Colorado Interstate Compacts

Why can’t Colorado use every drop of water that falls in the state? The following provides a list of interstate compacts that limit how much Colorado can use from each basin:

Colorado River Compact (1922): Divides the waters of the Colorado River between Upper Basin states (Colorado, New Mexico, Utah, Wyoming) and Lower Basin states (Arizona, California, Nevada). A 1944 treaty with Mexico also promises deliveries.
La Plata River Compact (1922): Requires Colorado to deliver water to New Mexico during low-flow periods.
South Platte Compact (1923): Shares spring and summer flows with Nebraska.
Rio Grande Compact (1938): Regulates the waters of the river among Colorado, New Mexico and Texas. There is also a 1944 treaty with Mexico.
Republican River Compact (1942): Limits Colorado water use in an agreement with Kansas and Nebraska.
Arkansas River Compact (1948): Requires Colorado to not “materially deplete” flows at the state line.
Upper Colorado River Compact (1948): Apportions water among the Upper Basin states on the Colorado River.
North Platte River Litigation Decree (1954): A U.S. Supreme Court decree (rather than a compact) that governs water use among Colorado, Wyoming and Nebraska.
Laramie River Litigation Decree (1957): The U.S. Supreme Court decree that allows Colorado to divert water from the Laramie River.
Animas-La Plata River Compact (1963): Clarifies the relationship between New Mexico and Colorado in a federal water project.
Costilla Creek Compact (1963): Apportions water between Colorado and New Mexico.

Source: Pueblo Chieftain