Minute 319 water release will rebuild a habitat

A special water release this weekend from the Morelos Dam on the
U.S.-Mexico border may send water for the first time in more than 50 years into this parched section of the Colorado River delta in Mexico.

Water managers and resource advocates across the Southwest are awaiting Sunday’s release of a pilot “pulse flow” of water into the long-depleted delta of the Colorado River, where water has not flowed regularly since Dwight Eisenhower was president.

This historic event, stemming from the Colorado River agreement between the U.S. and Mexico known as Minute 319, will help efforts by the U.S. and Mexico to re-establish riparian habitat, providing benefits to wildlife species and communities along the Colorado River in both countries and in the Colorado River Delta region in Mexico.

The framework of the agreement signed in November 2012 allows the U.S. and Mexico to share surplus when water is plentiful and share shortage when water is scarce.

The agreement also commits the two nations to work together on water conservation and restoration of the Colorado River’s long-desiccated delta by committing water to sustain it.

“This demonstrated commitment to environmental restoration is a shining example of what two nations can achieve when we work together,” said Jennifer Pitt, director of the Colorado River Project at Environmental Defense Fund (EDF) and U.S. co-chair of the environmental work group that helped negotiate the framework agreement for the pulse flow.

The release “will be very helpful for both governments to obtain information that becomes increasingly relevant as we face droughts with more frequency, not only in the Colorado River Basin, but also in other watersheds,” Pitt said.

Starting Sunday, the two countries will release approximately 105,000 acre-feet ­— around 0.7 percent of the annual average flow of the Colorado River — into the delta below Morelos Dam, which straddles the Colorado River on the U.S.-Mexico border.

The pulse flow from Lake Mead through Hoover Dam will peak for several days at high flow and will last for nearly eight weeks, mostly at a reduced flow rate.

“The pulse flow is a vital part of our ongoing restoration efforts,” said Francisco Zamora Arroyo, director of the Colorado River Delta Legacy Program at Sonoran Institute. “We know that relatively small amounts of water can make a big difference in the health of the delta region.”

According to researchers, a periodic pulse flow is essential to scour the channel and floodplain, thwart the growth of salt cedar and help establish willows and cottonwoods, which require flooding for seed germination.

The other third of the Minute 319 water will create a base flow that keeps the river corridor wet and flowing.

A team of scientists from U.S. and Mexican federal agencies and universities, as well as from the Sonoran Institute, The Nature Conservancy and Mexico-based Pronatura Noroeste, will monitor the event to determine its impacts and learn how water can stimulate river health.

“Some 380 bird species are expected to benefit from this return of water to the delta,” said Osvel Hinojosa, water and wetlands program director at Pronatura Noroeste, and Mexico co-chair of the environmental work group. “So will the local Mexican farming communities that long ago watched the Colorado River delta dry up.”

An add-on to an existing 1944 treaty between the U.S. and Mexico, Minute 319 provides numerous benefits for water users throughout the Colorado River Basin — in seven U.S. and two Mexican states — including broader sharing of water when supplies are plentiful and in times of reduced supplies, investments in water conservation, and new opportunities to store water in upstream reservoirs such as Lake Mead. Lake Mead is the major water-storage reservoir in the Lower Colorado River Basin.

The pulse flow is an important element of Minute 319, a component that both countries agreed to implement in 2014.

“This flexible approach will be particularly important given the 14-year drought in the Colorado River Basin,” said Taylor Hawes, director of The Nature Conservancy’s Colorado River Program. “The agreement benefits water users throughout the basin as well as the environment, by limiting the impact of water shortages on any one user and providing incentives for leaving water in storage while paving the way for funding future water-conservation projects.”


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