Geography - Rivers

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  • Created by: LCD
  • Created on: 02-06-10 11:54

The Hydrological System

The hydrological system describes the continuous transfer of water from stores such as oceans or lakes into the atmosphere, then back to the land as precipitation (rain), finally returning to the original stores.

It can be seen as a natural system that recycles water, so it is globally sustainable.

It is increasingly adapted to for human use and parts of it are modified after extreme climatic events.

(See diagram of System)

The River System

This is part of the Hydrological System. It is made up of four main parts:

  • Inputs: water entering the system through precipitation.
  • Stores: water stored in lakes, rocks, soil or vegetation. Storage can be temporary and is linked to the amount of rainfall.
  • Transfers: processes that move water through the system such as surface runoff, infiltration and underground flow.
  • Outputs: where water is lost to the system as rivers reach the sea through evapotranspiration.

Key Words: - Evaporation, Evapotranspiration, Groundwater flow, Infiltration, Interception, Precipitation, Surface runoff, Sustainable, Through-flow, Transpiration and Water Table.

A Drainage Basin and its Features

A drainage basin, or catchment, is an area of land that is drained by a river and its tributaries. Precipitation falling within the catchment area finds its way into streams and rivers and flow towards the sea.

The edge of a drainage basin is called a watershed and is often a ridge of higher land.

Drainage Basins are adapted for human use in many ways. E.g. build dams and reservoirs, irrigation schemes for agriculture, water abstraction for industry and power stations, widening or straightening river channels for navigation and constructing flood protection walls and barriers.

Changes to any part of a drainage basin may affect the natural flows of the river within.

The Colorado River

The Colorado River and its tributaries run through seven American states before reaching the Gulf of California. Much of the catchment is a semi-desert landscape, making the rivers a vital source of water for over 15 million people.

It is said that the Colorado River is one of the most managed systems in the world and that very little of the system is in its natural state. Water flow is totally controlled and so much water is taken out of the river that during some months of the year it enters the Gulf of California as a mere trickle.

The Colorado River is home to the Hoover Dam which was built in 1935 to control the rising water levels in Spring and Summer and to reduce the risk of flooding. A further 18 dams have been constructed throughout the river basin, creating a number of artificial lakes. A number of these dams are used to generate hydro-electricity.

Increasing demand for water for agriculture has seen the development of a number of canals and aqueducts that transport water hundreds of kilometres to places such as the Central Valley


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