The Bureau of Reclamation’s Yuma Desalting Plant is scheduled to begin its operational test phase next week. In preparation, a U.S.-Mexican team is ramping up its monitoring efforts at the Cienega de Santa Clara, an accidental wetland in what was once the Colorado River delta. The Cienega is the inadvertent product of U.S. ag drainage that was too salty to put directly into the Colorado River. It’s diverted instead into a channel that bypasses most of the delta, ending at once was empty salt flats. It’s now a small but thriving ecosystem, as Mari Jensen explains in a nice piece on what’s happening in the Cienega now and what happens next:

Courtesy Francisco Zamora

The cienega currently receives about 107,000 acre-feet of agricultural runoff water per year. When the YDP is running, the cienega is projected to receive about 67,000 acre-feet of runoff plus about 10,000 acre-feet of effluent from the plant….

“I think we’ve got a good idea of what the natural range of variability is,” [University of Arizona researcher Karl Flessa] said. “So the question now is: When one-third of the water gets taken out to go through the Yuma Desalting Plant and a salty brine starts flowing toward the cienega instead, how will that affect the health of the cienega?”

To answer that question, the researchers placed instruments that record water quality and water level every 30 minutes at 20 locations all over the cienega. Some instruments are in open water, some are along the edges of the marsh, and others are deep in cattail thickets.

The Cienega raises interesting issues about how to maintain ecosystem flows across an international when no one quite owns the environmental problem. If this were in the United States, the actions of a U.S. government agency would be subject to the Endangered Species Act and other environmental laws.

But it’s in Mexico.

Past reporting on the Cienega and the YDP here, here and here.