Lower Colorado River Water Delivery Contracts
Questions and Answers
What is the source of Colorado River Water in the Lower Basin?
Most -- about 88 percent -- of the total annual flow of water in the Lower Colorado River Basin originates upstream of Glen Canyon Dam (in northern Arizona) as a result of natural runoff from precipitation and melting snow in the mountains of Colorado, Wyoming, Utah and New Mexico. The remaining 12 percent comes from rainfall and inflows into the river from washes and tributaries that enter the river downstream from Glen Canyon Dam.
Once water enters the lower Colorado River mainstream (the main channel of the river, including reservoirs), its use is subject to the "Law of the River." All water taken from the mainstream is accounted for as Colorado River water, whether the water is pumped or diverted directly from the river, or drawn from the mainstream aquifer through underground pumping.
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Updated: March 2005