Groundwater is the water supply stored in the ground. It is continually refreshed through rain and run-off. If this water is pumped out of the ground faster than nature can refill it, the supply diminishes . Since the advent of irrigation practices, aquifers across the United States have been challenged to keep up with demand. The decline in levels in the Ogallala aquifer are of particular concern because it supplies water to a large area and it is non-renewable resource due to its very slow recharge rate .
The Ogallala aquifer, also called the High Plains aquifer, is made up of water-saturated sand and gravel mixture with varying thicknesses across its extent (Terrell & Johnson, 1999). It lies beneath and is a major water supply to portions of eight states: Colorado, Kansas, Nebraska, New Mexico, South Dakota, Texas, and Wyoming (McGuire, 2013). Irrigation is the major factor in depletion due to these states having high farming and crop use. Since initial development of the aquifer, levels have dropped up to 100 feet in some areas and saturation thickness decreased by over half in other places (U.S. Geological Survey, 2014). Brownie Wilson, water data manager for the Kansas Geological Survey (KGS), explained the reason for the depletion of the aquifer in a 2012 news release for the KGS. “When precipitation is low over an extended period, especially in the Ogallala, a much greater quantity of water is pumped out of the ground than during wetter years,” Wilson said. “The amount of water taken out rather the amount going in has the greatest influence on water-level changes from one year to the next” (Evans, 2012).
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Effects of Declining Groundwater
Diminishing the groundwater supply has multiple negative impacts: lowering of the water-table, increased cost of water use, decreasing surface levels, land subsidence, and saltwater intrusion. Wells pump water from below the water- table, the upper limit of ground that is water-saturated. When the water-table lowers, wells dry up or yield inadequate amounts of water. New wells may need to be drilled. Wells that use pumps to suck the water upwards require more energy, and thus more expense to operate. Water flows between the surface and ground through seepage. Less groundwater means less seepage occurs into rivers and lakes. This occurs when support is removed below ground. When water is removed, the density of the soil decreases and it can collapse. Sinkholes and mudslides are examples of land subsidence. Very deep groundwater has a high saline content. Freshwater floats above saltwater in the groundwater supply. As the water is pumped out of the system, the boundary between the freshwater and saltwater can change. Freshwater can become contaminated by the saltwater .
Impact of Decline of Water in the Ogallala Aquifer
The economy of states in the Great Plains region of the United States is largely dependent on agriculture. The growth of crops in this area requires extensive irrigation. The heavy water use for irrigation has outstripped the aquifer’s rate of recharge .
In 1999, Terrell and Johnson predicted a shift of regional crop patterns toward dryland agriculture as a result of the declining aquifer level. This shift would cause a decrease in the production of grains used for cattle feed. As a result, the feedlot sector of the region was expected to experience losses. Because cotton is an optimal choice for dryland agriculture due to its low water needs and high output per acre, they predicted that cotton would become the crop of choice in the Texas region.
Terrell and Johnson’s predictions did not come to fruition and water levels in the aquifer continue to decline – especially in the drought stricken southern regions of the Ogallala. Cattle feedlots comprise a significant portion of the Texas panhandle’s economy. The growth of the cattle industry instigated increased production of feed grains to meet the growing needs. This led to increased use of irrigation (Almas, Colette, & Wu, 2004).
Terrell and Johnson recommended a change to water efficient dryland crops versus planting of crops that require irrigation. Despite the declining water supply, grain production in the Texas panhandle was at its peak level in 2004, indicating an increase in irrigation efficiency. It is unclear how long this trend can continue (Almas, Colette, & Wu, 2004). Profits, rather than conservation, continue to fuel agricultural choices. Farmers have developed more efficient irrigation methods though, and need to continue to do so (1999).
Long-term effects include a higher unemployment rate and lowered household consumption rates as the decline in irrigated crop production impacts the economy. The greatest economic impact will likely felt in agricultural and rural communities. These impacts include reduced agricultural production, reduced personal and business revenues, lower tax revenues, and decreased availability of community services (Almas, Colette, & Wu, 2004).
Current Status
The development of irrigation for agriculture in the 1950s marked the onset of declining water levels in the aquifer. At the request of Congress, the U.S. Geological Survey began monitoring the aquifer’s water levels. The latest report reveals continued declines (McGuire, 2013). The overall water level decline from predevelopment to 2011 ranged from an increase of 85 feet in Nebraska to a decrease of 242 feet in Texas. Average level changes across the area resulted in an overall decrease of 14.2 feet. Water storage in the aquifer over the same time period also declined about 8 percent. The aquifer’s saturated thickness decreased more than 25 percent (McGuire, 2013).
Conclusion
The effects of water loss in the Ogallala are already being felt across the Great Plains region. While some efforts have been made to slow the rate of depletion, the primary concern remains immediate profits. Without improved water management programs, increased use of water-efficient crops, and increased use of conservative agriculture prospects for the future are grim.
- Almas, L. K., Colette, W. A., & Wu, Z. (2004). Declining Ogallala aquifer and Texas panhandle economy. . Retrieved from http://ageconsearch.umn.edu
- Evans, C. (2012, February 7). News release: Groundwater level decline continues across western and central Kansas. Retrieved from Kansas Geological Survey: http://www.kgs.ku.edu/General/News/2012/2012groundwaterlevels.html
- McGuire, V. L. (2013). Water-level and storage changes in the high plains aquifer, predevelopment to 2001 and 2009-11. Retrieved from U.S. Geological Survey Scientific Investigations Report 2012-5291: http://pubs.usgs.gov
- Terrell, B. L., & Johnson, P. N. (1999). Economic impact of the depletion of the Ogallala aquifer: A case study of the southern high plains of Texas. Retrieved from http://ageconsearch.umn.edu
- U.S. Geological Survey. (2014, March 17). Groundwater depletion. Retrieved from http://water.usgs.gov/edu/gwdepletion.html
