Replenishing the Colorado Delta

The Colorado River once drained to the Gulf of California, creating a delta that was rich with vegetation and home to many species of birds and fish, as well as jaguars, bobcats, coyotes, foxes, deer, and raccoons. Over the years most of the river’s flow has been diverted for agriculture, as well as to provide water for growing cities. The once-rich delta turned to salt-encrusted mudflats.

Today, the river flows between California and Arizona and into Mexico, where the Morelos Dam serves to capture Mexico’s share of the water—essentially stopping the river at that point.

During the El Niño years in the 1980s and ’90s, however, the river had enough water that some of it once again flowed through the delta. Scientists saw native plants like willow and cottonwood begin to thrive, instead of just the invasive salt cedar that had taken over during the dry period. After long negotiation, the US and Mexico reached an agreement to release water from dams on the southern part of the river to allow water into a small part of the delta—a couple thousand acres, as opposed to the more than 2 million acres of wetlands that once existed there. In March 2014, 34 billion gallons—less than 1% of the rivers annual flow—was released as part of a pilot project, to be followed by smaller periodic releases to maintain a base flow. The initial release was intended to mimic traditional spring flooding.

This article  and accompanying photos provide a detailed look at what has happened since the initial release of water. Vegetation has increased by 43%, and workers are beginning to clear away the invasive plants and hand-plant saplings at select restoration sites.