What is a dam? “A dam is an engineering structure built to block a valley or other low lying area for the purpose of storing water” (Hancock and Skinner, 2000). How many? From 1992 there was over 10 thousand dams worldwide. About 500 dams are being creating every year, which exceed 15metres in height. (Jiles and Spencer, 1995). About 500 dams are being creating every year, which exceed 15metres in height. (Jiles and Spencer, 1995).

The main Advantages  Regulate water flow and Flood Control  Sediment Control  Drought Control  Time for endangered species to be moved To another suitable location.  Irrigation  Navigation Improvement  Generation of hydro-electric power  Can be made to suit geology, can be placed in narrow and Wide valleys. In rock or soil types.

“60% of total stream flow is regulated by dams and reservoirs for flood control” (Jiles and Spencer, 1995). “60% of total stream flow is regulated by dams and reservoirs for flood control” (Jiles and Spencer, 1995). This is due to flood peaks being reduced, and the uniformity in base flow being increased throughout. This is due to flood peaks being reduced, and the uniformity in base flow being increased throughout.

40% of rivers in Africa, Europe, North America were stabilized by dams. Below is a map showing the Europe dams. Map taken from http//

There is a reduction as the naturally eroding Cliffs now have basal protection. (Less fluvial Inputs). Deposition location has changed, sediment Is no longer built up in wetlands. Resulting in less Erosion in drainage basins.

Dams are needed in places of permanent Drought. To act as barriers to hold drinking Water.

Looking at three Gorges Dam scheme in China. What were its advantages?  Prevent flooding  Hydro-power electricity  Irrigation (agriculture)  Domestic use  Navigation

Advantages of the aswam dam: PPPPrevent flood and drought catastrophic conditions  F F F For irrigation  4 4 4 4000km2s of dessert can now be used by farmers FFFFloodplain has been converted from 1 crop rotation to 3 crop rotation. HHHHydro-electricity. CCCCountries income has increased by 500 million per year Since it was built. dcentre.org/aswpres a.jpg

Endangered species can be removed and put Into a suitable habitat. This occurred with the Species Percina tanasi (Snail darter minnow). However the dam did not really affect the Population as they were found naturally occurring In a near by stream. This was at the site of “Tellico Dam on the Little Tennessee river in Tennessee” (Freeman, 1995).

Transport on the River Ferry transportation began in 1860s, they now use barges Ferry transportation began in 1860s, they now use barges Economical Economical Consumer Benefits Consumer Benefits Relieves rail congestion Relieves rail congestion The Pacific Northwest Barge Industry on the Columbia-Snake River System by American Waterways Operation

16 cents per bushel by barge 32 cents per bushel by rail (if available) 92 cents per bushel by truck DAMS How important are they ? Provide water for transport Provide water for transport

Provide Electricity for the community Roll on Columbia By Beth Gibson Columbia and Snake River supply 63% of hydro electric energy Columbia and Snake River supply 63% of hydro electric energy Grand Coulee when built provided work after great depression Brought cheap electricity to the area Brought cheap electricity to the area Helped with the war effort Helped with the war effort Later Industry moved to Pacific west because of Later Industry moved to Pacific west because of cheap energy supply

Ecology Friendly 96%-98% pass safely through turbines96%-98% pass safely through turbines Dams and turbines are not huge blendersDams and turbines are not huge blenders

Ecology Friendly H:\COLUMBIA RIVER BASIN - DAMS AND SALMON.htm Fish Barges are a partial solution Fish Barges are a partial solution

A Commissioner’s Story Les Wigen Whitman County Commissioner

References  Anon, 1998 acessed at: http//  Buchal James NG & 60 Min    Gibson Beth Roll on Columbia By   Hancock and Skinner, 2000, “The oxford companion to the earth”. Oxford University Press, Great Clarendon Street, Oxford.  Park, C., 1997, “The environment”, 29 West 35 th Street, New York.  S Army Corps of Engineers, Northwestern Division  S Army Corps of Engineers, Northwestern Division POC: Adele Merchant, Pacific Salmon Coordination, (503)   Page Updated: Thursday September  H:\COLUMBIA RIVER BASIN - DAMS AND SALMON.htm   The Pacific Northwest Barge Industry on the Columbia-Snake River System by American Waterways Operation   Spencer, T., and Jules, H. 1995, “Coastal Problems”, Oxford University Press Inc, 198 Madison Avenue, New York.