More than 15.9 million water wells for all purposes serve the United States and approximately 500,000 new residential wells are constructed annually, according to National Ground Water Association (NGWA) estimates. In addition, the United States uses approximately 79.6 billion gallons per day of fresh groundwater for public supply, private supply, irrigation, livestock, manufacturing, mining, thermoelectric power and other purposes.
According to the NGWA, more than 90 percent of the groundwater pumped from wells in the Ogallala, the nation’s largest aquifer stretching from Texas to South Dakota, is used for agricultural irrigation. Representing about one-third of all U.S. irrigated agriculture it creates about $20 billion annually in food and fiber.
The trouble is we are using more than is being replenished at an alarming rate and on crops like corn not equipped to handle heat and drought. In fact, some officials are wondering how much longer we can use this aquifer before irrigation is no longer an option.
While we do not have the exact answers to this and many other water-related questions, this trend has state and federal officials in the Great Plains concerned. $20 billion looks good, for now, but then what? Will irrigation wells in this area even be an option in 50 years? The water level in an aquifer like the Ogallala that supplies irrigation wells does not always stay the same.
Droughts, seasonal variations in rainfall, and overpumping affect the height of the underground water levels. If a well is pumped at a faster rate than the aquifer around it is recharged by precipitation or underground flow, water levels can be lowered.
Some residents wonder what would cause their well to run dry.
A well is said to have gone dry when water levels drop below a pump. This does not mean that a dry well will never have water in it again, as the water may return as recharge increases. But the timing on that is anyone’s guess. The water level in a well depends on well depth, the type (confined or unconfined) of aquifer the well taps, the amount of pumping occurring in that aquifer and the amount of recharge occurring. 2011 and 2012 were examples of years where recharging of some aquifers was dramatically less in some areas compared to wet years.