- Effective Acquisition Protocol of Terrestrial Laser Scanning for
Underwater Topography in a Steep Mountain Channel
- Authors: N. Miura; Y. Asano
Abstract: For better risk management, detailed and quantitative measurement of channel and stream‐bed structure is required to understand and predict water and sediment flow in mountain channels. Our previous research demonstrated good performance of green‐wavelength Terrestrial laser scanning (TLS) for measurement of submerged stream‐bed in a steep mountain channel. This paper examines how the acquisition protocol of TLS affects the accuracy of data collected in the mountain channel. First, it was tested whether varying the scanner height, i.e., incident angle affects the data acquisition in terms of point density and accuracy in the pool unit of step‐pool channel. Then, the effect of varying the minimum point spacing on the derived Digital terrain model (DTM) was examined. It was also analyzed whether a combination of multiple TLS data acquired from different directions would improve the accuracy of data compared to data acquired by a single measurement. Furthermore, TLS data were acquired over a cascade unit of the channel and examined whether TLS is capable of capturing reliable underwater data. All the acquired underwater data by TLS were corrected for water refraction and validated using manual surveyed data. The results showed that the accuracy of derived DTM was improved when the scanner height was increased or data was acquired from multiple directions, however, acquiring denser point cloud with a minimum point spacing of 1 mm did not improve the accuracy of the data. Accuracy of TLS measurement in the cascade unit was considerably lower. Special consideration is required for this area.
- Establishing Environmental Water Requirements for the Murray–Darling
Basin, Australia's Largest Developed River System
- Authors: J. L. Swirepik; I. C. Burns, F. J. Dyer, I. A. Neave, M. G. O'Brien, G. M. Pryde, R. M. Thompson
Abstract: There is a global need for management of river flows to be informed by science to protect and restore biodiversity and ecological function while maintaining water supply for human needs. However, a lack of data at large scales presents a substantial challenge to developing a scientifically robust approach to flow management that can be applied at a basin and valley scale. In most large systems, only a small number of aquatic ecosystems have been well enough studied to reliably describe their environmental water requirements. The umbrella environmental asset (UEA) approach uses environmental water requirements developed for information‐rich areas to represent the water requirements of a broader river reach or valley. We illustrate this approach in the Murray–Darling Basin (MDB) in eastern Australia, which was recently subject to a substantial revision of water management arrangements. The MDB is more than 1 million km2 with 18 main river valleys and many thousands of aquatic ecosystems. Detailed eco‐hydrologic assessments of environmental water requirements that focused on the overbank, bankfull and fresh components of the flow regime were undertaken at a total of 24 UEA sites across the MDB. Flow needs (e.g. flow magnitude, duration, frequency and timing) were established for each UEA to meet the needs of key ecosystem components (e.g. vegetation, birds and fish). Those flow needs were then combined with other analyses to determine sustainable diversion limits across the basin. The UEA approach to identifying environmental water requirements is a robust, science‐based and fit‐for‐purpose approach to determining water requirements for large river basins in the absence of complete ecological knowledge. Copyright © 2015 John Wiley & Sons, Ltd.
- Effects of Dam Removal on Tule Fall Chinook salmon Spawning Habitat in the
White Salmon River, Washington
- Authors: J. R. Hatten; T. R. Batt, J. J. Skalicky, R. Engle, G. J. Barton, R. L. Fosness, J. Warren
Abstract: Condit Dam is one of the largest hydroelectric dams ever removed in the USA. Breached in a single explosive event in October 2011, hundreds‐of‐thousands of cubic metres of sediment washed down the White Salmon River onto spawning grounds of a threatened species, Columbia River tule fall Chinook salmon Oncorhynchus tshawytscha. We investigated over a 3‐year period (2010–2012) how dam breaching affected channel morphology, river hydraulics, sediment composition and tule fall Chinook salmon (hereafter ‘tule salmon’) spawning habitat in the lower 1.7 km of the White Salmon River (project area). As expected, dam breaching dramatically affected channel morphology and spawning habitat due to a large load of sediment released from Northwestern Lake. Forty‐two per cent of the project area that was previously covered in water was converted into islands or new shoreline, while a large pool near the mouth filled with sediments and a delta formed at the mouth. A two‐dimensional hydrodynamic model revealed that pool area decreased 68.7% in the project area, while glides and riffles increased 659% and 530%, respectively. A spatially explicit habitat model found the mean probability of spawning habitat increased 46.2% after dam breaching due to an increase in glides and riffles. Shifting channels and bank instability continue to negatively affect some spawning habitat as sediments continue to wash downstream from former Northwestern Lake, but 300 m of new spawning habitat (river kilometre 0.6 to 0.9) that formed immediately post‐breach has persisted into 2015. Less than 10% of tule salmon have spawned upstream of the former dam site to date, but the run sizes appear healthy and stable. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
- Selecting Between One‐Dimensional and Two‐Dimensional
Hydrodynamic Models for Ecohydraulic Analysis
- Authors: S. A. Gibson; G. B. Pasternack
Abstract: Aquatic habitat assessment and river restoration design require geospatially explicit maps of hydraulic conditions. Diverse mechanistic ecohydraulic models compute spatially explicit depth and velocity results to evaluate habitat suitability spatially as a function of these abiotic conditions. This study compared depth and velocity results from two‐dimensional (2D) and one‐dimensional (1D) hydraulic models with algorithms that laterally discretize 1D velocity and interpolate depth and velocity spatially based on the Laplacian heat mapping approach. These ‘conveyance distributed’ methods constitute ‘best 1D modelling practice’ and were compared with 2D results for the first time. The 1D and 2D models were applied to three morphologically distinct reaches (leveed, meandering, and anastomosing) for three flows (base, bankfull, and flood flows) of the partially regulated, gravel/cobble lower Yuba River in north–central California. The test metrics were the coefficient of determination (R2) and the median absolute residual (
ε˜). These metrics quantified the incremental uncertainty 1D approximation incurs, results which make explicit cost–benefit processes of model selection possible. Finally, velocity residual maps were analysed to identify regions and processes where residuals were high, indicating divergence from the 1D assumptions. Paired data (1D–2D) fell between 0.94 ≥ R2 ≥ 1.00 (R2mean = 0.98 and R2median = 0.99) for depth and median absolute residuals were all 3.8 ≤
ε˜ ≤ 7.2% (i.e. 50% of residuals are approximately within ±1.7 to 3.6%). Higher flows and lower gradient reaches had lower residuals and higher R2. Velocity diverged more, particularly for base flow in anastomosing reaches (0.42
- Abundance of Invasive, Non‐Native Riparian Herbs in Relation to
- Authors: D. W. Perkins; M. L. Scott, T. Naumann
Abstract: River regulation is associated with vegetation encroachment and invasions of some non‐native species in the semi‐arid west. Shifts in the abundance of native and non‐native woody riparian species are an interplay of regulation, life history traits and an array of flow and physical environmental variables. We sought to compare plant densities and per cent cover of several invasive species over two time periods in a paired river study, contrasting three different degrees of regulation along reaches of the Green and Yampa rivers in Colorado and Utah, USA. We censused patches of non‐native plants and recorded per cent cover in quadrats along 171 river km. The upper Green (10.1 patches ha−1) had the highest invasive plant patch density followed by the lower Green (4.4 per ha) and the Yampa (3.3 per ha). Invasive species were present in 23%, 19% and 4% of sample quadrats, and an average of 0.28, 0.22 and 0.04 invasive species detected per square metre was recorded along the upper Green, lower Green and Yampa Rivers, respectively. Most species had significantly (p ≤ 0.02) higher percent cover on the upper Green than either or both the lower Green and the Yampa River. Whereas the less regulated river reaches maintain lower densities of invasive species than the most regulated reach, long‐term persistence of this pattern is still in question as some species patches showed notable increases on the Yampa and lower Green Rivers from 2002–2005 to 2010–2011. Although invasion is enhanced by flow regulation, life history traits of some species suggest invasion is likely, regardless of flow regulation. Published 2015. This article is a U.S. Government work and is in the public domain in the USA
- Assessment of Water Capacity and Availability from Unregulated Stream
Flows Based on Ecological Limits of Hydrologic Alteration (ELOHA)
Environmental Flow Standards
- Authors: Z. Zhang; J. W. Balay, K. M. Bertoldi, P. O. MaCoy
Abstract: Determination of water resources management thresholds, such as conservation releases, passby flows, and water availability limits, is a contemporary challenge facing water resources managers. With recent advancements in environmental flow science, including the ecological limits of hydrologic alteration (ELOHA) framework, environmental flow standards can be developed for a variety of stream types throughout a particular region or watershed. Environmental flow standards typically cover the entire natural flow regime, including low‐flow, seasonal‐flow (medium), and high‐flow components. However, it can be difficult for water resources managers to directly apply these standards to establish practical management thresholds.
This study proposes a novel approach to assessing water capacity based on ELOHA environmental flow standards. The procedure entails iterative simulations to identify withdrawal limits for gaged streams and regional regression analysis to predict withdrawal limits for ungaged streams. The approach was applied for 63 reference gages with long‐term, continuous, minimally altered, daily streamflow records within the Susquehanna River basin. The results of the investigation demonstrate that the approach can be used to assess water capacity from gaged and ungaged streams via iterative withdrawal simulations and regional regression analysis respectively. The regression equation developed through analysis of the reference gages has an adjusted R‐square value of 0.96 and a standard error of 27%. Determination of a water capacity value, based on a suite of environmental flow standards, provides water resources managers with a valuable tool for informing the establishment of water resources management thresholds. Copyright © 2015 John Wiley & Sons, Ltd.
- Longitudinal Plankton Dynamics in the Rivers Rhine and Elbe
- Abstract: We compared the longitudinal plankton development in the two large rivers Rhine and Elbe by means of four Lagrangian sampling campaigns performed within the time span 2009–2011. The campaigns revealed low chlorophyll concentrations in the Rhine along a long river stretch (Rhine‐km 170 to 854) with maximum values below 5 µg L−1 in 2010. In contrast, the Elbe (Elbe‐km 4 to 582) showed high and longitudinally increasing chlorophyll concentrations with maximal values of 174 µg L−1 in 2009 and 123 µg L−1 in 2011. Additional samples of the benthic bivalves along the river stretches revealed high densities of the filter feeders in the Rhine that could potentially explain losses of plankton production. Their densities in the Elbe were significantly lower, making important losses to benthic filter feeders unlikely. However, strong phytoplankton growth was observed during the sampling campaign in 2011 in the Rhine coinciding with a low discharge event. This resulted in an exceptionally high chlorophyll value of up to 244 µg L−1 in the lower river sections, a value that was not reached in the last two decades of continuous water quality monitoring in the Rhine. Even though we cannot fully explain this phenomenon, it shows that phytoplankton has a high growth potential in the Rhine but is usually controlled by other mechanisms. Tributaries represented an additional and important source of plankton biomass and suspended substances in the Rhine, whereas they primarily diluted the plankton concentrations in the Elbe. Copyright © 2015 John Wiley & Sons, Ltd.
- A Watershed Integrity Definition and Assessment Approach to Support
Strategic Management of Watersheds
- Authors: J. E. Flotemersch; S. G. Leibowitz, R. A. Hill, J. L. Stoddard, M. C. Thoms, R. E. Tharme
Abstract: Watersheds are spatially explicit landscape units that contain a range of interacting physical, ecological and social attributes. They are social–ecological systems that provide a range of ecosystem services valued by the society. Their ability to provide these services depends, in part, on the degree to which they are impaired by human‐related activity. An array of indicators is used by natural resource managers, both private and government, to assess watersheds and their sub‐components. Often these assessments are performed in comparison with a reference condition. However, assessments can be hampered because natural settings of many systems differ from those sites used to characterize reference conditions. Additionally, given the ubiquity of human‐related alterations across landscapes (e.g. atmospheric deposition of anthropogenically derived nitrogen), truly unaltered conditions for most, if not all, watersheds cannot be described. Definitions of ‘integrity’ have been developed for river ecosystems, but mainly at the reach or site scale and usually for particular species, such as fish or macroinvertebrates. These scales are inappropriate for defining integrity at the watershed scale. In addition, current assessments of endpoints do not indicate the source of impairment. Our definition of watershed ‘integrity’ is the capacity of a watershed to support and maintain the full range of ecological processes and functions essential to the sustainability of biodiversity and of the watershed resources and services provided to society. To operationalize this definition as an assessment tool, we identify key functions of unimpaired watersheds. This approach can then be used to model and map watershed integrity by incorporating risk factors (human‐related alterations or stressors) that have been explicitly shown to interfere with and degrade key functions in watersheds. An advantage of this approach is that the index can be readily deconstructed to identify factors influencing index scores, thereby directly supporting the strategic adaptive management of individual components that contribute to watershed integrity. Moreover, the approach can be iteratively applied and improved as new data and information become available. © 2015 The
Authors . River Research and Applications published by John Wiley & Sons Ltd.
- Lowland River Flow Control by an Artificial Water Plant System
- Authors: N. Zdankus; P. Punys, E. Martinaitis, T. Zdankus
Abstract: This article concerns the influence of water plants on the river flow. It is known that the influence of the plants is rather strong. Colonies of water plants with long afloat culms create considerable forces of resistance to the flow. They reduce flow velocity and increase a stream depth, what often is desirable. Water plants location in a stream is uncontrollable. They appear in not suitable locations of the river and mostly obstruct than help to control the river flow. Water plants and their colonies served for us as a prototype for creation of the flow control system. A method of computation and field tests that enables designing and arranging an artificial water plant system is presented in this article, and it may be used successfully to increase the river flow depth and to improve navigation, free‐flow (kinetic) hydropower development and recreation conditions. The suggested system for river flow control is simple, cheap and friendly to the environment. Copyright © 2015 John Wiley & Sons, Ltd.
- Leaf‐Nets (LN): A New Quantitative Method for Sampling
Macroinvertebrates in Non‐Wadeable Streams and Rivers
- Authors: A. Di Sabatino; G. Cristiano, D. Di Sanza, P. Lombardo, C. Giansante, R. Caprioli, P. Vignini, F. P. Miccoli, B. Cicolani
Abstract: The ecological knowledge of large rivers is still scarce or highly fragmented mainly because of complex, laborious and expensive procedures to collect informative samples from the benthic biota. Standard sampling protocols for macroinvertebrates were mainly developed and calibrated for wadeable streams, while a number of heterogeneous non‐standard sampling procedures are available for large rivers. We propose the new, easy‐to‐build and cost‐effective leaf‐nets (LN) method to quantitatively sample benthic invertebrates in non‐wadeable waterways. The LN method uses Phragmites australis leaves as substrate and combines the characteristics of the leaf‐bags and the Hester–Dendy (HD) multiplates methods. We compared the effectiveness of the LN and HD methods in a near‐pristine and in an impacted stream‐reach (downstream an aquaculture plant) of a non‐wadeable second‐order stream of Central Apennines (Italy). Twenty‐five of the 34 cumulatively collected macroinvertebrate taxa were common to both methods, while seven taxa were found only on LN and two only on HD. Taxonomic richness and total macroinvertebrate abundance were higher for LN assemblages. Number of Ephemeroptera, Plecoptera and Trichoptera taxa (EPT) also tended to be higher on LN. Assemblage composition was different on LN and HD. Both methods documented a significant decrease in EPT taxa and a concomitant increase in the total abundance of more pollution‐tolerant taxa in the impacted stream‐reach, but the LN method was more sensitive to impact‐associated changes in macroinvertebrate assemblage structure. In contrast to the hardboard plates of HD, the assembled leaves of the LN may act as a direct or indirect food source and may better mimic the texture and composition of more heterogeneous natural substrates thus favouring the migration–colonization process from both bottom and littoral benthic invertebrates. The sampling efficiency, cost effectiveness and simplicity warrant the routine use of the new LN method in large‐river ecological assessment. Copyright © 2015 John Wiley & Sons, Ltd.
- Temporal and Spatial Patterns of Fish Response to Hydromorphological
- Authors: C. Wolter; A. D. Buijse, P. Parasiewicz
Abstract: This paper relates life cycle characteristics of fishes, their environmental tolerances, habitat requirements, and resilience against hydromorphological disturbances to a recently developed river typology providing a hierarchy of spatial units. It aims to identify the most relevant spatiotemporal scales for river restoration and environmental assessment.
Most fish species, except diadromous and some potamodromous species, can complete their life cycle within a river reach and form sustainable populations within a river segment. They typically move within the spatial scale of river segments and have their home range within the river reach. By comprising heterogeneous patterns of different geomorphic and hydraulic units, the reach provides habitat complexity and heterogeneity that supports river‐type‐specific fish assemblages. The single units are often used temporarily or by specific life stages only underpinning the need for habitat diversity. Further, they might be only temporarily available. River fishes have evolved several life cycle adaptations to improve their resilience against stochastic disturbances, as high fecundity, multiple spawning, batch‐spawning, a protracted annual spawning season, and long life‐time fecundity with multi‐cyclic spawning. Therefore, they are well adapted to environmental variations driven by hydromorphological processes.
Considering the home range of most species, representative sampling at the reach scale will cover all functional river elements, hydraulic, and geomorphic units, while accounting for their temporary or sporadic use by fish. Therefore, the reach scale appears as practicable and sufficient scale for fish‐based assessments and as highly relevant planning unit in hydromorphological river restoration practise. Nonetheless, reach‐scale characteristics are largely inherited from large‐scale geomorphic processes and multiple pressures at the catchment scale that may impact aquatic communities and river restoration success at the lower spatial scales. Copyright © 2015 John Wiley & Sons, Ltd.
- Applicability of Geostatistical Tools and Fractal Theory for the
Estimation of the Effect of a River on Water Relations in Adjacent Area
- Abstract: The paper presents a new method of estimation of the effect of a river on the ground waters of the adjacent area, different than the one used so far and based on the application of geostatistical methods and the fractal theories. An analysis was performed of a 14‐year series of daily observations of ordinates of water level in the river Oder and ordinates of ground water levels in five piezometers situated at various distances from the riverbed, within the range from 120 to 1000 m. The first stage of the analysis was devoted to evaluation of the applicability of classical statistical measures. It was found that only selected ones display a relation with the distance. Those included maximum value, ranges, coefficients of variation, and variances. The remaining ones proved to be non‐applicable. The next stage was the analysis of correlations between the parameters of semivariograms of ground water levels in the piezometers and the parameters of semivariograms of water levels in river Oder. It was demonstrated that the values of each parameter were related with the distance of a given piezometer from the riverbed. This means that they are useful for the estimation of the effect of the river Oder on the adjacent areas, as are the fractal dimensions. Copyright © 2015 John Wiley & Sons, Ltd.
- Assessment of Trends in Stream Temperatures in the North of the Iberian
Peninsula Using a Nonlinear Regression Model for the Period
- Authors: B. Soto
Abstract: A nonlinear regression model was used to estimate mean daily stream water temperature in 11 rivers of the North of the Iberian Peninsula employing as the only predictor variable the air temperature. The weighted mean value of air temperature of a variable number of preceding days was used as a predictor variable.
To obtain the weight of air temperature of each preceding day, initially, we calculate the weight of air temperature of current day. For this, we have included in the model the air temperature of current day and the water temperature of preceding day—representative of long‐term effects of air temperature on current water temperature. Subsequently, the weight of remaining days was calculated by a negative exponential function.
The weight of air temperature of current day ranges between 0.28 and 0.10, and it was correlated to length of river (R2 = 0.69) and to time of concentration (R2 = 0.66). This fact implies that the number of preceding days required to obtain a good estimation differs across the rivers.
The results show that the mean root mean square error (RMSE) between observed and estimated water temperatures was 1.23 °C (±0.30 °C), employing a number of days so that the sum of their weights was 0.65. For the validation period, RMSE was 1.20 °C (±0.18 °C).
For the period 1986–2013, estimated temperature of water was 0.6 °C higher than that estimated for the period 1950–1986. This increase value is slightly lower than that observed in the air temperature (0.8 °C). On the other hand, during the period 1986–2013, water temperature showed a rate of increase of 0.16 °C/decade, similar to the increase of air temperature (0.15 °C/decade). Copyright © 2015 John Wiley & Sons, Ltd.
- Annual Variation in Larval Fish Assemblages in a Heavily Regulated River
During Differing Hydrological Conditions
- Abstract: One of the most severe anthropogenic impacts on river systems worldwide has been alterations to the natural flow regime. Understanding biological responses to altered flow regimes is critical to effectively rehabilitate aquatic ecosystems. This study investigated changes in the larval fish assemblages during varying hydrological conditions over 5 years in the lower River Murray, in south‐eastern Australia. Larval fish were sampled during spring/summer during three distinct hydrological periods: under a within‐channel flow pulse and a water level raising (2005); during a drought with very low flows and stable water levels (2006, 2007 and 2008); and during an overbank flow (2010). Data were analysed for annual, spatial and seasonal variations, and correlations were examined between changes in larval assemblages and environmental variables. Hydrology was a key driver in inter‐annual variation in larval fish assemblages. High abundances of small‐bodied to medium‐bodied native species were recorded under low flows, while for other species, abundance was more strongly correlated to temperature, representing seasonal variation. Two large‐bodied species were only recorded during the within‐channel flow pulse and overbank flow conditions, and significant increases in larval abundances were recorded during overbank flow conditions. We suggest groupings based on species response to hydrology (low‐flow to medium‐flow spawners, high‐flow spawners or seasonal spawners). This study suggests that a range of conditions (low flows and overbank flows) are required to maintain a diverse and abundant native fish fauna in the lower River Murray. Copyright © 2015 John Wiley & Sons, Ltd.
- Seasonal Rearing Habitat in a Large Mediterranean‐Climate River:
Management Implications at the Southern Extent of Pacific Salmon
- Authors: J. E. Merz; D. G. Delaney, J. D. Setka, M. L. Workman
Abstract: Pacific salmon (Oncorhynchus) use a variety of rearing environments prior to seaward migration, yet large river habitats and their use have not been well defined, particularly at the southernmost salmon range where major landscape‐level alterations have occurred. We explored juvenile Chinook salmon (Oncorhynchus tshawytscha) and steelhead (Oncorhynchus mykiss) presence along the river continuum and in main‐channel and off‐channel habitats of a regulated California Mediterranean‐climate river. Over an 8‐year period, off‐channels of the lower Mokelumne River exhibited slower and warmer water than the main‐channel. Probability of salmonid presence varied by stream reach and habitat types. Steelhead and Chinook salmon both demonstrated transitional responses to the dry season, with juveniles leaving off‐channels by midsummer. This corresponded to flow recession, increasing water temperatures, salmonid growth and end of emigration period. Main‐channel steelhead observations continued until the following storm season, which brought cool flood flows to reconnect off‐channels and the next juvenile cohort of both species to the river. Within arid climates, low‐gradient off‐channels appear more transiently used than in cooler and more northern humid climate systems. Within a highly regulated Mediterranean‐climate river, off‐channel habitats become increasingly scarce, disconnected or temperature limiting in low‐gradient reaches both seasonally and due to anthropogenic modifications. These observations may provide guidance for future management within large salmon streams. Copyright © 2015 John Wiley & Sons, Ltd.
- Hydrogeomorphic and Biotic Drivers of Instream Wood Differ Across
Sub‐basins of the Columbia River Basin, USA
- Abstract: Instream wood promotes habitat heterogeneity through its influence on flow hydraulics and channel geomorphology. Within the Columbia River Basin, USA, wood is vital for the creation and maintenance of habitat for threatened salmonids. However, our understanding of the relative roles of the climatic, geomorphic, and ecological processes that source wood to streams is limited, making it difficult to identify baseline predictions of instream wood and create targets for stream restoration. Here, we investigate how instream wood frequency and volume differ between seven sub‐basins of the interior Columbia River Basin and what processes shape these differences within these sub‐basins. We collected data on wood volume and frequency, discharge and stream power, and riparian and watershed forest structure for use in modelling wood volume and frequency. Using random forest models, we found that mean annual precipitation, riparian tree cover, and the individual watershed were the most important predictors of wood volume and frequency. Within sub‐basins, we used linear models, finding that some basins had unique predictors of wood. Discharge, watershed area, or precipitation often combined with forest cover, riparian conifer, and/or large tree cover in models of instream large wood volume and frequency. In many sub‐basins, models showed at least one hydrologic variable, indicative of transport competence and one ecological variable, indicative of the reach or upstream watershed's capability to grow measurable instream wood. We conclude that basin‐specific models yield important insights into the hydrologic and ecological processes that influence wood loads, creating tractable hypotheses for building predictive models of instream wood. Copyright © 2015 John Wiley & Sons, Ltd.
- Microhabitat Partitioning of an Assemblage of Darter Species Within Two
Tributaries of the Tennessee River in Alabama
- Authors: B. Thompson; B. Stallsmith
Abstract: Habitat partitioning among syntopic darter species (Percidae: Etheostomatini) was examined in the Flint River and Estill Fork of the Paint Rock River in northeast Alabama from September 2010 to September 2011. Substrate composition, depth, and water velocity were important variables by which species segregated. Niche overlap values also indicated a high degree of habitat partitioning among species at both study sites, although a substantial amount of overlap was seen between Etheostoma simoterum and Etheostoma caeruleum at the Estill Fork site. Segregation among species was present throughout the year, but the significance of differences in habitat preferences did vary seasonally, especially during the post‐spawn period when habitat heterogeneity was reduced. Intra‐specific variation in habitat utilization was present among some species, with male species generally preferring higher flow and coarser substrates than female species. Habitat segregation was a well‐structured mechanism allowing the coexistence of ecologically similar species. Copyright © 2015 John Wiley & Sons, Ltd.
- Recolonization Process and Fish Assemblage Dynamics in the Guadiamar River
(SW Spain) After the Aznalcóllar Mine Toxic Spill
- Abstract: The Guadiamar River (SW Iberian Peninsula) received a major toxic spill (6 hm3) from a tailing pond in 1998 that defaunated 67 km of the main stem. Following early mud removal works, the fish assemblage was annually monitored at four affected sampling sites and one located in the upstream non‐affected reach of the Guadiamar River as reference. Fish abundance and assemblage structure were analysed. Principal response curve was applied to assess the recovery trends and to identify the most influential species. A non‐metric multidimensional scaling ordination and permutational multivariate analysis of variance were applied to evaluate changes in fish assemblage structure between sites and years. Overall, the affected reaches harboured fish within 2 years of the spill. Colonists arrived mainly from the upstream and downstream non‐affected Guadiamar River reaches and, to a lesser extent, from three lateral tributaries. It is likely that the proximity, connectivity and environmental conditions of non‐affected fish sources greatly influenced the recolonization process in each site. The structure of the fish community in the affected sites was initially similar to that in the unaffected reference stretch but changed dramatically with time, and each site followed its own trajectory. Currently, long‐term threats such as mining leachates, urban sewage, agricultural pollution and exotic fish species expansion have probably exceeded the initial spill effect. This highlights the large effect of anthropogenic factors on freshwater ecosystem resilience, and the need to significantly reduce both pollution and exotic species if the affected reach of the Guadiamar River is to recover fully. Copyright © 2015 John Wiley & Sons, Ltd.
- The Use of Evolutionary Trajectories to Guide ‘Moving Targets’
in the Management of River Futures
- Authors: G. J. Brierley; K. A. Fryirs
Abstract: River histories provide important guidance with which to inform river management. Evolutionary trajectories and appraisals of system responses to changing flux conditions and disturbance events can be used to determine the range of potential future states and associated behavioural regimes, assessing the likelihood that that these states will be attained over a given timeframe. In these analyses, natural or historical reference reaches may not provide a realistic basis to set target conditions for management actions, as what has gone before does not necessarily provide a complete and reliable picture of prospective future conditions. This paper outlines the use of a conceptual tool, the river evolution diagram, as a geomorphic platform to assess river history and the potential range of river futures for any given system. Evolutionary adjustments of a sand bed river in southeastern Australia are used to demonstrate the application of this approach. Applying adaptive management principles, ‘moving targets’ for river management are framed in relation to the range of likely future states and trajectories of adjustment. Copyright © 2015 John Wiley & Sons, Ltd.
- Fluvial Hydrodynamics: Hydrodynamic and Sediment Transport Phenomena.
Subhasish Dey. Springer, Berlin, 2014. No of pages 687. Price: £
117.00. ISBN 978‐3‐642‐19061‐2
- Authors: Oscar Link
- Increased Sediment Loads in Alpine Streams: An Integrated Field Study
- Authors: F. Bona; A. Doretto, E. Falasco, V. La Morgia, E. Piano, R. Ajassa, S. Fenoglio
Abstract: The ecological impact of fine sediments is one of the major causes of ecological degradation affecting lotic systems. Interestingly, many studies have investigated the impact of increased sediment loads on specific compartments of the lotic system, but little or no information is available about the overall impact of sedimentation. Aim of this paper was to analyse the influence of fine sedimentation on allochthonous and autochthonous energy inputs and on the structural and functional characteristics of diatom and macroinvertebrate communities. Data were collected in two Alpine streams in NW Italy, one interested by the presence of an intense mining area and the other pristine, used as a control. The two rivers greatly differed in terms of suspended solids and bed load characteristics. From 10 stations, we analysed main physico‐chemical characteristics, fine sediment indicators (using 60 sediment traps), coarse particulate organic matter (CPOM) and photosynthetic pigments amounts, taxonomic and functional characteristics of macroinvertebrate communities. We tested several causal models via path analysis. Functional traits seem to better reflect the integrated impact originating from quarries in the river basin than traditional community metrics like total abundance and specific richness. This outcome was enforced through the co‐inertia analysis, which took in consideration also metrics based on diatom communities. Our study yielded quantitative relations between sediment loads induced by quarrying activities and the degree of biological impairment and suggests which metrics are more suitable to assess this specific impact. Copyright © 2015 John Wiley & Sons, Ltd.
- Secondary Production of Highly Unsaturated Fatty Acids by Zoobenthos
Across Rivers Contrasting in Temperature
- Authors: M. I. Gladyshev; N. N. Sushchik, S. P. Shulepina, A. V. Ageev, O. P. Dubovskaya, A. A. Kolmakova, G. S. Kalachova
Abstract: Highly unsaturated fatty acids (HUFA), namely eicosapentaenoic acid (20:5n‐3, EPA) and docosahexaenoic acid (22:6n‐3, DHA), which are essential for many animals, including humans, are mainly produced in aquatic trophic webs. In fast‐flowing rivers, macrozoobenthos is the main source of HUFA for fish and may be particularly vulnerable to thermal alterations associated with climate change. We studied benthic communities in a unique natural ecosystem: the Yenisei River downstream of the dam of Krasnoyarsk Hydroelectric Power Station with very low temperature in summer because of discharge of cold water from deep in the reservoir and its tributaries with high summer temperature. This ‘natural experiment’ allowed to get rid of confounding factors, such as differences in light, seasonality, geology (biogeochemistry) and biogeography (regional species pools). As found, in spite of an increase of biodiversity and rates of daily production in warm rivers compared with cold sites, DHA and partly EPA production of zoobenthos decreased with the increase of temperature because of changes in species composition. Thus, in a climate warming context, we can predict a decrease of production of these HUFA by river zoobenthos and thereby a diminishing of their supply for fish and next to humans. Copyright © 2015 John Wiley & Sons, Ltd.
- Plant Traits Relevant To Fluvial Geomorphology and Hydrological
- Authors: M. T. O'Hare; J. O. Mountford, J. Maroto, I. D. M. Gunn
Abstract: Plants can slow water and trap sediment with their canopies and stabilise sediment with their roots. These influences are mediated by the characteristics or traits of the vegetation. Here, we review and investigate the flexibility, size, root form, clonal growth, perennation and Ellenberg F values of 459 European riverine species, considering their role in physical and ecological processes. We make use of existing plant trait datasets to create two typologies: one that identifies the role vegetation has in channel blockage (conveyance) and sediment accrual and a second typology, that indicates vegetation's ability to stabilize sediment. The two typologies are tools for interpreting botanical survey data collected using standard techniques across large numbers of sites as part of the European Union Water Framework Directive monitoring programmes. As such, they are designed to be used to indicate broad‐scale patterns across sites rather than detailed insights into site‐specific processes. Copyright © 2015 John Wiley & Sons, Ltd.
- Two Dimensional Heavy Metal Transport Model for Natural Watercourses
- Authors: Z. Horvat; M. Horvat
Abstract: This work presents the development and calibration of a two‐dimensional (depth‐averaged) river flow, sediment transport and heavy metal transport model in natural watercourses. Because heavy metals occur in dissolved and adsorbed phases, implementing the active‐layer concept for sediment transport computation enabled the development of a heavy metal transport model that accounts for pollutant moving in dissolved phase, adsorbed on suspended sediment, adsorbed on bed‐load, deposited in the active‐layer of the river bed or adsorbed on sediment in deeper strata. The proposed concept also enables the modelling of pollutant exchange processes using accessible sediment particle surface area for suspended and bed sediment separately. The presented heavy metal transport model is able to manage sediment mixtures found in natural watercourses using an arbitrary number of sediment size‐classes, distinguishing in this way smaller size‐classes that engage in interaction with the pollutant. Using field measurements for a reach of the Danube River, simulations were conducted for water flow, sediment transport and heavy metal transport. While some discrepancies between measured and computed values for pollutant concentrations were observed, the model reproduced the water and sediment contamination quite reasonably with acceptable mass conservation errors. The simulations also gave an insight in the general behaviour of the monitored heavy metals in the considered river reach. Therefore, it can be concluded that the developed model is suitable for simulating complex flow, sediment transport and heavy metal transport conditions in natural watercourses. Copyright © 2015 John Wiley & Sons, Ltd.
- An Evaluation of Streamflow Augmentation as a Short‐Term Freshwater
Mussel Conservation Strategy
- Authors: J. M. Wisniewski; S. Abbott, A. M. Gascho Landis
Abstract: Recurrent and prolonged droughts, coupled with increased water resource demand, threaten freshwater mussel populations through stream drying and water quality degradation. Augmentation of stream discharge was proposed as a short‐term strategy to maintain adequate streamflows and water quality in reaches with important freshwater mussel populations during exceptionally low flow periods. We investigated the effects of water augmentation on seven freshwater mussel species in a small creek between 2011 and 2014. Using capture‐mark‐recapture methods, we monitored mussel populations in a control reach upstream of an augmentation outlet and two reaches immediately downstream of an augmentation outlet. Water quality measurements during our study indicated that augmentation improved water temperature and dissolved oxygen conditions during low flow periods. For all mussel species, apparent survival was positively related to minimum streamflows and declined precipitously as streamflows decreased. However, mean apparent survival between sampling occasions was high among all species but did not differ among treatment units, suggesting that flow augmentation rates in this study were insufficient for abating the effects of basin‐wide reductions in streamflow. Temporary emigration differed among study reaches but did not support hypothesized relationships because it increased with stream stage and was highest in an augmented reach. This suggests that streamflows did not drop below thresholds, which invoked burrowing as a response to decreased streamflows. Streamflow augmentation may be a viable short‐term mussel conservation strategy in small streams but will likely require higher augmentation volume capacity than evaluated during our study. Copyright © 2015 John Wiley & Sons, Ltd.
- Physical and Biological Responses to an Alternative Removal Strategy of a
Moderate‐sized Dam in Washington, USA
- Authors: S. M. Claeson; B. Coffin
Abstract: Dam removal is an increasingly practised river restoration technique, and ecological responses vary with watershed, dam and reservoir properties, and removal strategies. Moderate‐sized dams, like Hemlock Dam (7.9 m tall and 56 m wide), are large enough that removal effects could be significant, but small enough that mitigation may be possible through a modified dam removal strategy. The removal of Hemlock Dam in Washington State, USA, was designed to limit channel erosion and improve fish passage and habitat by excavating stored fine sediment and reconstructing a channel in the former 6‐ha reservoir. Prior to dam removal, summer daily water temperatures downstream from the dam increased and remained warm long into the night. Afterwards, a more natural diel temperature regime was restored, although daily maximum temperatures remained high. A short‐lived turbidity pulse occurred soon after re‐watering of the channel, but was otherwise similar to background levels. Substrate shifted from sand to gravel–cobble in the former reservoir and from boulder to gravel–cobble downstream of the dam. Initially, macroinvertebrate assemblage richness and abundance was low in the project area, but within 2 years, post‐removal reaches upstream and downstream of the dam had diverse and abundant communities. The excavation of stored sediment and channel restoration as part of the dam removal strategy restored river continuity and improved benthic habitat while minimizing downstream sedimentation. This study provides a comparison of ecological effects with other dam removal strategies and can inform expectations of response time and magnitude. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
- Sensitivity of Intermittent Streams to Climate Variations in the USA
- Authors: K. Eng; D. M. Wolock, M. D. Dettinger
Abstract: There is a great deal of interest in the literature on streamflow changes caused by climate change because of the potential negative effects on aquatic biota and water supplies. Most previous studies have primarily focused on perennial streams, and there have been only a few studies examining the effect of climate variability on intermittent streams. Our objectives in this study were to (1) identify regions of similar zero‐flow behaviour and (2) evaluate the sensitivity of intermittent streams to historical variability in climate in the USA. This study was carried out at 265 intermittent streams by evaluating (1) correlations among time series of flow metrics (number of zero‐flow events, the average of the central 50% and largest 10% of flows) with climate (magnitudes, durations and intensity) and (2) decadal changes in the seasonality and long‐term trends of these flow metrics. Results identified five distinct seasonality patterns in the zero‐flow events. In addition, strong associations between the low‐flow metrics and historical changes in climate were found. The decadal analysis suggested no significant seasonal shifts or decade‐to‐decade trends in the low‐flow metrics. The lack of trends or changes in seasonality is likely due to unchanged long‐term patterns in precipitation over the time period examined. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
- Quantification of Freshwater Pearl Mussel Entrainment Velocities and
Controlling Factors; a Flume Study
- Authors: F. Thompson; D. Gilvear, A. Tree, R. Jeffries
Abstract: Increased flood frequency and magnitude are predicted for Scotland, and the country contains several of the world's largest recruiting populations of freshwater pearl mussel (Margaritifera margaritifera). This study provides a unique flume experiment to measure the near‐bed velocities required for freshwater pearl mussel entrainment and factors affecting their movement. It represents the first quantitative attempt at examining the precise water velocities at which freshwater pearl mussel become vulnerable to displacement during high flow events. Measurement of the near‐bed velocities at which the mussels moved was undertaken using an indoor recirculating flume. The effect of the different parameters (bed substrate, mussel burial depth, mussel curvature, mussel alignment, shell curvature and the presence of a simulated foot) on entrainment velocity was tested in the flume and their significance was verified using Kruskal–Wallis and Mann Whitney tests. Bed substrate was found to have the biggest influence on mussel entrainment velocities with averages of 0.86 ms−1, 0.95 ms−1, 1.01 ms−1 and 1.42 ms−1 for sand, gravel, mixed bed and boulder beds respectively. Stepwise logistic regression showed that bed substrate, foot presence, mussel length, mussel burial depth and shell curvature were sufficient to explain mussel entrainment velocity. These findings provide valuable information for the modelling of freshwater pearl mussel dynamics in streams systems and assessing the vulnerability of endangered mussel populations to higher flows associated with climate change in Scotland. Copyright © 2015 John Wiley & Sons, Ltd.
- Evidence for Serial Discontinuity in the Fish Community of a Heavily
- Authors: L. E. Miranda; D. J. Dembkowski
Abstract: In the Tennessee River, USA, we examined lengthwise patterns in fish community structure and species richness within and among nine reservoirs organized in sequence and connected through navigational locks. Within reservoirs, the riverine, transition and lacustrine zones supported distinct, although overlapping, nearshore fish assemblages; differences were also reflected in measures of species richness. Spatial patterns were most apparent for rheophilic species, which increased in species richness and representation upstream within each reservoir and downstream across the chain of reservoirs. This pattern resembled a sawtooth wave, with the amplitude of the wave peaking in the riverine zone below each dam, and progressively higher wave amplitude developing downstream in the reservoir chain. The observed sawtooth pattern supports the serial discontinuity concept in that the continuity of the riverine fish community is interrupted by the lacustrine conditions created behind each dam. Upstream within each reservoir, and downstream in the chain of reservoirs, habitat characteristics become more riverine. To promote sustainability of rheophilic fishes and maintain biodiversity in impounded rivers, conservation plans could emphasize maintenance and preservation of riverine environments of the reservoir's upper reaches, while remaining cognizant of the broader basin trends that provide opportunities for a lengthwise array of conservation and management policy. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
- Assessing Juvenile Salmon Rearing Habitat and Associated Predation Risk in
a Lower Snake River Reservoir
- Authors: K. F. Tiffan; J. R. Hatten, D. A. Trachtenbarg
Abstract: Subyearling fall Chinook salmon (Oncorhynchus tshawytscha) in the Columbia River basin exhibit a transient rearing strategy and depend on connected shoreline habitats during freshwater rearing. Impoundment has greatly reduced the amount of shallow‐water rearing habitat that is exacerbated by the steep topography of reservoirs. Periodic dredging creates opportunities to strategically place spoils to increase the amount of shallow‐water habitat for subyearlings while at the same time reducing the amount of unsuitable area that is often preferred by predators. We assessed the amount and spatial arrangement of subyearling rearing habitat in Lower Granite Reservoir on the Snake River to guide future habitat improvement efforts. A spatially explicit habitat assessment was conducted using physical habitat data, two‐dimensional hydrodynamic modelling and a statistical habitat model in a geographic information system framework. We used field collections of subyearlings and a common predator [smallmouth bass (Micropterus dolomieu)] to draw inferences about predation risk within specific habitat types. Most of the high‐probability rearing habitat was located in the upper half of the reservoir where gently sloping landforms created low lateral bed slopes and shallow‐water habitats. Only 29% of shorelines were predicted to be suitable (probability >0.5) for subyearlings, and the occurrence of these shorelines decreased in a downstream direction. The remaining, less suitable areas were composed of low‐probability habitats in unmodified (25%) and riprapped shorelines (46%). As expected, most subyearlings were found in high‐probability habitat, while most smallmouth bass were found in low‐probability locations. However, some subyearlings were found in low‐probability habitats, such as riprap, where predation risk could be high. Given their transient rearing strategy and dependence on shoreline habitats, subyearlings could benefit from habitat creation efforts in the lower reservoir where high‐probability habitat is generally lacking. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
- Geomorphic Responses to a Large Check‐Dam Removal on a Mountain
River in Taiwan
- Abstract: The ability to understand and predict the impacts of dam removal in river systems is important, especially as dam decommissioning is becoming increasingly popular. In this study, we document the morphological and sediment impact of the removal of Chijiawan Check Dam in May 2011; a 13‐m‐high dam located on a coarse‐grained, steep mountain river channel in Taiwan. An estimated 0.2 million m3 of sediment had accumulated within the impoundment before its removal. Longitudinal and bankfull cross‐sectional surveys and a detailed sediment textural survey were undertaken along a 3.2‐km study reach of the Chijiawan Creek between 2010 and 2012. A rotating knickpoint with migration rates of up to 22 m/day was observed along the study reach, following dam removal. The rate and character of channel change, associated with the dam removal, appear to be driven as much by channel morphology and distance from the dam as by the hydrology variability. Our results suggested that relatively small amounts of sediment were eroded during the first 3 weeks following dam removal because of low discharge conditions. However, after 1 and 15 months, 10 and 75% of the sediment that had accumulated within former impounded was eroded, respectively. Sites near the former dam had a sediment texture that reflected the transport of released sediment, and this suggested that basin‐wide sediment processes exerted a strong influence. The removal of Chijiawan Dam offers unique insight on how sediment processes can drive river channel responses to sediment pulses may vary with discharge and sediment load, in areas subject to remarkably high flows and sediment loads. Copyright © 2015 John Wiley & Sons, Ltd.
- Specification of Flows for Flushing Surficial Sand from Cobble Riffles
- Authors: C. S. James
Abstract: Maintenance of habitat for benthic organisms and fish spawning may require flushing of sand from gravel or cobble river beds. An approach is proposed for specifying both the magnitude and duration of flow necessary to scour sand to a desired depth over a specified length of riffle bed. Scour is assumed to begin at the upstream end of the reach to be flushed and to progress downstream. The flow magnitude necessary for scour to an equilibrium depth was found from previously published laboratory data to be related to the median sand grain size and its movability number (the ratio of shear velocity to settling velocity). The required flow duration is determined by the time for scour to progress over the specified distance. The progression rate was determined through new laboratory experiments to be related to the flow velocity and depth, the distance advanced, the sand movability number and the channel slope. Application of the approach is illustrated by example. Copyright © 2015 John Wiley & Sons, Ltd.
- A Conceptual Model of Vegetation–hydrogeomorphology Interactions
Within River Corridors
- Abstract: We propose a conceptual model of vegetation–hydrogeomorphology interactions and feedbacks within river corridors (i.e. river channels and their floodplains) that builds on previous similar hydrogeomorphologically centred models by
incorporating hydrogeomorphological constraints on river corridor vegetation from region to reach scales;
defining five dynamic river corridor zones within which different hydrogeomorphological processes are dominant so that plants and physical processes interact in different ways, and considering the potential distribution of these zones longitudinally from river headwaters to mouth, laterally across the river corridor, and in relation to different river planform styles;
considering the way in which vegetation‐related landforms within each zone may reflect processes of self‐organization and the role of particular plant species as physical ecosystem engineers within the context of the dominant hydrogeomorphological processes;
focussing, in particular, upon a ‘critical zone’ at the leading edge of plant–hydrogeomorphological process interactions that is located somewhere within the area of the river corridor perennially inundated by flowing water (zone 1) and the area that is frequently inundated and subject to both sediment erosion and deposition processes (zone 2). Within the critical zone some plant species strongly influence the position and character of the margin between the river channel and floodplain, affecting channel width, channel margin form and dynamics, and the transition from one river planform type to another; and
considering the vegetated pioneer landforms that develop within the critical zone and how their morphological impact needs to be scaled to the river size.
The model is illustrated using three example reaches from rivers within different biogeographical zones of Europe, and its potential application in the context of river management and restoration/rehabilitation is discussed. Copyright © 2015 John Wiley & Sons, Ltd.
- Fish Assemblage and Ecosystem Metabolism Responses to Reconnection of the
Bird's Point‐New Madrid Floodway during the 2011 Mississippi River
- Authors: H. Rantala; D. Glover, J. Garvey, Q. Phelps, S. Tripp, D. Herzog, R. Hrabik, J. Crites, M. Whiles
Abstract: Understanding the ecological function of developed large rivers remains elusive because these systems have long been altered for multiple uses. In particular, floodplains of large rivers, such as the Mississippi River, have been contained behind extensive levees. A historic flood occurred in the lower Mississippi River system during spring of 2011, prompting the US Army Corps of Engineers to activate the Bird's Point‐New Madrid floodway, a 55 000‐ha, agriculturally dominated, leveed area. Water entered the floodway at flows >1 m s−1 through two crevasses created in the upper portion of the levee and exited through a crevasse at the lower end. During the month, the floodway was inundated; we quantified discharge, water chemistry, primary production and fish production in the floodway and the adjacent river. Water entering the floodway was retained
- Pulsed Flow Wave Attenuation on a Regulated Montane River
- Authors: C. Fong; S. Yarnell, J. Viers
Abstract: This study investigated the effects of hydrograph shape on attenuation of regulated pulsed flow events below a hydropower dam by categorizing and modelling the downstream movement of representative pulses on the upper Tuolumne River in the Sierra Nevadas of California, USA. We extracted underlying hydrograph shape patterns using principal component analysis on individual pulsed flow events released from 1988 to 2012 (n = 4439). From principal component loadings, six shape categories were determined: rectangular, front‐step, back‐step, goalpost, centred tower, and other. Attenuation of representative pulses from each shape type was then modelled using a one‐dimensional hydraulic model of 42 river km. Model results demonstrated a durational threshold for representative pulses (~3–5 h) over which the degree of attenuation of ramping rates and peak discharge approached a limit. Simulations of front and back‐step representative pulses showed trade‐offs between attenuation of peak magnitudes and steepness of rising ramping rates. Reshaping pulses to reduce the adverse ecological effects of rapid changes in stage and velocity downstream was infeasible if the system was required to maintain current electricity production and recreational service levels. Copyright © 2015 John Wiley & Sons, Ltd.
- Modelling Whitewater Park Hydraulics and Fish Habitat in Colorado
- Authors: E. Kolden; B. D. Fox, B. P. Bledsoe, M. C. Kondratieff
Abstract: Whitewater parks (WWPs) are increasingly popular recreational amenities, but the effects of WWPs on fish habitat and passage are poorly understood. This study investigated the use of a two‐dimensional (2‐D) model as compared with a three‐dimensional (3‐D) hydrodynamic model (flow‐3D®) for assessing effects of WWPs on fish habitat. The primary aims of this study were to (1) examine the utility of 3‐D modelling versus 2‐D modelling in a hydraulically complex WWP and (2) compare modelled habitat quality for resident fishes with actual fish abundance and biomass generated from field sampling surveys. Two reaches of a wadeable river in Colorado were modelled: a natural reach and a reach containing a WWP. A 2‐D habitat suitability analysis for juvenile and adult brown trout, juvenile and adult rainbow trout, longnose dace and longnose sucker predicted the same or higher habitat quality in the WWPs than the natural pools for all four species and for all modelled flow rates; however, results from fish sampling found significantly higher fish biomass for all four species in natural pools compared with WWP pools. All hydraulic metrics (depth, depth‐averaged velocity, turbulent kinetic energy, 2‐D and 3‐D vorticity) had higher magnitudes in WWP pools than in natural pools. In the WWP pools, 3‐D model results described the spatial distribution of flow characteristics or the magnitude of variables better than 2‐D results. This supports the use of 3‐D modelling for complex flows found in WWPs, but improved understanding of linkages between fish habitat quality and 3‐D hydraulic descriptors is needed. Copyright © 2015 John Wiley & Sons, Ltd.
- Implications of Genome Alterations in Chironomus bernensis Klȍtzli
- Authors: P. Michailova; J. Ilkova, K. White
Abstract: This study assesses the effect of sediment contaminants as indicated by the measurement of trace metal levels in two large Bulgarian rivers (river Maritsa and a tributary and the river Chaya) on the genome of the abundant chironomid species Chironomus bernensis Klȍtzli. Six trace metals: Cd, Cr, Cu, Mn, Pb and Zn were analysed in the sediments plus the overlying water. The polytene chromosomes of C. bernensis were very sensitive to the pollutants on the basis of numerous somatic chromosome alterations. Two biomarkers based on the degree of somatic structural chromosome alterations—the somatic and cytogenetic indices were applied. Both indices are a sensitive and reproducible approach for assessing the genotoxic effect of contaminants in the sediments. The somatic index from the differentially contaminated sites varied from 1.93 to 2.61, indicating the sensitivity of the C. bernensis genome to anthropogenic stress. The cytogenetic index revealed a high level of pollution in the rivers with a score between 0.27 and 0.37 (
- Vegetation–Hydrogeomorphology Interactions in a Low‐Energy,
- Authors: A. M. Gurnell; R. C. Grabowski
Abstract: The geomorphological dynamics of rivers have been traditionally explained largely by the physical processes of water flow, and sediment erosion and deposition, but the significant role of a third element, vegetation, in driving geomorphological changes has been increasingly highlighted recently. However, few studies have documented how both aquatic and woody riparian plants interact with fluvial processes to induce landform development and initiate channel adjustment. This paper presents analyses of historical maps, recent aerial images and field observations from the River Frome (Dorset, UK), which, as a result of human pressures, has been subject to an increased supply of sand and finer sediment, particularly over the last 50–60 years. Analysis of these information sources indicates that this low‐energy river has adjusted to this delivery of finer sediment by narrowing and increasing its sinuosity. The analysis also indicates that this has been achieved through interactions amongst vegetation, water flow and sediment. Emergent aquatic macrophytes were observed to retain sediment, which leads to the development of submerged shelves that aggrade and become colonized by other plant species to form bars, berms and benches, eventually leading to the extension of river banks into the channel and also the formation of islands. Where woody riparian vegetation is well developed, complex geomorphic changes were observed, with fine sediment being absorbed into a diverse mosaic of geomorphic features initiated by living trees and large wood. These observations underline the importance of vegetation for the geomorphic dynamics and adjustment of lowland, low‐energy rivers and its potential for inclusion in the development of sustainable, process‐based river management and restoration strategies. Copyright © 2015 John Wiley & Sons, Ltd.
- Post‐Spawning Survival and Downstream Passage of Landlocked Atlantic
Salmon (Salmo salar) in a Regulated River: Is There Potential for Repeat
- Authors: D. Nyqvist; O. Calles, E. Bergman, A. Hagelin, L. A. Greenberg
Abstract: Repeat salmonid spawners may make large contributions to total recruitment and long term population stability. Despite their potential importance, relatively little is known about this phase of the life history for anadromous populations, and nothing has been reported for landlocked populations. Here, we studied post‐spawning behaviour and survival of landlocked Atlantic salmon in relation to downstream dam passage in the River Klarälven, Sweden. Eight hydropower stations separate the feeding grounds in Lake Vänern from the spawning grounds in the River Klarälven, and no measures to facilitate downstream migration are present in the river. Forty‐nine percent of the salmon survived spawning and initiated downstream migration. Females and small fish had higher post‐spawning survival than males and large fish. The post‐spawners migrated downstream in autumn and spring and remained relatively inactive in the river during winter. Downstream migration speed in the free flowing part of the river was highly variable with a median of 9.30 km/day. Most fish passed the first hydropower station via upward‐opening spill gates after a median residence time in the forebay of 25 min. However, no tagged fish survived passage of all eight hydropower stations to reach Lake Vänern. This result underscores the need for remedial measures to increase the survival of downstream migrating kelts. Copyright © 2015 John Wiley & Sons, Ltd.
- Effect of Small Impoundments on Leaf Litter Decomposition in Streams
- Abstract: Leaf litter decomposition is an important process providing energy to freshwater biota. Flow regulation and dams can strongly alter freshwater ecosystems, but little is known about the effect of small impoundments on leaf litter decomposition rates in headwater streams. In this study, we examined the effect of small water storage impoundments (80 to 720 m3) on leaf litter decomposition by comparing sites located within 10‐m upstream and downstream of nine impoundments (Rhineland Palatinate, Germany) and sites located further upstream and downstream. The impoundments did not have a statistically significant effect on most physico‐chemical variables. However, the abundance of shredders and leaf litter decomposition rates decreased in study sites located within 10‐m upstream of the area flooded by impoundments. Small impoundments can locally reduce leaf litter decomposition rates in headwater streams. The effect of small impoundments on ecosystem functioning is minor and may require less attention by freshwater managers than other stressors, though this may differ for other ecological aspects such as connectivity. Copyright © 2015 John Wiley & Sons, Ltd.
- Pikeperch, Sander lucioperca Invasion in the Neretva River Watershed
(Bosnia and Herzegovina, Croatia) After Alteration of River Flow
- Abstract: The invasion history and the recent distribution, abundance and prey composition of pikeperch, Sander lucioperca in Neretva River watershed (Bosnia and Herzegovina and Croatia) are presented. The species was illegally/unintentionally introduced in Ramski Reservoir in the upper river part in 1986, while establishment of its abundant populations was reported during the 1990s in two connected artificial reservoirs. The research on the present abundance and food composition was executed during the 2012–2014 period. The results showed that pikeperch occupied most of the water bodies of the Neretva River, with an exception of natural river parts with gravel sediment and fast flow: all five artificial reservoirs (Ramski, Jablanički, Grabovica, Salakovac and Mostarski reservoirs) and lower wetland zone. However, the success and impact of colonization differ among water bodies, indicating pikeperch preference for warm and shallow reservoirs. Pikeperch prey is composed of different fish species abundant in specific water bodies. In artificial reservoirs, it preys mostly on introduced fish species, with a potential for controlling pumpkinseed abundance and biomass. Sampling carried out in Ramski Reservoir between 2013 and 1014 showed exclusive feeding on the introduced Leucaspius delineatus, and the establishment of a new food web, where only introduced species play significant roles. Copyright © 2015 John Wiley & Sons, Ltd.
- Assessing Groundwater Contribution to Streamflow of a Large Alpine River
with Heat Tracer Methods and Hydrological Modelling
- Authors: G. Ravazzani; D. Curti, P. Gattinoni, S. Della Valentina, A. Fiorucci, R. Rosso
Abstract: The contribution of groundwater to streamflow in Alpine catchments is still poorly understood, despite the fact that it may heavily impact hydrological balance and stream habitats. This paper presents the results of a field campaign based on experiments with heat tracer methods to assess the hyporheic flow during the low‐flow period of a large Alpine river in Italy. These measurements were employed to validate a distributed hydrological model that can be used to asses river–groundwater interaction in both low‐flow and high‐flow conditions. The results show that groundwater may have a relevant role during low‐flow periods, by increasing river discharge and during floods, by subtracting direct run‐off that is stored in river banks. Copyright © 2015 John Wiley & Sons, Ltd.
- Evaluation of the Logarithmic Law of the Wall for River Flows
- Authors: J. Petrie; P. Diplas
Abstract: The logarithmic law of the wall is commonly used to determine the shear stress applied to the river bed by the flow field. The shear stress calculation requires a velocity profile at the location of interest—data that can be obtained with a boat‐mounted acoustic Doppler current profiler (ADCP). ADCP survey procedures use either a fixed‐vessel (FV) or moving‐vessel (MV) with each providing different spatial and temporal resolution. MV procedures require significantly less field effort but the data lack the temporal resolution of FV measurements. This fact has motivated investigators to seek MV procedures and analysis techniques that provide equivalent results to FV measurements. This study compares results of the two survey procedures for depth‐averaged quantities (velocity and flow direction), mean velocity profiles, shear velocity and equivalent sand grain roughness. Mean velocity profiles are produced by time averaging for the FV measurements and spatial averaging for the MV measurements. Shear velocity and equivalent sand grain roughness are determined using simple linear regression applied to the logarithmic law of the wall. These procedures are demonstrated using data obtained during bankfull flow on the lower Roanoke River, North Carolina, USA. The results indicate comparable estimates of depth‐averaged quantities from both survey procedures. Estimates of the mean velocity profiles were found to be more variable. The agreement for shear velocity and equivalent sand grain roughness was generally poor indicating that further work is necessary to produce comparable results with MV survey procedures. Copyright © 2015 John Wiley & Sons, Ltd.
- A Twofold Strategy for Riparian Restoration: Combining a Functional Flow
Regime and Direct Seeding to Re‐establish Cottonwoods
- Authors: S. B. Rood; S. Kaluthota, K. M. Gill, E. J. Hillman, S. G. Woodman, D. W. Pearce, J. M. Mahoney
Abstract: The transboundary St Mary River drains Glacier National Park, USA, and was progressively dammed and diverted over the 20th century to support agricultural irrigation in northern Montana and southern Alberta, Canada. Following reduced instream flows, the riparian cottonwoods collapsed, and by 2000, few parental trees remained to provide seeds for cottonwood replenishment. As a novel twofold restoration strategy we: (1) worked with the dam operators to deliver a functional flow regime, a regulated instream flow pattern intended to recover some ecological function and specifically seedling recruitment, and (2) delivered cottonwood seeds by direct spreading and by sticking cuttings with seed catkins to allow gradual seed dispersal. The combination of river regulation and seeding enabled cottonwood colonization, and around 1.5% of the applied seeds produced seedlings after the first summer, at sites without livestock or heavy recreational use. Around 15% of those seedlings survived through the fourth summer, with mortality due to drought stress and flood scour, and establishment and survival were higher for the prairie cottonwood, Populus deltoides, than the narrowleaf cottonwood, Populus angustifolia. This study confirmed that the lack of seed source trees limited cottonwood colonization and demonstrated that the twofold restoration strategy provides promise for severe situations where parental trees have been lost. However, this would require substantial effort, and it would be more efficient to provide survivable instream flow patterns that avoid cottonwood collapse. Copyright © 2015 John Wiley & Sons, Ltd.
- Assessment of the Ecological Reservoir Operation in the Yangtze Estuary
Based on the Salinity Requirements of the Indicator Species
- Authors: C. Wang; Y. Yu, P. F. Wang, Q. Y. Sun, J. Hou, J. Qian
Abstract: In conventional reservoir operations, energy and economic benefits are typically optimized, and ecosystem values are only addressed as constraints. To reduce the negative influence of reservoir operation on the downstream ecological environment, ecological targets should be incorporated into reservoir operations. The concept of environmental flow was developed to define the quantity, quality and timing of water flows that are required to sustain freshwater and estuarine ecosystems. Based on the salinity requirements of the indicator species and the relationship between salinity and the freshwater inflows, environmental flows for the Yangtze Estuary were determined. Subsequently, an ecological reservoir operation model was established that incorporated the ecological target for the protection of the Qingcaosha water source; the Non‐dominated Sorting Genetic Algorithm II was applied to the model. Three typical periods of wet, normal and dry years were selected, and the operation results were analysed for the downstream Datong cross‐section and the environmental flows. The results showed that joint scheduling should be performed for the reservoirs upstream of the Yangtze Estuary. In June of wet and normal years, the current run‐off of the Datong should be reduced by 13.5% and 5%, respectively. In July and September of wet years, current run‐off should be reduced by 30.6% and 25.5%, respectively, as these reductions will not negatively affect the drinking‐water sources. The results of this study should provide guidance in decision‐making to improve the operation of the Three Gorges Reservoir. Copyright © 2015 John Wiley & Sons, Ltd.
- Diet Breadth and Variability in Sander spp. Inferred from
- Authors: M. J. Fincel; S. R. Chipps, B. D. S. Graeb, M. L. Brown
Abstract: We used stable isotopes of carbon and nitrogen to evaluate trophic similarity between sauger Sander canadensis and walleye S. vitreus in three Missouri River impoundments characterized by unique differences in riverine habitat. Mean δ15N was similar for sauger and walleye in each reservoir ranging from 15.7 to 17.8‰ for sauger and 15.2 to 17.7‰ for walleye. However, mean δ13C was greater for sauger (−24‰) than for walleye (−25‰) in Lake Oahe (lacustrine habitat), where rainbow smelt Osmerus mordax is an important prey species for walleye. Variation in δ15N and δ13C values was similar between walleye and sauger in Lewis and Clark Lake (riverine habitat), but was greater for sauger than for walleye in Lake Oahe, implying that in pelagic environments, sauger exhibit a larger diet breadth and lower diet consistency compared with walleyes. Isotope analyses support observations from traditional gut content studies that diet overlap between sauger and walleye varies with environmental conditions and is more similar in riverine food webs than in large lakes and impoundments. Copyright © 2015 John Wiley & Sons, Ltd.
- The Effects of Improved Water Quality on Fish Assemblages in a Heavily
Modified Large River System
- Authors: J. Parker; J. Epifanio, A. Casper, Y. Cao
Abstract: A long history of human alterations has affected the hydrology, physical habitat and water quality of most large river ecosystems. For more than a century, the Illinois River Waterway has been subject to channelization, damming, dredging, agricultural runoff and industrial and municipal effluents. This study evaluates how subsequent improvements in water quality have influenced long‐term changes in fish assemblages (1983–2010). We used five metrics to characterize the changes in fish assemblages. These metrics depicted shifts in the abundance and biomass of predatory and native fishes and species richness. Random forests (RF) and multiple linear regressions (MLRs) were used to relate the fish metrics to individual water quality and weather variables, with weather primarily used to account for inter‐annual variation. Model performances varied spatially and among fish metrics (0 ≤ pseudo‐R2 ≤ 0.73 for RF; 0.10 ≤ adjR2 ≤ 0.88 for MLR), but dissolved oxygen, un‐ionized ammonia and water clarity were often the best predictors. As the distance downstream of major pollutant sources increased, water quality became less important for explaining the changes in fish metrics and weather more important. These results indicate that water quality improvement largely accounts for fish assemblage recovery in the river system, although within some reaches we examined, weather had substantial compounding effects. The results could be used to prioritize water quality variables for long‐term monitoring and aid in predicting fish assemblage responses to future changes in water quality and climate. Copyright © 2015 John Wiley & Sons, Ltd.
- Numerical Modelling of Braided Rivers with
Structure‐from‐Motion‐Derived Terrain Models
- Authors: L. Javernick; D. M. Hicks, R. Measures, B. Caruso, J. Brasington
Abstract: The development of three‐dimensional reconstructions of channel morphology has historically been limited by the high costs of geospatial data collection and software modelling. Advances in image processing, sensor technology and portable remote‐sensing platforms, however, now offer the opportunity to derive survey quality terrain models at significantly reduced cost and without traditional deployment and logistical constraints. There is a pressing need to establish whether new geospatial technologies such as structure‐from‐motion photogrammetry can be used to deliver topographic data products that are suitable for higher‐dimensional hydrodynamic modelling. To address this question, we evaluate the results of simulations using Delft3D that were designed to model distributed, depth‐averaged flows in a wide, shallow, gravel‐bed braided river. The topography for these simulations was derived from digital elevation models (DEMs) generated using structure‐from‐motion and optical bathymetric mapping of two linked reaches of the Ahuriri River, New Zealand. The DEM quality achieved vertical surface errors of 0.10 m in non‐vegetated areas and 0.20 m in inundated areas. Simulations with 1.5 m and 2.5 m resolution grids for low‐flow, medium‐flow and high‐flow conditions were calibrated and tested against field real‐time kinematic‐global navigation satellite system observations. Results revealed that modelled depth errors were comparable to the DEM uncertainty, while simulated and observed inundation patterns achieve a maximum of 81% agreement. Given the complexity of the braided network and shallow flow depths, these simulations provide a powerful demonstration of the suitability of these terrain models for hydrodynamic applications. Copyright © 2015 John Wiley & Sons, Ltd.
- Evaluating Uncertainty in Physical Habitat Modelling in a
High‐Gradient Mountain Stream
- Authors: D. Turner; M. J. Bradford, J. G. Venditti, R. M. Peterman
Abstract: Predictions of habitat‐based assessment methods that are used to determine instream flow requirements for aquatic biota are uncertain, but instream flow practitioners and managers often ignore those uncertainties. Two commonly recognized uncertainties arise from (i) estimating the way in which physical habitat within a river changes with discharge and (ii) the suitability of certain types of physical habitat for organisms. We explored how these sources of uncertainty affect confidence in the results of the British Columbia Instream Flow Methodology (BCIFM), which is a commonly used transect‐based habitat assessment tool for small‐scale water diversions. We calculated the chance of different magnitudes of habitat loss resulting from water diversion using a high‐gradient reach of the North Alouette River, BC, as a case study. We found that uncertainty in habitat suitability indices for juvenile rainbow trout generally dominated uncertainty in the results of the BCIFM when large (>15) numbers of transects were used. In contrast, with small numbers of transects, variation in physical habitat among sampled transects was the major source of uncertainty in the results of the BCIFM. Presentations of results of the BCIFM in terms of probabilities of different amounts of habitat loss for a given flow can help managers prescribe instream flow requirements based on their risk tolerance for fish habitat loss. Copyright © 2015 John Wiley & Sons, Ltd.
- The Effect of Hydrologic Alteration on Capture Efficiency of Freshwater
Fishes in a Highly Modified Prairie Stream
- Authors: K. R. Neufeld; M. S. Poesch, D. A. Watkinson
Abstract: Hydrology is a defining feature of aquatic ecosystems. Changes in stream hydrology, due to climate change, water use and impoundment, have been shown to negatively affect fish populations. Assessing changes in hydrology and its effect on fish populations and communities remains an important consideration for aquatic monitoring programmes across the globe. In this study, we used the Milk River in southern Alberta as a model system to understand how hydrologic alteration may also affect capture probabilities of fishes and impact instream monitoring programmes. The Milk River receives the majority of its April to October flow via an inter‐basin transfer from the St. Mary River, drastically altering the hydrologic regime and instream habitats for fishes during this augmentation period. We estimated species‐specific seine net capture probabilities of fishes in the Milk River during augmentation and natural flow periods using depletion surveys in both open and enclosed sites. Using habitat data collected during the seine surveys, linear mixed‐effects models were created with capture efficiency as the dependent variable. Models were compared using corrected Akaike's information criterion, and the relative contributions of the different variables to the top models were examined. We found that species and flow characteristics, such as water velocity and the state of augmentation, played a prominent role in many of the top models explaining variation in capture efficiency. These results demonstrate that changes to stream hydrology clearly have the potential to impact gear efficiency and individual species assessments. Stream monitoring programmes, which aim to determine long‐term trends in aquatic ecosystem health, need to be mindful that any change to stream hydrology—from climate change, fragmentation or stream alteration—can alter capture efficiency of the sampling gear and inadvertently alter species‐specific trends. Copyright © 2015 John Wiley & Sons, Ltd.
- Advances on Modelling Riparian Vegetation—Hydromorphology
- Abstract: Riparian vegetation actively interacts with fluvial systems affecting river hydrodynamics, morphodynamics and groundwater. These interactions can be coupled because both vegetation and hydromorphology (i.e. the combined scientific study of hydrology and fluvial geomorphology) involve dynamic processes with similar temporal and spatial scales. To predict and assess the consequences of restoration measures, maintenance operations or human pressures in rivers, managers and planners may wish to model these interactions considering the different and interdisciplinary implications in the fields of ecology, geomorphology and hydrology. In this paper, we review models that are currently available and that incorporate the processes that relate riparian vegetation to hydromorphology. The models that are considered include those emphasizing hydraulic‐geomorphological processes (such as flow resistance, sediment transport and bank dynamics) as well as those emphasizing ecological processes (seed dispersal, plant survival, growth, succession and mortality). Models interpreting the coupled evolution between riparian vegetation and river morphology and groundwater are also presented. The aim is to provide an overview of current modelling capabilities and limitations and to identify future modelling challenges. Copyright © 2015 John Wiley & Sons, Ltd.
- Downstream Swimming Behaviour of Catadromous and Potamodromous Fish Over
- Authors: A. T. Silva; C. Katopodis, M. F. Tachie, J. M. Santos, M. T. Ferreira
Abstract: Flow characteristics associated with spillways are important to restore ecological connectivity because spillways can either constrain or offer safe routes for downstream passage of fish. We studied the hydrodynamics of flow and downstream movement behaviour of the catadromous European eel (Anguilla anguilla) and the potamodromous Iberian barbel (Luciobarbus bocagei) in spillways with upstream face inclinations of θ = 90° (standard) 45° and 30° (modified). The standard spillway was tested for two water depths (H = 32 and 42 cm). Modified spillways facilitated downstream passage and reduced delay times of passage of the European eel. Upstream of the 90° spillway, distinct recirculation areas were observed, and associated turbulence strongly hampered downstream passage of fish. Both species were found to avoid turbulence, but barbel displayed stronger avoidance for areas of rapid changes in flow velocity when comparing to eels. Overall, eels were faster in passing the spillway and had a higher downstream passage success (80%) than barbel (32%). Eels were predominantly thigmotactic in contrast to barbel, which showed limited contact with structures. The results suggest that modified spillways may enhance passage survival. Copyright © 2015 John Wiley & Sons, Ltd.
- From the Source to the Outlet: understanding the Distribution of Invasive
Knotweeds along a North American River
- Abstract: Understanding the drivers of exotic plant invasions along waterways is crucial for helping environmental managers devise effective control strategies. We combined a field survey, molecular data and a logistic regression model to further our understanding of the spatial distribution of Japanese (Fallopia japonica) and Bohemian (Fallopia × bohemica) knotweeds along the entire course (185 km) of a river located in Québec (Canada). Both knotweeds were abundant along the river, but each had a distinct spatial distribution pattern. Only one genotype for each knotweed species or hybrid was found, suggesting that the individuals established along the Chaudière River resulted from the propagation of rhizome or stem fragments. The distance from the nearest town or village was the only explanatory variable significantly correlated to the spatial distribution of knotweeds. However, spatial autoregressive coefficients were significant, indicating that knotweeds were more likely to occur close to other knotweeds. In summary, the invasion was probably initiated by the introduction, in riverside towns and villages, of a few individuals of the same genotype. The clones then spread vegetatively, probably during spring floods. The rhizome and stem fragments spread over short distances, dispersing downstream from urban centres. The introduction of just two knotweed genotypes along the Chaudière River was sufficient to initiate a massive riverside colonization, as few riparian vegetation types were apparently able to resist knotweed invasion. Copyright © 2015 John Wiley & Sons, Ltd.
- Path Selection of Atlantic Salmon (Salmo salar) Migrating Through a
- Abstract: We constructed a model that predicted path selection of Atlantic salmon. Our basic assumption for the model was that Atlantic salmon optimize migration by selecting a path that minimizes water resistance. The model prediction was compared with observations in a fishway, and the results were within expectations. It appeared like the fishway design and flow configuration at our study site caused some problems for the fish to discover both of the available paths. Therefore, only 53% of female fish and 67% of male fish selected the optimal path in the beginning of the fishway, but 92% of female fish and 97% of male fish selected the optimal path at the end of the fishway. Velocity over ground was very low, which is likely because every weir in the fishway was an obstacle for the fish. This knowledge can be used to improve future fishway design, or improve flow configuration for existing fishways. Copyright © 2015 John Wiley & Sons, Ltd.
- Effect of Adverse Pressure Gradient and Different Vegetated Banks on Flow
- Authors: H. Afzalimehr; M. Moradian, J. Gallichand, J. Sui
Abstract: This study examines velocity components in 3D and shear stress distributions in flows with adverse pressure gradient over a gravel‐bed channel using three types of vegetation on banks, rice, straw and Typha stems. Results of this experimental study are compared with those for flows in the bare bank channel. Results show that the flows with adverse pressure gradient are not self‐similar in vegetated and bare banks channels. The logarithmic law and parabolic law can be used to well describe flow in the inner and outer regions, respectively, but with different relative flow depths. Shear stress distributions depend on nature of bank roughness and the secondary flow effects because of small values of the aspect ratio and adverse pressure gradient. Quadrant analysis is performed to investigate the effect of different vegetation covers on the Reynolds stress distributions at the central axis of channel and near the vegetated banks. Vegetation covers influence the contributions of different quadrants to the shear stress distribution, showing that sweeps and ejections are dominant events for all vegetated banks for near bed region. However, near the water surface the contributions of outwards and inwards for banks with Typha stems are more important than those for rice and straw. Instead of using a single value for friction factor, for different vegetated banks, a range of friction factor has to be applied in river restoration projects. Vegetated banks result in an increase of more than 60% in friction factor in comparison with that for bare banks under adverse pressure gradient flows. Copyright © 2015 John Wiley & Sons, Ltd.
- Fragmentation of an Intermittent Stream During Seasonal Drought:
Intra‐annual and Interannual Patterns and Biological Consequences
- Authors: J. L. Hwan; S. M. Carlson
Abstract: Intermittent streams lose surface flow during some portion of the year and can be important breeding and rearing habitats for stream biota. However, habitat contraction and deteriorating water quality across the summer can result in harsh conditions and mortality. We explored patterns of drying in a small intermittent stream across the summer in Mediterranean‐climate California, including across 4 years that differed in antecedent precipitation. Wet–dry mapping revealed earlier stream fragmentation following dry winters and that entire sections of the stream varied in their propensity to dry suggesting an important influence of geomorphology on drying. Within two ‘slow‐drying’ reaches, initial riffle volumes were higher following wetter winters, but the rate of riffle drying was higher following wet years, presumably because higher initial volumes resulted in greater drying capacity. Initial pool volumes were similar across years, but the rate of pool drying was faster following dry versus wet winters (pool half‐life ranged from 9.7 weeks in the driest year to 26.3 weeks in the wettest year). Stream temperature differed among years, but differences were slight, and temperatures rarely exceeded optimal conditions for trout growth. We observed limited movement of trout during drier years and found that movement was negatively associated with pool depth, riffle length and date, and positively associated with riffle volume. Overall, we found that antecedent rainfall influenced variability in pool drying more than riffle drying, that entire sections of the creek varied in their propensity to dry and that biological fragmentation preceded physical fragmentation by 3 to 7 weeks. Copyright © 2015 John Wiley & Sons, Ltd.
- A Classification of Stream Water Temperature Regimes in the Conterminous
- Abstract: Temporal variability in water temperature plays an important role in aquatic ecosystems, yet the thermal regime of streams has mainly been described in terms of mean or extreme conditions. In this study, annual and diel variability in stream water temperature was described at 135 unregulated, gauged streams across the USA. Based on magnitude, amplitude and timing characteristics of daily water temperature records ranging from 5 to 33 years, we classified thermal regimes into six distinct types. This classification underlined the importance of including characteristics of variability (amplitude and timing) in addition to aspects of magnitude to discriminate thermal regimes at the continental scale. We used a classification tree to predict thermal regime membership of the six classes and found that the annual mean and range in the long‐term air temperature average along with spring flows were important variables defining the thermal regime types at the continental scale. This research provides a framework for a comprehensive characterization of the thermal regimes of streams that could provide a basis for future assessment of changes in water temperature caused by anthropogenic activities such as dams, land use changes and climate change. Copyright © 2015 John Wiley & Sons, Ltd.
- Forecasting of Hydrographs to Simulate Long Term Recharge From Rivers in
Numerical Models of Mining Reservoirs; Application to A Coal Mine in NW
- Abstract: Although the natural permeability of rocks in the Asturian Central Coal Basin (NW Spain) is generally low, intensive mining activities over many decades has given rise to fracture flow paths that are far more permeable than those associated with the natural lithology. Abandoned and flooded mining works set up artificial ‘pseudo‐karst’ aquifers, which can act as underground reservoirs, with many potential applications. In particular, a mining reservoir shaped by two connected mining shafts within the River Turón basin has been studied. A runoff model was used to produce accurate simulations of streamflow in three different gauging stations during a monitored period of 2 years. The purpose was to use this model in the forecast situation, in order to predict long‐term situations in a hydrogeological FEFLOW model. It was necessary to develop depletion curves for each gauging station based on the available daily effective rainfall and measured flow data, as well as the knowledge of the basin characteristics. The resulting simulated hydrographs were very similar to the measured hydrographs during the monitored period, so the adequate adjusting allows input of the flow for forecast purposes. The model produced forecast hydrographs that had a r = 0.8 and difference in annual volume ranging from 1.6% to 5%. The defined model was applied to a rainfall data set of 30 years, and the average recharge from the river to the mining reservoir could be adequately estimated. The method developed needs to be refined and tested on additional years, but the approach appears to be applicable to operational runoff forecasting for numerical models input data. Copyright © 2015 John Wiley & Sons, Ltd.
- Predicting Floodplain Hypoxia in the Atchafalaya River, Louisiana, USA, a
Large, Regulated Southern Floodplain River System
- Authors: T. E. Pasco; M. D. Kaller, R. Harlan, W. E. Kelso, D. A. Rutherford, S. Roberts
Abstract: The Atchafalaya River Basin Floodway (ARBF), a regulated river/floodplain distributary of the Mississippi River, experiences an annual flood pulse that strongly influences floodplain physicochemistry. We developed several metrics to investigate the relationship between the timing and magnitude of the flood pulse and floodplain hypoxia, which in most years is a spatially extensive and temporally prolonged problem in the lower ARBF. Principal components analysis of flood metrics from 2001 to 2009 revealed contrasting flood types (early cool and late warm), but component‐based general linear models were unable to predict the magnitude of hypoxia in ARBF water management areas (WMAs). Further analyses based on temperature and geographic information system‐determined WMA inundation with generalized additive models (GAMs) revealed WMA‐specific patterns of hypoxia, but the likelihood of hypoxia consistently increased when temperatures approached 20°C and inundation rose above 20–30%. Validation with held‐out data based on logistic regression indicated that the models constructed with the 2001–2009 temperature and inundation data were able to accurately predict the probabilities of hypoxia in two WMAs based on data collected from 2010 to 2013. The GAMs were an effective tool for visualizing and predicting the probability of hypoxia based on two easily generated parameters. Our analyses indicate that modification of the Atchafalaya River flood pulse could reduce the magnitude of hypoxia within the lower ARBF, subject to engineering (control structure operation) and economic (commercial fisheries production) constraints, by minimizing floodplain inundation after water temperatures reach 20°C. Copyright © 2015 John Wiley & Sons, Ltd.
- Fish Movements and Passage Through a Water Control Structure: River Stage
and Floodplain Connectivity
- Authors: S. Tripp; K. Jack Killgore, J. E. Garvey
Abstract: The St. John's Bayou water control structure near New Madrid, MO, connects the main Mississippi River to two large backwater areas called the New Madrid Floodway and St. John's Bayou. While this area has been altered, the New Madrid Floodway and St. John's Bayou account for the only substantial portion of the historic Mississippi River floodplain that remains and provides the only critical connection between backwater/floodplain habitat and the river. Fish passage was evaluated during April–December 2010 using ultrasonic telemetry. Stationary receivers were placed strategically at five locations above and below the structure in St. John's Bayou, in the floodway and the outlet to the Mississippi River. A total of 100 individuals representing 14 species were tagged. Total number of detections during an 8‐month period was 1 264 717. Fifteen individuals representing five species moved into the Mississippi and Ohio rivers; seven individuals returned to St. John's Bayou. Thirteen of the 14 species moved upstream through the structure. Of the 85 individuals that stayed in the bayou, 29 fish passed through the structure for a total of 92 passage events. The downstream : upstream passage was roughly 50:50. Passage was correlated with river rise, with frequency of passage being higher in spring, but passage occurred each month during the study. Copyright © 2015 John Wiley & Sons, Ltd.