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Tiny fish behind Rio Grande water plan

Copyright © 2016 Albuquerque Journal

More than 19 miles of the Rio Grande dried up in July along the Bosque del Apache Wildlife Refuge south of Socorro due to excessively hot temperatures and very little rain.

“The river was dry for two-and-a-half to three weeks starting in the middle of July,” said David Gensler, water operations manager for the Middle Rio Grande Conservancy District, which delivers water to 70,000 acres of cropland. “It got wet again with the rains the first of August.”

It is not unusual for the Rio Grande to run dry. The river dries up along some stretches almost every year, 2008 being a recent exception. About 30 miles of the river dried out last year and more may dry out this year before the irrigation season winds up at the end of October.

“In almost every year going back to 1895, there was a major river drying,” Gensler said. “There has been far less drying since 1996 than there was before then. Every year since 1996, there has been something done by water managers to prevent drying.”

That’s because the Rio Grande silvery minnow was declared an endangered species in 1994. Gensler said nothing needed to be done in 1995, which was an exceptionally wet year, but efforts to protect the minnow kicked in the following year.

“Everyone is working to shape a hydrograph that is favorable to the fish,” Gensler said. “The last three years, we have diverted less than 300,000 acre-feet per year for irrigation. We were diverting roughly 600,000 acre-feet in the 1990s.” An acre-foot is the amount of water required to cover an acre at a depth of a foot.

“We are careful not to remove anything (water) we don’t have to,” Gensler said.

But in a statement released last week, WildEarth Guardians, a Santa Fe-based organization whose mission is the protection of wildlife, wild places and wild rivers, claims that the silvery minnow population has declined since the fish was given protected status.

WildEarth Guardians attributes that in part to a 2003 agreement that allows water managers, such as the MRGCD, to allow the river to go dry below the Isleta Diversion Dam, near Isleta Pueblo, each year between June 15 and Oct. 31.

“This section of the river provides the best (silvery minnow) habitat and is where the majority of the population is found,” according to the Guardians’ statement.

Each year, the U.S. Fish and Wildlife Service determines the number of silvery minnow allowed to be lost as a consequence of otherwise lawful projects, such as irrigation. That number is derived from a formula based on the number of silvery minnow counted in the river the prior year. This year, the incidental take, or allowable loss, number is 1,109.

During recent rescue and salvage operations along the dry stretch of river, Fish and Wildlife found 46 dead adult silvery minnow and more than 10,000 dead young silvery minnow.

Thomas Archdeacon, fish biologist with Fish and Wildlife’s Albuquerque office, said only the 46 dead adult fish count against the permitted limit because high mortality rates among young fish are considered part of nature’s scheme.

“The amount of water in spring is what controls the (silvery minnow) population,” Archdeacon said.

To that end, water was released from El Vado Reservoir, 80 miles northwest of Santa Fe, in May in an effort to pump up the spring runoff and produce the robust river flow that cues silvery minnow spawning.

But the WildEarth Guardians contend that allowing the river to dry in the summer, killing tens of thousands of young fish in the process, negates the efforts to spark spawning with big flows of water in the spring.

“There is a huge disconnect in strategy,” said Jen Pelz, director of WildEarth Guardians’ wild rivers program. “Sucking a river dry to irrigate alfalfa in the desert is not a sound strategy for recovering a critically imperiled species. The only way to break the downward spiral of the minnow and improve the health of the river is to keep the river flowing and connected.”

Gensler said he does not disagree with that.

But he maintains that a lot more of the Rio Grande would go dry each year if the river were allowed to do what it does naturally rather than go dry now that the river’s flow is controlled by dams and supplemented by reservoirs.

“Entering the middle valley, the river spreads out along dry, sandy wash, and gets smaller and smaller as you go downstream,” he said. “With evaporation, the ground, the trees, it would not even get to Bernalillo.”

He said that, over the past seven or eight years, the MRGCD has been working to put into effect a “string of pearls” approach that would inject water into dry stretches of the river to create wet spots or refuges for the minnow.

“We’d like to create a series so, when the river does go dry, there is not too far a distance to a wet spot,” he said. “We have been doing it. We think we can do better.”

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