Topeka ? Massive irrigation in western Kansas is depleting the Ogallala Aquifer from 5 percent to 7 percent every 25 years, according to a new report by the Kansas Geological Survey.

“We have a few generations before the economy starts closing down on agriculture,” Lee Allison, state geologist and director of the Kansas Geological Survey, told lawmakers Thursday. “This is a warning that we have time to make changes.”

State Rep. Joann Freeborn, R-Concordia, and chairwoman of the House Environment Committee, said the state and agricultural interests — which use 96 percent of the aquifer’s water in western Kansas — were responding to the problem.

“We have known there was depletion, and we have tried to find ways to reduce water use,” Freeborn said.

Freeborn said farmers were looking at more efficient ways to irrigate land and switching to crops that need less water.

Charles Benjamin, an attorney who represents the Kansas chapter of the Sierra Club, said the KGS report showed that the state was far behind in reacting to the aquifer’s declining water level.

“The state has had a policy of planned depletion. We’re growing corn in a desert to feed to cattle that will be slaughtered in southwest Kansas. This is not a sustainable system in the long run,” Benjamin said.

The Ogallala is the major water source for western and central Kansas, supplying 70 percent of the water used by Kansans daily. But heavy pumping from the aquifer has led to lower water levels, especially in southwest Kansas, Allison said.

Since major irrigation started after World War II, 6 percent of the aquifer has dropped below what is considered usable. Current irrigation rates will use up another 5 percent to 7 percent every 25 years, he said.

“We are not going to lose the Ogallala in one generation,” he said.

Replenishing the aquifer in western Kansas cannot be done naturally “unless we see a 1,000 percent increase in rainfall,” he said.

Though the problems are critical, Allison said that the KGS, which is part of Kansas University, has become the leader in studying and monitoring the High Plains Aquifer, which includes the Ogallala.

The High Plains Aquifer runs under parts of Kansas, Nebraska, Colorado, Wyoming, South Dakota, Oklahoma, Texas and New Mexico.

“We are far ahead of the curve. We are doing more than all the other states combined,” Allison said.