Crop circles — irrigated agriculture

Graphic credit: RogerWendell.com

Groundwater movement via the USGS

Significant portions of the Ogallala Aquifer, one of the largest bodies of water in the United States, are at risk of drying up if it continues to be drained at its current rate. Courtesy of MSU

Kansas Aqueduct route via Circle of Blue

Ogallala aquifer boundaries

From The Mountain Town News (Allen Best):

Dick Wolfe, Colorado’s state water engineer, recently defined “sustainable groundwater supply” as one that is managed so that recharge matches withdrawals in a way to avoid long-term depletion of the aquifer.

By that definition, Colorado is not, for the most part, using its aquifers sustainably. Nor, for that matter, is most of the nation or world.

That much was made clear at a conference on Dec. 4 that was conducted by the American Ground Water Trust. Andrew Stone, the organization’s executive director, said 14 percent of all water used to irrigate crops in the United States comes from mining groundwater aquifers. This started slowly, but picked up as pumps and cheap energy became available around the end of World War II. The extraction by farmers and cities of water above the rate of recharge is now close to 400 cubic kilometers.

“We are robbing our savings account,” he said.

Driven by population growth and the uncertain effects of climate change, pressures on these subterranean savings accounts will only worsen, he said. This is not inevitable. He cited Los Angeles, which after World War II turned to groundwater exploitation to satisfy growth. “In the 1960s, it was pretty clear that the LA Basin was cruising for big trouble,” he said. But unsustainable exploitation has ended.

Problems of groundwater exploitation are common in many areas of the country, but solutions must be forged locally, “aquifer by aquifer, region by region,” said Stone.

Sobering statistics

The day was littered with fascinating statistics. Jeff Lukas, of the Western Water Assessment, explained that of the 95 million acre-feet that falls on Colorado, only 14 million acre-feet end up as runoff in our streams and rivers. The remainder, 80 million acre-feet, evaporates or gets drawn back into the atmospheric through transpiration. Together, the two are called evapotranspiration, or ET.

This rate of ET will almost certainly rise as the atmosphere warms. In the last 30 years, temperatures have ratcheted up 2 degrees Fahrenheit. Climate models forecast another increase of between 2.5 to 5 degrees by mid-century in Colorado. By mid-century, the hottest summers of the last 50 to 100 years will become the norm.

Too, everything from corn to urban lawns will need 5 to 30 percent more moisture during the longer, hotter summers—assuming precipitation does not increase.

How much precipitation will change as the result of elevated greenhouse gases in the atmosphere remains a mystery. Unlike temperatures, average precipitation in Colorado has not changed appreciably in the last three decades. Climate models have been clear about increasing temperatures, but precipitation remains a flip of the coin.

However, warming alone will drive changes, “pushing both the supply and demand in the wrong direction,” said Lukas. Increased evapotranspiration will reduce runoff and the amount of moisture available to percolate into soils and down into aquifers. Spring runoff has already accelerated and will come one to three weeks earlier.

Bottom line: Hotter temperatures will drive farmers to suck up more subterranean water. If anything, aquifers will recharge more slowly.

Wolfe, in his turn at the microphone, had even more statistics: Of Colorado’s 16 million acre-feet, 10 million acre-feet flow out of state, mostly as a result of compacts governing the Colorado and other rivers.

“That leaves us about 6 million acre-feet in Colorado to use,” he said. This surface water provides about 83 percent of water used in Colorado, and the other 17 percent comes from aquifers, which are tapped by 270,000 wells.

Of this groundwater, 85 percent goes to agriculture, for more than 2 million acres, but there’s also a strong urban component. One in five Coloradans get their water from wells. Most prominent are Denver’s southern suburbs in Douglas County.

Denver’s South Metro

South Metro has been a poster child for living in the moment. It’s affluent and rapidly growing. Served almost exclusively by wells, the residents of Castle Park, Parker and adjoining areas comprise about 6 percent of Colorado’s population but command 30 percent of income. Today’s population of 300,000 residents is projected to grow to 550,000 by mid-century.

Wells have been dropping rapidly, five feet in just one year in Dawson, one of the aquifers.

Eric Hecox, executive director of the South Metro Water Supply Authority, explained that it was always understood that wells would not last forever. The area had hoped to benefit from Denver’s Two Forks Dam, which was to have been filled primarily by expanded diversions from the Western Slope.

Two Forks was sunk by environmental concerns in the early 1990s. Inconveniently, Douglas County surged in population, routinely landing in the top 10 of the nation’s fastest-growing counties, a distinction that only lately has abated.

Other projects have also nudged the South Metro area off its exclusive dependence on groundwater, but even collectively they do not provide the answer. Hecox called for continued efforts to pinpoint needs while creating a new generation of partnerships and infrastructure.

Can South Metro’s needs for sustainable water supplies be answered by building a giant pipeline from Flaming Gorge Reservoir, on the Utah-Wyomng border? That idea was proposed in 2006 by entrepreneur Aaron Million, and then echoed by Frank Jaeger, the now-retired director of Parker Water and Sanitation District.

Hecox said the Bureau of Reclamation study about water availability from Flaming Gorge has not been completed. That study will provide the 14 members in Hecox’s South Metro coalition “base information on which to decide whether we want to pursue it any further,” he said.

Two key agriculture areas

Two agriculture areas in Colorado that rely upon aquifers are in arguably worse shape. The San Luis Valley has an area called the Closed Basin. With the arrival of electricity to farms in the 1950s, large-scale pumping began and, for a number of years, all went well, said Steve Vandiver, general manager of the Rio Grande Water Conservation District.

Despite earlier hints of problems, the magnitude of over-pumping started becoming apparent in 1998. One million acre-feet had been pumped from the aquifer above the amount of recharge. Figuring out what to do took time and negotiation. “There have been rocks thrown from every quarter,” he said.

The plan now in place has cut pumping by 30 percent during the last three years. The amount of irrigated acreage has declined from 175,00 to 150,000 acres. Water use on those remaining acres has been reduced in some cases by planting different, less water-intensive crops and also by using different irrigation methods.

Up to 300,000 cubic feet per second of water continues to be pumped on the fields in the Closed Basin on hot summer days.

And the Ogallala….

The Ogallala Aquifer is perhaps America’s best-known story of groundwater depletion. It extends over parts of eight states, from Texas to South Dakota, and the aquifer has declined at a shocking rate in several of those states, but more slowly or not at all in places, especially the Nebraska Sand Hills.

The Republican River Basin of northeastern Colorado is emblematic of many. Farmers working with local districts and the state government have been shifting the paradigm. Whether they’re shifting rapidly enough is an open question.

The river and its tributaries originate on the high plains, gaining no benefit from mountain snowpack. Yet this region had 480,000 irrigated acres in an area where annual precipitation is only 17 inches a year.

The key: mining the Ogallala. In the late 1970s, Colorado began taking action to slow the unsustainable over-pumping, but more radical measures were triggered by the need to comply with the interstate compact governing the river shared with Nebraska and Kansas. Colorado was forced to release more water downstream.

It did this partly by abandoning Bonny Reservoir, eliminating the evaporative losses. At greater expense, the district constructed an expensive pipeline and now pumps water—ironically from wells—to release into the Republican River at the state line. The total cost of the pipeline and the purchase of water rights was $48 million.

Much is being done to steer the Titanic away from the iceberg of exhausted aquifer water, but Deb Daniel, general manager of the Republican River Water Conservation District, suggested the magnitude of the challenge when she said: “Sustainable, that’s a scary word where I come from.”

(For a story I recently wrote about the Ogallala in Colorado, see the Headwaters Magazine website).

Wells along the South Platte

Unlike everything else said in the day, several speakers argued that not enough pumping has been occurring along the South Platte River. Their solution: more reservoirs and also more acreage returned to production.

Robert A. Longenbaugh, a consulting water engineer, pointed to 400,000 acre-feet average annually flowing into Nebraska above the compact requirement. “I call that a waste of water,” he said. At the same time, he and others pointed to reports of basements in Weld County getting flooded because of rising groundwater levels.

Even in the 1960s, a Colorado law was adopted that formally recognized that aquifers and surface streamflows comingled waters . In other words, if you have a well a quarter-mile from the South Platte River at Greeley and pump it, that might mean less water in the river as it flows toward Fort Morgan.

The drought of 2002 forced the issue, and in 2006 the state put well irrigators into the priority system. In 2012, a hot and dry year, many wells had to be shut down and corn and other corps left to dry up. Longenbaugh called for changes.

“Strict priority administration of ground and surface rights does not maximize the beneficial use,” he declared. Instead, he wants to se a “real-time management of the South Platte, to monitor surface and ground water and “make short-term decisions” looking out six months ahead while still maintaining the priority-appropriation doctrine that is the bedrock of Colorado water law.

A panel of state legislators later in the day acknowledged varying degrees of agreement with Longenbaugh’s statement. Sen. Mary Hodge, a Democrat from Brighton, described a pendulum that went from “too lax” to now one of being “too stringent.”

Sen. Vicki Marble, a Republican from Fort Collins, described the situation as deserving of an “emergency measure.” She later added: “We should let people self-regulate,” while suggesting that the wells should be allowed to pump. “It’s their right,” she said.

More groundwater coverage here.