Environmental effects of reservoirs

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  • Environmental effects of reservoirs
    • Habitat Change
      • Flooding destroys previous habitats but also creates new ones possibly valuable ones
      • Wetlands are uncommon habitats so new habitat created may be more valuable than previous habitat
      • dam and reservoir act as barrier against migratory wildlife going along river e.g. salmon
      • Species living in river have population booms/collapses.
      • Free movement along river is an important part of recolonising areas that have become vacant in bad years (dam may prevent this)
    • Changes in river flow
      • water abstracted from reservoir and piped to consumers, so flow regime downstream maintained but volume changed
      • water may be used to regulate river flow, holding water back during times of surplus to ensuring adequate river flow in times of shortage so water can be abstracted from river further downstream
      • reducing flood risk downstream, but reduces periods of low flow which is important for river turtles for laying eggs on sandbanks
      • periods of rapid flow also important to wash away sediments from gravel riverbeds in which salmon lay eggs.
      • Changes in flow fluctuations can also change river erosion and sedimentation therefore the development of meanders
    • Sedimentation
      • sediments that settle in reservoir will no longer be carried further downstream
      • In past they may have been important to fertilise the floodplain downstream during times of flood
      • may have also been important in building up riverbanks and coastlines and counteract erosion
    • Reservoir microclimate
      • large body of water in reservoir may change the local climate
      • high heat capacity of water helps reduce temperture fluctuations, therefore warmer in winter and cooler in summer
      • water provides less friction than land = stronger winds
      • greater evaporation from reservoir surface may increase humidity, cloud cover and precipitation downwind of reservoir


Sam Barnwell



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