The Ogallala Aquifer which underlies much of the High Plains in the United States is one of the world’s largest aquifers and arguably one of the most important. It underlies small parts of South Dakota, Wyoming, Colorado, and New Mexico, the panhandles of Texas and Oklahoma, about a third of Kansas and most of Nebraska, a total area of about 174,000 square miles. It is a shallow water table aquifer which means that the pressure head at the top of the saturated zone is the same as atmospheric pressure.
A little more about this important aquifer: The Rocky Mountains lie west of the High Plains. Four to six million years ago, the Rockies were still tectonically active and alluvial (water borne) and aeolian (air borne) material eroded from the Rockies were deposited in the High Plains and now comprise the Ogallala. The saturated thickness of the gravels, sands and silts of the Ogallala range from just a few feet at the edge of the aquifer to more than 1000 feet in the sand hills of Nebraska.
More than 2 million people living above the aquifer obtain their drinking water from it. Some might say that even more importantly, the land surface overlying the Ogallala is the breadbasket of the United States. Some 27 percent of the irrigated acreage in the United States obtains its water from the Ogallala or about 30 percent of the irrigation water used in the country. Corn, soybeans and wheat are the principal row crops.
So why am I writing about the Ogallala Aquifer? It sounds like there is plenty of water if the thickness of the aquifer is over 1000 feet in places. Yes, but in many areas the Ogallala is being mined. So how do you mine water? Water is mined when more water is withdrawn from an aquifer during a given period than can be replaced by the natural process of recharge.
Development of the Ogallala for irrigation began in earnest following World War Two and has continued through the present. The 100th meridian bisects the Ogallala. West of the meridian, the high plains are semiarid with an average rainfall of 15 inches per year. Prior to irrigation, crop failures happened with frequency due to cycles of drought. The drilling of irrigation wells accelerated through the 1950’s and 1960’s and became even more rapid in the 1970’s with the advent of center pivot systems. If you fly over western Kansas now, the center pivot circles stretch as far as the eye can see.
As a result, water levels in the Ogallala primarily in Texas, Oklahoma and Kansas have declined rapidly and significantly. Declines of more than 300 feet have become the norm in the Texas panhandle. Wells have gone dry and have had to be deepened at great cost to landowners. The Ogallala is in danger of becoming dewatered completely in some areas.
So what is the answer? Unfortunately, there isn’t a good one. There have been proposals to divert surface water from other parts of the country and transport it to areas where the Ogallala is depleted. But, so far, this solution has not been implemented because of costs, engineering problems, and even State laws. Couple this with climate change and the likelihood that the high plains will probably get warmer and experience even less precipitation and the problem becomes even more urgent. But who knows? American ingenuity may still be able to solve the problem. Stay tuned.
Note: Some of the information in this article was derived from Wikipedia and other internet sources.