Climate Change and the Ogallala Aquifer

The Ogallala (pronounced “oh-ga-la-la”) Aquifer is the largest aquifer in the United States and among the largest in the world.  It got its name from the Ogala Sioux Indian Tribe. The Ogallala Aquifer, also known as the High Plains Aquifer, lies under the High Plains region of the U.S., an area comprising eight states, stretching from South Dakota in the north to Northern Texas in the south and covering an area of 174,000 square miles ranging from a depth of a few feet to 1,200 feet.

Before the Aquifer formed, the land now known as the Great Plains looked nothing like it does now. It was a land of low hills, shallow valleys, and meandering streams. The Ogallala was formed beginning 10 million years ago as east-bound streams coming down from the Rockies began depositing sand, gravel, silt, and clay into the valleys. Over millions of years, the sediment filled and covered the dips and slopes of the land. This porous material became the water-bearing Ogallala Aquifer while also creating the flat land now known as the Great Plains.

The Ogallala was first tapped for irrigation in 1911. The amount drawn from the Aquifer was minimal

until the 1930s when a series of droughts caused the infamous Dust Bowl. To keep farmers on the land, the federal government began to subsidize irrigation projects. These subsidies along with improved drilling technologies resulted in the extracting of vast amounts of water that enabled the development of extensive tracts of farmland.

Today water from the Ogllala irrigates 14 million acres, primarily in Nebraska, Kansas, and Texas.  It provides water for 80% of the residents living above it and is key to the region’s energy production, but 94% of the water is used for irrigation. Agriculture uses 80% of the land and in 2012  was estimated to have a total market value of $92 billion, made up largely of crops (43%) and livestock (46%). The grain-growing region in the High Plains, known as America’s breadbasket, relies entirely on the Aquifer, which essentially makes the current way of life on the Plains possible.

The problem is that, because the area is semi-arid, replenishment of the Aquifer is slow and so the high rate of water usage is draining it. It is uncertain how much longer it will last.  Some say 50 years, others say less.  Some areas in Texas and Kansas are already depleted. The region produces one fifth of the wheat, corn, cotton, and cattle produced in the United States and one sixth of all the grain produced in the world, so its depletion will have a world-wide impact.

What impact will climate change have on the area and in particular on the Ogallala Aquifer?  Warming temperatures are being felt across the Great Plains (North Dakota’s average temperature has increased faster than any other state in the contiguous United States), but the impact of climate change will vary by latitude.

In the Northern Plains the number of days with temperatures over 100°F is projected to double by 2050.   Crop yields may benefit from increased precipitation in winter and spring, however, if the fields become too wet, planting may be delayed which will reduce yields. The projected heavier winter and spring rainfall will increase erosion and nutrient runoff, which could have a detrimental effect on crops and agricultural soil quality. Summer precipitation is not projected to rise, which will increase vulnerability to drought conditions, while higher summer temperatures are likely to reduce plant productivity. Winter temperatures will also increase and may lengthen the growing season, which could increase plant growth or allow for a second planting.  Higher levels of carbon dioxide may also increase plant growth.

In the Central and Southern Plains, the higher temperatures and decreased precipitation will increase irrigation demands. If irrigation is reduced to conserve water and farmers transition to dryland agriculture, crop yields could be reduced by a factor of two. The Southern Plains are projected to experience more extreme heat, with four times the number of days over 100°F than is currently experienced in the area. These temperature changes are expected to occur largely in the summer. Higher temperatures lead to greater evaporation and surface water losses, more heat stress, and increased energy demand for cooling.

The Great Plains is already experiencing warmer winters, and further temperature increases are projected for this season. These conditions can increase the survival of some pests and invasive weeds. Additionally, the dormancy period for winter crops is shortening, increasing the potential for damage by spring freezes and reducing yields of some important livestock feed crops, such as winter wheat. As climate impacts worsen in the future, agricultural practices will face increased risks that require new considerations and management strategies.

In the long-term, climate impacts will have increasingly detrimental effects that increase variability in crop and agricultural production. Climate change may also cause a northward shift in lands used for agricultural production as temperature and water stresses rise, especially in the southern portion of the region.

Conclusion: One of the most dangerous impacts of climate change is the reduction in agricultural production. The High Plains region is an important food producer not only for the U.S. but for the world. The impact of climate change will accelerate the depletion of the Ogallala Aquifer, and this will exacerbate the effects of climate change. This will have global ramifications with respect to the price and availability of food.

Acknowledgements: