Water for the Colorado River Delta in a Dry Year

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The Colorado River is once again flowing in its delta. The flows, which began on May 1, are the result of binational collaboration and deliberate management. The water is dedicated to supporting the ecosystem and local communities in a landscape where the river has not flowed  for most years in the past half century. It is a heartening bit of good news for the Colorado River, which earlier this year was designated as America’s most endangered river.  

This year’s flow will be very similar to the managed flow in the delta in 2021. The water purposefully bypasses the driest reaches of the delta, diverted from the Colorado River at the border into Mexico’s irrigation system, where it travels via concrete lined canals to be reconnected with the river some 40 miles downstream. From there water flows down the river’s channel, past more than 1000 acres of painstakingly restored riverside forest, towards the Upper Gulf of California. Like last year, this year’s flow is about 35,000 acre-feet of water (11.4 billion gallons), delivered over nearly 5 months from May 1 to September 20. In a year where we cannot seem to escape horrible news about climate change, wildfires, and water shortages, the delta flow is a sign that it is still possible to improve management on the Colorado River. As climate change impacts continue to bear down on the region, this type of management will be more important than ever.

Dozens of scientists are deployed to the field to measure the impact of this water delivery and provide suggestions for how to use a managed flow to improve environmental benefits in a region known to support some 380 bird species including Yellow-billed Cuckoos and Heermann’s Gulls. With continued input of scientists over the years, the design of these flows aims to optimize the location and timing of water deliveries to support restored and remnant river habitats, the birds that use them, and residents of nearby Mexican communities that are rediscovering a river in their midst.

The managed delta flow is the result of improved hydro-diplomacy between the United States and Mexico. The U.S. and Mexican sections of the International Boundary and Water Commission, along with federal water agencies in both countries—the U.S. Bureau of Reclamation and CONAGUA—today operate under Minute 323, a 2017 treaty agreement that modernized Colorado River management first established in a 1944 Treaty. Minute 323 recognizes the value of water for the environment, for the river itself, a value the original Treaty did not consider.

Minute 323 may sound like an arcane bit of law, but consider its impact: in 2022, for the first time, a shortage was declared on the Colorado River, and Mexico along with Arizona and Nevada received less than its full allocation of water (there is a parallel U.S. domestic agreement, the Lower Basin Drought Contingency Plan). This could have been the beginning of a major international conflict—in the 1960’s more than 10,000 Mexicali farmers protested for days on the steps of the American consulate in response to degraded Colorado River water quality from the United States, and eventually Mexico’s President Echeverria brought the concern to an Oval Office conversation with President Nixon. But in 2022, the United States reduced deliveries of Colorado River water to Mexico, and with Minute 323 in place, it was implemented without remark.

As climate change continues to aridify the Colorado River basin, and water availability continues to decline, the provisions in Minute 323 to share water shortages proportionally – equitably – stands as a model of good management. It might even be a helpful model for the seven U.S. states (Ariz., Calif., Colo., N.M., Nev., Utah, and Wyo.) that must develop shortage-sharing agreements among themselves sufficient to adapt to the river’s declining water supply.

Minute 323’s impact goes further: under its provisions, the United States committed millions of dollars to help upgrade agricultural water supply infrastructure in the Mexicali Valley, and Mexico has conserved and stored more than 150,000 acre-feet of water in Lake Mead in the United States, helping to prop up water storage in a reservoir that is dwindling too quickly.

Under Minute 323, the United States and Mexico successfully began to manage the declining Colorado River water supply, helping to improve conditions for water users in both countries, while also making environmental water commitments. Colorado River water users and river lovers alike owe a debt of gratitude to the leaders who negotiated Minute 323, and should ask for nothing less from future Colorado River management agreements.