and prediction in ungauged basins (PUB) are important in management of water resources. However, specific studies on comparison of methods for predicting hourly flow regime relevant to ecological study in regulated (hydropeaking) rivers are rare in literature. Therefore, using catchments in mid Norway, we performed comparative evaluation of prediction of hourly streamflow series and flow duration curves (FDCs) in ungauged basins. We developed a regional regression model based on relationships among streamflow percentiles and drainage areas and performed a regional calibration of a streamflow recession based precipitation–runoff (P–R) model.
A leave one out cross‐validation procedure was used to evaluate the regional models. The results indicate that the regional regression model with transferring of streamflow information based on the nearest neighbour performed better than both transferring optimal parameters from local calibration and regional parameter sets corresponding to maximum regional weighted average Nash–Sutcliffe efficiency of the P–R model (NSEMRWA). We also evaluated the models based on prediction of some environmental indices: the daily range, daily standard deviation, flashiness, maximum ramping rate, number of rise and falls and daily flow changes. However, both modelling strategies predicted hourly streamflow indices well and appeared stable over most indices while the largest differences occurred in the rise and fall counts.
The models were further applied for prediction of the natural streamflow time series at Sokna hydropeaking plant. The observed hydrograph exhibits continuous sudden fluctuations while the predicted natural flow hydrograph exhibits smooth pattern. The within a year FDCs for observed flow exhibits sharp transitions from high to low flows. There is clear differences between the environmental indices obtained for the observed and the modelled data series, with the general observation that the NSEMRWA computing a smaller variability than the regression model. Copyright © 2016 John Wiley & Sons, Ltd.
- Comparison of Direct and Indirect Boundary Shear Stress Measurements along
- Abstract: Estimates of boundary shear stress along vegetated streambanks are needed to predict streambank fluvial erosion. Because fluvial shear stress cannot be directly measured in the field, reliable estimation techniques using field instrumentation are needed. This study evaluated local bank shear stress estimation methods applicable to sloping, vegetated streambanks. Two reaches of a second order stream were modelled in a flume using a fixed‐bed Froude‐scale modelling technique. One reach was dominated by dense shrubs while the other reach was located in a mature forest. Direct measurements of local bank shear stress using a hot‐film anemometer were compared to estimates based on velocity measurements (logarithmic method, Reynolds stresses, and turbulent kinetic energy). For channels with no or widely spaced vegetation, the velocity‐based estimates underestimated the bank shear stress due to secondary flow contributions. For banks with dense vegetation, Reynolds stresses and turbulent kinetic energy estimates were statistically similar to direct measurements on average, but substantial error occurred when making point comparisons. Velocity‐based estimates generally over predicted bank stress in areas of high shear at the vegetation edge and underpredicted stress within dense vegetation. Ultimately, results suggest that none of tested techniques can be broadly applied to streambanks, and flow structure is critical in selecting the appropriate estimation technique. Copyright © 2016 John Wiley & Sons, Ltd.
- Classification of US Hydropower Dams by their Modes of Operation
- Abstract: A key challenge to understanding ecohydrologic responses to dam regulation is the absence of a universally transferable classification framework for how dams operate. In the present paper, we develop a classification system to organize the modes of operation (MOPs) for US hydropower dams and powerplants. To determine the full diversity of MOPs, we mined federal documents, open‐access data repositories, and internet sources. We then used CART classification trees to predict MOPs based on physical characteristics, regulation, and project generation. Finally, we evaluated how much variation MOPs explained in sub‐daily discharge patterns for stream gages downstream of hydropower dams. After reviewing information for 721 dams and 597 power plants, we developed a two‐tier hierarchical classification based on (i) the storage and control of flows to powerplants, and (ii) the presence of a diversion around the natural stream bed. This resulted in nine tier‐1 MOPs representing a continuum of operations from strictly peaking, to reregulating, to run‐of‐river, and two tier‐2 MOPs, representing diversion and integral dam‐powerhouse configurations. Although MOPs differed in physical characteristics and energy production, classification trees had low accuracies (≤62%), which suggested that accurate evaluations of MOPs may require individual attention. MOPs and dam storage explained 20% of the variation in downstream subdaily flow characteristics and showed consistent alterations in subdaily flow patterns from reference streams. This standardized classification scheme is important for future research including estimating reservoir operations for large‐scale hydrologic models and evaluating project economics, environmental impacts, and mitigation. Copyright © 2016 John Wiley & Sons, Ltd.
- Age‐0 Shovelnose Sturgeon Prey Consumption in the Lower Missouri
- Authors: N. J. C. Gosch; M. L. Miller, T. R. Gemeinhardt, T. A. Starks, A. P. Civiello, J. M. Long, J. L. Bonneau
Abstract: A lack of nutritious food during the first year of life is a hypothesized factor that may limit survival of endangered pallid sturgeon Scaphirhynchus albus in the lower Missouri River (LMOR). Unfortunately, information for age‐0 pallid sturgeon diets remains limited, but diet analyses for age‐0 Scaphirhynchus spp. (sturgeon hereafter) have occurred. Little information, however, exists on age‐0 sturgeon diets in the LMOR; thus, our primary objective was to document age‐0 sturgeon diets in this system. We examined guts contents from 30 individuals, which were genetically identified as shovelnose sturgeon Scaphirhynchus platorynchus, and three stomachs were empty. The remaining age‐0 shovelnose sturgeon consumed chironomid larvae almost exclusively (>98% of prey items consumed). Our results were similar to studies conducted in other systems, and it appears unlikely that a lack of nutritious food was a major factor affecting the individuals captured during this study. This effort provides important information to help guide ongoing adaptive management efforts in the LMOR. © 2016 The
Authors . River Research and Applications published by John Wiley & Sons Ltd.
- Restoration of Hydrochory Following Dam Removal on the Elwha River,
- Authors: E. S. Cubley; R. L. Brown
Abstract: Hydrochory, seed dispersal by water, affects riparian vegetation by contributing to downstream community composition and diversity. However, dams can block hydrochory, reducing downstream species diversity and fragmenting riparian corridors. Dam removal is becoming more prevalent for economic and ecological reasons and is expected to restore hydrochory; however, this has never been documented in rivers. The largest dam removal project to date was the 2011 to 2014 removal of the Glines Canyon and Elwha dams on the Elwha River in Washington. Prior to dam removal, hydrochory was lower below Glines Canyon Dam compared with an upstream reach; our objective was to test the hypothesis that dam removal would restore downstream hydrochory to levels observed in the upstream reach. To test this, we collected seeds in nets above and below the dam during three sample periods (early July, late July and early August), growing out seeds in a greenhouse and comparing seed abundance and species richness above and below dams, before and after dam removal. We found that after dam removal, the average number of hydrochorous seeds and species increased below Glines Canyon Dam to levels similar to or higher than that of the upstream reach; hydrochory levels in the upstream reach did not change. This study is the first to document the restoration of hydrochory in rivers following removal of a large dam. Restoration of hydrochory may ultimately increase downstream vegetation diversity and play a role in the recolonization of reservoir sediments deposited in the riparian zone in the years following dam removal. Copyright © 2016 John Wiley & Sons, Ltd.
- A Quantitative Framework to Derive Robust Characterization of Hydrological
- Authors: T. J. Brummer; A. E. Byrom, J. J. Sullivan, P. E. Hulme
Abstract: If ecological management of river ecosystems is to keep pace with increasing pressure to abstract, divert and dam, we must develop general flow–ecology relationships to predict the impacts of these hydrologic alterations. Regional flow gradient analyses are a promising tool to quickly reveal these functional relationships, but there are considerable uncertainties in this method because of variability in the historical extent of flow data across different rivers, combined with multiple indices characterizing the ecological attributes of flow regimes. In response, we outline an objective framework for analysing spatial hydrologic gradients that addresses three major sources of uncertainty: robust estimation of flow indices, the potential for temporal trends to confound spatial variation in flow regimes and the statistical robustness to detect underlying hydrological gradients. The utility of our framework was examined in relation to flow regimes across multiple braided river catchments in Canterbury, New Zealand. We found that a subset of flow indices could be robustly estimated using only 10 years of flow data, although indices that captured flow ‘timing’ required longer time series. Temporal trends were unlikely to confound conclusions from a spatial hydrologic gradient analysis, and there were three statistically supported hydrologic gradients related to flow magnitude, flow variability and low flow events. The widespread application of robust spatial flow gradient analyses has the potential to further our understanding of how altered flow regimes affect the ecology of freshwater and riparian ecosystems, thereby providing the evidence base to inform river management. Copyright © 2016 John Wiley & Sons, Ltd.
- Long‐reach Biotope Mapping: Deriving Low Flow Hydraulic Habitat from
- Abstract: Understanding of the type and distribution of hydraulic habitat along watercourses is valuable from an ecological and a morphological perspective. The data quantify system state and may be used against benchmark criteria to define system status level and degradation. Current mapping techniques are subjective, time consuming and expensive when carried out over long reaches often requiring specialist field skills. This paper proposes a novel approach to hydraulic habitat mapping using readily available aerial imagery (GoogleEarth and Bing maps) to generate long‐reach digital elevation models, which are subsequently used in a 2D modelling domain (JFlow+) to predict hydraulic habitat in the form of biotope types and distribution from Froude number classification. The approach is tested on a 1‐km reach of the river Wharfe, England, a morphologically and hydraulically varied watercourse. Biotope mapping of the study reach recorded a distribution of 49% pools, 33% glides and 17% riffles, compared with an observed 54% pools, 32% glides, 13% riffles and 1% broken standing waves/chutes, suggesting that gross biotope distribution may be reliably mapped using the technique when compared with field mapping but that depth estimation error leads to classification issues around transition zones. The improved spatial detail and objective mapping achieved by the technique also provide valuable sub‐feature detail on hydraulic habitat variation not picked up by conventional survey. The ease of digital elevation model construction allows for rapid assessment of extended reaches offering an efficient mechanism for whole river ecological assessment, flagging critical sites that would benefit from more detailed field assessment. Copyright © 2016 John Wiley & Sons, Ltd.
- Benthic Response to Flow Alteration in a New Mexico Arid Mountain Stream
- Authors: C. Wiseman; B. Marotz, J. Caldwell, R. Sherrick, D. Ward
Abstract: Past and current pressure on streams and rivers for consumptive use requires the development of tools and decision‐making processes for water managers to minimize impacts on ecological function. This paper examines the utility of modeling benthic biomass in relation to benthic macroinvertebrate (BMI) community attributes for water resource management scenarios in the Cliff‐Gila Valley of the Gila River, New Mexico, USA. The river benthos biomass model (RivBio) was used in conjunction with hydraulic modeling to predict growth and decline of benthic biomass. BMI community attributes were compared along gradients of hydrologic impact (successive existing diversions) in the Cliff Gila Valley and were compared to community attributes in similar regional streams. Benthic biomass was minimally affected by proposed diversions at flows above 4.25 cms (150 cfs), but was severely reduced downstream because of existing diversions during lower flow periods. Riffle habitat was disproportionately affected during extreme low and interrupted flow, which may have resulted in BMI communities shifted towards multi‐habitat generalists that can persist in lentic conditions. Flow augmentation from proposed diversions and storage would greatly mitigate these existing biomass losses by providing consistent base flow and lotic conditions in riffle habitat. Both benthic biomass and BMI community endpoints were useful when comparing water management scenarios. Copyright © 2016 John Wiley & Sons, Ltd.
- Predicting Thermally Stressful Events in Rivers with a Strategy to
Evaluate Management Alternatives
- Authors: K. O. Maloney; J. C. Cole, M. Schmid
Abstract: Water temperature is an important factor in river ecology. Numerous models have been developed to predict river temperature. However, many were not designed to predict thermally stressful periods. Because such events are rare, traditionally applied analyses are inappropriate. Here, we developed two logistic regression models to predict thermally stressful events in the Delaware River at the US Geological Survey gage near Lordville, New York. One model predicted the probability of an event >20.0 °C, and a second predicted an event >22.2 °C. Both models were strong (independent test data sensitivity 0.94 and 1.00, specificity 0.96 and 0.96) predicting 63 of 67 events in the >20.0 °C model and all 15 events in the >22.2 °C model. Both showed negative relationships with released volume from the upstream Cannonsville Reservoir and positive relationships with difference between air temperature and previous day's water temperature at Lordville. We further predicted how increasing release volumes from Cannonsville Reservoir affected the probabilities of correctly predicted events. For the >20.0 °C model, an increase of 0.5 to a proportionally adjusted release (that accounts for other sources) resulted in 35.9% of events in the training data falling below cutoffs; increasing this adjustment by 1.0 resulted in 81.7% falling below cutoffs. For the >22.2 °C these adjustments resulted in 71.1% and 100.0% of events falling below cutoffs. Results from these analyses can help managers make informed decisions on alternative release scenarios. Copyright © 2016 John Wiley & Sons, Ltd.
- Determining the Efficacy of a Submersible in situ Fluorometric Device for
Cyanobacteria Monitoring Coalesced with Total Suspended Solids
Characteristic of Lowland Reservoirs
- Authors: E. Symes; F. Ogtrop
Abstract: The purpose of this study was to ascertain the effect of turbid water on a fluourometric device designed to detect phycocyanin and chlorophyll a in cyanobacteria cells in vivo. Cell densities corresponding to the Blue Green Algae Alert levels endorsed by the Australian National Health and Medical Research Council and adopted by numerous water resource managers were coalesced with a range of total suspended solids at defined gradients characteristic of lowland freshwater ecosystems. The parameters of interest were phycocyanin and chlorophyll a. Microcystis aeruginosa was the experimental organism used to establish cell densities consistent with the three‐stage alert level framework. We found phycocyanin to be an effective measure for detecting M. aeruginosa at concentrations prescribed within the cyanobacterial alert levels (Green, Amber and Red) in turbid waters up to 200 Nephelometric Turbidity Units. Copyright © 2016 John Wiley & Sons, Ltd.
- Time and Intensity Weighted Indices of Fluvial Processes: a Case Study
from the Kootenai River, USA
- Authors: G. Egger; E. Politti, E. Lautsch, R. M. Benjankar, S. B. Rood
Abstract: Within riparian landscapes, river flows and stages determine habitat gradients from less to more dynamic, and these support different plant species and their life history stages that are adapted to specific positions along these gradients. The gradients are characterized by physical processes that vary in magnitude and duration, and these shape the riparian vegetation communities. Consequently, natural riparian ecosystems are very dynamic, and the river disturbance regime is essential for sustaining ecosystem health. However, although the importance of disturbance is well accepted, disturbance regimes are poorly understood. This study was undertaken to develop indices capable of characterizing riparian habitats by considering flood magnitude and the elapsed time after flood disturbance, that is, the history that influenced the present vegetation composition. The indices were tested along two reaches of the Kootenai River in Idaho, USA, with braided versus meandering channel forms. The case study spanned a 31‐year period and emphasized two major disturbance components, the morphodynamic influence of velocity and shear stress and the flood or inundation duration. Computed indices were tested for consistency and then used to characterize different riparian vegetation development and succession phases. The statistical analysis revealed high correspondence among the calculated indices and differences across the different successional stages and between the two reaches. This demonstrated the utility of the time and intensity weighted indices to analyse the fluvial patterns that support different riparian vegetation communities, and this could be applicable for riparian management, mitigation, conservation and restoration. Copyright © 2016 John Wiley & Sons, Ltd.
- Issue Information ‐ TOC
- Pages: 821 - 822
Abstract: No abstract is available for this article.
- Vale Keith Walker 1946 – 2016
- Authors: F. Sheldon; M. Geddes
Pages: 1138 - 1139