The Aquifer as a Water Resource

Resource Use

As the primary groundwater source for much of central Oklahoma, the Central Oklahoma (Garber-Wellington) Aquifer supports more than 925,000 residents across parts of Oklahoma, Cleveland, Logan, and Pottawatomie Counties (OWRB, 2019). It supports a range of uses, with the largest withdrawals occurring for municipal and public water supply, particularly in cities like Norman, Edmond, Moore, and Midwest City (Mashburn et al., 2019). Smaller-scale withdrawals also support domestic wells, light industry, and limited irrigation, especially in rural areas.

Although the aquifer underlies Oklahoma City, the city does not rely on it as a major water source. Instead, it draws primarily from surface water reservoirs including Lake Hefner, Canton Lake, and Atoka Lake, supported by an established infrastructure network. This choice is influenced by both historical investment in surface water and water quality concerns within the aquifer. Specifically, naturally elevated concentrations of arsenic have been documented in several wells, with some exceeding the EPA’s maximum contaminant level of 10 µg/L during the 1987–1990 USGS assessment (Parkhurst et al., 1994). These conditions are especially prevalent in deeper, confined parts of the aquifer and may increase the cost and complexity of treatment (Layden, 2013).

Resource Managment and Allocation

Groundwater from the Central Oklahoma (Garber-Wellington) Aquifer is managed under Oklahoma state water law, which distinguishes between surface water (stream water) and groundwater. The aquifer is classified as a major groundwater basin, and its use is regulated by the Oklahoma Water Resources Board (OWRB). Groundwater withdrawals are subject to permitting based on land ownership and estimates of the maximum annual yield of the aquifer (OWRB, 2019).

In 2019, the OWRB issued a tentative order establishing a maximum annual yield of 78,404 acre-feet per year and an equal proportionate share (EPS) of 0.2 acre-feet per acre of land overlying the basin. These official figures are presented in the Tentative Order (OWRB, 2019), but are based on groundwater flow modeling and storage analyses performed in the USGS study by Mashburn et al. (2019).

Oklahoma’s groundwater law follows a modified reasonable use doctrine, allowing landowners to use groundwater beneath their property so long as it does not exceed their allocated EPS or impair other users. However, unlike surface water, groundwater is not treated as a public trust resource. This legal distinction reflects historical tensions between the riparian and prior appropriation doctrines, which Oklahoma sought to resolve through the 1963 groundwater statute and later court decisions (National Water Rights Digest).

The OWRB is responsible for reviewing water rights applications, tracking withdrawals, and reassessing yield estimates approximately every 20 years (OWRB, 2019). Permits may be issued as temporary or regular, depending on whether a hydrologic determination has been completed. While the aquifer is not currently over-appropriated, continued monitoring is necessary, especially as urban demand increases and climate variability affects long-term recharge rates (Mashburn et al., 2019; OWRB, 2019).