3 research outputs found
Over 200,000 kilometers of free-flowing river habitat in Europe is altered due to impoundments
European rivers are disconnected by more than one million man-made barriers that physically limit aquatic species migration and contribute to modification of freshwater habitats. Here, a Conceptual Habitat Alteration Model for Ponding is developed to aid in evaluating the effects of impoundments on fish habitats. Fish communities present in rivers with low human impact and their broad environmental settings enable classification of European rivers into 15 macrohabitat types. These classifications, together with the estimated fish sensitivity to alteration of their habitat are used for assessing the impacts of six main barrier types (dams, weirs, sluices, culverts, fords, and ramps). Our results indicate that over 200,000 km or 10% of previously free-flowing river habitat has been altered due to impoundments. Although they appear less frequently, dams, weirs and sluices cause much more habitat alteration than the other types. Their impact is regionally diverse, which is a function of barrier height, type and density, as well as biogeographical location. This work allows us to foresee what potential environmental gain or loss can be expected with planned barrier management actions in rivers, and to prioritize management actions
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Session D7: Optimization of Efficiency of Step-Pool Fish-Pass Channel
Abstract:
Seven years monitoring of the operation of a step-pool fish-pass channel was conducted at the hydropower plant on the River Neisse, Poland. Initial observations, after fishway construction showed that the fish can’t pass it. The reason was the high water velocity and the highly turbulent nature of water flow. Also the attraction flow was to slow. Accordingly, measures to improve fish-pass efficiency were undertaken. Initially the water velocity was reduced by throttling of inflow by one third. After this a few fish were found in the trap placed at the exit of the fishway. As a next step the thalweg in the lower part of fishway channel was raised by stone layer and 3 additional steps were constructed. Also other parts of the channel bottom were elevated with stones, to reduce slope at some steps. Additionally the openings on each fishway chute were narrowed, in order to further reduce water velocity and to create a sinuous pattern of water flow. These changes lead to a significant reduction of average water velocity. The observations after these modifications showed significant increase of fish-pass efficiency reaching 1.5 fish per hour. Last modification applied was to narrow the attraction flow stream with stones. This resulted in substantial increase of fishpass efficiency – up to 5.8 fish per hour
Over 200,000 kilometers of free-flowing river habitat in Europe is altered due to impoundments
European rivers are disconnected by more than one million man-made barriers that physically limit aquatic species migration and contribute to modification of freshwater habitats. Here, a Conceptual Habitat Alteration Model for Ponding is developed to aid in evaluating the effects of impoundments on fish habitats.
Fish communities present in rivers with low human impact and their broad environmental settings enable classification of European rivers into 15 macrohabitat types. These classifications, together with the estimated fish sensitivity to alteration of their habitat are used for assessing the impacts of six main barrier types (dams, weirs, sluices, culverts, fords, and ramps). Our results indicate that over 200,000 km or 10% of previously free-flowing river habitat has been altered due to impoundments. Although they appear less frequently, dams, weirs and sluices cause much more habitat alteration than the other types. Their impact is regionally diverse, which is a function of barrier height, type and density, as well as biogeographical location. This work allows us to foresee what potential environmental gain or loss can be expected with planned barrier management actions in rivers, and to prioritize management actions