A recent Facebook post to which I had a knee-jerk response caused me to go back and do some digging. The post said:
“Mexico Draws 1.5M AcreFeet of Water every year from the Colorado River (1 AcreFoot of Water is 325,851 Gallons of Water) That’s over 488B that’s 488 Billion with about Gallons of water. And Mexico is going to start releasing 400M Gallons of sewage,”
and was linked to a Fox News article.
I am aware that sewage overflows from Tijuana have been a problem for years, and have caused beach closures on the U.S. side of the border. However, the situation is much more complex than the ‘news’ article presents.
For one thing, the U.S. is obligated under treaty to deliver the 1.5 million acre-feet of water cited by the Facebook user, and much of that water is destined for Tijuana. I assume a lot of it originates at the last dam on the Colorado, the Morelos Dam. which straddles the border between Baja California and Yuma County, Arizona. I don’t know how the allotment is divided between the local agricultural needs of the Mexicali Valley (much of the products of which are exported to the U.S.) and the portion sent to Tijuana via the Alamo Canal and the Tijuana Aqueduct.
The Wikipedia article on Mexicali, Baja California, Mexico, also says that,
“…a proposed concrete lining in the United States on the All-American Canal [which transports water from the Colorado River at Yuma westward to Southern California] would cut off billions of leaked gallons of water, which is used to irrigate onions, alfalfa, asparagus, squash and other crops in Mexicali.”
That implies that Mexico has significant effort involved in pumping the water out of the ground. I’m doubtful that this pumping counts against the 1.5M acre-feet, but cutting the source of it would certainly burden the users in Mexico.
The water delivery obligation derives from the 1944 Water Treaty, which covers both the Colorado River and the Rio Grande.
The annual cross-border allocations were defined as follows:
- 350,000 acre-feet from Mexico (Rio Grande) to the U.S.
- 1,500,000 acre-feet from the U.S. (Colorado River) to Mexico.
The details of how this is accomplished are complicated. But clearly the greater obligation is from the U.S. to Mexico.
Those two watersheds are very geographically different. But it appears to me that the U.S. has used Mexico’s shortages related to the Rio Grande to short our obligation related to the Colorado.
“On 20 March 2025, the U.S. had for the first time in history refused the delivery of water to Mexico from the Colorado river.”
Are you starting to see the picture; the linkage between Colorado River water and sewage outflows from Tijuana?
I’m not aware of how this delivery refusal actually occurs, since the outlet for the Morelos Dam is on the Mexican side of the border.
I might also add that some of the problem with raw sewage release in Tijuana has to do with problems at the International Boundary Wastewater Treatment Plant and associated infrastructure, which was mostly built, and is currently owned by the U.S.
But back to the Colorado River: I have posted many times before about the shamefully small amount of Colorado River water that reaches the Colorado River Delta at the top of the Sea of Cortez (aka the Gulf of California), above Puerto Peñasco (aka “Rocky Point,” to the gringos), Sonora, Mexico.
“Prior to the construction of major dams along its route, the Colorado River fed one of the largest desert estuaries in the world. Spread across the northernmost end of the Gulf of California, the Colorado River delta’s vast riparian, freshwater, brackish, and tidal wetlands once covered 7,810 km2 (1,930,000 acres) and supported a large population of plant, bird, aquatic, and terrestrial life…Decades of dam construction and water diversions in the United States and Mexico have reduced the delta to a remnant system of small wetlands and brackish mudflats.”
I’ve written about species indigenous to the delta, including Palmer’s saltgrass (Distichlis palmeri), a wild grain that grows in salty soil, and could hold profound significance for us in this time of drought. I’ve also written about the Vaquita (“Little Cow”) porpoise, which may be functionally extinct by now; and about the giant totoaba fish, also virtually extinct, that grows up to 2 m (7 ft) and 136 kg (300 pounds).
The demise of the Colorado River Delta isn’t all our (U.S.) fault. But we are the vast majority of the consumption of its water, and we sure haven’t done a lot to address the problem, either.