Optimising hydropower development and ecosystem services in the Kafue River, Zambia

Fisheries are an important resource in Zambia, but are experiencing overexploitation and are under increasing pressure from external development activities that are compromising river ecosystem services and functioning. One such system is the Kafue Flats floodplain, which is under threat from hydropower development. This paper reviews the impact of potential hydropower development on the Kafue Flats floodplain and explores mechanisms to optimise the expansion of hydropower whilst maintain the ecosystem functioning and services the floodplain delivers.Since completion of the Kafue Gorge and Itezhi-tezhi dams, seasonal fluctuations in the height and extent of flooding have been suppressed. This situation is likely to get worse with the proposed incorporation of a hydropower scheme into Itezhi-tezhi dam, which will operate under a hydropeaking regime. This will have major ramifications for the fish communities and ecosystem functioning and likely result in the demise of the fishery along with destruction of the wetlands and associated wildlife. To redress the problem it is recommended that an environmental flows study is conducted, as initiated by World Wildlife Fund, to protect the existing ecosystem services provision and optimise hydropower development, thus ensuring sustainability of the aquatic resources of the Kafue Flats for future generations

Win, win, win: Low cost baffle fish pass provides improved passage efficiency, reduced passage time and broadened passage flows over a low-head weir

The number of low-head barriers to fish migration far outweighs the number of large magnitude barriers and thus the cumulative negative impact on fish communities could also be far greater. Removal of man-made obstructions to fish migration is the most beneficial mitigation measure for reconnecting fragmented rivers but is not always possible and thus fish passes must be constructed. Given the large number of low-head barriers, cheap but effective fish passes must be identified. This study measured passage of brown trout (Salmo trutta L.) at a low-head gauging weir on Eshton Beck, England, before and after low cost baffle (LCB) fish pass construction using passive integrated transponder (PIT) telemetry. The LCB fish pass significantly improved overall passage efficiency from a maximum of 64% to 91%. There was a significant decrease in delay at the obstruction after the LCB fish pass was constructed and fish passed on a greater range of flows (0.08 – 5.39 m3s-1) in comparison to before (0.56 - 1.92 m3s-1). Fish ascended the fish pass through the low velocity channel (gaps in the baffles) as well as over the baffles, though a higher proportion were detected ascending over baffles at higher flows. It was therefore concluded that similar low-head structures should incorporate this style of fish pass to improve longitudinal connectivity for brown trout and other species with similar passage capabilities

Efficiency of a nature-like bypass channel for restoring longitudinal connectivity for a river-resident population of brown trout

Man-made, physical barriers have disrupted longitudinal connectivity for migratory fish in many river systems throughout the world for centuries. These barriers are considered to be a key reason for the decline of many fish species in river systems. To date, most research to ease movement of anadromous salmonids past such barriers to help dwindling populations has focused on the use of technical fishways. More recently emphasis has been placed on nature-like fishways to enable a wider range of fish species to bypass these barriers, but few studies have examined their efficacy. In this study, Passive Integrated Transponder (PIT) telemetry was used to assess the upstream-directed movements of 111 river-resident brown trout (length, 151–510-mm) into and through a 150-m long, nature-like bypass on the River Aire, England. Attraction (51%), entrance (86%), passage (78%) and exit (97%) efficiencies were high, and trout of a wide range of sizes entered and exited (197–510 mm) the pass across a wide range of flows (entrance = 3.55–67.44 m 3 s −1 and exit = 3.89–35.5 m 3 s −1 ). There was evidence that two trout inhabited the pass during the day, entering at sunrise and exiting at sunset. This information is important to improve understanding of fish pass performance, thus informing future best practice guidance of fish passage designs

A dynamic dendritic connectivity assessment tool for the planning and design of barrier mitigation strategies in river networks

Context: Increasing fragmentation of rivers caused by barriers continues to impact watersheds, especially disruption of fish migration patterns and loss of access to spawning and nursery habitats. Infrastructure expansion and ageing installations exacerbate the problem, reducing effectiveness of management in addressing barriers. Reduction in watershed connectivity requires effective tools capable of guiding river managers in remediation actions. Objectives: Our objective was to develop a watershed dynamic connectivity assessment tool (D-CAT), a customizable geospatial tool capable of river analyses at varying watershed scales. The tool uses proven watershed connectivity modelling combined with an effective evaluation approach to provide measurable change model outcomes. Methods: Three different barrier encounter scenarios were examined using the D-CAT tool to study watershed connectivity. The tool was tested on a watershed area of the River Derwent, a major tributary of the River Trent system in the United Kingdom. Results: For each barrier scenario tested, the D-CAT tool indicated which barriers could be removed or modified to provide the greatest watershed connectivity improvement. The tool provided a prioritized list of barriers for each scenario under varying choices for the number of barriers to remove, demonstrating the utility of the D-CAT tool to planning and design. Conclusions: The D-CAT tool is built to handle geographical data and variable user input, allowing in-depth watershed connectivity analysis. The tool forecasts the cumulative effects of alternative change scenarios for watershed connectivity, providing prioritization and optimization of removal strategies. The D-CAT tool offers significant support for landscape management towards better barrier removal/remediation decisions

Establishment of self-sustaining populations of non-native fish species in the River Trent and Warwickshire Avon, UK, indicated by the presence of 0+ fish

This study investigated the reproduction of non-native fish species, inferred from the presence of 0+ fish, in three English lowland rivers over an 8 year period. Evidence of self-sustaining populations was found for three non-native fish species, namely zander Sander lucioperca (in the River Trent and Warwickshire Avon), bitterling Rhodeus amarus (in the Trent) and carp Cyprinus carpio (in the Trent and Avon). Notwithstanding, such fishes are currently rare, accounting for < 1% of the 0+ fish communities of these two rivers, and no non-native species were recorded from the Yorkshire Ouse. It is possible, however, that improvements in water quality and habitat, together with the potential effects of climate change, may facilitate consolidation and expansion of their populations, as well as those of other non-native fish species already present or introduced in the future. This could have repercussions for the ecology and management of non-native fishes in the UK. © 2007 The Author(s)

Session B5: Efficiency of a Nature-Like Bypass Channel at Rodley Weir, River Aire

Abstract: Man-made physical barriers (weirs) have disrupted longitudinal connectivity in many river systems around the world for centuries. Impacts of weirs on fish communities centers on the reduced ability of fish to perform upstream migrations. To counter the potential effects these structures are having on fish communities, a number of fish pass designs have been developed to ease passage around potential barriers. To monitor the effectiveness of a recently constructed nature like bypass on the River Aire, Passive Integrated Transponder (PIT) systems were installed to observe movements of brown trout (Salmo trutta). The array consists of four swim through antennas, two at either end of the pass so that swimming direction could be determined. A total of 111 wild brown trout were caught, PIT tagged and released 380 m downstream of the fish pass entrance. In total 57 brown trout (51%) were detected on the most downstream loop, and of these 49 successfully entered the pass (86%). Thirtyeight of these successfully exited the pass in an upstream direction (78%). Further analysis found that a select number of fish used the pass as an area of refuge during high flows. The possible reasons for these findings are discussed in relation to flow, temperature, time of day, season and fish size. This information is important to improve our understanding of fish pass performance, thus informing future best practice guidance of fish passage designs

Win, win, win: Low cost baffle fish pass provides improved passage efficiency, reduced passage time and broadened passage flows over a low-head weir

The number of low-head barriers to fish migration far outweighs the number of large magnitude barriers and thus the cumulative negative impact on fish communities could also be far greater. Removal of man-made obstructions to fish migration is the most beneficial mitigation measure for reconnecting fragmented rivers but is not always possible and thus fish passes must be constructed. Given the large number of low-head barriers, cheap but effective fish passes must be identified. This study measured passage of brown trout (Salmo trutta L.) at a low-head gauging weir on Eshton Beck, England, before and after low cost baffle (LCB) fish pass construction using passive integrated transponder (PIT) telemetry. The LCB fish pass significantly improved overall passage efficiency from a maximum of 64% to 91%. There was a significant decrease in delay at the obstruction after the LCB fish pass was constructed and fish passed on a greater range of flows (0.08 – 5.39 m3s-1) in comparison to before (0.56 - 1.92 m3s-1). Fish ascended the fish pass through the low velocity channel (gaps in the baffles) as well as over the baffles, though a higher proportion were detected ascending over baffles at higher flows. It was therefore concluded that similar low-head structures should incorporate this style of fish pass to improve longitudinal connectivity for brown trout and other species with similar passage capabilities

Linking environmental flows to sediment dynamics

© 2017 The Authors. This is a policy discussion paper aimed at addressing possible alternative approaches for environmental flows (e- Flows) assessment and identification within the context of best strategies for fluvial restoration. We focus on dammed rivers in Mediterranean regions. Fluvial species and their ecological integrity are the result of their evolutionary adaptation to river habitats. Flowingwater is themain driver for development and maintenance of these habitats,which is why e-Flows are needed where societal demands are depleting water resources. Fluvial habitats are also shaped by the combined interaction ofwater, sediments,woody/organicmaterial, and riparian vegetation.Water abstraction, flowregulation by dams, gravel pits or siltation by fine sediments eroded fromhillslopes are pressures that can disturb interactions among water, sediments, and other constituents that create the habitats needed by fluvial communities. Present e-Flow design criteria are based only on water flow requirements. Here we argue that sediment dynamics need to be considered when specifying instream flows, thereby expanding the environmental objectives and definition of e-Flows to include sediments (extended e-Flows). To this aim, a hydromorphological framework for e-Flows assessment and identification of best strategies for fluvial restoration, including the context of rivers regulated by large dams, is presented

Upstream passage of adult sea trout (Salmo trutta) at a low-head weir with an Archimedean screw hydropower turbine and co-located fish pass

© 2018 CSIRO. The exploitation of riverine systems for renewable energy has resulted in large numbers of small-scale hydropower schemes on low-head weirs. Although considered a clean and 'green' energy source in terms of emissions, hydropower can affect upstream migrating species by diverting flow away from viable routes over the impoundment and attract fish towards the turbine outfall. In an attempt to reduce this negative effect, hydropower outfalls with co-located fish-passage entrances are recommended, utilising turbine flows to attract fish towards the fish pass. The present study used acoustic telemetry to understand the performance of a co-located Larinier fish pass at a low-head hydropower scheme at a weir on the tidal Yorkshire Esk, England. The majority of the sea trout (anadromous Salmo trutta L) individuals that approached the impediment were attracted to the hydropower and the co-located fish pass. Fish ascended through the pass under a wide range of river flows, tide heights, downstream river levels and hydropower flows, and there was no evidence that the hydropower operation affected fish-pass ascent. The information presented is urgently required to inform management decisions on the operation of hydropower schemes during the migratory period of salmonid fish, and help determine best-practice designs and operation at these facilities

Session B4: Fine-Scale 2D Acoustic Tracking of the Behaviour of Salmonids to Investigate Delays and Failures in Fish Passage; Implications for Assessing the Efficiency of Fish Passes

Abstract: Many studies of fish passage are limited to consideration of coarse scale efficiency metrics; however the level of resolution they have for explaining changes in these metrics is often limited. In many cases assessments of fish pass performance are instigated due to (and complicated by) factors such as changes in fish pass design, construction of hydropower schemes and/or associated changes in hydro-morphology. In such cases finer scale descriptions of passage behaviour and fish pass proximity behaviour may be required to identify changes in passage efficiency and elucidate the factors influencing them. This presentation describes a five year acoustic tracking study (3 years pre and 2 years post installation of a co-located hydropower scheme with Larinier fish pass) of the 2D behaviour of 138 sea trout and 18 salmon as they approached the fish pass entrance and hydropower outfall on Ruswarp Weir (River Esk, England). The study determined the fine scale (sub-metre resolution) spatial and temporal utilisation of the fish pass pool and approach behaviours; analysing these in relation to river flows, tidal conditions, operation of the hydropower scheme, a change in design of the fish pass and the associated changes in pool morphology. In particular the analysis considered the delays in fish passage and behaviours of fish that were successful or unsuccessful in using the fish pass, and the different conditions they encountered whilst approaching the fish pass. The results showed that alongside a significant increase in the proportion of failed passages (reduced fish pass efficiency from 100% to 69% for sea trout) there was a significant increase in delay of passages and changes in the behaviour of fish and spatial utilisation of the pool. Some of these changes potentially relate to operation of the hydropower whilst others may relate to changes in the pool morphology and fish pass