Topics for today Dams - Geography –Elwha River Dams –Glen Canyon Dam –Colorado Compact (1922) Ground water Chapter IX pp 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 management 2.Naturalized ecosystem 3.Simulated natural ecosystem 4.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?