The Colorado River effectively dries up at Morelos Dam, a diversion structure located about a mile south of the U.S.-Mexico border near the cities of Los Algodones in Baja California and Yuma, Arizona. Under normal operations, Morelos Dam diverts the entirety of the remaining river water into Mexico’s Reforma Canal for agricultural use. Below the dam, the Colorado is either a minimally flowing trickle fed by seepage or a completely dry streambed for most of the year, running empty for roughly 90 miles before it would otherwise reach the Gulf of California.
What Happens at Morelos Dam
Morelos Dam sits approximately 1.1 miles downstream of the international border on the main Colorado River channel. By the time the river reaches this point, it has already passed through more than 80 major diversions and a series of massive reservoirs in the United States, including Lake Powell and Lake Mead. Whatever water remains in the channel at the border is captured at Morelos and routed into the Reforma Canal, which feeds irrigation districts in Mexico’s Mexicali Valley.
The only water that continues past the dam in the natural riverbed is seepage, the small amount that leaks under and around the structure. Releases from the dam’s spillway for flood control or environmental purposes have occurred, but they are rare events rather than regular flows. The result is a river that, for most practical purposes, ends at a concrete wall.
Why the River Runs Dry
The Colorado River supplies water to roughly 40 million people and irrigates millions of acres of farmland across seven U.S. states and Mexico. Agriculture is the dominant consumer, accounting for about 75% of all direct human use and roughly 52 to 60% of total consumptive uses and losses across the basin. In Mexico alone, 1.2 to 1.3 million acre-feet of Colorado River water are consumed annually on about half a million acres of crops and pasture.
The river has been over-allocated by more than 20%. Legal agreements carved up its water based on flow estimates from an unusually wet period in the early 1900s, and actual supply has never consistently matched those promises. Every drop is spoken for before the river reaches its natural endpoint. The combination of upstream reservoirs, canal diversions, and municipal pipelines means the lower river is essentially a plumbing system rather than a free-flowing waterway.
How Reservoirs Control What’s Left
Lake Mead, the largest reservoir in the United States, serves as the final major control point before water reaches Mexico. Under the 1944 Water Treaty between the U.S. and Mexico, the standard annual delivery to Mexico is 1.5 million acre-feet. That amount can increase slightly when Lake Mead levels are high, up to a maximum of 1.7 million acre-feet in any given year.
When conditions are bad, deliveries shrink. If Lake Mead’s water level drops to 1,075 feet above sea level or below, Mexico’s allocation gets cut by 50,000 to 125,000 acre-feet depending on severity. In 2022, water redistribution cuts hit Arizona with an 18% reduction, Nevada with 7%, and Mexico with 5%. If Lake Mead ever reached “dead pool,” water would sit too low behind Hoover Dam to flow downstream at all.
What the Dry Delta Looks Like
The Colorado River Delta once covered 780,000 hectares of riparian forests, freshwater marshes, estuarine habitat, and tidal flats where the river met the Sea of Cortez. It has been reduced to roughly 10% of its original size. The combination of upstream diversion and conversion of delta land to agriculture has transformed what was one of North America’s great wetlands into a landscape of dry channels, salt flats, and invasive vegetation.
The ecological damage has been severe. Bird abundance and diversity in the delta have declined substantially. Eleven bird species have been lost from the region entirely, and riparian specialists like the Yellow-billed Cuckoo have seen sharp population drops. The loss of freshwater flow has disrupted the entire food web that once depended on the river reaching the sea.
Efforts to Bring Water Back
The U.S. and Mexico have committed modest volumes of water specifically for environmental restoration in the delta. Under an international agreement known as Minute 323, both governments pledged a combined 210,000 acre-feet of water for environmental purposes spread over the agreement’s duration, with each country providing one-third. Occasional “pulse flows,” deliberate releases of water past Morelos Dam, have temporarily reconnected the river to portions of its historic floodplain, greening stretches of the channel and attracting wildlife. But these events are brief, and the volumes are a tiny fraction of what the river once carried.
Several key agreements governing Colorado River operations expire at the end of 2026, including the 2007 Interim Guidelines, the 2019 Drought Contingency Plans, and the international agreements with Mexico. The Bureau of Reclamation released a draft environmental impact statement in January 2026 outlining alternatives for how the river will be managed in the decades ahead. The decisions that come out of this process will determine whether any additional water reaches the delta on a regular basis, or whether the river continues to vanish at Morelos Dam.