Water to Supply the Land: Irrigated Agriculture in the Colorado River Basin

Published: May 9, 2013
Authors: Michael Cohen, Juliet Christian-Smith, and John Berggren

The Colorado River, recently named America’s most endangered river, supports millions of people in the American Southwest and northwest Mexico and helps irrigate millions of acres of land. Yet demands on the river already exceed the river’s average supply, a situation that is projected to get worse in coming years as climate change reduces runoff at the same time that fast-growing southwest cities demand more water. Irrigated agriculture currently consumes more than 70% of the water supply within the Colorado River basin, making it critical for more efficient water use.

For the first time, new research from the Pacific Institute describes the extent of irrigated agriculture throughout the seven Colorado River basin states and two additional states in Mexico, the types of crops grown, and the amount of water used to grow these crops. In addition, the new report – Water to Supply the Land: Irrigated Agriculture in the Colorado River Basin – compares several agricultural management scenarios and the potential water savings and costs associated with each. Importantly, none of the scenarios remove agricultural land from production.

View our interactive map of Colorado River basin agriculture, showing federal and state agency information on the amount of irrigated and total harvested acreage in the basin by county, and total reported water use as reported by USGS.

More than 90% of pasture and cropland in the 256,000-square-mile Colorado River Basin requires irrigation, with about 60% of the irrigated acreage devoted to pasture, alfalfa, and other forage crops used to feed cattle and horses. These forage crops consume about 5 million acre-feet per year, equivalent to a third of the river’s annual flow. Employing innovative irrigation techniques more strategically and in more places – techniques that many farmers are already using – can help ensure agriculture in the basin states continues in the face of rising demand and climate change’s projected impact on supply.

Modeling a series of agricultural water management conservation strategies – including regulated deficit irrigation, crop shifting, and advanced irrigation technologies – the Pacific Institute compared potential water savings and costs associated with individual scenarios. The analysis shows considerable water savings are possible. For example, almost a million acre-feet of water may be generated by irrigating alfalfa less often (a practice known as “regulated deficit irrigation”) throughout the basin in the U.S., at an estimated base cost of approximately $81 per acre-foot.

Other scenarios, such as shifting to less water-intensive crops, also yield impressive water savings with relatively low costs and without reducing the total amount of irrigated acreage in the basin. For example, replacing about 10% of the basin’s irrigated alfalfa acreage with cotton and wheat could save about 250,000 acre-feet of consumptive water use each year, with estimated base costs of less than $40 per acre-foot. Total reductions in water withdrawals and applied water would be even greater.

“We know water supply and demand don’t match up and it will get worse going forward. We know there is much that can be done; the question is how much and where, and how to get there,” said Michael Cohen of the Pacific Institute, lead author of the report. “This analysis improves understanding of crop acreages and water use in the basin and offers a set of plausible scenarios in which some of the water currently devoted to irrigation could be conserved and used for other purposes – without taking agricultural land out of production.

“There are many proven water management techniques already in use in the basin states that – if expanded – could generate significant consumptive use water savings that could be transferred to other users. This report considers different alternative futures and it is important to develop the right incentives to encourage more efficient water use as the gap between water supply and demand grows,” said Juliet Christian-Smith, report co-author.

“State and federal agencies frequently report inconsistent irrigated land and water use information for areas within the Colorado River Basin, obscuring key basin issues and hampering efforts to reconcile the basin’s water supply and demand challenges,” said Cohen. “This lack of comprehensive and reliable water data makes life difficult for water managers and decision makers. Better reporting is going to be absolutely essential to managing the diminishing water supply and maintaining thriving agriculture in the basin.”

Download the full report.
Download the Executive Summary.
View the interactive map.

 

To help defray the costs of preparing this report, please donate $5 or more to the Institute here.