A closer look at the change in the Ogallala aquifer water level from predevelopment s to Irrigated agriculture in the Oklahoma Panhandle has changed significantly during the past several decades. Figure 4 depicts two satellite images taken in July of and July of over the city of Guymon and its surrounding area. Green squares are typically flood gravity irrigated fields, while green circles represent center pivot sprinkler irrigation. As it can be observed, the majority of irrigated fields were under flood irrigation in , with only a few center-pivot systems present in the satellite image.
During the next 33 years, most of irrigated fields switched to center-pivot systems. Compared to flood irrigation, center-pivot systems can apply water in smaller amounts and more uniform patterns, resulting in reduced deep percolation and improved crop yield.
In addition, the new center pivot systems have nozzles at a lower elevation, which helps reduce direct evaporation and wind drift losses. Figure 4. Satellite images taken in July top and July bottom show the changes in irrigated areas around Guymon, OK. The decline in the Ogallal water level has created numerous challenges for irrigated agriculture in the Oklahoma Panhandle.
A main challenge is the reductions in pumping rates, resulting in higher energy costs and decreased revenue, as crop yields are decreased due to not meeting the full crop water requirement or planting a smaller area. In addition, as the Ogallala level decline and water is being extracted from deeper parts of the aquifer the quality of water may degrade [2]. Since the Ogallala aquifer has a very low recharge rate [7] and other water resources are so scarce, efforts to increase the life of this valuable resource should focus on managing demand.
Local groups of stakeholders, such as the Oklahoma Panhandle Agriculture and Irrigation Association, have been active in this field. An example of their efforts is the development of the Panhandle Regional Water Plan in collaboration with other local groups. Gollehon, Noel and Winston, Bernadette.
Hart, D. S Geological Service Report. Houston, Natalie A. Geological Service Report. Luckey, Richard R. Hydrogeology, water use, and simulation of flow in the High Plains aquifer in northwestern Oklahoma, southeastern Colorado, southwestern Kansas, northeastern New Mexico, and northwestern Texas. S Geological Service Fact Sheet The deeper parts of the valleys were filled with river deposits, consisting largely of reworked volcanic debris of the Gering Formation.
Most of the remainder of the Arikaree Group is wind-deposited volcanic ash that fills the parts of the ancient valleys above the Gering. The Ogallala Group is a complex and heterogeneous mass of sediment mostly composed of river alluvium derived from erosion of the southern Rocky Mountains. During deposition of the Ogallala and the younger Broadwater Formation, rivers repeatedly eroded valleys and then filled these valleys.
Minor finer-grained lake sediments, volcanic ash deposits, and lime-cemented soil horizons occur throughout the Ogallala sequence. Wind-deposited sands are common in the Ogallala in the Southern High Plains.
Quaternary river alluvium, wind deposits, lake beds, and volcanic ash layers cover much of the High Plains and fill parts of valleys cutting across the High Plains.
The USGS estimates that in the aquifer contained about 3. If impounded on the surface, this volume of water would cover the High Plains region to an average depth of about thirty feet. Most of the water in the aquifer comes from precipitation on the High Plains. With the increase of irrigated agriculture, water levels have dropped in places where the groundwater from the aquifer was pumped out faster than water from precipitation moved through the sediments and rocks to replace it.
In other areas, water levels have risen where precipitation has allowed water to infiltrate the aquifer at rates greater than those at which water was pumped out, or where reservoirs and canals have lost water to the aquifer at rates greater than the withdrawal. Diffendal Jr. Before European settlers arrived, the billion acres of grasses that blanketed the High Plains were home to pronghorn antelope and swift fox, lesser prairie chickens and burrowing owls as well as buffalo. Blue grama, green needle grass and other drought-resistant plants thrived in the short growing season.
More than half these native grasslands have been converted to crops, including nearly 25 million acres since , according to a General Accounting Office study. In a project she is coordinating, farmers are experimenting with grassland restoration on fields they have been forced to retire because of groundwater depletions. In addition to providing wildlife habitat, grasslands could be grazed by cattle or even buffalo.
And once a national carbon market is established, farmers could sell credits for storing carbon in grassland soil. Several federal government programs provide economic incentives for conservation of existing grasslands—recognizing their role in reducing erosion, sequestering carbon, and providing habitat for the lesser prairie chicken and other endangered species. But these programs often work at cross-purposes with federal price-support incentives to produce corn and other commodities.
Subsidies for crops are generally higher than subsidies for grassland conservation, making the choice simple for most growers.
Eventually the nation will need a strategy to end its dependence on this finite resource, says Stone, the Groundwater Trust executive. For Funk in Garden City, it already has. Using technology and foresight, he has transformed his farm into a business he believes can continue into the distant future without draining the Ogallala. Note: This article was originally printed with the title, "Saving the Ogallala Aquifer".
Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. If spread across the U. Get smart. Sign up for our email newsletter. Sign Up. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? The Ogallala Aquifer is the largest aquifer in the United States and is a major aquifer of Texas underlying much of the High Plains region.
The aquifer consists of sand, gravel, clay, and silt and has a maximum thickness of feet. Freshwater saturated thickness averages 95 feet.
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