Lecture 10: Dams (Contd.)
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What is an Earthen dam?
A dam made of low permeability material (at least 50% has to be compacted sand, silt or clay).
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.
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.
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.
Re < 500 means ___.
Re > 2000 means ___.
What is laminar flow?
Flow that follows straight of gently curving stream flow lines. There is no mixing.
What is turbulent flow?
- - An increase in the flow velocity
- - flow is no longer in parallel layers
- - velocity is highly variable
Resistance in turbulent flow depends on:
- - channel configuration
- - size of bedload
What does riparian mean?
Beside a river.
Gibe III is located in ___.
The Omo River in Ethiopia.
Gibe III is ___ long.
Gibe III construction (years).
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.
Gibe III: Impacts on reservoir:
- - increased water level
- - increased Co2 emissions (submerged biomass) and methane.
Gibe III: Impacts on Lake Turkana:
- - reduced water level
- - reduced inflow
- - increased salinity
Social/Economic impacts of Gibe III dam:
- - eliminates traditional farming techniques.
- - reduces fish catches
- - conflict between indigenous tribes in Lower Omo River Valley.
Gibe III will produce ___ energy available for export.
> 1800 MW.
Gibe III will produce ___ in revenue.
Gibe III will increase annual per capita income above ___.
Gibe III can store ___ of water.
11.75 billion m3
When water availability in a country of region is < 2000 m3 per person per year.
When water availability in a country of region is < 1000 m3 per person per year.
Rich tend to get their water from ___, whereas poor tend to get their water from ___.
Pipes. Wells, surface water/tanker trucks, etc.
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