LAWRENCE — 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.
Most of western Kansas gets its water from the Ogallala Aquifer - a large underground reservoir that spans eight states. More than 95 percent of the water is used by irrigators to water crops such as corn.
But the aquifer has been declining since the advent of irrigation in the 1930s through the 1960s, which began drawing more water than what was being recharged.
Such declines will continue unless pumping is reduced, according to the survey, which is based at the University of Kansas.
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, according to a press release by the University of Kansas.
“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 said in the release. “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, Governor 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.
Sheridan 6, located in Groundwater Management District No. 1 in northwest Kansas, is a 99-mile section of Sheridan County and one township in Thomas County that was seeing high declines and had been targeted by the state. At times, the Sheridan 6 area was seeing drops in the water table of 2 to 3 feet a year, Brownie Wilson, the Kansas Geological Survey’s water data manager, said last year.
They began the LEMA in January 2013. Some of the actions farmers have taken include shutting irrigation systems off when it rains, growing more drought-resistant crops and growing a variety of crops that use less water. Farmers may plant a half circle to corn and the other half to wheat or milo. Some are planting cover crops to help keep water on fields. They also are embracing technologies, including soil-moisture probes that indicate whether the soil needs irrigation, as well as more efficient irrigation pivots that don't lose as much water to evaporation.
While Sheridan 6 members aimed to reduce pumping by 20 percent, they have actually achieved a 35 percent reduction in a four-year span, according to the news release.
“The result is that the decline rate there has gone from about two 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, in southwest Kansas, water levels have dropped as much as 80 feet in since just 1996 and 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 Sheridan 6 LEMA will inspire others to follow suit,” Butler said.
The Sheridan 6 LEMA is the only one implemented in the state so far and was recently renewed for a second five-year period. LEMAs are under consideration elsewhere including for the entire GMD 4. Irrigators north of the Arkansas River in Finney and Kearny counties are looking at a LEMA, as well. KGS analysis shows that a 28 percent reduction in pumping in their area would stabilize water levels.