Salt in the Colorado River could threaten drinking water for millions of people dependent on its runoff.
The Colorado is the most significant water supply source in the West, but it carries an annual salt load of nine to 10 million tons, said Don Barnett, executive director of the Colorado River Basin Salinity Control Forum. That’s salt that has to be removed from the river to improve water quality.
For the past 40 years, the the forum has been “silently working away” at improving water quality and lowering salt content on the Colorado, which supplies water to 40 million people in seven states and Mexico. Barnett called the salinity control program the “greatest water quality improvement effort in the history of the world” — only slightly tongue in cheek — during last week’s Colorado Water Congress conference in Steamboat Springs.
That effort involves multiple federal agencies; hundreds of local agencies, organizations and companies; thousands of water users and the seven states that rely on the river (Colorado, New Mexico, Utah and Wyoming in the upper basin; Arizona, Nevada, California and the Republic of Mexico in the lower basin).
“We’ve reduced the salt load by 1.33 million tons per year” at a cost of about $1 billion, Barnett explained. Those costs are shared by the federal government and by the program’s participants.
The salt comes from the ground the river traverses. Experts say that 100 million years ago, tectonic plates plates collided and resulted in thousands of feet of salty marine shale beneath Colorado's topsoil.
That salt has been dumped in the Colorado River basin over the millennia. That means a salt concentration that rises from 50 milligrams per liter of water to 80 milligrams per liter as the Colorado flows from its headwaters near Rocky Mountain National Park to its lowest point, in Mexico.
Concerns about the salt arose in Mexico in the 1970s, leading to the creation of the salinity control program.
In 1972, Congress began actions on water quality standards, and states pushed back. In 1973, the Colorado River Basin Salinity Control program was initiated. Congress approved it the following year, and a year after that, and the Environmental Protection Agency adopted rules requiring basin states to come up with water quality standards for salinity.
The effort includes monitoring ditches and canals and persuading farmers not to flood irrigate their crops.
In Montrose County's Paradox Valley, water contains 250,000 milligrams of salt per liter. A Bureau of Land Management program has removed 100,000 tons of salt from the valley's water, which discharges into the Delores River.
It’s not just about water quality. Removing the salt saves money, too, Barnett said.
According to the Bureau of Reclamation, high salt damages appliances, impacts water utilities and hinders agricultural crop revenues. In 2008-09, the Bureau of Reclamation estimated the annual damages from high salt loads at $376 million.
Barnett refers to the salinity program as “the grand deal” with the EPA. The goal is to keep salinity at the 1972 levels. While water usage in the upper basin has increased since 1972, salinity levels have dropped, “and that’s why the grand deal works,” Barnett added.
But salinity isn't just a problem in the Colorado River. Most of the major rivers in Colorado have the same problem.
For example, six projects on the Lower Arkansas River deal with salinity problems, said Mike Weber of the Lower Arkansas Water Conservancy District.
“We are being progressive, putting projects together on water-short ditches, dryland farming” and other areas with poor water supply, Weber said.