River Regime of the Colorado River

Key Facts• Source in the Rock mountains• Mouth is in the Gulf of California• 11 major dams along its course (Hoover Dam).• 1000km long• Highest temperature in July (26oC)• 2400mm of snow can fall at source in winter

River regime graph of Colorado River

jan feb mar apr may june july aug sept oct nov dec0

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Peak discharge occurs in mid-May

A rapid increase in discharge occurs in April from 510 to 1100m3s-1

The discharge stays relatively constant from July through to January.

Rapid decrease in discharge in July

• Relief-The rocky mountains are 4000m high with very steep relief and this means that when precipitation falls, it will reach the river quickly due to surface runoff. This is because the precipitation will have a lot of gravitational potential energy and so very little interception will occur. Therefore, when there is an increase in precipitation there should be an increase in discharge too.

Steep relief means that precipitation will reach the river channel faster.

• Temperature is at its highest in July where the average temperature is 26oC. This means that there would be more evapotranspiration and therefore less water reaching the river channel. This would lead to a decrease in discharge, which can be seen in the graph in July where the discharge falls from 1570 to 460 m3s-1.

The lowest temperature is in December where it falls below 0oc. This means that precipitation can fall as snow, therefore leading to a decrease in discharge. This is due to the fact that it takes longer for snow to melt and be transported to the river channel. The graph shows that there is a decrease in discharge from 530 m3s-1 in November to 510 m3s-1 in December.

• Dams-The Hoover Dam was the first of a series of 11 dams to be built on the river back in 1931. This affects the regime because the dams control river flow and store water thus ‘flattening’ the regime.