By Robert Marcos, photojournalist
Grand Junction, Colorado
Most of you have heard that California’s Salton Sea would not currently exist were it not for the nearly 1 million acre feet of agricultural runoff that’s drained into it every year. Paradoxically – the sea is both being kept alive by this salty runoff and being killed by it, in part because the Sea’s evaporation rate of six feet per year is continually concentrating its chemical-laden waters. 1
As you might expect the Salton Sea’s water is dominated by high salinity from salts, which increases dramatically as the lake shrinks. Selenium ranks next as a major metalloid of concern, often reaching ecologically harmful concentrations from runoff. Other notable contaminants include heavy metals like cadmium, copper, zinc, and nutrients driving algal blooms.2
Meanwhile 132 miles south in Sonora another body of water has formed from American-made runoff, and it’s also a paradox. Ciénega de Santa Clara is technically a brackish water wetland consisting of marshlands and lagoons, and its classification as “anthropogenic” stems from the fact that it was inadvertently created by, and entirely sustained by human engineering.3
This “human engineering” began in 1965 after the U.S.Bureau of Reclamation rerouted approximately 100,000 acre feet of salty runoff from the Wellton-Mohawk Irrigation District away from the Colorado River and 13 miles into Mexico – as a temporary way to reduce the excessively salty Colorado river water that had been killing crops in Mexico. By 1973 a permanent bypass canal was built which carried that salty runoff 50 miles further, to the Ciénega de Santa Clara in Sonora.4
But to everyone’s shock and surprise the salty runoff that was dumped at Cienega de Santa Clara resulted in the rebirth of an amazing ecosystem. The sprawling 40,000-acre wetland, now a UNESCO-recognized biosphere reserve, transformed a desolate salt flat into a lush expanse of emergent marshes dominated by dense stands of southern cattail interspersed with bulrushes and submerged aquatics. The nutrient-rich, albeit salty, waters fostered rapid plant growth, creating tangled corridors of green that ripple across the landscape, their feathery seed heads swaying in desert breezes amid shallow, mirrored pools teeming with microbial life.5
But the oasis’s vitality depends upon consistent inflows. Disruptions, like the one in 1993 that occurred during canal repairs caused a dramatic loss of vegetation, confining green regrowth to low-lying faults until the runoff flows resumed. But today “La Cienaga” endures as a testament to ecological opportunism, though looming desalination plans at Yuma threaten its future by potentially diverting the life-sustaining drainage. 6
- The Salton Sea. Physical and Chemical Characteristics
https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1958.3.4.0373 - NIH: National Library of Medicine
https://pmc.ncbi.nlm.nih.gov/articles/PMC7232737/ - From accident to management: The Cienega de Santa Clara ecosystem
https://www.sciencedirect.com/science/article/abs/pii/S0925857413001079#:~:text=rights%20and%20content-,Abstract,that%20flows%20to%20the%20Cienega. - Colorado River Basin Salinity Control Project
https://www.usbr.gov/projects/pdf.php?id=96#:~:text=In%201961%2C%20two%20major%20problems,Project%2C%20Delivery%20of%20Water%20to - Audubon: “Water Flows in Colorado River Delta Again”
https://www.audubon.org/news/water-flow-colorado-river-delta-again - Sonoran Institute
https://sonoraninstitute.org/files/pdf/colorado-river-delta-research-la-cienega-de-santa-clara-06152011.pdf