For those curious why many state resources and agricultural leaders are expressing growing concerns about groundwater depletion in Oklahoma and other states in the Midwest, a recent detailed explanation was offered by Oklahoma Water Resources Center Director Dr. Kevin Wagner.
It not only is an interesting read but a most informative explanation of the importance of water in the state:
While you may not see the water lying beneath our feet, it is one of our most valuable resources. Stored in the water table and in aquifers, groundwater accounts for just 0.61% of Earth’s total water but is 98% of Earth’s freshwater. Just the United States alone uses 82.3 billion gallons of groundwater every day.
Groundwater is classified as water beneath the Earth’s surface. It fills spaces between soil particles, gravel and cracks in rock, and is stored and flows through aquifers.
Wells drilled into the aquifers provide about 37% of public water supply and over 90% of water for rural populations. Throughout Oklahoma, entire cities – like Guymon with the Ogallala aquifer – receive all of their water from aquifers.
All groundwater begins as precipitation, as a portion of the water that falls as rain and snow will infiltrate into the subsurface soil and rock. The amount that infiltrates varies greatly, depending on where it falls. Naturally occurring aquifer recharge is a slow process, but is key.
Did you know that Oklahoma has almost 600 natural lakes (see picture)? Playa lakes are one of the most numerous lakes in the Great Plains region, with over 80 thousand across six states.
Playa lakes are round, shallow depressions found at the lowest points of a watershed which fill with water during rainy seasons and aid in aquifer recharge. When properly maintained, playa lakes create wildlife habitat and clean aquifer recharge.
In Oklahoma, playa lakes are a primary source of recharge for the Ogallala aquifer. They also provide water filtration, erosion and flood control and upland game bird hunting and wildlife viewing opportunities. Because of agricultural and other land use activities, playas are critically threatened, with over 80% of these lakes impacted, according to the Playa Lakes Joint Venture.
Where is the Ogallala Aquifer?
Oklahoma has 23 major aquifers, which includes bedrock and alluvial aquifers. Bedrock aquifers include sandstone aquifers, soluble carbonate and evaporite (limestone, dolomite and gypsum) aquifers and the semi-consolidated sand and gravel underlying the High Plains. The alluvium and terrace aquifers consist of unconsolidated deposits of sand and gravel along rivers and streams. Major aquifers are those that can yield an average of at least 50 gallons per minute for bedrock and 100 gallons per minute for alluvium and terrace aquifers, according to Oklahoma Water Resources Board.
Figure 2 (Oklahoma Groundwater Resources) shows locations of major alluvial and major bedrock aquifers in Oklahoma.
Oklahoma has 320 million acre-feet of water in aquifers and over 120,000 groundwater wells. Wells that are hundreds of miles apart can draw from the same aquifer, making it essential to protect both your well and the shared water source.
Reduce risk of groundwater quality contamination with:
- Proper well maintenance & construction
- Limit chemical use & storage near wells
- Responsible contaminant disposal
- Plug abandoned wells
- Ensure safe distance of wells & septic systems
- Protecting recharge areas
Current Trends and Agricultural Use
According to the U.S. Geological Survey Integrated Water Availability Assessment, both the central and southern region of the High Plains Aquifer has shown declining levels for the water years of 2010-2020. A major portion of the High Plains Aquifer system, the Ogallala Aquifer, spans over the panhandle of Oklahoma.
Hydrologically, the Ogallala is highly variable with saturated thickness (the distance between the water table and the base of the aquifer) levels prior to intensive development of wells ranging from less than 50 feet to greater than 1,000 feet.
Figure 3 (10-yr. Avg. Water Level Changes) shows county specific water level changes in the Ogallala. Figure 4 (Median Groundwater-Level Percentiles) indicates that water levels were considerably lower than normal during water years 2010-20, relative to the 21-year period analyzed.
The Ogallala is a globally significant resource, supporting agricultural communities across eight states in the western Great Plains. Over 85% of the water pumped from the Ogallala goes to support irrigated cropping, in turn supporting the large animal production sector that provides much of the employment and economic benefits to the region. Agricultural sales in the region contribute billions of dollars to local economies and national Gross Domestic Product every year. For example, Texas County, Oklahoma – the largest agricultural producing county in Oklahoma, completely reliant on the Ogallala Aquifer – represents $1.16 billion in total annual agricultural sales (USDA NASS, 2022).
Figure 5 (Average Value of Ag. Products) indicates high agricultural products sold per farm in 2022..
Due to use at rates exceeding recharge, water levels in the Ogallala have declined, particularly in the southern and western portions where saturated thickness was generally thinner to begin with. Based on current trends, the anticipated lifespan of some of the most productive areas of the aquifer can be measured in the order of decades (Deines et al. 2020).
Irrigated acres in the Texas Panhandle and High Plains regions have declined by 40% since the early 1980s, alongside population growth of 25%. Agriculture still remains the region’s primary economic driver, as shown in the map above.
Source: Dr. Kevin Wagner, Oklahoma Water Resources Center