Hydrology of the Arbuckle Mountain area, south-central Oklahoma

Abstract

Rocks that make up the Arbuckle-Simpson aquifer crop out over about 500 square miles in the Arbuckle Mountains province in south-central Oklahoma. The aquifer consists of limestone, dolomite, and sandstone of the Arbuckle and Simpson Groups of Late Cambrian to Middle Ordovician age and is about 5,000 to 9,000 feet thick. The rocks were subjected to intensive folding and faulting associated with major uplift of the area during Early to Late Pennsylvanian time. Water in the aquifer is confined in some parts of the area, while in other parts it is unconfined. The average saturated thickness of the aquifer is about 3,500 feet in the outcrop area. Water levels measured in wells fluctuated from 8 to 53 feet each year, primarily in response to recharge from rainfall. Recharge to the aquifer is estimated at about 4.7 inches per year. The average storage coefficient of the aquifer is estimated at 0.008, and the average transmissivity is estimated at 15,000 feet squared per day. Based on an average saturated thickness of about 3,500 feet and a storage coefficient of 0.008, the volume of ground water contained in the 500-square-mile outcrop area is about 9 million acre-feet. An undetermined amount of fresh water probably exists in the aquifer around the periphery of the aquifer outcrop. Base flow of streams that drain the aquifer accounts for about 60 percent of the total annual runoff from the outcrop area and is maintained by numerous springs. The close hydraulic connection between streams in the outcrop area and the aquifer is shown by a close correlation between base flow in Blue River and the fluctuation of ground-water levels in five wells in the Blue River basin. This correlation also exists between the discharge by Byrds Mill Spring and the fluctuation in water level in a nearby observation well; increase and decrease in spring discharge correspond to rise and fall of the water level in the well. The chemical quality of water from the Arbuckle-Simpson aquifer is suitable for most industrial and municipal uses. The water is hard and of the bicarbonate type; the average hardness is about 340 milligrams per liter, and the average dissolved-solids concentration is about 360 milligrams per liter. Because springs issue from the aquifer and discharge to streams in the area, the quality of water from springs and base flow in streams is similar to that of ground water. The average dissolved-solids concentration of stream water is slightly less than that of water from wells and springs.