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Going Green: The Silvery Minnow, Drought and the Rio Grande

Albuquerque District Public Affairs
Published March 25, 2013

The bosque, or forest, surrounding the Rio Grande River, is the longest continuous forest of cottonwood trees in the world. As signs of spring begin to show in the bosque, environmentalists, biologists and others continue their efforts to understand river flow issues along the Middle Rio Grande. River flow issues along the Middle Rio Grande impact all life in New Mexico. Of particular interest are endangered species in relation to water use and jurisdiction. 

In an effort to find a balance, the Middle Rio Grande Endangered Species Collaborative Program (MRGESCP) was created. The MGESCP, comprised of 16 federal, state and tribal, non-governmental and local agencies, continually works to help support and improve the status of endangered species, protect current and future water use and comply with state and federal laws.  The Rio Grande silvery minnow is of particular concern in New Mexico. 

While protection of the silvery minnow is always important, within the past three years, the drought has proven to be a constant challenge to create and maintain a balanced environment for the silvery minnow to continue to spawn. For the third straight year, the snowpack, which supplies water to the Rio Grande, is down approximately 50 percent from a normal year. The silvery minnow relies on flooded islands and cottonwood forests for spawning and raising their offspring. Because of the drought, the environment needed for natural spawning is not present. 

“The Rio Grande has been too dry for the minnows to spawn as usual,” said Michael Porter, fishery biologist for the Corps.

As a result, for the last year, the number of silvery minnows has decreased dramatically. In coordination with MRGESCP, the Corps is measuring a large number of possible spawning areas on the Rio Grande.

“We are here today doing this survey with this calibrated survey rod to measure the difference between the river and the surrounding bank,” he said. “From these measurements, we will calculate how much water is needed in order to create the proper environment for proper minnow spawning.”  

Measuring the natural snowmelt of the spring runoff helps water managers throughout the state decide what measures to take in order to meet the Rio Grande river flow goals. One possible measure being considered is to release a calibrated amount of water, called a deviation, from Cochiti Lake.

“This special, one-time release would create flooding, or overbanking, in a number of areas which creates the proper habitat for the silvery minnows to spawn and grow,” said Ryan Gronewold, Rio Grande coordinator with the Corps. 

And why is survival of the silvery minnow important? “The silvery minnow evolved in the Rio Grande,” said Porter.  “If the minnow does not survive in this desert environment, neither will people,” he said.

The U.S. Army Corps of Engineers strives to protect, sustain, and improve the natural and man-made environment of our nation, and is committed to compliance with applicable environmental and energy statutes, regulations, and Executive Orders. Sustainability is not only part of the Corps' decision processes, but is also part of its culture.