Principal Karst Aquifers of the United States

Principal Karst Aquifers

• Arbuckle-Simpson aquifer — Underlies more than 500 square miles in south central Oklahoma and is the principal water source for about 40,000 people. Many springs and small karst features, but only a few air-filled caves.
• Basin and Range and Bear River range carbonate aquifers — Some fractured carbonate rocks beneath alluvial basin fill. Includes areas near Cedar Break Nat. Monument, Great Basin Nat. Park, and the Bear River Range.
• Colorado Plateau karst
• Edwards Balcones Fault Zone aquifer — Highly faulted and fractured carbonate rocks of Cretaceous age in an area of about 4,000 square miles in south-central Texas. Primary drinking-water supply for San Antonio, TX.
• Edwards-Trinity Plateau aquifer — Consists of rocks of Cretaceous age that are present in an area of about 35,500 square miles in west-central Texas.
• Floridan and Biscayne aquifers
• Madison aquifer — An important water resource in the northern plains states, where surface-water supplies are limited and population is increasing. It is one of the largest confined aquifer systems in the U.S.
• Midwest Paleozoic Carbonate aquifers — Karst developed in several Paleozoic aquifers that span the Midwest from Michigan to Tennessee. Contains some of the longest mapped caves in the world, including Kentucky's Mammoth Cave Nat. Park.
• New England karst aquifers — Solution terrain in crystalline limestones and marbles mainly in northeastern Maine, western Vermont, and western Massachusetts.
• Ozark Plateau karst aquifers — Paleozoic carbonate rocks underlying several mid-continent states. Comprises two aquifers (Springfield and Ozark) and an intervening confining unit, and yields modest amounts of water.
• Roswell Basin aquifer — An eastward-dipping carbonate aquifer overlain by a leaky evaporitic confining unit and an unconfined alluvial aquifer. Decades of intensive pumping have caused substantial declines in hydraulic head.
• Pacific Northwest basalt aquifers — Late Cenozoic basalt lava fields that contain lava tubes, fissures, open sinkholes, and caves formed by extrusion of the still-liquid portion of the lava.
• Valley and Ridge, Piedmont, and Blue Ridge aquifers — Extensive areas of karst within complex geologic structures, resulting in highly variable karst-aquifer characteristics. Includes the Great Valley aquifer, an important water resource for many cities.