The Ogallala Aquifer, also known as the High Plains Aquifer, is one of the world’s largest underground freshwater reservoirs, spanning approximately 174,000 square miles beneath the central United States. This immense geologic feature is the foundational resource supporting a significant portion of the nation’s agriculture. The water it provides sustains the economy of the semi-arid Great Plains, enabling the production of crops and livestock.
Formation and Geographic Scope
The Ogallala Aquifer is not a single underground lake but rather a massive layer of porous rock, sand, gravel, and silt that holds water within its pore spaces. This geologic formation originated from the erosion of the ancient Rocky Mountains, with sediments carried eastward by streams and rivers over the last ten million years. It stretches across portions of eight states: South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas.
The water contained within the aquifer is largely considered “fossil water,” meaning it accumulated primarily from runoff and precipitation during the last Ice Age. Modern natural recharge rates are minimal, often averaging less than an inch per year in the drier, southern sections of the aquifer. This slow replenishment means that the water is essentially a non-renewable resource when measured against the rapid pace of human use. The saturated thickness varies dramatically; it can be over 1,000 feet thick in parts of Nebraska but is often less than 100 feet in the southern High Plains.
The Era of Intensive Extraction
The ability to tap into this immense underground supply began to shift dramatically after World War II, initiating the rapid expansion of irrigated agriculture. Technological advancements, including the invention of the center-pivot irrigation system in 1952, made watering large, uneven fields efficient. This new technology, combined with the availability of inexpensive natural gas to power large pumps, allowed farmers to withdraw water at high rates.
The number of irrigated acres overlying the aquifer exploded from just over two million acres in 1949 to more than 15 million acres within a few decades. This change converted vast tracts of drought-prone prairie into highly productive cropland, making the region a major global food producer. Water was being withdrawn at rates estimated to be between three and fifty times faster than the slow natural recharge could replenish it. This period established a pattern of resource use that treated the aquifer as a limitless supply.
Current State of Depletion
Decades of high-volume pumping have led to a measurable decline in the aquifer’s total volume. Since large-scale pumping began around 1950, the Ogallala Aquifer’s saturated volume has been reduced by an estimated nine percent. The U.S. Geological Survey (USGS) tracks these changes, reporting that the cumulative net water loss has reached hundreds of millions of acre-feet.
This decline is not uniform across the eight states, with the most severe water level drops occurring in the central and southern regions, particularly in parts of Texas and Kansas. The crucial measure is the saturated thickness, which represents the actual height of the water column available for extraction. When the saturated thickness falls too low, wells either fail or become too costly to operate. Recent reports have shown continued declines in the Texas Panhandle and southwest Kansas.
Economic and Environmental Fallout
The loss of groundwater has consequences for the region’s economy and its natural environment. Economically, the increasing depth to the water table means that farmers must spend significantly more on energy to pump water to the surface. This rising operational cost is making irrigated farming financially unsustainable for many producers, especially those in the southern areas where the aquifer is thinnest.
As a result, some farmers are shifting away from water-intensive crops like corn and cotton toward less demanding, dryland agriculture, which reduces overall crop yield and regional agricultural revenue. Environmentally, the depletion impacts surface water bodies that are connected to the aquifer. Groundwater provides the base flow for many streams and rivers in the Great Plains, and as the water table drops, these surface waters and associated wetlands can dry up. This loss of surface water alters local ecosystems and places stress on wildlife that rely on these sources.