Much of Colorado's water leaves the state in its rivers. That can be explained by the state's obligations under interstate and international compacts. Additionally, Colorado has not fully developed - put to use - all of its water. The amount of water yet to be stored in reservoirs for consumptive use is a matter of discussion. The Colorado Water Conservation Board pegs the amount of Colorado River water yet to be developed at 400,000 acre-feet.
In an average year, about 16 million acre-feet flows through Colorado rivers. The Water Conservation Board estimates that after accounting for water consumed by human activities, 9.25 million acre-feet flows to the Pacific side of the Continental Divide.
Under the Colorado River Compact of 1922, the upper basin states of Colorado, Utah, New Mexico and Wyoming are obligated to allow 75 million acre-feet of water, spread over a span of 10 years, to flow to the lower basin states. Consequently, Lake Powell is managed to deliver about 7.5 million acre-feet annually to lower basin states.
- Tom Ross