The Great Plains aquifer system (Dakota Sandstone and associated strata) varies considerably in lithology, depth of occurrence, hydraulic properties, and resource development (water and petroleum) throughout 170,000 square miles of Nebraska, Colorado, Kansas, and adjacent areas. Porosity, hydraulic conductivity, and flow rates generally decrease from eastern and southern outcrop areas toward western basins. Hydraulic-head distribution indicates a west-to-east gradient of regional flow. Distribution of dissolved solids is related mainly to environment of deposition, with limited modification by post-depositional flow patterns. Water in much of the aquifer system is brackish (1,000 to 10,000 milligrams per liter dissolved solids). Flow model simulations indicate a predevelopment steady-state flow through the system of about 340 cubic feet per second. Regional hydraulic-head declines in response to oil and gas development have been several hundreds of feet; declines resulting from the most intensive freshwater withdrawals have been several tens of feet. Rates of water withdrawal greatly exceed the natural recharge, but the aquifer system is a potential long-term source of water if some storage depletion is tolerated. The system also offers potential for liquid injection, artificial recharge, and geothermal-energy development.
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