Manhattan ? Over-pumping of the High Plains Aquifer beyond its recharge rate peaked overall in 2006, while aquifer’s rate of depletion in the portion underlying Kansas reached its high point in 2010, a study released Monday shows.

The Kansas State University study also projected the aquifer’s use would decrease by about half over the next 100 years.

Researchers studied the water depletion in 3,200 Kansas wells and 11,000 wells from the other seven states where the aquifer is located, looking at historic and projected future groundwater use rates.

The High Plains Aquifer — which underlies parts of Kansas, South Dakota, Wyoming, Nebraska, Colorado, Oklahoma, New Mexico and Texas — provides 30 percent of the irrigation water for those key agricultural states.

“We tried to understand how aquifer depletion has manifested itself across the aquifer as well as that has changed over time and how aquifer depletion would be extended into the future,” said David Steward, a civil engineering professor and a researcher on the project.

Steward and doctoral student Andrew Allen found that the aquifer’s depletion followed a south to north progression, and that some portions of the aquifer are depleting, while others are not.

In Texas, the depletion peaked in 1999. In New Mexico, that point was reached in 2002. In Oklahoma, it was 2012. Depletion of the portion of the aquifer underlying Colorado is projected to peak in 2023. Three states — Nebraska, South Dakota and Wyoming — are not projected to reach their depletion peaks before 2110.