Hydrologic Investigation of the Rush Springs Aquifer
Christopher R. Neel
Oklahoma Water Resources Board
Abstract
The Rush Springs aquifer of Oklahoma lies in the counties of Blaine, Caddo, Canadian, Comanche, Custer,
Grady, Stephens, and Washita Counties and includes the communities of Anadarko, Clinton, and
Weatherford, among others. The aquifer underlies about 2,400 square miles and is predominantly used
for municipal and irrigation purposes, although other uses include agricultural (non-irrigation),
industrial, commercial, and domestic water supplies. Estimated withdrawal from the aquifer in 1990 of
about 54.7 million gallons per day, or 61,272 acre-feet per year; 77.8 percent was used for irrigation
(Becker and Runkle, 1998).
The predominant geologic formation in the Rush Springs aquifer is the Permian-age Rush Springs
Formation. The composition of the Rush Springs Formation is an “orange-brown, cross-bedded, finegrained sandstone with some dolomite and gypsum beds” and ranges in thickness from 186 to 300 feet
(Carr and Bergman, 1976). The Rush Springs Formation is underlain by the well-cemented Marlow
Formation, which according to Becker and Runkle (1998), “acts as a confining unit that significantly
retards downward movement of water from the Rush Springs aquifer to underlying units”. The western
portion of the Rush Springs Formation is capped by the Cloud Chief Formation, confining the aquifer and
minimizing recharge in that area.
Major streams emanating from the aquifer include Cobb Creek, Deer Creek, and Sugar Creek. Washita,
Canadian, and North Canadian rivers have a significant baseflow component from the Rush Springs
aquifer. Groundwater/surface water interaction plays a significant role in the hydrology of the area as
baseflow discharges into streams and helps maintain storage in Ft. Cobb Reservoir. The reservoir is
maintained by the U.S. Bureau of Reclamation and provides a water supply to the communities of
Bessie, Clinton, Cordell, and Hobart.
The 2012 Oklahoma Comprehensive Water Plan (Oklahoma Water Resources Board, 2011) anticipates
that several Planning Basins in the current Rush Springs aquifer boundary will experience significant
groundwater depletion by 2060. One of these Planning Basins is located upstream from Ft. Cobb
reservoir, where groundwater depletions could cause a significant decline of base flow into the
reservoir. Additionally, a majority of the groundwater permits in the aquifer are concentrated around
and upstream from Ft. Cobb reservoir. Concerns on future reservoir yield and storage have also been
identified by the Bureau of Reclamation (Bureau of Reclamation, 2006; Ferrari, 1993).
The objective of the Rush Spring hydrologic study is to conduct an investigation focused on the
hydrogeology of the aquifer that will supply the OWRB information needed to determine the Maximum
Annual Yield and Equal Proportionate Share based on various proposed management scenarios. This
will be accomplished through development of a groundwater-flow model, which will provide insight
about the flow regime of the aquifer and allow simulations of management options. Once a maximum
annual yield is determined for the aquifer, the OWRB can assist local entities in determining the most
feasible water supply alternatives to meet area needs. Other goals of the study include characterization
of the aquifer in terms of geological setting, aquifer boundaries, hydraulic properties, water levels,
groundwater flow, and water budget, among others.
The study design and preliminary data from the investigation will be presented; input and feedback will
be welcomed.
References
Becker, M.F. and Runkle D.L., 1998, Hydrology, water quality, and geochemistry of the Rush Springs
aquifer, western Oklahoma: U.S. Geological Survey Water-Resources Investigations Report 98-4081,
37 p.
Bureau of Reclamation, 2006, Concluding appraisal report: conveyance system expansion, Fort Cobb
Division, Washita Basin Project, Oklahoma, 30 p.
Carr J.E. and Bergmann D.L., 1976, Hydrologic Atlas 5: Reconnaissance of the water resources of the
Clinton Quadrangle, West-Central Oklahoma.
Ferrari, R.L., 1994, Fort Cobb Reservoir: 1993 sedimentation survey, 33 p.
Oklahoma Water Resources Board, 2011, Oklahoma Comprehensive Water Plan west-central Watershed
planning region draft report, 84 p.