Ogallala Aquifer Depletion

The Ogallala aquifer was named for Ogallala, Nebraska in 1898, but it actually lies under 225,000 square miles of the Great Plains of the U.S., 800 miles long from North to South and 400 miles wide, including eight states: southern South Dakota, most of Nebraska, southeast Wyoming, eastern Colorado, eastern New Mexico, the western half of Kansas, the Oklahoma panhandle, and north central Texas (the High Plains of Texas). The Ogallala supplies the irrigation water for $20 billion of food and fiber, one-fifth of the U.S. agricultural harvest, each year. It also supplies 70% of all the water used daily in Kansas. There is just one problem – it’s drying up.

The problems with supply from the aquifer have been known for decades. These problems vary with locales, some regions using more water than others and some having deeper reserves than others. Nebraska has the most favorable recharge rate, that is water returning when removed, and the southern-most portion of the aquifer in Texas appears to have one of the bleakest outlooks for depletion.

Ninety percent of the water taken from the underground water supply in the Ogallala aquifer goes to irrigation. The other water is tapped into by wells to bring up water used by households and small farms. The well depth depends on the amount of sediment that was deposited over the aquifer formation when it formed, and how deep it has to go to get to the water. In some areas of the Ogallala, the rock layer above the water is only 50 feet, in others it is 200 feet, but it can be 500 feet or deeper as well. Deeper wells require bigger machinery and cost. As the water depletes, the wells have to go deeper. Also as the water depletes, sinkholes (caused by cones of depression in the water table) can form, filling in the area where the water once was and damaging structures and land above it.

The Great Plains have a semi-arid climate. Water used for irrigation evaporates rather quickly. This requires more water to be used, and the aquifer quickly depletes. Because of a lack of recharging and the heavy reliance on the groundwater for irrigation, 6% of the aquifer is dry (that is the water level is too low to be pumped or used). The aquifer is said to have first been tapped in 1911 by a hand-dug well. Now an estimated 12 billion cubic meters of water is removed from the aquifer each year. Because it would take 6,000 years to replace the water in the Ogallala aquifer, it is expected that 6% of the aquifer will dry up every 25 years, leaving the residents and farmers of the Great Plains unsure about how long their water supply will last