@NSF: How much water flows into agricultural irrigation? New study provides 18-year water use record

Here’s the release from the National Science Foundation (Cheryl Dybas/Val Ostrowski):

Irrigation for agriculture is the largest use of fresh water around the globe, but precise records and maps of when and where water is applied by farmers are difficult to locate. Now a team of researchers has discovered how to track water used in agriculture.

In a paper published in the journal Geophysical Research Letters, the researchers detail their use of satellite images to produce annual maps of irrigation. The findings, the scientists said, will help farmers, water resource managers and others understand agricultural irrigation choices and make better water management decisions.

“We want to know how human activities are having an impact on the environment,” said hydrogeologist David Hyndman of Michigan State University (MSU), principal investigator of the project. “Irrigation nearly doubles crop yields and increases farmer incomes, but unsustainable water use for irrigation is resulting in depletion of groundwater aquifers around the world. The question is: ‘How can we best use water?'”

The paper highlights the need to know when and where irrigation is occurring to effectively manage water resources.

The project focuses on an economically important agricultural region of the central U.S.–the Republican River Basin–that overlies portions of Colorado, Nebraska and Kansas, and provides surface water and groundwater to the High Plains Aquifer. The team found that irrigation in this area roughly doubled between 2002 and 2016.

Water use in this region can be complicated because it is regulated to preserve stream flow into Kansas in accordance with the Republican River Compact of 1942.

“Previously, we knew what farms were equipped to irrigate, but not which fields were actually irrigated in any particular year,” said Jillian Deines, also of MSU and the paper’s lead author. “Our irrigation maps provide this information over 18 years and can be used to understand the factors that contribute to irrigation decisions.”

The researchers used Google Earth Engine, a cloud-computing platform that makes large-scale satellite and environmental data analyses available to the public, to quantify changes in irrigation from year to year–an important finding for farmers, crop consultants and policymakers working to improve the efficiency of irrigation.

Google Earth Engine has been an asset for computing the large number of satellite images needed, the scientists said. “It allows researchers to use consistent methods to examine large regions through time,” Deines said.

The project, which also involves MSU research associate Anthony Kendall, is supported by the joint National Science Foundation (NSF)-USDA National Institute of Food and Agriculture (NIFA) Water, Sustainability and Climate (WSC) program and the joint NSF-NIFA Innovations at the Nexus of Food, Energy and Water Systems (INFEWS) program.

“Knowing what to plant, how much land to plant, and how much irrigation water is necessary to support a crop through harvest has been a challenge for farmers throughout time,” said Tom Torgersen, NSF program officer for WSC and INFEWS. “Farmers can now envision a future where models will provide options to help guide decisions for greater efficiency and crop productivity.”

Program managers at USDA-NIFA said that demand for agricultural products will likely increase in the future, while water for irrigation may decrease due to water quality issues and competitive uses.

The Republican River Basin researchers “leveraged new computing power to handle the ‘Big Data’ of all available Landsat satellite scenes, and developed irrigation maps that help explain human decisions about irrigation water use,” said Jim Dobrowolski, program officer in NIFA’s Division of Environmental Systems. The maps hold the promise, he said, of the ability to make future water use predictions.

A NASA graduate fellowship program award also funded the research.

High Plains Aquifer pumping is impacting surface water and native fish

High Plains Aquifer via Colorado State University.

From The Denver Post (Bruce Finley):

The agricultural overpumping from thousands of wells continues despite decades of warnings from researchers that the aquifer — also known as the Ogallala, the world’s largest underground body of fresh water — is shrinking.

Even if farmers radically reduced pumping, the latest research finds, the aquifer wouldn’t refill for centuries. Farmers say they cannot handle this on their own.

But there is no agreement among the eight affected states (Colorado, Kansas, Nebraska, New Mexico, Texas, Oklahoma, Wyoming, South Dakota) to try to save the aquifer. And state rules allow total depletion.

Republican River Basin by District

In fact, Colorado officials faced with legal challenges from Kansas over dwindling surface water in the Republican River have found that their best option to comply with a 1942 compact is to take more water out of the aquifer. The state bought wells from farmers during the past decade and has been pumping out 11,500 acre-feet of water a year, enough to satisfy a small city, delivering it through a $60 million, 12-mile pipeline northeast of Wray to artificially resuscitate the river.

The overpumping reflects a pattern, seen worldwide, where people with knowledge that they’re exceeding nature’s limits nevertheless cling to destructive practices that hasten an environmental backlash.

The depletion of the High Plains Aquifer has been happening for decades, according to bulletins U.S. Geological Survey has put out since 1988. Colorado farmers this year pumped groundwater out of 4,000 wells, state records show, siphoning as much as 500 gallons a minute from each well to irrigate roughly 580,000 acres — mostly to grow corn, a water-intensive crop.

The depth where groundwater can be tapped has fallen by as much as 100 feet in eastern Colorado, USGS data show. That means pump motors must work harder to pull up the same amount of water, using more energy — raising costs for farmers. The amount of water siphoned from the aquifer since 1950 to irrigate farm fields across the eight states tops 273 million acre-feet (89 trillion gallons) — about 70 percent of the water in Lake Erie.

On one hand, the industrial center-pivot irrigation techniques perfected after World War II have brought consistency to farming by tapping the “sponge” of saturated sediment that links the aquifer to surface water in streams and rivers. America’s breadbasket produces $35 billion of crops a year. On the other hand, intense irrigation is breaking ecosystems apart.

Overpumping has dried up 358 miles of surface rivers and streams across a 200-square-mile area covering eastern Colorado, western Kansas and Nebraska, according to U.S. Fish and Wildlife-backed researchers from Colorado State University and Kansas State University who published a peer-reviewed report in the Proceedings of the National Academy of Sciences. The researchers also determined that, if farmers keep pumping water at the current pace, another 177 miles of rivers and streams will be lost before 2060…

Disappearing fish species — minnows, suckers, catfish that had evolved to endure periodic droughts — signal to biologists that ecological effects may be reaching a tipping point.

The amount of water held in the aquifer under eastern Colorado decreased by 19.6 million acre-feet — 6.4 trillion gallons — from 1950 until 2015, USGS records show. That’s an average loss of 300,000 acre-feet a year. Between 2011 and 2015, records show, the water available under Colorado in the aquifer decreased by 3.2 million acre-feet — an annual average shrinkage of 800,000 acre-feet. Climate change factors, including rainfall, play into the rate of the drawdown…

They say they’re trying. They’ve reduced the land irrigated in eastern Colorado by 30,000 acres since 2006. They plan to retire another 25,000 acres over the next decade, said Rod Lenz, president of the Republican River Water Conservation District, who for years has advocated use of technology to grow more crops with less water…

Farmer and cattleman Robert Boyd, a leader of the Arikaree Groundwater Management District, said the federal government should intervene to ensure survival of High Plains agriculture…

Kansas Aqueduct route via Circle of Blue

He pointed to proposals to divert water from the Missouri River Basin and move it westward through pipelines across the Great Plains…

But drawing down the aquifer does not violate any law in Colorado. The state engineer’s office monitors well levels and requires permits for wells, limiting the number of acres a farmer can irrigate. But there’s no hard limit on how much water can be pumped…

[Mike] Sullivan and state engineer Kevin Rein emphasized that thousands of acres no longer are irrigated. “And there need to be some more retirements of land to get us into a more balanced situation,” Sullivan said.

They defended Colorado’s practice of pumping more groundwater out of the aquifer, saying this is necessary to comply with the Republican River Compact. Disputes over river flows have risen as far as the U.S. Supreme Court and Colorado’s legal obligations to deliver water to Nebraska and Kansas are clear.

Solving the problem of the declining Ogallala aquifer: “It’s for the generation that’s not here” — Dwane Roth

The High Plains Aquifer provides 30 percent of the water used in the nation’s irrigated agriculture. The aquifer runs under South Dakota, Wyoming, Nebraska, Colorado, Kansas, Oklahoma, New Mexico and Texas.

From The Hutchinson News (Amy Bickel):

Because of technology, [Dwane] Roth is working to embrace what might seem like an unfathomable concept in these parts – especially when you can’t see what is happening underground.

Sometimes the crop isn’t thirsty.

“It’s difficult to shut off,” Roth said. “But I called my soil moisture probe guy. He said the whole profile was full and it was only the top 2 inches that was actually dry. So there was no need to turn that irrigation engine on and pump from the Ogallala.”

Now he is hoping to change the mindset of his peers across a landscape where corn is king and the Ogallala Aquifer – the ocean underneath the High Plains – has been keeping the decades-old farm economy going on the semi-arid Plains.

At least it is for now.

Underlying eight states across the Great Plains, the Ogallala provides water to about one-fifth of the wheat, corn, cotton and cattle production in the United States. It’s also a primary drinking water supply for residents throughout the High Plains.

But the aquifer that gives life to these fields is declining. It took 6,000 years to fill the Ogallala Aquifer from glacier melt. It has taken just 70 years of irrigation to put the western Kansas landscape into a water crisis.

An economy centered on water is drying up.

With his own water levels declining, Roth wants to make sure there is water for the next generation, including his nephews who recently returned to the farm.

On this hot, summer day, water seeped out of a high-tech irrigation system he is testing on his Finney County farm. Soil probes are scattered about, telling him what is happening below the surface.

Roth also has pledged to the state to cut back his usage by 15 percent through changing farming practices and implementing new technology.

He wants to make a difference, but, he stressed, he can’t slow the decline alone.

For the past two years, Roth’s fields have been part of a closely watched demonstration project aimed at showing farmers how to use less irrigation water on their crops. Now he he is taking it a step further.

With some areas in northern Finney County declining by more than 70 feet since 2005, Roth is helping spearhead a regional effort to curtail pumping through a Local Enhanced Management Area. LEMAs were implemented five years ago as a tool to extend the life of the state’s water resources.

He’s not the only one looking toward the future. A small but growing group of irrigators are considering different tools to cutback water use. Some are implementing technology. Some are looking at LEMAs. Others are forming their own, farm-wide plans for mandatory cutbacks.

“It’s for the kids you don’t see yet,” Roth said of why he’s doing this. “It’s for the generation that’s not here.”

Ogallala aquifer via USGS

Stabilizing water levels in [High Plains Aquifer] possible, survey shows — @KUnews

Graphic via the Kansas Geological Survey.

Here’s the release from the University of Kansas:

For at least the next one to two decades, irrigators in western Kansas may not have to cut groundwater use nearly as drastically as once thought to stem declines in the High Plains aquifer, according to water experts at the Kansas Geological Survey based at the University of Kansas.

Most water in western Kansas is drawn from the expansive High Plains aquifer, an underground network of water-bearing sediments whose main component is the Ogallala aquifer. Underlying portions of eight states, the High Plains aquifer is the primary source of irrigation, municipal, industrial and domestic water for western and central Kansas.

As groundwater pumping from the aquifer increased significantly over the last 70 years, groundwater levels have fallen precipitously in some parts of the aquifer compared with pre-pumping levels. Such declines will continue unless pumping is reduced.

The critical question is how much should pumping be reduced to make a significant impact on the decline rate. To help irrigators with that question, KGS scientists developed a method to determine how much of a reduction in water use would be needed to achieve a specific decline rate or even stabilize water levels in the aquifer.

“We came up with a new approach for estimating the impact pumping reductions have on the rate of water-level declines,” said Jim Butler, KGS senior scientist and geohydrology section chief. “It’s tailor-made for the High Plains aquifer in Kansas, where groundwater is pumped mainly during the growing season, and exploits the great groundwater data we have in the state.”

Scientists originally predicted groundwater use might have to be reduced 75 percent or more to maintain the aquifer in western Kansas at or near current water levels. Based on their new analyses, Butler and his colleagues assert that can be achieved with just 25 percent to 45 percent reductions in most areas. Promising results for irrigators who reduced pumping at those lower levels have already been seen in one area of northwestern Kansas.

In mid-July, Kansas Gov. Sam Brownback asked Butler to accompany him to present the KGS findings to a group in Hoxie in Sheridan County, where local irrigators had initiated a Local Enhanced Management Area, or LEMA, to reduce usage on a voluntary basis. Water users within the LEMA’s boundaries created a plan to reduce pumping in a way that would not hinder crop production.

Actions that can be taken to achieve reductions include shutting off irrigation pivots when it rains, growing more drought-resistant crops and growing a greater variety of crops. Technologies such as soil-moisture probes that indicate when irrigation is or isn’t needed and high-efficiency irrigation systems that lose less water to evaporation have made reduction efforts easier.

Although members of the Sheridan County, or SD-6, LEMA were aiming to reduce pumping by 20 percent, in actuality they achieved a 35 percent reduction over four years.

“The result is that the decline rate there has gone from about 2 feet per year to about 5 inches per year without affecting the bottom line of producers in the area,” Butler said. “That’s a big deal.”

However, water levels, which have dropped as much as 80 feet in southwest Kansas since just 1996, will never be restored to pre-pumping levels.

“Realistically, we are talking about reducing the rate of decline or stabilizing water levels,” Butler said. “Replenishment of the aquifer is really not in the cards.”

Even if pumping were stopped completely, it would take hundreds of years to recharge the aquifer.

“The hope is that the success of the SD-6 LEMA will inspire others to follow suit,” Butler said.

The SD-6 LEMA is the only one implemented in the state so far, although LEMAs are under consideration elsewhere. On the trip to western Kansas with the governor, Butler also presented the KGS findings to an interested group of irrigators north of Garden City. KGS analysis shows that a 28 percent reduction in pumping in their area would stabilize water levels.

Besides encompassing the Ogallala aquifer, the High Plains aquifer includes the smaller Equus Beds aquifer around Wichita and Hutchinson and Great Bend Prairie aquifer in the vicinity of Great Bend, Kinsley, Greensburg and Pratt. Because the central part of the state generally receives more annual precipitation than far-western Kansas, stable water levels appear to be attainable in the Equus Beds and Great Bend Prairie with pumping reductions of less than 10 percent.

The KGS researchers’ new approach to estimating pumping reductions was inspired by groundwater flow patterns observed in the real-time data from several wells they monitor continuously. Results found with the approach are based on pumping data recorded by flow meters that the state of Kansas requires on all nondomestic wells as well as water-level data collected annually by the KGS and the Kansas Department of Agriculture’s Division of Water Resources (DWR) from more than 1,400 wells in western and central Kansas.