Topics for todayDams - Geography

– Elwha River Dams– Glen Canyon Dam– Colorado Compact (1922)

Ground water Chapter IX pp 260-266• Importance• Processes

– Hydraulic gradient– Permeability

• Ground water pollution• Ground water surface water interactions

– Gaining Streams– Loosing streams

• Supply and demand• Focus study 9-2• Subsidence

DAMS AN D DAM REMOVAL

Washington state DAMS

Grand Coulee Dam

Elwha River Dam

Glen Canyon Dam

Colorado Pike Meadow

Reading discussion

“Science and Values in River Restoration in the Grand Canyon”

Deciding what to do with the Grand Canyon ecosystem rehabilitated/or not?

25,000 float the Canyon every year

Razorback sucker(Xyrauchen texanus)

Humpback chub(Gila cypha)

Endemic endangered fish species

Kanab ambersnail

Willow flycatcher

Rainbow trout

• Colorado Compact, 1922• Why put all this effort in saving a

bunch of sucker fish?• How are we restoring for? Fish?

Rafters?• Table 3

Management approaches

1. Traditional river management2. Naturalized ecosystem3. Simulated natural ecosystem4. Substantially restored river 5. Full restored river

Traditional river management

• Accepts the river as a transformed ecosystem

• Maximizes power revenues• Ecological integrity is a second value

Naturalized ecosystem

• Blend of the old and the new• Management with minor flow

releases • Mixture of native and introduced

organisms

Simulated natural ecosystem

• Simulated some pre-dam ecological processes

• Dan releases that resemble pre dam conditions

• Aim to restore sand bars and fish habitat

• Seasonal affect of energy production

Substantially restored river

• Restore pre-dam hydrological variability (more sediment transport)

• Construction of facilities to transport sediment from the lake downstream

• Built of structures that allow releases of water at different temperatures

• Constrains in power production and water availability to lower basins

Full restored river

• Ambiguous management goal• Removal of flow regulation• Removal of the dam• Eradication of non-native species• No power production

Dilemmas..

• Unvegetated bars versus riparian vegetation

• Reduction of marsh area ….• Is lost of biodiversity acceptable to

restore pre-dm conditions?