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Barrage
Attrition
The wearing away of particles of rock as they bounce together in moving water.
Attrition is partly responsible for the rounded shape of river- borne material and for the way that pebbles become reduced in size to make sand grains. (See also: Abrasion.)
B
Badlands
A pattern of gullies in a landscape of soft rocks where there is no plant cover to hold the soil in place.
Badlands are a feature of river basins in semiarid parts of the world. Badlands National Park in South Dakota shows these features
clearly. However, overfarming has also produced badlands in places where they would not naturally occur.
Barrage
A large barrier across a river, intended to control the flow of water. Contrast it to a weir, which is a barrier across a small river.
A barrage is made out of concrete and has steel gates. The gates are lowered or raised to allow more or less water to flow through
Barrage—A barrage on the Mississippi River.
them. The height of the gates is constantly adjusted to keep the water level above the barrage deep enough for boats to navigate, but low enough to allow the river to flow as naturally as possible without flooding the valley above the barrage. (See also: Dam; Hydroelectric power; Water power.)
Aquifer/Artesian water—If an aquifer is trapped between two aquicludes, the water filling up the aquifer comes under pressure. It is artesian water. It can be released by drilling wells. This makes a water supply that, at least to begin with, does not require pumps to
bring it to the surface.
Flood irrigation
Rain falls on porous rock
Layer of water in rock
Sprinkler irrigation
Wind-powered pump
Direction of water flow underground
Animal trough
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