Get Letter & Forms 04.doc. Water Resources Data, Colorado, Water Year 2003--v. 2, Colorado River

Flows originating above Lees Ferry represent the majority of Colorado River runoff. Tributaries between there and Imperial Dam near the US–Mexico border contribute a further 1.1 million acre-feet (1.4 km3), and the Gila–Salt River system historically accounted for another 1.7 million acre-feet (2.1 km3).

Supply. Colorado is known as the "Headwaters State" because several of the West's most important rivers rise in its Rocky Mountains. Colorado has eight major river basins and several aquifers. The majority of the water supply falls as snow in the Rocky Mountains.

The Colorado River is a critical resource in the West, because seven basin states (Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming) depend on it for water supply, hydropower production, recreation, fish and wildlife habitat, and other benefits.

It's well-known that crop irrigation is the largest water user worldwide. The Colorado River Basin is no different, crops consume three times more water than all other direct human uses combined (municipal, commercial and industrial).

California takes the biggest share of Colorado River water, with a yearly allocation of 4.4 million acre-feet.

How much water does Colorado get from the Colorado River? It varies. Each year, Colorado can use up to 51.75% of the river's available water supply for the Upper Basin states. If the basin's full allocation of 7.5 million acre-feet of water was put to use, Colorado would receive about 3.85 million acre-feet of water.

The Compact divides the states into two basins: the Upper Basin, (CO, NM, UT, WY) and the Lower Basin (AZ, CA, NV). Colorado River water is to be shared equally between the two basins. Even during drought, the Colorado River has been a reliable source.