Lecture 10: Dams (Contd.)

  1. What is an Earthen dam?
    A dam made of low permeability material (at least 50% has to be compacted sand, silt or clay).
  2. Why are most streams steeper in their upper reaches and gentler as we approach the mouth?
    • - there is more area contributing to deposition in the downstream area.
    • - there is a balance between the erosion of the channel and sedimentation in the channel.
  3. What happens to the longitudinal profile if the seal level rises? drops?
    • Rises: where dep/erosion occurs will be higher.
    • Drops: where dep/erosion occurs will be lower.
  4. What happens to the longitudinal profile if a dam is added?
    This recreates the base level for the region. Deposition will occur behind the dam, other side: erosion.
  5. Re < 500 means ___.
    Laminar flow.
  6. Re > 2000 means ___.
    Turbulent flow.
  7. What is laminar flow?
    Flow that follows straight of gently curving stream flow lines. There is no mixing.
  8. What is turbulent flow?
    • - An increase in the flow velocity
    • - flow is no longer in parallel layers
    • - velocity is highly variable
  9. Resistance in turbulent flow depends on:
    • - channel configuration
    • - size of bedload
  10. What does riparian mean?
    Beside a river.
  11. Gibe III is located in ___.
    The Omo River in Ethiopia.
  12. Gibe III is ___ long.
    150 km.
  13. Gibe III construction (years).
  14. Environmental impacts of Gibe III:
    • - eliminates the natural flood cycle which affects fish spawning.
    • - degraded habitats/ecosystems (e.g. wetland ecosystems like the Omo National Park).
    • - lake-dependent forests.
    • - reduced replenishing of natural minerals.
    • - upstream flooding.
  15. Gibe III: Impacts on reservoir:
    • - increased water level
    • - increased Co2 emissions (submerged biomass) and methane.
  16. Gibe III: Impacts on Lake Turkana:
    • - reduced water level
    • - reduced inflow
    • - increased salinity
  17. Social/Economic impacts of Gibe III dam:
    • - eliminates traditional farming techniques.
    • - reduces fish catches
    • - conflict between indigenous tribes in Lower Omo River Valley.
  18. Gibe III will produce ___ energy available for export.
    > 1800 MW.
  19. Gibe III will produce ___ in revenue.
    $407 million.
  20. Gibe III will increase annual per capita income above ___.
  21. Gibe III can store ___ of water.
    11.75 billion m3
  22. When water availability in a country of region is < 2000 m3 per person per year.
    Water stress.
  23. When water availability in a country of region is < 1000 m3 per person per year.
    Water scarcity.
  24. Rich tend to get their water from ___, whereas poor tend to get their water from ___.
    Pipes. Wells, surface water/tanker trucks, etc.
Card Set
Lecture 10: Dams (Contd.)
Lecture 10: Dams (Contd.)