Ground-water resources of arid and semi-arid basins in the southwestern United States are generally developed within bounds imposed by physical, legal, and economic constraints. In Ash Meadows, a portion of the Amargosa Desert of southwestern Nevada, ground-water development is subject to the additional constraint of preserving the rare desert pupfish (Cyprinodonts) which inhabit spring pools within the area. Continued withdrawal of ground water for agricultural purposes will eventually decrease water levels to the extent that the natural habitats of the pupfish may be damaged. An unsteady state digital ground-water model is developed to assist in evaluation of these ground-water problems.