6.9 Hydroelectric Power

hydroelectricity

power generated by the kinetic energy of moving water

run of the river

retained behind a low dam, no reservoirs

* pro: little flooding, river flow is not disrupted
* cons: smaller, unpredictable

water impoundment dams

largest reservoir

* Grand coube dam (WA)
* largest dam: three gorge dam (yangtze river, china)

tidal systems

* efficient (80% can be converted)
* cant be a widespread energy source because tidal difference is not enough in most places

biggest potential

tidal systems in France, Korea, Canada

tidal difference

difference in height of high tide and low tide

benefit

water for year round irrigation

benefit

drinking water

benefit

recreation and fishing in reservoirs

benefit

hydropower is cheap

benefit

reduce down stream flooding

drawback

newly flooded land destroys cropland and forests, displaces people

drawback

water loss due to evaporation

drawback

down stream land deprived of nutrients

drawback

risk of catastrophic failure/flooding

drawback

fish migration/spawning disrupted

dam removal

* habitat restoration
* danger of failing structures ( consider cost of repair)
* restore

dam removal problems

* might change flow direction
* legacy sediment (mental contamination)

three gorge dam

* yangtza river china
* 2 kilometers long
* the electric output of 18 large coal-burning or nuclear power plants
* displaced 12 million people
* dam is built over seismic fault and already has small crack
* erosion, sedimentation, flooding

fish ladders

assist fish in migration, help with fish producing spawn

fingerlings

* spawn of fish
* get back downstream past the dam through nets, channels, and transport pipes