Death of a River

From eastern Colorado, the dry prairies of the Great Plains spread north, south and east for 500,000 square-miles — a swath of land covering one-sixth of the continental United States. These are the plains of the Dust Bowl, and farmers here are facing a similar disaster — this time one caused by over-pumping of groundwater.

Deep below the surface lies the largest aquifer in North America — the Ogallala or High Plains Aquifer, responsible for growing some 30% of irrigated agriculture in the United States. But the technological innovations that brought farming back here after the Dust Bowl are now running the aquifer dry.

“The advent of center pivot irrigation that relies on deep groundwater transformed agriculture in the Great Plains,” explains John Sanderson, director of science for The Nature Conservancy in Colorado. “Since the middle of the 20th century, we've pumped almost the equivalent of Lake Erie — about 100 trillion gallons — from the aquifer.”

In some areas, the aquifer has dropped more than 150 feet. Scientists estimate the entire aquifer could be completely depleted within 50 years.


  Brassy minnow from the Arikaree River, CO © Kurt Fausch (CC BY 2.0)

Brassy minnow from the Arikaree River, Colorado © Kurt Fausch


As the Arickaree Dries, so Go its Fish

In eastern Colorado, many rivers wouldn’t exist without groundwater seeping from below – as the groundwater is lost, so too are the streams and rivers, the fish and the riparian habitat.

“At current rates of pumping, by 2050 we will have dried up almost a third of all our streams,” says Sanderson. “Because of pumping, the Arikaree River — home to the Conservancy’s Fox Ranch — lost 60% of its water during the last half of the 20th century.”

A paper published by Sanderson and colleagues in Proceedings of the National Academy of Sciences shows what this groundwater loss is doing to fish species.

“We found that seven of the Arikaree’s 16 native fish species have disappeared as the river has dried. At the rate we are going, the remaining species may not be able to survive another 25 years from now,” says Sanderson.

It’s the loss of fish that gives Sanderson heartache.

“Many of these small fish species have survived over millennia,” says Sanderson. “If we lose the Arikaree, we lose these fish, we lose the history and stories about those fish that no other species will ever replace.”

Species such as the brassy minnow and the orangethrought are perfectly adapted to the conditions of the landscape, where drought can force fish into pools of oxygen-poor, 100 degree water, then follow with violent thunderstorms that wash the fish 20 miles downstream.

“Though small, many of these fish are really beautiful. For me, it’s a special gift when I hold one in my hand,” says Sanderson.


  Irrigation at Colorado’s Arikaree River © The Nature Conservancy (CC BY 2.0)
Center pivot sprinkler in the Arikaree River basin used to irrigate corn. Each sprinkler is supplied by deep wells drilled into the High Plains aquifer. © John Sanderson/The Nature Conservancy


What Can Be Done?

What’s happening in the Ogallala is not unique, says Sanderson — groundwater is being over-pumped on every continent, with tremendous consequences for agriculture, rivers and fish.
Consider the economics: the Ogallala supports an agricultural industry worth more than $20 billion, producing a huge amount of wheat, corn and other products including the majority of cattle feed grown in the United States. 

“You or someone you know is consuming Ogallala water today,” says William Burnidge, director of the Conservancy’s Colorado Sustainable Grazing Lands Program. “The water crisis of the Ogallala threatens food security for the country and the world.”

But it’s the local impact that Burnidge and Sanderson are focused on addressing. For the 15,000 people who live in the community around Fox Ranch, agriculture is their lifeblood and has been for generations. The Conservancy is supporting efforts by the Three Rivers Alliance, a local group of landowners trying to reduce the rate of water depletion in the river basin.

“There are reasons for optimism now that the community is starting to organize and seek viable options for sustainability,” says Burnidge.

The Conservancy collaborated with Three Rivers Alliance on one such option — a pilot project using variable rate irrigation technology, which applies water based on need, soil type and other factors to reduce the amount of water used.

And keeping places like Fox Ranch healthy makes a difference. The ranch is both a working cattle ranch and a stronghold for many native fish species. To help ensure the health of the Arikaree, the Conservancy helped fund the retirement of some wells along the river and supported a regional program of well retirement.

“It’s because of the Arikaree that Fox Ranch is an oasis on the eastern plains,” says Sanderson. “We don’t want to lose this special place and by working with partners to chart a course that helps the environment and the community, we won’t have to.”

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