By Robert Marcos, photojournalist
Grand Junction, Colorado
A political brouhaha erupted in the early 1960s after the Wellton‑Mohawk irrigation project in Arizona discharged very saline return flows into the Colorado River, which raised salinity at the border from 800 ppm to about 2,700 ppm. In Mexicali Valley farmers said the water was virtually “useless for irrigation purposes,” and led to widespread crop failure in one of Mexico’s largest and most fertile regions.
It took the United States 12 years to find a definitive, long-term solution: from the initial crisis in 1961 to the signing of a permanent agreement, known as “Minute 242” in 1973. This agreement led with the Bureau of Reclamation investing $250 million in the development of the Yuma Desalting Plant, which would use a reverse-osmosis system to filter a percentage of salts from the river before it entered Mexico.
The expensive plant was completed in 1992 but was used for only a few months. Because in 1977 a temporary measure enacted by the BOR diverted (the salty) Wellton-Mohawk runoff to Mexico’s Ciénega de Santa Clara. This action brought the river water back into compliance while the Yuma Desalting Plant was still being built. But this “temporary measure” worked so well that it obviated the need for the expensive desalting plant.
The Bureau of Reclamation had known since the 1970’s that the Dolores River had, (for millions of years), been a significant source of the Colorado River’s salinity and in 1996 they took action. The Paradox Valley Unit removes between 50,000 to 180,000 tons of salt annually from a facility west of Montrose, Colorado. In a nutshell the operation works by intercepting saline-rich groundwater before it enters the Dolores River by the use of nine extraction wells. These wells pump out this naturally occurring brine -which is eight times saltier than seawater, before it can seep into the Dolores River.
The brine is piped to a facility where it’s injected under high pressure 3 miles down into the earth – underneath a natural salt layer that prevents it from rising back to the surface. Unfortunately, as is often seen with other types of deep fluid injections, a 4.5 magnitude earthquake was triggered and the unit had to be shut down for two years. When operations resumed it was at a reduced rate of 67% in an attempt to mitigate the seismic risks. Even so, in 2024 the unit still managed to remove 62,913 tons of salt …salt which used to show up in Mexicali Valley.
The very different types of operations that have succeeded in lowering Grand Valley’s once-massive salt load will be addressed in a future post. Thank you.
Sources:
https://www.usbr.gov/history/ProjectHistories/Yuman-AZ-Desalting-Plant.pdf