Going With The Flow… Or Not. One Dam’s March For Freedom

Why? Hydroelectricity Allocating water to other resources, such as farming Control flooding of inhabited areas

What Happens After? Sediment starved downstream, sometimes % River banks become easily eroded, beaches disappear River bed becomes “armoured” with rocks, this means no gravel for spawning of fish or other benthic organisms. Typically eroded several meters within a decade of first closing in a dam, after the Hoover Dam was built, the sediment starved water washed away more than 110 million cubic meters of material, lowering the river more than 4 meters

Riverbed Deepening Riverbed deepening also lowers the groundwater table along a river, this causes a drop in the level of water in wells on the floodplain, and threatens to dry out local vegetation Impacts agriculture by loss of nutrient rich sediment being deposited downstream Sediment starvation also affects the coastlines, since the 1920’s, dams have reduced 4/5ths the sediment reaching the coast of Southern California. This leads to cliff collapse…

Water Quality The chemical, thermal and physical changes that flowing water undergoes when it is stilled can seriously contaminate a reservoir and the river downstream Temperature changes affect life cycles of aquatic animals that rely on season changes in temperature Reservoirs can become oxygen depleted due to detritus build up, the bacteria that feed on the build up of dead organic matter can transform inorganic mercury found in the plants into methylmercury, a neurotoxin which is then moved up the food chain. Salt concentrations can also build up on reservoirs due to increased evaporation