How Much Water Does the Rio Grande Need?

It stands to reason that rivers need water. But how much?

For the Rio Grande it's not just an academic question. The river in southern New Mexico and west Texas is fully appropriated for agriculture. Every drop belongs to someone, but none belongs to the river itself. Any water flowing in the river is there only incidentally, on its way to the next farmer downstream.

This is the way the river has been managed for the past 99 years, since Elephant Butte Dam was completed in 1916. Not surprisingly, the river ecosystem has suffered. The river dries to a trickle or entirely during winter months, when irrigation releases are curtailed. Two-thirds of the 20+ native fish species originally found in this reach have disappeared.

Determining how much water the Rio Grande needs to function is a first step towards restoring it to ecological health. In 2015, the Southwest Environmental Center led an effort to make that determination.

By our calculation, the Rio Grande needs a minimum of 75,000 acre-feet annually be healthy, i.e. to sustain fish, wildlife, trees, and boating all year-round. Learn how we derived this estimate here.

This turns out to be roughly 10 percent of the volume of water released from Caballo Reservoir in a full supply year--not an unreasonable amount of water to leave for the river itself.