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Back to usesUses for Reservoirs - Flood Control

The River Rother flooded Robertsbridge

The River Rother flooded Robertsbridge,
in Sussex, England in October 2000

Water from snow and rainfall will find its way into stream and rivers and eventually into the sea. After severe storms, or heavy snow or rain over a number of days, the water level in rivers can rise dramatically. Sometimes, the water flows over riverbanks or walls causing flooding of farmland, property, and in the worst cases, loss of life.

Paritally opened floodgates

Paritally opened floodgates
on Tarbela Dam is Pakistan

A reservoir can be used to control the amount of water flowing in a river after heavy rain. The water level in the reservoir is kept low during the rainier periods of the year. When heavy rain occurs, it is stopped by the dam and held back in the reservoir. When the reservoir gets too full, the floodwater can be passed downstream over a spillway.

Sometimes, floodgates are used on top of spillways, and they can be fully or partly opened to control the amount of water let out into the river downstream.