- ECO‐FRIENDLY COUNTERMEASURES FOR ENLARGED BASINS EROSION
- Authors: S. Pagliara; M. Palermo, R. Das
Pages: n/a - n/a
Abstract: Eco‐friendly hydraulic structures (such as block ramps, rock weirs and stepped gabion weir) are generally made of rocks placed in two or more layers on a sloped bed. They are usually used in mountainous rivers to control sediment transport. The downstream stilling basin plays an important role in terms of both energy dissipation and erosion control. In addition, a correct design of the downstream stilling basin can create an optimal habitat for fish species in the river. Therefore, in the present work, an attempt was made to control the scour depth downstream of a block ramp using rock structures. In particular, the analysis was focused on scour characteristics in the presence of a protected and enlarged downstream channel. Namely, an abrupt symmetrically enlarged channel was simulated downstream of block ramps. Eco‐friendly protection structures, such as rock sills, were tested to limit the erosive process. Rock sills were placed transversally at different longitudinal and vertical positions in the stilling basin and scour morphology variations were investigated. Experiments were carried out for two different ratios of the width of the channel to the width of the ramp and three different ramp slopes. Several scour morphologies were distinguished and classified. In addition, empirical relationships were derived, by which it is possible to estimate the main scour geometry characteristics. Copyright © 2015 John Wiley & Sons, Ltd.
- Small Weirs, Big Effects: Disruption of Water Temperature Regimes with
Hydrological Alteration in a Mediterranean Stream
- Authors: M.‐J. Bae; R. Merciai, L. Benejam, S. Sabater, E. García‐Berthou
Pages: n/a - n/a
Abstract: The effects of hydrological alterations on thermal regimes due to small water provisioning schemes are poorly understood. We studied the alteration of thermal regimes in a Mediterranean stream, where a weir and a water abstraction have been previously shown to severely affect the flow regime (e.g. frequency and duration of drought) and fish assemblage. Compared to non‐impacted sites, the daily water temperature was more variable downstream of the weir, where water flow was reduced and drying occurred every summer. However, water temperature variation was smaller in a nearby downstream site dominated by effluents from a wastewater treatment plant. In addition, compared to all other sites, the times of the day to reach minimum and maximum water temperatures were markedly different in this site receiving the wastewater plant effluents and occurred earlier in the day in the site below the weir. The relationships between air and water temperatures were tight downstream but became looser and anomalous at the sites affected by water abstraction and effluent inputs. Overall, our results show that water temperature regimes in small streams are abruptly disrupted with water provisioning schemes with unknown consequences for aquatic organisms and ecosystems. Effects may be particularly stressful in Mediterranean‐climate streams, where water is scarce and hydrological alterations pervasive. Copyright © 2015 John Wiley & Sons, Ltd.
- SPAWNING MIGRATION OF WILD AND SUPPLEMENTARY STOCKED LANDLOCKED ATLANTIC
SALMON (SALMO SALAR)
- Authors: A. Hagelin; O. Calles, L. Greenberg, J. Piccolo, E. Bergman
Pages: n/a - n/a
Abstract: Upstream migration by adult salmonids is impeded by dams in many regulated rivers, as is the case for landlocked Atlantic salmon, Salmo salar, in the River Klarälven, Sweden. There, the salmon cannot reach the spawning grounds due to the presence of eight dams. Hence, hatchery‐reared smolts are released downstream of the dams, and upstream migrating spawners are caught in a trap at the lowermost dam before transported by truck to the spawning grounds past the dams. To identify the spawning grounds and compare the behavior of wild and hatchery‐reared Atlantic salmon during upstream migration and spawning, 34 wild and 28 hatchery‐reared, radio‐tagged Atlantic salmon were followed during their spawning migration from August to October 2011. Half (50%) of the hatchery fish, but only 11,8% of the wild fish ended up as fallbacks, i.e. they migrated past the first downstream power station, and did not spawn. A significantly higher proportion (21.4%) of hatchery‐ reared salmon moved in an erratic way, with several up and down stream movements, when compared to the wild salmon (5.9%). When looking at the salmon that stayed in the river (exc. fallbacks), wild individuals exhibited a holding behavior (little or no movements before presumed spawning) more often (86.7%) than the reared ones (50%). The wild salmon also held position (and presumably spawned) for longer time (25.4 days) than the reared salmon (16.1 days). Reared salmon held position, on average, 10 km further upstream than wild salmon, passing the presumed best‐quality spawning habitat. The migration speed (average 17.4 km/day) between two logger stations did not differ between wild and reared fish or between sexes. Our results suggest that the reproductive success of hatchery‐reared Atlantic salmon is relatively low and their capacity as supplementary spawners to the wild population in the Klarälven, is probably small. Copyright © 2015 John Wiley & Sons, Ltd.
- DRAG FORCES ON LARGE CYLINDERS
- Authors: Benoit Turcotte; Robert G. Millar, Marwan A. Hassan
Pages: n/a - n/a
Abstract: Introducing large woody debris into streams is a common practice in restoration projects. Beyond the complexity of flow patterns and sediment movements in streams where woody debris are found or placed, it seems that our understanding of the basic hydraulics of large roughness elements in small channels remains limited. Underestimating the drag force affecting large roughness elements can compromise the success of stream restoration projects. Results from a simple experimental setting confirm that drag force estimates based on approaches developed for small cylinders are not valid when applied to large cylinders. Indeed, the classic drag force equation that uses an empirical drag coefficient is found to significantly underestimate measured drag forces, even when corrected for the ‘blockage ratio’. In contrast, application of specific momentum can yield good estimates of the drag force. A dimensionless depth is defined in a 1D context as a function of the flow depth, critical flow depth and cylinder diameter. A cylinder is considered to be ‘large’ when this dimensionless depth is smaller than 2. In this instance, a relationship is established to estimate the upstream flow depth and the drag force acting on the cylinder. This research bridges the small roughness element theory widely recognized in hydraulic engineering with the theory applicable to large, flow controlling structures such as weirs. From a practical perspective, this research can be used to assist in the design of engineered large woody debris structures. Copyright © 2015 John Wiley & Sons, Ltd.
- IDENTIFYING TEMPERATURE THRESHOLDS ASSOCIATED WITH FISH COMMUNITY CHANGES
IN BRITISH COLUMBIA, CANADA, TO SUPPORT IDENTIFICATION OF TEMPERATURE
- Authors: E. A. Parkinson; E. V. Lea, M. A. Nelitz, J. M. Knudson, R. D. Moore
Pages: n/a - n/a
Abstract: We collected fish samples and measured physical habitat characteristics, including summer stream temperatures, at 156 sites in 50 tributary streams in two sampling areas (Upper Fraser and Thompson Rivers) in British Columbia, Canada. Additional watershed characteristics were derived from GIS coverages of watershed, hydrological and climatic variables. Maximum weekly average temperature (MWAT), computed as an index of summer thermal regime, ranged from 10 to 23 °C. High values of MWAT were associated with large, warm, low relief watersheds with a high lake influence. Measures of community similarity suggested that the fish community changed most rapidly through a lower transition zone at an MWAT of about 12 °C and an upper transition zone at an MWAT of about 19 °C. These results were confirmed using existing fisheries inventory data combined with predictions of MWAT from a landscape‐scale regression model for the Thompson River watershed. For headwater sites in the Chilcotin River watershed (which drains into the middle Fraser River), the relative dominance of bull trout versus rainbow trout (based on inventory data) decreased with increasing predicted MWAT although the distinction was not as clear as for the Thompson River sites. The fish communities in these watersheds can be characterized in terms of very cold water (bull trout and some cold water species), cold water (salmonids and sculpins) and cool water (minnows and some cold water salmonids). The two transition zones (ca 12 and 19 °C) can be used to identify thresholds where small changes in stream temperature can be expected to lead to large changes in fish communities. Such clear, quantifiable thresholds are critical components of a management strategy designed to identify and protect vulnerable fish communities in streams where poor land use practices, alone or in combination with climatic change, can lead to changes in stream temperatures. Copyright © 2015 John Wiley & Sons, Ltd.
- RE‐OPERATING THE THREE GORGES RESERVOIR FOR ENVIRONMENTAL FLOWS: A
PRELIMINARY ASSESSMENT OF TRADE‐OFFS
- Authors: D. E. Rheinheimer; P. Liu, S. Guo
Pages: n/a - n/a
Abstract: The Three Gorges Reservoir (TGR), located on the Yangtze River in China, is operated for hydropower, flood control and navigation, with minimal environmental releases. This study explored the potential trade‐offs between better environmental releases from the TGR and hydropower generation using three performance indicators. Spearman's rank correlation coefficient between unimpaired flows and regulated flows was used as an indicator of environmental performance (eco rho). Energy generation as a fraction of capacity (energy fraction) and power reliability were used as hydropower performance indicators. We first assessed TGR performance without and with basic instream flow requirements (IFRs). We then imposed an IFR consisting of a minimum release of fraction k of inflow and maximum release of 1/k of inflow and assessed the sensitivity of reservoir performance to different fixed k values. Finally, we allowed k to vary within the year in a genetic algorithm to estimate the Pareto optimal trade‐offs between performance indicators. In all cases, flood and navigation rules were prioritized over environmental and hydropower. With a fixed k of 1.0, eco rho increased from 0.865 to nearly 1.0 (completely natural). Energy fraction reduced from 43.5 to 39.3%, or about 9.5%, and power reliability decreased from 97.0 to 59.2%. The Pareto optimal trade‐off surface not only showed similar results but also indicated that energy fraction and environmental performance can both be increased together, up to a point, but at a cost of reliability. This study helps understand the potential costs of re‐operating the TGR. Limitations and potential future directions are discussed. Copyright © 2015 John Wiley & Sons, Ltd.
- A Landscape‐Based Regionalization of Natural Flow Regimes in the
Ebro River Basin and its Biological Validation
- Authors: M. A. Solans; A. Mellado‐Díaz
Pages: n/a - n/a
Abstract: Flow prediction in ungauged basins is an important task for water resources planning and management, and remains a fundamental challenge for hydroecological research. Based on a previous classification of streams and rivers in the Ebro River basin (Spain), where six natural flow‐regime types were identified, we apply a new predictive approach of the flow regime type based on climatic and physiographic descriptors. We used a set of easily available environmental variables as discriminant parameters: annual precipitation, annual evapotranspiration, annual air temperature, elevation, catchment area, drainage density and geology. A stepwise landscape‐based classification procedure consisting of several stepwise discriminant analyses and canonical discriminant analyses allocated a set of sites with poor or no natural flow data into the flow types defined. Misclassification rates obtained by cross‐validation ranged between 1.12% and 11.9%. Additionally, the ecological soundness of the proposed regionalization was tested by the concordance between macroinvertebrate communities and the proposed classification using NMDS and ANOSIM. NMDS resulted in a clear separation of sites into five NFR classes with available macroinvertebrate data, and ANOSIM found significant differences in macroinvertebrate communities among classes. Copyright © 2015 John Wiley & Sons, Ltd.
- Process, Policy, and Implementation of Pool‐Wide Drawdowns on the
Upper Mississippi River: A Promising Approach for Ecological Restoration
of Large Impounded Rivers
- Authors: K. P. Kenow; G. L. Benjamin, T. W. Schlagenhaft, R. A. Nissen, M. Stefanski, G. J. Wege, S. A. Jutila, T. J. Newton
Pages: n/a - n/a
Abstract: The Upper Mississippi River (UMR) has been developed and subsequently managed for commercial navigation by the U.S. Army Corps of Engineers (USACE). The navigation pools created by a series of lock and dams initially provided a complex of aquatic habitats that supported a variety of fish and wildlife. However, biological productivity declined as the pools aged. The River Resources Forum, an advisory body to the St. Paul District of the USACE, established a multiagency Water Level Management Task Force (WLMTF) to evaluate the potential of water level management to improve ecological function and restore the distribution and abundance of fish and wildlife habitat. The WLMTF identified several water level management options and concluded that summer growing season drawdowns at the pool scale offered the greatest potential to provide habitat benefits over a large area. Here we summarize the process followed to plan and implement pool‐wide drawdowns on the UMR, including involvement of stakeholders in decision making, addressing requirements to modify reservoir operating plans, development and evaluation of drawdown alternatives, pool selection, establishment of a monitoring plan, interagency coordination, and a public information campaign. Three pool‐wide drawdowns were implemented within the St. Paul District and deemed successful in providing ecological benefits without adversely affecting commercial navigation and recreational use of the pools. Insights are provided based on more than 17 years of experience in planning and implementing drawdowns on the UMR. Copyright © 2015 John Wiley & Sons, Ltd.
- Anticipatory Management for Instream Habitat: Application to Carneros
- Authors: J. R. Beagle; G. M. Kondolf, R. M. Adams, L. Marcus
Pages: n/a - n/a
Abstract: Ecological research increasingly demonstrates that the best fish habitat is associated with complex, dynamically migrating channels. Active erosion and deposition create pools, side channels, and surfaces for recruitment of riparian vegetation, resulting in hydraulic complexity. As such, the most effective and sustainable restoration strategies restore natural processes, and in turn, create biological habitat. Nevertheless, there exists a social–cultural preference for stable channels. Landowners are often unhappy with eroding banks and, more broadly, are uncomfortable with ‘messy’ ecosystems and the erosion, deposition, and channel migration that are essential components of the dynamic channels that provide the greatest floodplain biodiversity. Episodic bank erosion and failure are often treated with emergency response measures, such as riprap and bank hardening. This often results in simplified channels with minimized instream habitat. Here, we propose an alternative management approach for streams with cohesive banks, and where active erosion is concentrated in ‘hot spots’ that are roughly predictable based on geomorphic analysis. We term the approach anticipatory management and present an application of the approach to Carneros Creek, an incised tributary to the Napa River. We contrast the likely habitat values and agricultural land loss of the anticipatory management approach to: (i) a conventional bank stabilization project proposed for the creek, and (ii) a series of uniform setbacks. Copyright © 2015 John Wiley & Sons, Ltd.
- OPTIMAL FISH PASSAGE BARRIER REMOVAL—REVISITED
- Authors: S. King; J. R. O'Hanley
Pages: n/a - n/a
Abstract: Infrastructure, such as dams, weirs and culverts, disrupt the longitudinal connectivity of rivers, causing adverse impacts on fish and other aquatic species. Improving fish passage at artificial barriers, accordingly, can be an especially effective and economical river restoration option. In this article, we propose a novel, mixed integer programing model for optimizing barrier mitigation decisions given a limited budget. Rather than simply treating barriers as being impassable or not, we consider the more general case in which barriers may be partially passable. Although this assumption normally introduces nonlinearity into the problem, we manage to formulate a linear model via the use of probability chains, a newly proposed technique from the operations research literature. Our model is noteworthy in that it can be readily implemented and solved using off‐the‐shelf optimization modelling software. Using a case study from the US State of Maine, we demonstrate that the model is highly efficient in comparison with existing solution methods and, moreover, highly scalable in that large problems with many thounsands of barriers can still be solved optimally. Our analysis confirms that barrier mitigation can provide substantial ecological gains for migratory fish at low levels of investment. Copyright © 2014 John Wiley & Sons, Ltd.
- Synthesizing Environmental Flow Needs Data for Water Management in a
Water‐Scarce State: The Arizona Environmental Water Demands Database
- Authors: K. E. Mott Lacroix; B. C. Xiu, J. B. Nadeau, S. B. Megdal
Pages: n/a - n/a
Abstract: Water rights for environmental flows are not universal, and oftentimes, legal tools used to incorporate the environment into water management only require new users to consider their impact. It can be difficult to include the needs of riparian and aquatic ecosystems in new plans when relevant information is not always available, especially when other existing uses already outstrip available supplies. There is a need for easily accessible and understandable science on the water requirements for riparian and aquatic species, so managers can make informed decisions about whether or not to include riparian and aquatic species in their community's water management future. In this paper, we describe the current understanding of the link between hydrology and Arizona's riparian and aquatic ecosystems through the creation of a geospatial Environmental Water Demands database that can be used to determine the water needs to maintain habitat. Analysis of 121 studies reveals that there are very few analyses of the surface water and groundwater requirements for intermittent or ephemeral river systems, and there are only limited generalizable data for aquatic species. Except for a few species, such as Cottonwood (Populous fremontii) and Willow (Salix gooddingii), few data are available on the flow requirements for vegetation. The Environmental Water Demands database can be used to identify critical geographic and topical knowledge gaps where further research is needed, as well as serve as a single place for water and land managers to assess and use the most currently available information to make more informed management decisions and recommendations. Copyright © 2014 John Wiley & Sons, Ltd.
- A TEST OF THE SERIAL DISCONTINUITY CONCEPT: LONGITUDINAL TRENDS OF BENTHIC
INVERTEBRATES IN REGULATED AND NATURAL RIVERS OF NORTHERN CANADA
- Authors: L. E. Ellis; N. E. Jones
Pages: n/a - n/a
Abstract: Abiotic and biotic impacts below impoundments within the context of the River Continuum (RCC) and the Serial Discontinuity Concepts (SDC) have been the focus of many lotic studies. Recovery gradients, however, are rarely examined in sufficient detail below dams. Further refinement and understanding are needed to inform science and river managers about regulated river ecology. In this study, we examine longitudinal patterns in abiotic and biotic characteristics in two regulated rivers in Northern Canada. We also examine spatial patterns on two natural rivers: a lake outlet river and a river with no lakes. Direct gradient analysis revealed that increases in periphyton, planktonic drift, primary production, substrate size, and changes in thermal regime at sites closest to the dam drive benthic invertebrate community characteristics. We test the Serial Discontinuity Concept by comparing predicted functional forms of each environmental variable with the empirically derived forms. Substrate size, periphyton biomass, and drift density increased below dams and recovered quickly within 5 km downstream, following closely with SDC predictions. The response of organic matter and water quality was variable, and benthic invertebrate richness recovered relatively quickly, contrary to SDC predictions. Thermal regime and flow took much longer to recover than most variables and represent a second longer gradient type below dams. Plecoptera, Gomphidae, and Simuliidae were strongly influenced by altered resource and habitat and may be good candidates for indicators and predictive modelling. Our results generally support predictions from the Serial Discontinuity Concept and highlight the need for the further testing and refinement of this concept. Copyright © 2014 John Wiley & Sons, Ltd.
- SURVIVAL, GROWTH, AND MOVEMENT OF SUBADULT HUMPBACK CHUB, GILA CYPHA, IN
THE LITTLE COLORADO RIVER, ARIZONA
- Authors: M. C. Dzul; C. B. Yackulic, D. M. Stone, D. R. Van Haverbeke
Pages: n/a - n/a
Abstract: Ecologists estimate vital rates, such as growth and survival, to better understand population dynamics and identify sensitive life history parameters for species or populations of concern. Here, we assess spatiotemporal variation in growth, movement, density, and survival of subadult humpback chub living in the Little Colorado River, Grand Canyon, AZ from 2001–2002 and 2009–2013. We divided the Little Colorado River into three reaches and used a multistate mark‐recapture model to determine rates of movement and differences in survival and density between sites for different cohorts. Additionally, site‐specific and year‐specific effects on growth were evaluated using a linear model. Results indicate that summer growth was higher for upstream sites compared with downstream sites. In contrast, there was not a consistent spatial pattern across years in winter growth; however, river‐wide winter growth was negatively related to the duration of floods from 1 October to 15 May. Apparent survival was estimated to be lower at the most downstream site compared with the upstream sites; however, this could be because in part of increased emigration into the Colorado River at downstream sites. Furthermore, the 2010 cohort (i.e. fish that are age 1 in 2010) exhibited high apparent survival relative to other years. Movement between reaches varied with year, and some years exhibited preferential upstream displacement. Improving understanding of spatiotemporal effects on age 1 humpback chub survival can help inform current management efforts to translocate humpback chub into new locations and give us a better understanding of the factors that may limit this tributary's carrying capacity for humpback chub. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- IMPROVING ANN‐BASED SHORT‐TERM AND LONG‐TERM SEASONAL
RIVER FLOW FORECASTING WITH SIGNAL PROCESSING TECHNIQUES
- Authors: H. Badrzadeh; R. Sarukkalige, A. W. Jayawardena
Pages: n/a - n/a
Abstract: One of the key elements in achieving sustainable water resources and environmental management is forecasting the future condition of the surface water resources. In this study, the performance of a river flow forecasting model is improved when different input combinations and signal processing techniques are applied on multi‐layer backpropagation neural networks. Haar, Coiflet and Daubechies wavelet analysis are coupled with backpropagation neural networks model to develop hybrid wavelet neural networks models. Different models with different input selections and structures are developed for daily, weekly and monthly river flow forecasting in Ellen Brook River, Western Australia. Comparison of the performance of the hybrid approach with that of the original neural networks indicates that the hybrid models produce significantly better results. The improvement is more substantial for peak values and longer‐term forecasting, in which the Nash–Sutcliffe coefficient of efficiency for monthly river flow forecasting is improved from 0.63 to 0.89 in this study. Copyright © 2014 John Wiley & Sons, Ltd.
- LONG‐TERM DYNAMICS OF LARGE‐BODIED FISHES ASSESSED FROM
SPATIALLY INTENSIVE MONITORING OF A MANAGED DESERT RIVER
- Authors: N. R. Franssen; S. L. Durst, K. B. Gido, D. W. Ryden, V. Lamarra, D. L. Propst
Pages: n/a - n/a
Abstract: Imperilment of native fishes worldwide, and particularly in the American Southwest, has prompted management actions to protect and recover threatened populations. Implementation of management activities, however, often proceeds without clear understandings of ecological interactions between native fishes and other biotic and physical components of the environment. Using data obtained in a 19‐year, intensive monitoring effort across 288 km of the San Juan River in NM and UT, USA, we quantified relationships among large‐bodied fishes and longitudinal environmental gradients, tested for faunal breaks of fishes and habitat structure along the river's course, and assessed the response of fishes to mechanical removal of non‐native fishes and stocking of endangered fishes. Mesohabitat variation was not strongly linked to densities of large‐bodied fishes, but we found strong and temporally consistent longitudinal patterns of native and non‐native fishes: Native fish densities were highest upstream while non‐native fish densities where highest downstream, potentially driven by differential responses to temperature regimes. Two breaks in the longitudinal structure of large‐bodied fishes were identified and were associated with a man‐made barrier and changes in the width of the river's floodplain. While densities of common native fishes were relatively constant during the study, non‐native fish removal apparently reduced densities of one of two targeted species and densities of two endangered fishes increased as a result of stocking hatchery‐reared fish. Results of this study suggest that large‐bodied fishes of the San Juan River are responding to large‐scale longitudinal gradients rather than small‐scale habitat variation and management activities have altered densities of target species with limited responses by other fishes in the system. Copyright © 2014 John Wiley & Sons, Ltd.
- FATTY ACID PROFILES DISTINGUISH CHANNEL CATFISH FROM THREE REACHES OF THE
LOWER KASKASKIA RIVER AND ITS FLOODPLAIN LAKES
- Authors: M. P. Young; G. W. Whitledge, J. T. Trushenski
Pages: n/a - n/a
Abstract: Despite the increasing use of fatty acids (FAs) as biomarkers in aquatic food web analysis, little information is available regarding differences in FA profiles of fish among habitat types in river–floodplain ecosystems. The objectives of this study were to (i) test whether the FA profiles of channel catfish (Ictalurus punctatus) differed among three reaches of the lower Kaskaskia River and its floodplain lakes, and (ii) to compare FA profiles among muscle, liver, and adipose fin tissues collected from these fish. Profiles differed significantly among sites, especially between upper and lower river sites, and between river channel and oxbow lake sites, suggesting differences in FA availability for channel catfish occupying different habitats and river reaches in the Kaskaskia River system. Specifically, the essential FAs 18:2n‐6 and 18:3n‐3 increased in catfish tissues from upstream to downstream reaches, which could reflect increased floodplain connectivity and decreasing impoundment effects downstream. Ratios of n‐3 to n‐6 FAs were higher in fish from oxbow lakes, perhaps suggesting increased use of autochthonous production in the floodplain relative to the main river channel. Muscle and adipose fin FA profiles exhibited similar location‐related trends, whereas liver FA profiles were markedly different from the other tissue types. These results suggest that adipose fin tissue samples may be a viable, less‐invasive alternative to muscle tissue for analysis of FA profiles in channel catfish. Our study supports the use of tissue FA profiles in identifying habitat utilization by channel catfish, and perhaps habitat‐specific energy contributions to riverine consumers. Furthermore, our work highlights floodplain habitat as a potential source of essential n‐3 FA and the associated importance of maintaining river–floodplain connectivity to support aquatic food webs. Copyright © 2014 John Wiley & Sons, Ltd.
- NATURAL FLOW REGIMES OF THE OZARK–OUACHITA INTERIOR HIGHLANDS REGION
- Authors: D. R. Leasure; D. D. Magoulick, S. D. Longing
Pages: n/a - n/a
Abstract: Natural flow regimes represent the hydrologic conditions to which native aquatic organisms are best adapted. We completed a regional river classification and quantitative descriptions of each natural flow regime for the Ozark–Ouachita Interior Highlands region of Arkansas, Missouri and Oklahoma. On the basis of daily flow records from 64 reference streams, seven natural flow regimes were identified with mixture model cluster analysis: Groundwater Stable, Groundwater, Groundwater Flashy, Perennial Runoff, Runoff Flashy, Intermittent Runoff and Intermittent Flashy. Sets of flow metrics were selected that best quantified nine ecologically important components of these natural flow regimes. An uncertainty analysis was performed to avoid selecting metrics strongly affected by measurement uncertainty that can result from short periods of record. Measurement uncertainties (bias, precision and accuracy) were assessed for 170 commonly used flow metrics. The ranges of variability expected for select flow metrics under natural conditions were quantified for each flow regime to provide a reference for future assessments of hydrologic alteration. A random forest model was used to predict the natural flow regimes of all stream segments in the study area based on climate and catchment characteristics, and a map was produced. The geographic distribution of flow regimes suggested distinct ecohydrological regions that may be useful for conservation planning. This project provides a hydrologic foundation for future examination of flow–ecology relationships in the region. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- POPULATION TRENDS, BEND USE RELATIVE TO AVAILABLE HABITAT AND
WITHIN‐RIVER‐BEND HABITAT USE OF EIGHT INDICATOR SPECIES OF
MISSOURI AND LOWER KANSAS RIVER BENTHIC FISHES: 15 YEARS AFTER BASELINE
- Authors: M. L. Wildhaber; W.‐H. Yang, A. Arab
Pages: n/a - n/a
Abstract: A baseline assessment of the Missouri River fish community and species‐specific habitat use patterns conducted from 1996 to 1998 provided the first comprehensive analysis of Missouri River benthic fish population trends and habitat use in the Missouri and Lower Yellowstone rivers, exclusive of reservoirs, and provided the foundation for the present Pallid Sturgeon Population Assessment Program (PSPAP). Data used in such studies are frequently zero inflated. To address this issue, the zero‐inflated Poisson (ZIP) model was applied. This follow‐up study is based on PSPAP data collected up to 15 years later along with new understanding of how habitat characteristics among and within bends affect habitat use of fish species targeted by PSPAP, including pallid sturgeon. This work demonstrated that a large‐scale, large‐river, PSPAP‐type monitoring program can be an effective tool for assessing population trends and habitat usage of large‐river fish species. Using multiple gears, PSPAP was effective in monitoring shovelnose and pallid sturgeons, sicklefin, shoal and sturgeon chubs, sand shiner, blue sucker and sauger. For all species, the relationship between environmental variables and relative abundance differed, somewhat, among river segments suggesting the importance of the overall conditions of Upper and Middle Missouri River and Lower Missouri and Kansas rivers on the habitat usage patterns exhibited. Shoal and sicklefin chubs exhibited many similar habitat usage patterns; blue sucker and shovelnose sturgeon also shared similar responses. For pallid sturgeon, the primary focus of PSPAP, relative abundance tended to increase in Upper and Middle Missouri River paralleling stocking efforts, whereas no evidence of an increasing relative abundance was found in the Lower Missouri River despite stocking. Copyright © 2014 John Wiley & Sons, Ltd.
- HISTORICAL CHANGES IN FISH ASSEMBLAGE COMPOSITION FOLLOWING WATER QUALITY
IMPROVEMENT IN THE MAINSTEM TRINITY RIVER OF TEXAS
- Authors: J. S. Perkin; T. H. Bonner
Pages: n/a - n/a
Abstract: The Clean Water Act of 1972 is credited with improving water quality across the USA, although few long‐term studies tracking hydrologic, chemical, and biological responses to cleanup efforts exist. The Trinity River of Texas was plagued by poor water quality for more than a century before passage of legislation to reduce point source pollution from the Dallas–Fort Worth (DFW) Metroplex. We tracked changes in components of flow regime; concentrations of ammonia, nitrate, phosphorus, and biochemical oxygen demand (BOD); and fish assemblage composition in three mainstem reaches during a 40‐year period (1968–2008) following implementation of a large‐scale cleanup initiative. Results suggest little change in flow regime components such as magnitude, timing, and rate of change among the three reaches during 1968–2008. Concentrations of water quality parameters declined through time and with greater distance from DFW, including the lowest concentrations in the reach downstream of a mainstem reservoir (Lake Livingston). Fish assemblage composition shifts correlated with attenuated nutrient and BOD concentrations, and species richness generally increased among all reaches. Native and intolerant fishes consistently increased through time among all three reaches, although lentic and non‐native species also increased downstream of Lake Livingston. Our findings suggest a revitalization of the Trinity River fish assemblage associated with reduced nutrient pollution in DFW (even among distant reaches) and also illustrate potential confounding factors such as stream impoundment and continued nutrient deposition that likely preclude complete recovery. Copyright © 2014 John Wiley & Sons, Ltd.
- AT‐A‐STATION HYDRAULIC GEOMETRY SIMULATOR
- Authors: Daniel John McParland; Brett Eaton, Jordan Rosenfeld
Pages: n/a - n/a
Abstract: Presented in this paper is a hydraulic model that combines a rational regime theory with an at‐a‐station hydraulic geometry simulator (ASHGS) to predict reach‐averaged hydraulic conditions for flows up to but not exceeding the bankfull stage. The hydraulic conditions determined by ASHGS can be paired with an empirical joint frequency distribution equation and applicable habitat suitability indices to generate weighted usable area (WUA) as a function of flow. ASHGS was tested against a 2‐dimensional hydrodynamic model (River2D) of a mid‐size channel in the Interior Region of British Columbia. By linking ASHGS to a regime model, it becomes possible to evaluate the direction and magnitude of habitat changes associated with a wide range of environmental changes. Our regime model considers flow regime, sediment supply, and riparian vegetation: these governing variables can be used to simulate responses to forest fire, flow regulation and changes in climate and land use. Practitioners can examine ‘what‐if’ scenarios that otherwise would be too expensive and time consuming to fully explore. The model boundaries of commonly used data‐intensive hydraulic habitat models (e.g. PHABSIM) are not easily adjusted and such models are not designed to estimate future morphological and hydraulic habitat conditions in rivers the undergo significant channel restructuring. The proposed model has the potential to become an accepted flow assessment tool amongst practitioners due to modest data requirements, user‐friendliness, and large spatial applicability; it can be used to conduct preliminary assessments of channel altering projects and determine if in‐depth habitat assessments are justified.
- AN ESTIMATE OF BASIN‐WIDE DENITRIFICATION BASED ON FLOODPLAIN
INUNDATION IN THE ATCHAFALAYA RIVER BASIN, LOUISIANA
- Authors: M. G. Bennett; K. A. Fritz, A. Hayden‐Lesmeister, J. P. Kozak, A. Nickolotsky
Pages: n/a - n/a
Abstract: Maximizing the reduction of nitrate to dinitrogen gas (denitrification) has been advocated as a means to decrease nitrate pollution that causes eutrophication and hypoxia in estuaries worldwide. Managing this flux in bottomland forest wetlands of the Mississippi River could potentially reduce the world's second largest hypoxic zone. We used published denitrification rates, geospatial data on habitat area and inundation frequency, water level records (1963–2011), and average monthly temperatures to estimate annual denitrification in the Atchafalaya River Basin, the principal distributary of the Mississippi River. Denitrification rates ranged from 5394 kg N year−1 (3.07 kg N km−2 year−1) in 1988 to 17 420 kg N year−1 (9.92 kg N km−2 year−1) in 1981, and rates were consistently higher in fall compared with those in spring. Total NO3− denitrified in the basin was negligible compared with total NO3− entering the Gulf of Mexico. If all N denitrified in the basin instead entered the Gulf, the hypoxic zone was predicted to increase only 5.07 km2 (0.06%). This negligible effect of the basin on N dynamics in the Gulf agrees with other mass balance and isotopic studies in the region. Copyright © 2014 John Wiley & Sons, Ltd.
- ECOSYSTEM MANAGEMENT ALONG EPHEMERAL RIVERS: TRADING OFF
SOCIO‐ECONOMIC WATER SUPPLY AND VEGETATION CONSERVATION UNDER FLOOD
- Authors: S. Arnold; S. Attinger, K. Frank, P. Baxter, H. Possingham, A. Hildebrandt
Pages: n/a - n/a
Abstract: In ecosystems driven by water availability, plant community dynamics depend on complex interactions between vegetation, hydrology, and human water resources use. Along ephemeral rivers—where water availability is erratic—vegetation and people are particularly vulnerable to changes in each other's water use. Sensible management requires that water supply be maintained for people, while preserving ecosystem health. Meeting such requirements is challenging because of the unpredictable water availability. We applied information gap decision theory to an ecohydrological system model of the Kuiseb River environment in Namibia. Our aim was to identify the robustness of ecosystem and water management strategies to uncertainties in future flood regimes along ephemeral rivers. We evaluated the trade‐offs between alternative performance criteria and their robustness to uncertainty to account for both (i) human demands for water supply and (ii) reducing the risk of species extinction caused by water mining. Increasing uncertainty of flood regime parameters reduced the performance under both objectives. Remarkably, the ecological objective (species coexistence) was more sensitive to uncertainty than the water supply objective. However, within each objective, the relative performance of different management strategies was insensitive to uncertainty. The ‘best’ management strategy was one that is tuned to the competitive species interactions in the Kuiseb environment. It regulates the biomass of the strongest competitor and, thus, at the same time decreases transpiration, thereby increasing groundwater storage and reducing pressure on less dominant species. This robust mutually acceptable strategy enables species persistence without markedly reducing the water supply for humans. This study emphasises the utility of ecohydrological models for resource management of water‐controlled ecosystems. Although trade‐offs were identified between alternative performance criteria and their robustness to uncertain future flood regimes, management strategies were identified that help to secure an ecologically sustainable water supply. Copyright © 2014 John Wiley & Sons, Ltd.
- HYDROLOGIC VARIABILITY INFLUENCES LOCAL PROBABILITY OF PALLID STURGEON
OCCURRENCE IN A MISSOURI RIVER TRIBUTARY
- Authors: M. J. Hamel; J. J. Spurgeon, M. A. Pegg, J. J. Hammen, M. L. Rugg
Pages: n/a - n/a
Abstract: A river's flow regime creates and maintains spatial variability in habitat and dictates the distribution and abundance of riverine fishes. Changes to patterns of natural hydrologic variation and disturbance create novel flow conditions and may influence distribution of native fishes. We examined local and regional‐scale factors that influenced the presence of pallid sturgeon Scaphirhynchus albus in the Platte River, a large tributary to the Missouri River in Nebraska, USA. Daily river discharge, diel flow variability, season and location in the study area were the most supported variables in logistic regression models explaining pallid sturgeon distribution. The probability of pallid sturgeon occurrence was greatest during periods of high discharge (>90th percentile flows) in the spring and fall. Pallid sturgeon occurrence was always lower when variability in diel flow patterns was high (i.e. hydropeaking). Our results indicate that pallid sturgeon use of the lower Platte River was strongly tied to the flow regime. Therefore, the lower Platte River may provide an opportunity to preserve and restore sturgeon and possibly other large‐river fishes through appropriate water management strategies. Copyright © 2014 John Wiley & Sons, Ltd.
- MONITORING OF RIVER CONTAMINATION DERIVED FROM ACID MINE DRAINAGE USING
AIRBORNE IMAGING SPECTROSCOPY (HyMap DATA, SOUTH‐WEST SPAIN)
- Authors: J. Buzzi; A. Riaza, E. García‐Meléndez, V. Carrère, S. Holzwarth
Pages: n/a - n/a
Abstract: Imaging spectroscopy is used in this work as an essential mapping tool to monitor changes in contaminated river sediments. Multidate hyperspectral image data (HyMap) are utilized to identify spatial mineral patterns, to detect temporal changes in mineralogy and to link these changes with geochemical processes and short‐term climate characteristics.
River sediments contaminated by acid mine drainage are covered by crusts with variably hydrated iron sulphate. The mineralogy of the crusts and the grain size of the underlying fluvial sediments overlap. The spectra used to build up maps from HyMap data are diagnosed mineralogically with archive spectral libraries from pyrite oxidation minerals from well‐known sequences of minerals.
The maps compiled from hyperspectral imagery display generalized oxidation shown by the coatings over river sediments following warm and dry periods with low water level. After the wet periods, the area covered by oxidized mineralogical phases recedes in favour of hydrated sulphate.
The iteration of image processing algorithms and the mineralogical and potential contamination in a geological context are described. Change detection of the mineral crusts on the river sediments by mapping using hyperspectral remote sensing data may thus enable a quantitative and qualitative environmental evaluation by the regulators. Copyright © 2014 John Wiley & Sons, Ltd.
- DO MANAGEMENT ACTIONS TO RESTORE RARE HABITAT BENEFIT NATIVE FISH
CONSERVATION? DISTRIBUTION OF JUVENILE NATIVE FISH AMONG SHORELINE
HABITATS OF THE COLORADO RIVER
- Authors: M. J. Dodrill; C. B. Yackulic, B. Gerig, W. E. Pine, J. Korman, C. Finch
Pages: n/a - n/a
Abstract: Many management actions in aquatic ecosystems are directed at restoring or improving specific habitats to benefit fish populations. In the Grand Canyon reach of the Colorado River, experimental flow operations as part of the Glen Canyon Dam Adaptive Management Program have been designed to restore sandbars and associated backwater habitats. Backwaters can have warmer water temperatures than other habitats, and native fish, including the federally endangered humpback chub Gila cypha, are frequently observed in backwaters, leading to a common perception that this habitat is critical for juvenile native fish conservation. However, it is unknown how fish densities in backwaters compare with that in other habitats or what proportion of juvenile fish populations reside in backwaters. Here, we develop and fit multi‐species hierarchical models to estimate habitat‐specific abundances and densities of juvenile humpback chub, bluehead sucker Catostomus discobolus, flannelmouth sucker Catostomus latipinnis and speckled dace Rhinichthys osculus in a portion of the Colorado River. Densities of all four native fish were greatest in backwater habitats in 2009 and 2010. However, backwaters are rare and ephemeral habitats, so they contain only a small portion of the overall population. For example, the total abundance of juvenile humpback chub in this study was much higher in talus than in backwater habitats. Moreover, when we extrapolated relative densities based on estimates of backwater prevalence directly after a controlled flood, the majority of juvenile humpback chub were still found outside of backwaters. This suggests that the role of controlled floods in influencing native fish population trends may be limited in this section of the Colorado River. Copyright © 2014 John Wiley & Sons, Ltd.
- HYDROMORPHOLOGY MEETS MAMMAL ECOLOGY: RIVER MORPHOLOGICAL QUALITY, RECENT
CHANNEL ADJUSTMENTS AND OTTER RESILIENCE
- Authors: V. Scorpio; A. Loy, M. Di Febbraro, A. Rizzo, P. Aucelli
Pages: n/a - n/a
Abstract: The need for a multidisciplinary approach for characterizing water bodies in terms of morphological, chemical and ecological quality has hastened the growth of hydromorphology as a cross‐disciplinary topic at the interface of hydrology, geomorphology and ecology. Many authors have analysed how hydroecology may affect freshwater biodiversity, although little is known about how this biodiversity might be affected by river morphological quality. We examined how well the presence of the semi‐aquatic Eurasian otter can be predicted by the rivers' morphological quality and its adjustments over the last decades. We tested the morphological quality index (MQI) methodology in 38 reaches of five rivers in southern Italy, 23 of which were positive to otter presence. In each reach, we examined 28 indicators contributing to the MQI and its 11 sub‐indices. The results showed a significant relationship between the probability of the presence of otters, MQI, and some sub‐indices. The best performing sub‐indices were related to channel adjustments and the continuity of river processes. A more detailed analysis of channel adjustments showed a detrimental effect of channel incision (>3 m) and a positive effect of narrowing, particularly where it occurred simultaneously with the development of forest in the new floodplain. The continuity of river processes has driven the migration of river banks and the development of ponds and secondary channels, likely increasing the availability of dens and resting sites and the hunting capabilities of otters. Our results stressed the importance of fluvial dynamics and sustainable adaptive river management for the habitat quality of semi‐aquatic species. Copyright © 2014 John Wiley & Sons, Ltd.
- RAPID RESPONSE OF A SAND‐DOMINATED RIVER TO INSTALLATION AND REMOVAL
OF A TEMPORARY RUN‐OF‐THE‐RIVER DAM
- Authors: K. H. Costigan; C. M. Ruffing, J. S. Perkin, M. D. Daniels
Pages: n/a - n/a
Abstract: Run‐of‐the‐river dams (RORDs) comprise the vast majority of dams on river systems and are commonly removed as a part of stream restoration strategies. Although these dams are routinely removed, few studies have documented the geomorphological responses of sand‐bed rivers to the removal of RORDs. We examined the response of a large sand‐bed river located in South‐Central Kansas, USA, to the installation and removal of a dam that is installed annually for seasonal recreational purposes. Channel adjustments were tracked using cross‐sections sampled over the course of 7 months as the dam was installed and subsequently removed. Multivariate spatiotemporal analysis revealed emergence of channel stability when the dam was in place for most cross‐sections, except for those immediately adjacent to or at great distances from the dam. Our results provide an approximation for how sand‐bed rivers respond to RORD construction and removal and are useful for guiding management decisions involving preservation or restoration of connectivity. Results of this study suggest that sand‐bed rivers are resilient and recover quickly when transient RORDs are removed. Copyright © 2014 John Wiley & Sons, Ltd.
- HEADWATER STREAMS OF FLORIDA: TYPES, DISTRIBUTION AND A FRAMEWORK FOR
- Authors: W. R. White; T. L. Crisman
Pages: n/a - n/a
Abstract: Using geographic information system and topographic maps, 5829 headwater streams in Florida were surveyed for several parameters including elevation, stream length, flow regime and surrounding geology, and vegetation. Each was assigned to one of four headwater types: wetland, seep, lake, and spring. Wetland headwaters were the most common and widespread followed by seeps, many displaying temporary flow, while springs were perennial and least numerous. Four groups of Florida rivers were identified through cluster analysis of drainage densities (number headwaters/km of river length). Group 1 consisted of six rivers with lowest drainage densities (0.30–1.39 streams/km main channel). All were coastal rivers of peninsular Florida and, with one exception, drain to the Gulf of Mexico. Seven of eight rivers (group 2) with intermediate drainage densities (1.77–3.04 streams/km main channel) were located in peninsular Florida. Only three of 12 rivers comprising the two groups (groups 3 and 4) with greatest drainage densities (5.16–9.37 and 15.49–16.96 streams/km main channel) were not located in the Florida panhandle. Stream conservation efforts should focus on both highly complex dendritic river networks of the panhandle and on the 7000 km2 area in central Florida mostly lacking headwaters that may become a significant dispersal bottleneck for aquatic biota seeking refugia farther north from projected climate change. Copyright © 2014 John Wiley & Sons, Ltd.
- ANTHROPOGENIC DISTURBANCE AND ENVIRONMENTAL ASSOCIATIONS WITH FISH
ASSEMBLAGE STRUCTURE IN TWO NONWADEABLE RIVERS
- Authors: T. P. Parks; M. C. Quist, C. L. Pierce
Pages: n/a - n/a
Abstract: Nonwadeable rivers are unique ecosystems that support high levels of aquatic biodiversity, yet they have been greatly altered by human activities. Although riverine fish assemblages have been studied in the past, we still have an incomplete understanding of how fish assemblages respond to both natural and anthropogenic influences in large rivers. The purpose of this study was to evaluate associations between fish assemblage structure and reach‐scale habitat, dam, and watershed land use characteristics. In the summers of 2011 and 2012, comprehensive fish and environmental data were collected from 33 reaches in the Iowa and Cedar rivers of eastern‐central Iowa. Canonical correspondence analysis (CCA) was used to evaluate environmental relationships with species relative abundance, functional trait abundance (e.g. catch rate of tolerant species), and functional trait composition (e.g. percentage of tolerant species). On the basis of partial CCAs, reach‐scale habitat, dam characteristics, and watershed land use features explained 25.0–81.1%, 6.2–25.1%, and 5.8–47.2% of fish assemblage variation, respectively. Although reach‐scale, dam, and land use factors contributed to overall assemblage structure, the majority of fish assemblage variation was constrained by reach‐scale habitat factors. Specifically, mean annual discharge was consistently selected in nine of the 11 CCA models and accounted for the majority of explained fish assemblage variance by reach‐scale habitat. This study provides important insight on the influence of anthropogenic disturbances across multiple spatial scales on fish assemblages in large river systems. Copyright © 2014 John Wiley & Sons, Ltd.
- IMPACTS OF PROJECTED CLIMATE CHANGES ON STREAMFLOW AND SEDIMENT TRANSPORT
FOR THREE SNOWMELT‐DOMINATED RIVERS IN THE INTERIOR PACIFIC
- Authors: S. Praskievicz
Pages: n/a - n/a
Abstract: Anthropogenic climate change is likely to have significant impacts on river systems, particularly on rivers dominated by seasonal snowmelt. In addition to altering the timing and magnitude of streamflow, climate change can affect the energy available to transport sediment, as well as the availability of sediment to be transported. These hydrologic changes are sensitive to local climate, which is largely controlled by topography, but climate models cannot resolve processes at these scales. Here, I investigate impacts of climate change on streamflow and suspended‐sediment transport for three snowmelt‐dominated rivers in the interior Pacific Northwest – the Tucannon River in Washington and the South Fork Coeur d'Alene and Red rivers in Idaho – using downscaled climate simulations from regional climate models (a range of three models plus an ensemble average) to drive a basin‐scale hydrologic model. The results indicate that climate change is likely to amplify the annual cycle of river discharge, producing higher winter discharge (increases in ensemble mean January discharge ranging from 4.1% to 34.4% for the three rivers), an earlier spring snowmelt peak (by approximately one month), and lower summer discharge (decreases in ensemble mean July discharge ranging from 5.2% to 47.2%), relative to a late 20th‐century baseline. The magnitude of the largest simulated flood under the ensemble‐average climate change scenario increases by 0.6–41.6% across the three rivers. Simulated changes in suspended‐sediment transport generally follow the changes in streamflow. These changes in discharge and sediment transport will likely produce significant impacts on the study rivers, including changes in flooding, physical habitat, and river morphology. Copyright © 2014 John Wiley & Sons, Ltd.
- SIZE‐MEDIATED EFFECTS OF WATER‐FLOW VELOCITY ON RIVERINE FISH
- Authors: A. Del Signore; H. J. R. Lenders, A. J. Hendriks, J. A. Vonk, C. Mulder, R. S. E. W. Leuven
Pages: n/a - n/a
Abstract: We applied species sensitivity distributions (SSDs), commonly used in chemical risk assessment, to quantify the impact of water‐flow velocity on the presence of fish species in a river. SSDs for water‐flow velocity were derived from observational field data (maximal velocity at which species occur, Vmax) and laboratory measurements (critical swimming velocity, Vcrit). By calculating the potentially affected fraction of the fish species of the river Rhine, effects of water‐flow velocity on different life stages and guilds were estimated. Vmax values for adults were significantly higher than those for juveniles and larvae. At water‐flow velocity of 60 cm s−1, half of the adults were affected, while half of the non‐adult life stages were affected at velocities of 25 to 29 cm s−1. There was a positive correlation between body size and fish tolerance to water‐flow. As expected, rheophilic species tolerated higher water‐flow velocities than eurytopic and limnophilic species. Maximal velocities measured in littoral zones of the Rhine were, on average, 10 cm s−1, corresponding to an affected fraction of 2%. An increase in water‐flow velocity up to 120 cm s−1 as a result of passing vessels caused an increase in affected species to 75%. For a successful ecological river management, the SSD method can be used to quantify the trait‐mediated effects of water‐flow alterations on occurring species enabling to compare and rank the effects of chemical and physical stress. Copyright © 2014 John Wiley & Sons, Ltd.
- COMBINING POPULATION GROWTH MODEL AND GENERALIZED ADDITIVE MODEL TO
DETERMINE OPTIMAL WATER LEVEL FOR WATERBIRD CONSERVATION: A CASE STUDY OF
SIBERIAN CRANE (LEUCOGERANUS LEUCOGERANUS) IN LAKE POYANG, CHINA
- Authors: Y. Jia; L. Guan, Y. Wang, G. Liu, G. Lei, L. Wen
Pages: n/a - n/a
Abstract: Siberian crane (Leucogeranus leucogeranus) is one of the most endangered species in the world. The ecological integrity of its main wintering ground at Poyang Lake in China is crucial for the future of the species because Poyang Lake accommodates 99% of its global population. With the Three Gorges Dam fully operational, science‐based adaptive strategies are urgently needed to avoid catastrophic ecological consequences.
This study quantified the link between water level variation and population growth rate of the Siberian crane in Poyang Lake using a suite of advanced statistical techniques. We first used the stochastic Gompert growth model within the state space modelling (SSM) framework to infer population growth rate, density dependence, and process variability and observation errors. We then applied generalized additive models (GAMs) to the population growth rate to quantify the effects of environmental stochasticity.
Our SSM results indicated that there was little support for density dependence, and environmental stochasticity was the main forcing for Siberian crane population variations in Poyang Lake. Although the SSM suggested that water levels in both high‐ and low‐water seasons were important factors for Siberian crane population, inference on their effects were elusive because of large confidence intervals of the estimated coefficients. Using GAM, we confirmed the non‐linear effects of water level on population growth rate. Based on the modelled response curves, we proposed the optimal water level for Siberian crane conservation: (a) maximum summer water season level should be less than 19.5 m and (b) minimum winter water level should be between 8.7–10.2 m. Our methods of integrating population dynamic model and GAM have wide relevance for regional biological conversation efforts that seek to maintain a resilient population of threatened species. Copyright © 2014 John Wiley & Sons, Ltd.
- ISCHNURA GRAELLSII (INSECTA: ODONATA) A WATER POLLUTION BIOVULNERABILITY
INDICATOR—PROBABILITY MAPPING USING SPATIAL UNCERTAINTY
- Authors: F. Campos; T. Velasco, G. Sanz, P. Casanueva, M. T. D. Albuquerque, I. M. H. R. Antunes
Pages: n/a - n/a
Abstract: Monitoring changes of anthropogenic impacts from a broad scope of species in biodiversity research require practical, easy‐to‐use and efficient assessment as well as monitoring methods. Odonates (Insecta: Odonata) are a valuable tool for assessing freshwater systems' quality and have been used as bioindicators of environmental variety.
The Águeda watershed, located in the central west of the Iberian Peninsula, shows an exponential increase in the last 60 years of natural resource exploitation coupled with alterations in consumer habits, causing significant environmental changes and deferred direct effects on the natural habitats.
Fourteen river sites, selected a priori, were sampled. Adult odonates were collected using standardized methods. Selected environmental variables and water quality parameters were evaluated in situ. Precipitation and altitude were the most important physical, environmental variables in explaining the assemblage structure. Meaningful abiotic–biotic as well as biotic–biotic relationships were set up. Furthermore, situations in the urbanized watershed area showed to be highly impacted and closely related with damselfly Ischnura graellsii, which should be targeted as a possible vulnerability indicator for polluted fresh waters.
A probability map for Ischnura graellsii distribution was performed using indicator kriging with external drift and spatial uncertainty obtain through the calculation of two categorical maps (binary), corresponding to the mean (0.485) and the trimmed mean by discharging the 10% lower distribution tail (0.533). The subsequent overlapping of both categorical maps (binary) allowed the definition of the higher spatial uncertainty map for surface water contamination. Copyright © 2014 John Wiley & Sons, Ltd.
- AN EVALUATION OF THE STREAM SIMULATION CULVERT DESIGN METHOD IN WASHINGTON
- Authors: R. J. Barnard; S. Yokers, A. Nagygyor, T. Quinn
Pages: n/a - n/a
Abstract: Stream simulation has become an increasingly common culvert design method around the world. It is based on the assumption that geologic and hydraulic conditions in natural channels define passage characteristics for migrating fish and that water crossing structures that imitate these conditions can then achieve those same passage characteristics. This study expands on an initial evaluation of 19 culverts in 2003 to 50 culverts and includes methods and analyses comparing hydraulic characteristics based on cross sections, profile variation, and bed texture between each culvert and its paired reference reach situated in an adjacent section of the natural channel of each stream. Taken as a group, these culverts simulate bed texture, 100‐year recurrence interval flood velocity and 2‐year flood width but did not simulate thalweg complexity or other hydraulic metrics. Culvert span, relative to the bankfull width of the stream, does not by itself determine whether the culvert simulates the reference reach. Of the 50 culverts, many of which experienced record floods, only one showed significant bed degradation. Copyright © 2014 John Wiley & Sons, Ltd.
- INVASIBILITY DRIVES RESTORATION OF A FLOODPLAIN PLANT COMMUNITY
- Authors: L. A. Toth
Pages: n/a - n/a
Abstract: An understanding of the processes that determine plant community structure is a requisite for the planning and evaluation of restoration efforts on river floodplains. Variable disturbance regimes derived from flood pulses increase the susceptibility of river floodplains to colonizations by new species and establish invasibility as a potentially important factor in plant community assembly and dynamics. The role of invasibility in the restoration of a wet prairie community on the Kissimmee River floodplain in central Florida was evaluated by quantifying temporal species turnover rates during wet and dry season sampling over a 12‐year pre‐restoration and post‐restoration period. Turnover rates increased with reestablishment of annual inundation regimes and were significantly greater on the reflooded floodplain than on the drained, channelized floodplain. Recurrent periods of increased invasibility were associated with repeated high‐amplitude flood pulses and accompanied by increased diversity of plant communities within the wet prairie landscape. Neither invasibility nor beta diversity was strongly related to the variable hydroperiods or depths provided by local topography and restoration of seasonal hydrologic regimes. Results suggest that invasibility is a functional process by which the restored flood pulse has reestablished the structure and diversity of the wet prairie. Copyright © 2014 John Wiley & Sons, Ltd.
- AN EVALUATION OF THE RELATIONS BETWEEN FLOW REGIME COMPONENTS, STREAM
CHARACTERISTICS, SPECIES TRAITS, AND META‐DEMOGRAPHIC RATES OF
WARM‐WATER‐STREAM FISHES: IMPLICATIONS FOR AQUATIC RESOURCE
- Authors: J. T. Peterson; C. P. Shea
Pages: n/a - n/a
Abstract: Fishery biologists are increasingly recognizing the importance of considering the dynamic nature of streams when developing streamflow policies. Such approaches require information on how flow regimes influence the physical environment and how those factors, in turn, affect species‐specific demographic rates. A more cost‐effective alternative could be the use of dynamic occupancy models to predict how species are likely to respond to changes in flow. To appraise the efficacy of this approach, we evaluated relative support for hypothesized effects of seasonal streamflow components, stream channel characteristics, and fish species traits on local extinction, colonization, and recruitment (meta‐demographic rates) of stream fishes. We used 4 years of seasonal fish collection data from 23 streams to fit multistate, multiseason occupancy models for 42 fish species in the lower Flint River Basin, Georgia. Modelling results suggested that meta‐demographic rates were influenced by streamflows, particularly short‐term (10‐day) flows. Flow effects on meta‐demographic rates also varied with stream size, channel morphology, and fish species traits. Small‐bodied species with generalized life‐history characteristics were more resilient to flow variability than large‐bodied species with specialized life‐history characteristics. Using this approach, we simplified the modelling framework, thereby facilitating the development of dynamic, spatially explicit evaluations of the ecological consequences of water resource development activities over broad geographic areas. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- DIVERSITY AND COMMUNITY STRUCTURE OF FISHES IN THE REGULATED VERSUS
UNREGULATED TRIBUTARIES OF THE MEKONG RIVER
- Authors: P. Phomikong; M. Fukushima, B. Sricharoendham, S. Nohara, T. Jutagate
Pages: n/a - n/a
Abstract: Diversity and community structure of fishes were studied in three neighbouring tributaries of the Mekong River in Thailand, namely the Mun, Songkhram and Gam Rivers. The rivers are located in the same ecoregion but have contrasting levels of both hydrological regulations and mitigation measures; the Mun River has a hydropower dam with a fish ladder and sluice gates that are opened during the wet season each year, the Gam River has several irrigation dams with a fish ladder at each dam site, and the Songkhram River has no dams along its river course. A total of 124 freshwater fish species were sampled in these rivers from August 2009 to June 2010. Overall species richness was highest in the Songkhram River (112), followed by the Mun (97) and Gam (54) Rivers. Average per site species richness was also significantly different among rivers but not among sampling months. Abundance–biomass comparison plots revealed considerably overlapping distributions of these two metrics from the dry to early rainy seasons in the Songkhram River and, to a lesser extent, in the Mun River. Fish assemblage data were classified into six clusters with similar community structure. Fish assemblages in the Gam River constituted a single cluster, while those in the other two rivers formed multiple clusters depending on the sampling season. The results of the cluster analysis are discussed in relation to the dominance of the three migration guilds (white, black, and grey fishes) of the Mekong River fishes. The effectiveness of the mitigation measures was determined to be limited in alleviating adverse impacts of dams in these tributaries of the Mekong River. Copyright © 2014 John Wiley & Sons, Ltd.
- GLOBAL WARMING EFFECTS ON FAECAL COLIFORM BACTERIUM WATERSHED IMPAIRMENTS
- Authors: A. Fonseca; C. Botelho, R. A. R. Boaventura, V. J. P. Vilar
Pages: n/a - n/a
Abstract: Impairment of surface water quality by faecal coliform bacteria is an issue of great importance across the globe. A water quality model, Hydrological Simulation Program FORTRAN, was used to predict the impacts of farming and climate change on faecal coliform loads and concentrations in streams of the Lis River watershed, in the Leiria region, Portugal. The calibrated faecal coliform model simulated well the patterns and range of observed faecal coliform concentrations. The accuracy of the model was evaluated by the per cent bias coefficient and the coefficient of determination. The results indicate a general deterioration of the water quality regarding faecal contamination in Lis River. Maximum daily loads were calculated for each of the impaired streams; an average of 77% reduction in the current faecal coliform load from the watershed is necessary to achieve the established water quality goals by the Council Directive 75/440/EEC (). Climate change scenarios (increments on temperature and precipitation) were assumed to predict the behaviour of faecal coliform bacteria in the watershed. The simulated results showed that an increase of 1°C in air daily temperature results in an increase of water temperature of 1.1°C and a 1.5% decrease on faecal coliform bacteria in stream concentration. The combined effect of air temperature (+1°C) and precipitation (+7%) increment leads to an increase of ~2% in bacteria inflow to the basin. Copyright © 2014 John Wiley & Sons, Ltd.
- FLOODING AND SURFACE CONNECTIVITY OF TAXODIUM‐NYSSA STANDS IN A
SOUTHERN FLOODPLAIN FOREST ECOSYSTEM
- Authors: J. A. Kupfer; K. M. Meitzen, P. Gao
Pages: n/a - n/a
Abstract: An understanding of the factors controlling the permanent and episodic links between the main stem of a river and the ecosystems of its alluvial floodplain is necessary for evaluating the influence of modern river processes on floodplain ecology and habitat diversity and for the successful implementation of flow regimes that meet human needs for water in a manner that sustains the ecological integrity of affected systems. In this study, we examined relationships between river hydrology and lateral hydrological connectivity, which is crucial to directing fluxes of water, material, and organisms into and across a floodplain. We did so by translating measures of river discharge for the Congaree River into high resolution maps of flood conditions for the floodplain at Congaree National Park using a 2D flood inundation model. Utilizing a graph network approach, we then analyzed the connectivity of a key wetland ecosystem, Taxodium‐Nyssa forested swamps, to the main stem river and to each other under different flows. Our results underscore that floodplain connectivity is initiated at sub‐bankfull discharges and does not depend on levee overtopping, while also clarifying that various sources of connectivity are triggered at different flow levels in specific reaches. Further, our findings demonstrate the sensitive and non‐linear response of floodplain connectivity to river flows and provide useful information to facilitate the management of flood processes in the Congaree River watershed. Copyright © 2014 John Wiley & Sons, Ltd.
- FATE, TRANSPORT AND EFFECTS OF POLLUTANTS ORIGINATING FROM ACID MINE
DRAINAGE IN THE OLIFANTS RIVER, SOUTH AFRICA
- Authors: J. M. Dabrowski; J. Dabrowski, L. Hill, P. MacMillan, P. J. Oberholster
Pages: n/a - n/a
Abstract: Concentrations of pollutants were measured in water, sediment and algal samples collected along a longitudinal gradient from a stretch of the Olifants River, South Africa, that receives acid mine drainage (AMD) from the Klipspruit River. The effects of AMD were determined through macroinvertebrate biotic indices (SASS5) and multivariate analysis of macroinvertebrate communities. The acidic Klipspruit River caused increased concentrations of total Al, Fe and Mn in the Olifants River. Upon mixing of the Klipspruit with that from the alkaline Olifants River, Al and Fe precipitate rapidly, leading to lower concentrations in the dissolved phase and higher concentrations in the suspended phase and in sediment at sites in close proximity to the confluence. Similarly, filamentous algae accumulated high concentrations of Al, Fe and Zn immediately after the confluence. Mn remains in the dissolved phase, and sediment and algal concentrations increase with increasing distance downstream. Metal speciation analysis indicate that Al is rapidly converted from more toxic forms (e.g. Al3+ and Al(OH)2+) to less toxic forms (e.g. Al(OH)3(aq) and Al(OH)4−). In contrast, Mn remains in the soluble Mn2+ form. Macroinvertebrate metrics and community structure showed clear signs of deterioration in water quality in the Olifants River downstream of the point of AMD input. While total TDS concentrations at all sites fall within ranges likely to affect macroinvertebrates, the relative composition of major ions changes as a result of AMD input, which may also account for the observed changes in macroinvertebrate communities. Further downstream, the Wilge River discharges into the Olifants River and significantly improves water quality downstream of the confluence. Future mining and development activities in the Wilge catchment should be carefully managed and monitored so as to ensure sufficient flows of acceptable quality to prevent further deterioration of water quality in the Olifants River and downstream reservoirs. Copyright © 2014 John Wiley & Sons, Ltd.
- LIFE‐HISTORY PLASTICITY OF RIPARIAN ANNUAL PLANTS ADAPTED TO EXTREME
VARIATIONS IN WATER LEVEL: MESOCOSM EXPERIMENTS
- Authors: Y. Song; X. Ke, W. Liu, A. J. Davy, G. Liu
Pages: n/a - n/a
Abstract: The riparian zones of reservoirs associated with regulated rivers in China experience annual fluctuations in water level of up to 30 m that may vary in timing from year to year. Few plant species can tolerate such hydrological perturbation, but short‐lived riparian annuals might be evolutionarily pre‐adapted to such conditions. This study investigated plasticity of life history in four annual species: one typically associated with free‐flowing rivers (Panicum bisulcatum) and three that colonize reservoir margins (Cyperus michelianus, Fimbristylis miliacea and Eclipta prostrata). We found that all four species produced non‐dormant seeds that survived prolonged submergence; germination percentage was independent of the time of exposure by receding waters. Although growth was reduced as a result of shorter growing seasons, all four species completed their life cycles and produced seeds before winter. In addition, P. bisulcatum and C. michelianus allocated biomass to seed production, at the expense of roots and stems, in response to later establishment. All species responded to later establishment with a reduced vegetative growth period before seed production. C. michelianus, F. miliacea and E. prostrate could also delay the onset of flowering time by up to 2 months. P. bisulcatum, a plant that can flower only after exposure to short days, consequently had a fixed flowering time and could accommodate delayed establishment only with a progressively shorter period of vegetative growth. This lower flexibility might explain its absence from reservoir margins. The conceptual framework presented here offers a tool to predict the establishment of vegetation under hydrological disturbance in riparian environments and thereby provides insights into improved restoration practice. Copyright © 2014 John Wiley & Sons, Ltd.
- A GENERAL APPROACH TO PREDICTING ECOLOGICAL RESPONSES TO ENVIRONMENTAL
FLOWS: MAKING BEST USE OF THE LITERATURE, EXPERT KNOWLEDGE, AND MONITORING
- Authors: J. A. Webb; S. C. Little, K. A. Miller, M. J. Stewardson, I. D. Rutherfurd, A. K. Sharpe, L. Patulny, N. L. Poff
Pages: n/a - n/a
Abstract: Around the world, governments are making huge investments in environmental flows. However, much of the rationale for these releases is based on expert opinion and is thus open to challenge. Empirical studies that relate ecological responses to flow restoration are mostly case studies of limited generality. Radically, different approaches are required to inform the development of general models that will allow us to predict the effects of environmental flows. Here, we describe the modelling framework being used in a major study of environmental flows in the Australian state of Victoria. The framework attempts to make best use of all the information available from the literature, experts, and monitoring data, to inform the development of general quantitative response models. It uses systematic review of the literature to develop evidence‐based conceptual models, formal expert elicitation to provide an initial quantification of model links, and data derived from purpose‐designed monitoring programs over large spatial scales. These elements come together in a Bayesian hierarchical model that quantifies the relationship between flow variation and ecological response and hence can be used to predict ecological responses to flow restoration. We illustrate the framework using the example of terrestrial vegetation encroachment into regulated river channels. Our modelling framework aims to develop general flow‐response models and can immediately be used to demonstrate the ecological return on investment from environmental flow programs. However, the framework also has the potential to be incorporated into planning and decision‐making processes, helping to drive a transformation in evidence‐based practice for environmental flow management. © 2014 The
Authors . River Research and Applications published by John Wiley & Sons, Ltd.
- EFFECTS OF WATER TEMPERATURE ON BREEDING PHENOLOGY, GROWTH, AND
METAMORPHOSIS OF FOOTHILL YELLOW‐LEGGED FROGS (Rana boylii): A CASE
STUDY OF THE REGULATED MAINSTEM AND UNREGULATED TRIBUTARIES OF
CALIFORNIA'S TRINITY RIVER
- Authors: C. A. Wheeler; J. B. Bettaso, D. T. Ashton, H. H. Welsh
Pages: n/a - n/a
Abstract: Many riverine organisms are well adapted to seasonally dynamic environments, but extreme changes in flow and thermal regimes can threaten sustainability of their populations in regulated rivers. Altered thermal regimes may limit recruitment to populations by shifting the timing of breeding activities and affecting the growth and development of early life stages. Stream‐dwelling anurans such as the foothill yellow‐legged frog (Rana boylii) in the Trinity River of northern California are model subjects for examining associations between water temperature and the timing of oviposition, hatching, and metamorphosis, and body condition and size of tadpoles and metamorphs. Breeding activity, hatching success, and metamorphosis occurred later, and metamorphs were smaller and leaner along the regulated and colder mainstem relative to six unregulated tributaries of the Trinity River. Persistently depressed summer water temperatures appear to play a seminal role in inhibited tadpole growth on the regulated mainstem and may be a causative factor in the pronounced decline of this population. Environmental flow assessments should account for the influence of the thermal regime on the development of vulnerable embryonic and larval life stages to improve outcomes for declining amphibian populations. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- DYNAMIC MODELLING OF SOIL NITROGEN BUDGET AND VEGETATION COLONIZATION IN
SEDIMENT BARS OF A REGULATED RIVER
- Authors: T. Asaeda; M. H. Rashid, R. Abu Bakar
Pages: n/a - n/a
Abstract: Intensive forestation widely occurs in East Asian rivers. It deteriorates the ecosystem of gravelly or sandy bars, affects flood protection, and changes the landscape of the river. For the regulation of forestation and vegetative succession on the bars, a suitable tool, through either a numerical simulation model or through empirical knowledge that will predict the future process after treatment, is required. With this background, a dynamic model is developed based on the empirical knowledge obtained by field observations in order to simulate the vegetative growth process on the bars. Observations were conducted at several Japanese rivers in order to better understand tree growth and biomass, herbaceous plant biomass, and soil nitrogen content. The model is composed of four modules: a hydrological module, which provides for flood inundation, flushing and sedimentation processes, a tree module, which describes the recruitment, growth and thinning of tree densities, and a herbaceous plant module, which describes the biomass of herbs as a function of environmental conditions. Finally, there is a soil module, which mostly describes nitrogen budgets. The model was successfully applied to the Arakawa River in central Japan in order to simulate a 30‐year process after a major flood. Simulations were conducted for several cases related to the processes of two tree species: Robinia pseudoacacia and Salix spp. The model was then applied in order to elucidate the forestation mechanism of the bar, which indicated a possible reason for the effect of decreasing the supply of coarse sediment. The impact of the tree and herbaceous plants by different hydrological processes is also discussed. Copyright © 2014 John Wiley & Sons, Ltd.
- RIPARIAN VEGETATION COMMUNITIES OF THE AMERICAN PACIFIC NORTHWEST ARE TIED
TO MULTI‐SCALE ENVIRONMENTAL FILTERS
- Authors: N. Hough‐Snee; B. B. Roper, J. M. Wheaton, R. L. Lokteff
Pages: n/a - n/a
Abstract: Riparia surrounding low‐order streams are dynamic environments that often support distinct biodiversity. Because of their connection to nearby uplands, riparian vegetation communities at these streams respond to many environmental filters—climatic, physical, chemical or biotic factors—that restrict what species can occur at a given location from within larger regional species pools. In this study, we examined how environmental filters originating at the landscape, watershed and reach scales correspond to riparian plant community composition across the interior Columbia and upper Missouri River basins, USA. We correlated riparian vegetation to environmental filters, identified unique communities and partitioned the variance within riparian vegetation data among filters originating at different scales. Riparian vegetation composition was strongly correlated to landscape‐scale filters including elevation, precipitation and temperature. Watershed‐scale filters such as grazing and reach filters indicative of fluvial setting were also correlated to vegetation composition, often differentiating communities with similar landscape settings. We identified 10 distinct vegetation communities. Forested communities occurred at higher elevation, moderate gradient reaches with high mean annual precipitation. Shrub–forb systems corresponded to fluvial and watershed disturbances and occurred within climates that could preclude forest establishment. Meadows corresponded to high water tables and/or high grazing activity. Variance partitioning showed that landscape‐scale filters explained the most variance within vegetation communities. Global change will alter many of the environmental filters that drive vegetation. Vegetation change may occur rapidly if local filters (e.g. fluvial process) change rapidly or may occur more slowly if larger‐order filters (e.g. climate) change slowly and without influencing local hydrogeomorphic filters. By identifying filter–vegetation relationships at large spatial scales, hypotheses can be constructed on how riparian vegetation communities may change under future environmental conditions. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
- DOWNSTREAM EFFECTS OF RECENT RESERVOIR DEVELOPMENT ON THE MORPHODYNAMICS
OF A MEANDERING CHANNEL: SAVERY CREEK, WYOMING, USA
- Authors: C. J. Legleiter
Pages: n/a - n/a
Abstract: Recent reservoir construction on Savery Creek provided an opportunity to examine the downstream effects of a dam on a small, meandering channel. The new dam, completed in 2005, modified the flow regime by reducing the magnitude of spring peaks and increasing baseflows, including a second period of high discharge in the fall. A time series of remotely sensed data spanning 1980–2011 was used to measure lateral migration rates, quantify areas of erosion and deposition, and map spatial patterns of channel change. Both migration rates, and gross erosion and deposition increased during the post‐dam era, although 2 years of exceptionally large snowmelt runoff also occurred during this time. Net sediment flux inferred from the image time series was negative for both the upper and lower reaches for the first photo pair after the dam's completion but became positive for the most recent photos. Detailed topographic surveys of five individual meander bends were used to produce digital elevation models of difference and infer bed material transport rates. For three sites located in the upper reach, downstream increases in transport rate implied a sediment deficit satisfied through channel incision and/or bank erosion. For two sites in the lower reach where sediment supply was greater, larger values of gross erosion were balanced by enhanced deposition and transport rates stabilized or increased along each bend. Together, these results suggest that Savery Creek has entered a period of adjustment as the channel adapts to altered, dam‐regulated supplies of water and sediment. Copyright © 2014 John Wiley & Sons, Ltd.
- CLIMATE‐INDUCED FLOW REGIME ALTERATIONS AND THEIR IMPLICATIONS FOR
THE LANCANG RIVER, CHINA
- Authors: J. Tang; X. A. Yin, P. Yang, Z. F. Yang
Pages: n/a - n/a
Abstract: Most studies of the Lancang River have focussed on the influence of hydropower generation on the riverine ecosystem. Few studies have explored climate‐induced flow regime alterations and their implications for the riverine ecosystem. There is a pressing need for improved understanding of the implications of such climate‐induced flow regime alterations in the Lancang River Basin. Future streamflow under the A2 and B2 scenarios of Hadley Centre coupled model version 3 (HadCM3) are predicted using a back propagation artificial neural network. Potential effects of flow regime alterations are tested by amended annual proportional flow deviation (AAPFD). Projected streamflow will decrease in wet season months and will increase in dry season months. Monthly streamflow at Jiuzhou station was projected to range from a 27.9% decrease to a 158.4% increase. For Gajiu station, the percent increase was projected to range from 1.4% to 70.4%, while the decrease ranged from 0.2% to 16.9%. Changes in streamflow at Yunjinghong station ranged from a 46.5% decrease to a 135.3% increase. Projected streamflow changes during high and low flow periods will have important implications for the ecological processes of the Lancang River Basin. AAPFD indicates that these changes will have serious effects on the Lancang River Basin ecosystem. Projected climate‐induced flow regime alterations during the period of 2071–2095 will have particularly serious effects on riverine ecosystem, especially in the upstream and downstream sections of the Lancang River. The A2 scenario will pose a more serious threat to riverine ecosystem health. Copyright © 2014 John Wiley & Sons, Ltd.
- THE SURVIVAL OF ATLANTIC SALMON (Salmo salar) EGGS DURING DEWATERING IN A
RIVER SUBJECTED TO HYDROPEAKING
- Authors: R. Casas‐Mulet; S. J. Saltveit, K. Alfredsen
Pages: n/a - n/a
Abstract: Hydropeaking in regulated rivers is likely to become more frequent with increasing demands for renewable energy. Sudden fluctuations affect surface and subsurface flow regimes and change hydrological interactions occurring in the hyporheic zone. The hyporheic zone plays an important role for salmon embryonic development, and groundwater influx may create refuges for egg survival during low flow in hydropeaking regulated rivers. The links between salmon embryo survival and hyporheic hydrological processes during hydropeaking have hardly been investigated.
A field experiment was undertaken in a 5 × 20 m side gravel bar subject to dewatering due to hydropeaking. Eleven cylindrical boxes composed of eight compartments were placed in the permanently wet area and the ramping zone. Sixty eggs were placed in two compartments (at 10 and 30 cm depth) in each box. Surface and interstitial water levels and temperatures were monitored at 2 min resolution. Data were collected for a period of 3 months, coinciding with early stages of salmonid egg development in this catchment. Egg compartments were checked on six occasions for survival after different hydropeaking events. Dead eggs were counted and removed. Survival rates were lower in the top compartments in the ramping zone (78%) compared with the boxes in the permanently wet area and the lowermost compartments in the ramping (survival rates >99%). With no water quality issues in the catchment and very low inputs of fine sediments in the egg compartments, exposure to dry conditions and subzero temperatures were the main factors explaining egg mortality in the top compartments of the ramping zone. The rate of survival will thus depend on the surface water and groundwater interactions. Site‐specific hydrological interactions occurring in the hyporheic zone should be actively considered when managing fish populations in rivers with hydropeaking. Copyright © 2014 John Wiley & Sons, Ltd.
- BIOFILM RESPONSES TO FLOW REGULATION BY DAMS IN MEDITERRANEAN RIVERS
- Authors: L. Ponsatí; V. Acuña, I. Aristi, M. Arroita, E. García‐Berthou, D. Schiller, A. Elosegi, S. Sabater
Pages: n/a - n/a
Abstract: Dams regulate downstream hydrology and modify water quality, which in turn can impinge on the biota, especially in rivers naturally subject to large hydrological variability, such as those under Mediterranean climate. The effect of dams on biofilms was analysed in three tributaries (Cinca, Siurana and Montsant) of the Ebro River (NE Spain). We hypothesized that flow regulation would lead to lower spatial variability of biofilms on the streambed and to a decrease in their metabolic rate per unit biomass, especially during low flow periods. Biofilm characteristics were studied in five transects evenly spaced along river reaches upstream (control) and downstream (impact) of dams in each river, along with riverbed granulometry, hydraulics and water chemistry. Chlorophyll‐a, respiratory activity, photosynthetic capacity and efficiency, and extracellular enzymatic activities (β‐d‐glucosidase, alkaline phosphatase and leucine‐amino‐peptidase) of epilithic biofilms were measured in different seasons. Spatial variability of chemical and biological variables was reduced downstream of the dams. Chlorophyll‐a concentration, photosynthetic efficiency and respiration capacity were higher in impact than in control reaches, but generally, low inorganic phosphorus concentrations resulted in comparable phosphatase activities downstream and upstream of dams. On the other hand, β‐d‐glucosidase and leucine‐amino‐peptidase activities were higher at impact reaches. Biofilms were thicker and metabolically more active at the impact reaches, with higher ability to transform dissolved organic matter. Overall, results from this study provide evidence that dams can largely affect the structure and activity of river biofilms, with foreseeable important consequences for river ecosystem functioning. Copyright © 2014 John Wiley & Sons, Ltd.
- LOG‐VANE SCOUR IN CLEAR WATER CONDITION
- Authors: S. Pagliara; L. Sagvand Hassanabadi, S. Mahmoudi Kurdistani
Pages: n/a - n/a
Abstract: Log‐Vane is a grade‐control structure of common use to stabilize river bed and river banks. The purpose of this paper is to study the scour phenomena downstream of Log‐Vanes in straight rivers. The main goal is to obtain design equations to determine the main scour parameters and the scour morphology. All the experiments have been carried out in a horizontal channel and in clear water conditions. Log‐Vanes made of wood, with different heights and vane angles, were tested. Different hydraulic conditions including densimetric Froude numbers, water drops and tail water values were tested. Results show that the tail water depth is an important variable to determine the maximum scour depth. The vane angle results to be an important parameter to predict the scour parameters. Dimensional analysis allows to derive design equations useful to estimate the maximum scour depth, maximum length of the scour and maximum height and length of the dune. Copyright © 2014 John Wiley & Sons, Ltd.
- OPTIMIZING A STANDARDIZED ELECTROFISHING SAMPLING PROTOCOL FOR WARMWATER
RESIDENT SPORTFISH IN THE TALLAPOOSA RIVER, ALABAMA, USA
- Authors: S. M. Sammons
Pages: n/a - n/a
Abstract: A two‐year electrofishing study was initiated in the Tallapoosa River, Alabama, to identify an optimal standardized sampling program for three principal resident sportfish: Alabama bass Micropterus henshalli, redbreast sunfish Lepomis auritus, and redeye bass Micropterus coosae. Samples were conducted in spring (May), summer (July), and fall (October) in 2010 and 2011 from seven 1‐h transects. Spring samples of Alabama bass had lower catch per effort (CPE) and were more skewed towards fish between 200 and 300 mm total length (TL) than samples in other seasons; whereas, fall samples collected more redeye bass >200 mm TL but CPE was similar among seasons. Fewer, but larger, redbreast sunfish were sampled during fall compared with other seasons. Mean CPE of all three species was independent of transect duration. The total time spent electrofishing and processing fish in order to estimate a mean CPE with a specified precision was a function of transect duration and CPE. More effort was needed as CPE decreased for most species, but the relations between transect duration and total effort were parabolic. A precision of within 10% of the mean CPE was unattainable for most species as a result of logistic considerations. Based on the results of this study, it appears that fall is the optimal sampling time for these species in the Tallapoosa River and the optimal transect duration is likely 10 min. At a precision level of 20% of the mean, the number of 10‐min transects required ranged from 5 to 40, with a total sample time for each individual species of 0.82–7.16 h. Copyright © 2014 John Wiley & Sons, Ltd.
- TEMPORAL VARIABILITY AND POTENTIAL PREDICTABILITY OF THE STREAMFLOW
REGIMES IN THE NORTH‐EASTERN IBERIAN PENINSULA
- Authors: M. Hernández‐Martínez; J. M. Hidalgo‐Muñoz, S. R. Gámiz‐Fortis, Y. Castro‐Díez, M. J. Esteban‐Parra
Pages: n/a - n/a
Abstract: This paper investigates the temporal variability and potential predictability of streamflow regimes in the north‐eastern Spain for the 1970–2010 period. Two different regimes are found, those characterized for having peak flows in the winter and those where this maximum appears in the spring. The main characteristic time scales of streamflows in each area are studied by singular spectral analysis (SSA). While winter streamflow regime only shows interannual variability (quasi‐oscillatory modes around 5.5 and 2.3 years), spring streamflow (2.6 and 6.6 years) also presents a decadal variability component. Based on this result, a modelling process is conducted using autoregressive moving average (ARMA) models, for interannual variability modelling, and stable teleconnections between global oceanic sea surface temperature (SST) anomalies and river flow, for decadal variability modelling. Finally, a one‐step‐ahead prediction experiment is computed to obtain forecasted streamflows.
The results for winter streamflow regime modelling show a phase concordance between the raw and the forecasted streamflow time series of around 70% and a correlation around 0.7, for the validation period (2001–2010). For spring streamflow, additionally to the ARMA modelling for the interannual component, a model based on the SST has been established that involves some oceanic regions from previous seasons located, fundamentally, not only in the North Atlantic but also in the Indian Ocean. The combined model (SST + ARMA) significantly improves the prediction based on the ARMA model alone, showing a phase concordance and a correlation around 90% and 0.7 respectively.
This modelling scheme provides predictability skills of the rivers from the Inland Catalan Basins at different time scales, representing an added value for water planning. Copyright © 2014 John Wiley & Sons, Ltd.
- WHY DO FISH STRAND? AN ANALYSIS OF TEN YEARS OF FLOW REDUCTION
MONITORING DATA FROM THE COLUMBIA AND KOOTENAY RIVERS, CANADA
- Authors: R. L. Irvine; J. L. Thorley, R. Westcott, D. Schmidt, D. DeRosa
Pages: n/a - n/a
Abstract: Stranding of fish due to flow reductions has been documented in the near shore of the Columbia and Kootenay Rivers, Canada, and can result in sub‐lethal or lethal effects on fish. Ten years (1999–2009) of monitoring data have been collected at sites below two hydro‐electric dams (Hugh‐L‐Keenleyside and Brilliant Dam) following flow reductions. A generalized linear mixed effects model analysed the probability of a stranding event in relation to environmental and operational variables including the rate of change in the water levels, the duration of shoreline inundation prior to a reduction (wetted history), the river stage, the magnitude of the reduction, distance downstream from the dam, time of day, day of year (season) and whether a site had been physically altered to mitigate stranding. The results demonstrated statistically significant effects on stranding risk from minimum river stage, day of the year and whether a site had been physically re‐contoured. The combination of investigated factors giving the highest probability of stranding was a large magnitude reduction completed in the afternoon in midsummer, at low water levels when the near shore had been inundated for a long period. This research is significant in its approach to assessing years of ecosystem scale monitoring data and using the modelling results to determine ways for these findings to be applied in regulated river management to minimize fish stranding. It also highlighted data gaps that require addressing and provides ecosystem scale results to compare with stranding studies carried out in mesocosms. Copyright © 2014 John Wiley & Sons, Ltd.
- CONCEPTUAL MODELLING TO ASSESS HYDROLOGICAL IMPACTS AND EVALUATE
ENVIRONMENTAL FLOW SCENARIOS IN MONTANE RIVER SYSTEMS REGULATED FOR
- Authors: J. Geris; D. Tetzlaff, J. Seibert, M. Vis, C. Soulsby
Pages: n/a - n/a
Abstract: To improve understanding of natural and managed flow regimes in data‐sparse regulated river systems in montane areas, the commonly used Hydrologiska Byråns Vattenbalansavdelning (HBV) conceptual run‐off model was adapted to incorporate water regulation components. The extended model was then applied to the heavily regulated river Lyon (391 km2) in Scotland to reconstruct the natural flow regime and to assess the impacts of regulation at increasing spatial scales. Multi‐criteria model evaluation demonstrated that the model performed well in capturing the dominant catchment processes and regulation effects, especially at the timescales at which operation rules apply. The main change as a result of regulation in the river Lyon is a decrease in inter‐annual and intra‐annual variability of all elements of the flow regime, in terms of magnitude, frequency, and duration. Although these impacts are most pronounced directly downstream of the impoundments, the regulation effects propagate throughout the river system. The modelling approach is flexible and widely applicable and only limited amounts of data are required. Moreover, results are easily communicated to stakeholders. It has the potential to contribute to the development of flow regimes that may be more beneficial to the ecological status of rivers. In the case of the river Lyon, it is likely that this involves a more variable release regime. The approach developed here provides a tool for assessing impacts on flow regimes and informing environmental flows in other data‐sparse regions with heavily regulated montane river systems. Copyright © 2014 John Wiley & Sons, Ltd.
- ABIOTIC ATTRIBUTES SURROUNDING ALLUVIAL ISLANDS GENERATE CRITICAL FISH
- Authors: W. D. Hintz; A. P. Porreca, J. E. Garvey, Q. E. Phelps, S. J. Tripp, R. A. Hrabik, D. P. Herzog
Pages: n/a - n/a
Abstract: Identifying the appropriate scale at which habitat is biologically relevant to riverine fishes in large, sand‐dominated rivers is a challenge. Alluvial islands are important to several of these fishes throughout the central USA, but there is a paucity of information on island habitat features that restoration efforts should try to replicate. We determined the physical characteristics of two island complexes in the middle Mississippi River that facilitate the settlement and survival of age‐0 shovelnose sturgeon Scaphirhynchus platorynchus at relatively large (mean 39,000 m2) and small (mean 320 m2) scales. Depth (m), flow rate (m s−1), substrate (sand, rock, silt) and vegetation were quantified at these two scales using hydroacoustic techniques (split‐beam sonar and acoustic Doppler current profiler). Abiotic attributes in the surrounding littoral zone of the island complexes were highly correlated but differed depending on location. At the coarse spatial scale, vegetation was positively related to shovelnose sturgeon abundance. At the fine spatial scale, age‐0 shovelnose sturgeon were restricted to flow rates
- USE OF STABLE ISOTOPES TO TRACE MUNICIPAL WASTEWATER EFFLUENTS INTO FOOD
WEBS WITHIN A HIGHLY DEVELOPED RIVER SYSTEM
- Authors: H. A. Loomer; K. D. Oakes, S. L. Schiff, W. D. Taylor, M. R. Servos
Pages: n/a - n/a
Abstract: Many anthropogenic inputs, such as municipal wastewater effluents (MWWEs), affect stable isotope signatures (δ13C and δ15N) at the base of exposed food webs creating spatial patterns reflecting their incorporation into aquatic food webs. The Grand River in southern Ontario, Canada, is a heavily modified, rapidly urbanizing river that assimilates wastewater from 30 municipal wastewater treatment plants. Stable isotope analysis was applied to resident aquatic invertebrates and fish influenced by three different wastewater outfalls in early, middle, and late summer to determine how values shifted seasonally and with differing effluent quality. There was a slight increase in δ13C in both invertebrates and fish in late summer downstream from the three outfalls, but it is difficult to separate effects of the effluents from downstream gradients. Downstream of two of the three outfalls, the δ15N tended to increase relative to upstream, while the remaining effluent, of the poorest quality, decreased δ15N values of both invertebrates and fish. Spatial trends in stable isotopes became more pronounced as the summer progressed with the greatest between‐site differences occurring in late summer. This study reflects the complex nutrient dynamics associated with MWWE inputs to rivers and contributes to our understanding and application of stable isotope analysis in impacted lotic ecosystems. Copyright © 2014 John Wiley & Sons, Ltd.
- EFFECTS OF ROAD CROSSINGS ON HABITAT CONNECTIVITY FOR
- Authors: M. W. Diebel; M. Fedora, S. Cogswell, J. R. O'Hanley
Pages: n/a - n/a
Abstract: Road crossings can act as barriers to the movement of stream fishes, resulting in habitat fragmentation, reduced population resilience to environmental disturbance and higher risks of extinction. Strategic barrier removal has the potential to improve connectivity in stream networks, but managers lack a consistent framework for determining which projects will most benefit target species. The objective of this study is to develop a method for identifying and prioritizing action on road crossings in order to restore stream network connectivity. We demonstrate the method using a case study from the Pine‐Popple watershed in Wisconsin. First, we propose a new metric for quantifying stream connectivity status for stream‐resident fish. The metric quantifies the individual and cumulative effects of barriers on reach and watershed level connectivity, while accounting for natural barriers, distance‐based dispersal limitations and variation in habitat type and quality. We conducted a comprehensive field survey of road crossings in the watershed to identify barriers and estimate replacement costs. Of the 190 surveyed road crossings, 74% were determined to be barriers to the movement of at least one species or life stage of fish, primarily due to high water velocity, low water depth or outlet drops. The results of the barrier removal prioritization show that initial projects targeted for mitigation create much greater improvements in connectivity per unit cost than later projects. Benefit–cost curves from this type of analysis can be used to evaluate potential projects within and among watersheds and minimize overall expenditures for specified restoration targets. Copyright © 2014 John Wiley & Sons, Ltd.
- A NEW METHOD TO ASSESS THE FLOW REGIME ALTERATIONS IN RIVERINE ECOSYSTEMS
- Authors: X. A. Yin; Z. F. Yang, G. E. Petts
Pages: n/a - n/a
Abstract: Assessing alterations of a river's flow regime provides the basis for river protection and restoration planning. The range of variation approach (RVA) is a commonly used method to evaluate alterations in a river's flow regime. However, RVA underestimates the degree of flow regime alteration potentially, because it only considers the difference in frequency between the pre‐impact and post‐impact hydrologic indicator values within certain target ranges and does not consider alteration of the order of hydrologic year types (HYTs; i.e. wet, average and dry years). The HYT order is an important holistic feature of the flow regime. The human‐induced change of HYTs, such as from a dry year to a wet year or from an average year to a dry year, can be a major cause of ecosystem alteration. For some species, the order of the HYTs was more important than single‐year events (such as the flood magnitude during a given year). To address this problem with the RVA, we proposed a modification of this method that accounts for alteration of the order of HYTs. We developed a metric for assessing the alteration of the HYT order based on Euclidean distance and then combined this metric with the RVA. We applied the revised method to a case study of the Sha River in northern China to test its effectiveness. The results demonstrated that the new method solved RVA's problem of potentially underestimating the degree of flow regime alteration and enabled a more comprehensive analysis of the alteration of the flow regime. Copyright © 2014 John Wiley & Sons, Ltd.
- IMPACT OF DROUGHT ON DIATOM COMMUNITIES AND THE CONSEQUENCES FOR THE USE
OF DIATOM INDEX VALUES IN THE RIVER MAUREILLAS
- Authors: A. Barthès; J. Leflaive, S. Coulon, F. Peres, J.‐L. Rols, L. Ten‐Hage
Pages: n/a - n/a
Abstract: In the context of climate change, with an increase in the incidence of seasonally dry streambeds, we examined the impact of drought, and its duration, on the structure of diatom communities and the consequences of this on diatom index values (Biological Diatom Index; Specific Polluosensitivity Index) in the Mediterranean river Maureillas. The effects of several durations of droughts or low flow events (1, 2 and 4 weeks) on diatom‐dominated biofilms were studied by removing pebbles from the river and comparing the growing communities after rewetting with those of control biofilms (pebbles left in the streambed) and with those of newly formed biofilms (cleaned‐up pebbles). Sampling was performed six times during the 28‐day rewetting phase. We determined the specific composition of diatom communities, the mortality rate after rewetting, and the Biological Diatom Index and Specific Polluosensitivity Index scores for each sample, distinguishing between potentially living diatoms (full frustules with chloroplasts) and dead diatoms (empty frustules). Our results showed a notable and durable impact of even short drought on diatom communities. The different trajectories of biofilm communities observed between the types of pebbles showed the importance of the biofilm history for the community structure. This should be taken into account to improve the sampling practices used for monitoring. We also observed a stable mortality rate whatever the drought duration was. Diatom index values were stable despite the observed impact of treatment on diatom communities. These results emphasize the reliability of the diatom index to evaluate biological quality according to European requirements. In addition, the distinction of empty and full frustules did not induce significant differences, but it may reduce biases in interpretation. Copyright © 2014 John Wiley & Sons, Ltd.
- MASS DISPERSAL OF TERRESTRIAL ORGANISMS DURING FIRST FLUSH EVENTS IN A
- Authors: J. Rosado; M. Morais, K. Tockner
Pages: n/a - n/a
Abstract: Temporary streams expand and contract seasonally, forming a complex mosaic of aquatic, amphibic and terrestrial habitats. We studied the terrestrial arthropod fauna at the surface of the dry river bed as well as the fauna of Coarse Particulate Organic Matter (CPOM) deposits 0, 5 and 10 days after first flush events (years 2004–2006) along the Pardiela stream (SE Portugal). During the dry period, large amounts of organic material accumulated at the surface of the dry bed, colonized by abundant terrestrial arthropods (mean density: 13.3 ± 15.29 Ind g DM (Dry Mass of CPOM)). Arthropod density peaked in fresh flood deposits (mean density: 35.8 ± 33.4 Ind g DM), and subsequently decreased within time. Concurrently, the relative composition of the arthropod community changed from Day 0 to Day 10. The present results demonstrated that the dry bed of temporary streams served as a major habitat for terrestrial arthropods. During the first flush events, a mass dispersal of terrestrial arthropods, rafting on floating CPOM, occurred, subsequently forming distinct deposits along the channel margin. These deposits may constitute critical habitats, refugia and food resources for local and regional terrestrial arthropod assemblages. Copyright © 2014 John Wiley & Sons, Ltd.
- What is the Relative Effect of Space and Time to Explain the Braided River
Width and Island Patterns at a Regional Scale?
- Authors: B. Belletti; S. Dufour, H. Piégay
Pages: 1 - 15
Abstract: Several decades of human activities have severely impacted braided rivers worldwide. Despite their widespread disappearance, some remnant braided sectors are still held in the French Rhone basin, mainly in the south‐east of France. In this paper, we analyse the evolutionary pattern of 53 braided reaches, focusing on the active channel width and island patterns, by comparing aerial photographs from the 1950s and 2000s (Institut Géographique National). Because different braided patterns exist (e.g. bar versus island‐braided), we tested the relative effect of geographical and temporal factors. The hypothesis is that three main biogeomorphological braided types exist (i.e. defined through the presence, the amount and the relative size of vegetated islands), based on the combined effect of the following: (i) their position along the river network (i.e. river gradient, altitude and sediment regime) and (ii) the temporal effect represented by the time since the last large flood, that is, the recent flood history. Our results show that even if the regional context (climate and sediment regime mainly) plays a key role, the temporal factor, represented by recent flood history, seems to heavily influence the response of the width pattern and vegetation recovery. Local factors (i.e. topography and groundwater) may also have an impact, but their influence has no effect at the regional level. These results support braided river management (conservation and/or restoration actions) in the Rhone basin and provide a better understanding of the range of braided rivers' functioning. Further studies (e.g. multidate retrospective survey) are needed to better understand the role of flood events on braided pattern and vegetation recovery. Copyright © 2013 John Wiley & Sons, Ltd.
- The Use of Stream Power as an Indicator of Channel Sensitivity to Erosion
and Deposition Processes
- Authors: S. Bizzi; D. N. Lerner
Pages: 16 - 27
Abstract: Stream power is a measure of the main driving forces acting in a channel and determines a river's capacity to transport sediment and perform geomorphic work. Recent digital elevation models allow the calculation of channel gradient and consequently stream power at unprecedented spatial resolution, opening promising and novel opportunities to investigate river geomorphic processes and forms. The present paper investigates the suitability of map‐derived information on total and specific stream power (SSP) to identify dominant processes within the channel (i.e. erosion, transport or deposition). SSP has been already used to identify a threshold for channel stability. This paper tests this knowledge and investigates whether or not attributes of stream power profiles are statistically correlated with distinctive field morphological forms. Two gravel bed single‐thread English rivers are used as case studies, the Lune and the Wye. Available deposition and erosion features surveyed in the field from 124 different locations are used to classify channel reaches as erosion, transport or deposition dominated. Meaningful patterns emerge between the stream power attributes and the field‐based channel classification. An SSP threshold, which erosion is triggered, compares favourably with the ones in the literature. Information about upstream stream power profiles helps to determine the dominant processes. The joint configuration of local and upstream stream power information uniquely classifies reaches into four classes of different sensitivity to erosion and deposition. Copyright © 2013 John Wiley & Sons, Ltd.
- Flow Analysis of a River Confluence with Field Measurements and Rans Model
with Nested Grid Approach
- Authors: S. Baranya; N. R. B. Olsen, J. Józsa
Pages: 28 - 41
Abstract: A comprehensive flow analysis for a confluence of two medium‐sized (Qmean ≈ 30–50 m3/s) Hungarian rivers was carried out by means of a three‐dimensional Reynolds‐averaged Navier–Stokes modelling. The model was validated against detailed fixed and moving Acoustic Doppler Current Profiler velocity profiling. Unsteady simulations with steady‐state boundary conditions were performed on a structured grid in order to reveal the characteristic large‐scale spatial behaviour of the flow, such as strong secondary currents because of the river bends upstream of the confluence. Secondary current vectors indicating the swirling character of the flow were derived both from field measurements and model results showing good agreements for two different discharge ratios. Additionally, a novel approach was used to simulate the unsteady vortex shedding implementing a nested grid into the previously used coarse grid. Using a considerable finer horizontal (~0.5 m) and time (1 s) resolution, the numerical model reproduced the unsteady character of flow between the two rivers. A qualitative assessment of the mixing processes was also introduced through the example of the propagation of plaster plume used to neutralize a disastrous red mud spillage that occurred in 2010. The results indicate the combined influence of secondary currents and vortex shedding. Copyright © 2013 John Wiley & Sons, Ltd.
- Sedimentology of New Fluvial Deposits on the Elwha River, Washington, USA,
Formed During Large‐Scale Dam Removal
- Authors: A. E. Draut; A. C. Ritchie
Pages: 42 - 61
Abstract: Removal of two dams 32 m and 64 m high on the Elwha River, Washington, USA, provided the first opportunity to examine river response to a dam removal and controlled sediment influx on such a large scale. Although many recent river‐restoration efforts have included dam removal, large dam removals have been rare enough that their physical and ecological effects remain poorly understood.
New sedimentary deposits that formed during this multi‐stage dam removal result from a unique, artificially created imbalance between fluvial sediment supply and transport capacity. River flows during dam removal were essentially natural and included no large floods in the first two years, while draining of the two reservoirs greatly increased the sediment supply available for fluvial transport. The resulting sedimentary deposits exhibited substantial spatial heterogeneity in thickness, stratal‐formation patterns, grain size and organic content. Initial mud deposition in the first year of dam removal filled pore spaces in the pre‐dam‐removal cobble bed, potentially causing ecological disturbance but not aggrading the bed substantially at first. During the second winter of dam removal, thicker and in some cases coarser deposits replaced the early mud deposits. By 18 months into dam removal, channel‐margin and floodplain deposits were commonly >0.5 m thick and, contrary to pre‐dam‐removal predictions that silt and clay would bypass the river system, included average mud content around 20%. Large wood and lenses of smaller organic particles were common in the new deposits, presumably contributing additional carbon and nutrients to the ecosystem downstream of the dam sites. Understanding initial sedimentary response to the Elwha River dam removals will inform subsequent analyses of longer‐term sedimentary, geomorphic and ecosystem changes in this fluvial and coastal system, and will provide important lessons for other river‐restoration efforts where large dam removal is planned or proposed. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.
- Exploring Particle Density Effects on Partial Mobility of Steelhead
- Authors: C. L. Nicol; D. P. Smith, F. G. R. Watson
Pages: 62 - 69
Abstract: Yellowbank Creek is a small stream in coastal central California being assessed for salmonid habitat limiting factors and restoration potential. Yellowbank flows through low‐density marine mudstone bedrock, which is the gravel source for the stream. To assess the potential effects of the low‐density substrate on spawning gravels, a tracer stone study comparing the incipient motion of low‐density mudstone particles and typical density granitic particles was used to populate a logistic regression particle entrainment model. A model comparison approach was used to test the strength of the model. Results demonstrate partial mobility of both mudstone and granitic particles under boundary shear conditions ranging from 6.9 to 42.2 N m‐2. The modelling results quantify the strong negative correlation between particle entrainment and particle density. Mudstone gravel was three times more likely to be entrained than granitic gravel, within the context of the experimental conditions. The effect of density difference on partial mobility was greater in smaller grain size fractions. This work has implications for salmonid spawning success in atypical geologic settings and may assist in prioritization of restoration efforts. Copyright © 2013 John Wiley & Sons, Ltd.
- Defining and Testing Targets for the Recovery of Tropical Streams Based on
Macroinvertebrate Communities and Abiotic Conditions
- Authors: M. J. Feio; W. R. Ferreira, D. R. Macedo, A. P. Eller, C. B. M. Alves, J. S. França, M. Callisto
Pages: 70 - 84
Abstract: Here, we set target values to measure the ecological improvement of streams, based on invertebrate communities, riparian vegetation, instream habitat conditions and water chemistry. The study area is a large tropical catchment (Rio das Velhas, Minas Gerais, Brazil) affected by pastures, mining areas and a large urbanized area but also includes natural protected areas. Two stream types were found in the catchment, based on stream size, elevation, climate and geology with significantly different macroinvertebrate communities. In spite of a marked wet/dry seasons' climatic pattern, that does not result in the segregation of communities. Four classes of global degradation (IV—bad to I—good condition) were defined based on the available abiotic information, corresponding to a gradient in structure and biotic metrics of macroinvertebrate communities, matching the current knowledge on taxa sensitivity to pollution and general disturbance. Class I corresponds to target conditions to be achieved under restoration programmes. Using this approach, we were able to detect an improvement of abiotic conditions in four urban streams that benefited from enhancement measures in 2007–2008. However, invertebrate communities improved clearly in only one site (biotic metrics and community structure). Our study highlighted that good water quality alone is not enough and that only the combined effect of water quality, riparian vegetation and instream habitat condition enhancement resulted in the improvement of invertebrate communities. An important limiting factor for macroinvertebrate communities' recovery may be the distance to source populations. We concluded that the combined use of biological and abiotic target values for measuring the recovery of streams is needed to fully achieve an ecological restoration. This approach can also be valuable in the regular monitoring of streams to assess stream degradation. Target values based on other biological elements, such as fishes and algae, and functional processes could also contribute to define more global and realistic goals. Copyright © 2013 John Wiley & Sons, Ltd.
- Effect of Spatial Heterogeneity on Zooplankton Diversity: A
Multi‐Scale Habitat Approximation in a Floodplain Lake
- Authors: G. Chaparro; P. Kandus, I. O'Farrell
Pages: 85 - 97
Abstract: Environmental heterogeneity is an essential quality of ecosystems as it has important implications in community structure. Macrophytes are a main component of environmental heterogeneity in floodplain lakes, and their dynamics are highly influenced by water level changes. In this context, we analysed at different spatial scales the relationship among hydrological variations, environmental heterogeneity associated to macrophytes and zooplankton regional diversity (γ diversity) in a South American floodplain lake adjacent to the Paraná River, and we also compared the local zooplankton diversity (α diversity) among the different environments that comprised the lake heterogeneity. At very low waters, the environmental heterogeneity was reduced as the lake was mainly limited to open water areas with low zooplankton diversity. At high waters, the profuse vegetation development (emergent and free‐floating), in mixed or homogeneous patches, determined a higher lake environmental heterogeneity with enhanced regional zooplankton diversity; littoral species increased over limnetic ones. Zooplankton α diversity was higher in environments with free‐floating macrophytes than in those without these plants. The structural complexity in the water column provided by plant roots would be closely related to the enhanced diversity found under free‐floating mats. This study contributes to the knowledge on the effects of strong water level variations on environmental heterogeneity, which is strongly associated to macrophytes and on zooplankton diversity, and highlights the role of free‐floating plants as diversity hosts and ‘key structures’ in floodplain lakes. Copyright © 2013 John Wiley & Sons, Ltd.
- Development of Habitat Suitability Criteria and In‐Stream Habitat
Assessment for the Benthic Cyanobacteria Phormidium
- Authors: M. W. Heath; S. A. Wood, K. A. Brasell, R. G. Young, K. G. Ryan
Pages: 98 - 108
Abstract: Global demand for freshwater has led to unprecedented levels of water abstraction from riverine systems. This has resulted in large alterations in natural river flows. The deleterious impacts of reduced flows on fish and macroinvertebrate abundances have been thoroughly investigated; in contrast, there is a limited understanding of the potential for changes in the abundance of nuisance benthic algal/cyanobacterial blooms. In New Zealand, Phormidium sp. blooms are common in numerous rivers during summer low flows. In this study, an in‐stream habitat assessment is used to examine the relationship between Phormidium habitat availability and reducing flows. Over 650 observations of Phormidium mats, from seven sites (Hutt River, lower North Island, New Zealand), were used to construct habitat suitability curves for depth, velocity and substrate. Preference curves were fitted using both the ‘forage ratio’ and ‘quantile regression’ methods. Phormidium growth, observed at all seven sites, increased significantly from upstream (uppermost site, 5.2% mat cover) to downstream (63.5%). The habitat suitability curves revealed Phormidium had a large tolerance to velocity, depth and substrate type. Consequently, decreases in flow had only negligible effects on available Phormidium habitat. During periods of stable flow, Phormidium abundance positively correlated with increased nitrogen concentrations, potentially explaining the large variation in Phormidium cover from upstream to downstream. Quantile regression generated habitat suitability criteria were a more accurate predictor of available Phormidium habitat than the forage ratio criteria. Copyright © 2013 John Wiley & Sons, Ltd.
- Predicting Long‐Term Changes in Riparian Bird Communities in
- Authors: Y. Yabuhara; Y. Yamaura, T. Akasaka, F. Nakamura
Pages: 109 - 119
Abstract: As anthropogenic impacts on riverine ecosystems expand, both aquatic and terrestrial ecosystems are influenced over large spatiotemporal scales. We predicted how riparian bird communities changed in response to long‐term changes in floodplain landscapes such as woodland expansion (i.e. rapid increases in vegetation cover on gravel bars and the progress of vegetation succession due to a decrease in the frequency and magnitude of flood disturbance). To test the hypothesis that woodland expansion after dam construction reduces the abundance of gravel bar‐nesting birds and increases the abundance of forest‐nesting birds, we estimated historical changes between past and present bird abundances using species distribution models across multiple rivers that were either unregulated or regulated by dams. We created past and present vegetation maps from remote sensing images and used habitat quantities as explanatory variables in the species distribution models. As we hypothesized, the estimated abundance of gravel bar‐nesting birds decreased and that of forest‐nesting birds increased because of woodland expansion in some regulated rivers. This suggests that anthropogenic alterations of riverine conditions (e.g. dam construction) can affect terrestrial ecosystems (e.g. riparian bird communities) through changes in floodplains (e.g. woodland expansion). In addition, our findings highlight the efficacy of combining spatial and temporal analyses when examining long‐term ecological dynamics. Copyright © 2013 John Wiley & Sons, Ltd.
- Spatial Distribution of Fishes in Hydropeaking Tributaries of Lake
- Authors: M. J. Bond; N. E. Jones
Pages: 120 - 133
Abstract: Deviation from a river's natural flow regime is considered to be one of the most serious and continuing threats to lotic ecosystems. Peaking hydroelectric facilities, which are designed to adjust the level of power generation in accordance with hourly energy demand, can dramatically alter flows and temperatures and ultimately lead to changes in the quantity and quality of habitat available to fish. In this study, we examine the spatial distribution of river fishes, benthic invertebrates and organic matter along lateral and longitudinal gradients in two hydropeaking and eight natural Lake Superior tributaries in Ontario, Canada. This study demonstrates that (i) hourly variation in flow, caused by hydropeaking, results in a varial zone that supports significantly fewer fish than the adjacent permanently wetted channel and (ii) strong longitudinal gradients in fish biomass, particularly for sedentary species such as slimy sculpin (Cottus cognatus), exist in regulated rivers, and fish biomass is up to four times greater at sites directly below the peaking dams than at sites further downstream or in nearby natural rivers. Gradients in the spatial distribution of fishes closely follow changes in food resources such as benthic organic matter and invertebrates, suggesting that these gradients are driven by spatial shifts in food availability and are ultimately caused by gradients in abiotic habitat variables. Monitoring and assessment efforts should take into account that lateral and longitudinal gradients exist in regulated rivers, and this understanding must be incorporated into sampling programmes. Failing to do so could alter the interpretation of river productivity, integrity and health. Copyright © 2013 John Wiley & Sons, Ltd.