Significant Figures by Peter Gleick

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. It is shared by seven states in the U.S. and Mexico, through a complex series of legal agreements and treaties.

Yet every drop of water on the river is accounted for, used, reused, and transpired away, and today, no water reaches the Colorado River delta in an average year. Quite simply, demands on the river exceed the river’s average supply, and this problem is projected to get worse as populations continue to grow and as climate changes increase temperatures and reduce runoff.

Today, irrigated agriculture consumes more than 70% of the water supply within the Colorado River basin. For the first time, new research from the Pacific Institute presents comprehensive data on 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.

More importantly, the new report – Water to Supply the Land: Irrigated Agriculture in the Colorado River Basin – explores the potential for agricultural management strategies to save water, without remove agricultural land from production – through changes in irrigation technology, management strategies, and cropping patterns.

 Colorado basin interactive

Click here to visit the 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.

The report shows that 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.

Innovative irrigation techniques, which many farmers around the world are already using, can help ensure continued agricultural production, while cutting water demands, even in the fact of the growing threat of climate change.

The new study evaluates specific water-efficiency strategies, including regulated deficit irrigation, crop shifting, and advanced irrigation technologies. The Institute’s results show considerable water savings are possible. For example, almost a million acre-feet of water may be saved cheaply and quickly by irrigating alfalfa less often (a practice known as “regulated deficit irrigation”), 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 at 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.

Lead author of the study, Michael Cohen, observed

“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. 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.

Dr. Juliet Christian-Smith, a report co-author, observed that the water management techniques proposed in the study are proven. She says that if efforts are made to expand use of them in the western U.S. it

“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.”

It is time to get serious about returning the Colorado River basin to even a semblance of hydrologic balance. This report shows how to start.

Download the full report (pdf).

Download the Executive Summary (pdf).

Download the interactive map.

 

Comments

  1. #1 Lyle
    May 10, 2013

    Actually this raises an interesting question, why are crops that do not require the kind of climate in the region grown. Do we have information on the breakdown of where the forage crops are grown, in the upper basin where that may be all that can be grown, or in the lower basin, Az, and Ca where fruits and vegetables could be grown at times that would not work elsewhere in the US? One wonders why originally La county was the biggest dairy county in the US, and now why the Central Valley is the leader. What is the price of water in the lower basin states that would crowd out the forage crops?

  2. #2 Carl
    May 12, 2013

    Very good article, but the fly in the ointment – How do you make farmers grow less profitable crops in a free market economy?

    The comment by Lyle also raises an efficiency issue that is not often recognized. An alfalfa farmer in the Imperial Valley of southeastern CA averages 7.5 ton/acre/year. In Colorado it would be more like 4 tons. Most of the CA hay is high quality dairy hay that is sold to the large dairy farms in the San Joaquin Valley. An astute economist might conclude that while water use per acre is higher in the Imperial Valley, increased production, higher quality and lower shipping costs make the cost per unit of water lower than moving hay production to Colorado. The same comparison can be made for most of the crops grown in the low desert valleys of CA and AZ.

    Another key point that Lyle is apparently not aware of; water is not sold; irrigation districts and tribes are allowed to take water out of the river based upon treaty rights. The cost to the end user is a function of the irrigation district’s costs of storage and delivery.

    One final point, having lived and worked in Ag in the Imperial Valley for 20 years and now living in San Diego, there is more need to change wasteful water use practices in SD than in Imperial.

  3. [...] A Step toward Fixing the Colorado River [Significant Figures by Peter Gleick] (scienceblogs.com) [...]

  4. [...] More importantly, the new report – Water to Supply the Land: Irrigated Agriculture in the Colorado River Basin – explores the potential for agricultural management strategies to save water, without remove agricultural land from …  [...]

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