Vegetation Response to Lower Colorado River pulse flow in 2014

It was 2000 the last time the Colorado River reached the Sea of Cortez, and over that time there has been a decline in the amount of healthy vegetation along the lower reaches of the river.

In 2014, the U.S. and Mexico made an agreement, known as Minute 319, to release an experimental flow through the Morelos Dam and down the riverbed. On March 23rd, the floodgates were opened and the water started to flow.

In total, 130 milion cubic meters (105,000 acre-feet) of water was sent through the dam. Though most of the water soaked into the ground in the first 37 miles, a portion of the flow did make it down to the delta. Water flowing on the surface reached areas that had been targeted for restoration, and the replenished groundwater revived vegetation along the entire route to the sea.

Pamela Nagler, of the U.S. Geological Survey’s Southwest Biological Science Center in Tucson, Arizona, compared satellite images of pre-flow August 2013 to post-flow August 2014. Using data from NASA/USGS's Landsat satellite, as well as data from NASA's Terra satellite, she calculated a 43 percent increase in green vegetation along the route wetted by the flow, called the inundation zone, and a 23 percent increase in greening of the overall river bed from bank to bank, called the riparian zone.

The Minute 319 pulse flow was the result of significant cooperation between a large group of partner organizations and agencies in the U.S. and Mexico, including the International Boundary and Water Commission, the U.S. Bureau of Reclamation, the USGS, the Sonoran Institute, the Environmental Defense Fund, the Mexican Comision Nacional de Areas Naturales Protegidas, and others.

See the following sources:

• NASA Earth Observatory
• NASA.gov