<P> Large scale extraction for agricultural purposes started after World War II due partially to center pivot irrigation and to the adaptation of automotive engines for groundwater wells . Today about 27 % of the irrigated land in the entire United States lies over the aquifer , which yields about 30 % of the ground water used for irrigation in the United States . The aquifer is at risk for over-extraction and pollution . Since 1950 , agricultural irrigation has reduced the saturated volume of the aquifer by an estimated 9 % . Once depleted , the aquifer will take over 6,000 years to replenish naturally through rainfall . </P>
<P> Large scale extraction for agricultural purposes started after World War II due partially to center pivot irrigation and to the adaptation of automotive engines for groundwater wells . Today about 27 % of the irrigated land in the entire United States lies over the aquifer , which yields about 30 % of the ground water used for irrigation in the United States . The aquifer is at risk for over-extraction and pollution . Since 1950 , agricultural irrigation has reduced the saturated volume of the aquifer by an estimated 9 % . Once depleted , the aquifer will take over 6,000 years to replenish naturally through rainfall . </P>
how long does it take for the ogallala aquifer to recharge
how long does it take for the ogallala aquifer to recharge
over 6,000 years
over 6,000 years