Abstract

Cedar Valley, Iron County, Utah, is a well-documented example of ground-water development in a small basin because it has been the focus of concern by the Utah Division of Water Rights and study by the U.S. Geological Survey for more than half a century. Basin-wide, ground-water levels have generally declined since development began in the 19th century. The potential for over-pumping was recognized early, and in 1935 the State Engineer suspended approval of new applications, pending study. In 1966 the basin was closed to new appropriation. In the short term (decades), water levels show a strong response to the balance between recharge and discharge, rising in wet years and declining in dry years. In the central basin, each 1-foot (.3-meter) of water-level change represents an estimated change in storage of 5,600 acre-feet (7×10⁶ m³). Much of the decline in water levels occurred early in the development stages of the basin and can be charged to “development cost”: the necessary emptying of the originally full reservoir to make space available for future recharge. A multi-decade cycle of water-level fluctuation suggests that a half-century is an appropriate time horizon for optimizing development of the ground-water reservoir. Urbanization of the recharge zone and continued conversion of agricultural to urban uses present future challenges for management of the Cedar Valley ground-water basin.