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Hydroelectric Dam (hydroelectric + dam)
Selected AbstractsEmigration patterns among trout, Salmo trutta (L.), kelts and smolts through spillways in a hydroelectric damFISHERIES MANAGEMENT & ECOLOGY, Issue 5-6 2008M. KRAABØL Abstract, The emigration patterns among radio-tagged trout, Salmo trutta L., kelts (n = 41, total length: 60,90 cm) and smolts [n = 27, total body length (BL): 22,30 cm] in the regulated River Gudbrandsdalslågen, south-east Norway, were studied by investigating the influence of sex (kelts) and BL (kelts and smolts) on the timing of emigration. In total, 49% of the kelts emigrated towards the hydroelectric dam shortly after spawning, whilst 51% over-wintered. Female kelts were five times more likely to initiate autumn emigration, and eight times more likely to descend the spillways during the first release of surface water than males. Large individuals of both sexes descended earlier than smaller individuals. Larger smolts were more likely to descend during the first release of surface water than smaller smolts. To safeguard the emigration of iteroparous trout kelts and smolts, the spillways should release surface water both in autumn and spring to avoid selective forces during emigration through spillways. [source] Fish community characteristics of the lower Gambia River floodplains: a study in the last major undisturbed West African riverFRESHWATER BIOLOGY, Issue 2 2009VASILIS LOUCA Summary 1.,The Gambia River is the last major West African river that has not been impounded. However, a hydroelectric dam is being constructed and substantial changes to the hydrology and ecology of the system are expected. 2.,Little information is available on the impact of water impoundments in semi-arid regions on downstream floodplain fish communities, due to the scarcity of pre-intervention data. Because profound impacts on physical habitat, salinity and nutrient transport can occur downstream of such impoundments, a knowledge of the species-habitat associations of biota such as fishes is necessary for understanding likely changes and how to limit them. 3.,Fish were sampled using cast and hand nets along two transects on the floodplain, and with fyke nets in two ,bolongs' (creeks) from May to November 2005 and 2006 in the lower reaches of the Gambia River, close to the salt water front where ecological changes due to the construction of the dam are likely to be pronounced. 4.,Greatest fish species richness was associated with low conductivity, low pH and deep water. Bolongs held greater species richness compared with other floodplain habitats, probably because they acted as conduits for fish moving on and off the floodplain. Species richness and catch biomass increased rapidly following the first rains and then declined. 5.,Using a multivariate analysis, three main species groups were identified on the floodplain; one associated with deeper water, one with less brackish water and one with shallow, open water. Tilapia guineensis was the commonest species on the floodplains. 6.,The floodplains provide nursery habitats as many fish captured were immature, particularly for species where adults are mainly encountered in the main channel. Several small-sized floodplain specialists were also represented by a high proportion of mature individuals. 7.,Impoundment is expected to reduce seasonal flooding of the floodplain in the lower Gambia River, downstream of the impoundment, resulting in reduced occurrence of aquatic habitats, especially bolongs, together with lower dissolved oxygen and increased salinity, leading to alteration of the floodplain fish communities, benefiting salt-tolerant species, reducing overall species richness and probably reducing floodplain fish production. [source] Long-distance downstream movements by homing adult chinook salmonJOURNAL OF FISH BIOLOGY, Issue 3 2006M. L. Keefer Unusually long downstream movements totalling several hundred kilometres to >1100 km were observed during upstream homing migrations of radio-tagged spring chinook salmon Oncorhynchus tshawytscha in the Columbia and Snake Rivers, U.S.A. Downstream migrants, identified by their repeated ascension and fallback over a series of large hydroelectric dams within the migration corridor, were primarily hatchery-origin males. [source] Improving public information about large hydroelectric dams: Case studies in France and West AfricaNATURAL RESOURCES FORUM, Issue 1 2003Armelle Faure It is becoming more common for public authorities in charge of dam construction and management to inform the population living in the area soon to be submerged by a proposed dam. However, populations living further downstream along a river to be dammed, have often been left to find out by chance, despite the fact that the changes to the river flow regime will have an important impact on their lives, sometimes serious negative impacts. This article makes a comparison between two dams, one at Bort-les-Orgues across the upper Dordogne River in southern France, the other the Bagré Dam over the Nakambé (or White Volta) River in south-eastern Burkina Faso. The article discusses dam construction and operation from the point of view of the concerned populations living in the reservoir and downstream areas. In 2000, a study was carried out in the Dordogne Valley to ascertain downstream impacts of dam operations and information needs of the population. Suggestions from local river users related mostly to improving public information about predicted and actual flow rates and actual flow in real time along the 300 km course of the Dordogne between the dams and the estuary. Such information should be disseminated as widely as possible through available media, including the Internet, and also displayed visibly in key locations along the length of the river. [source] | ||||||||||