Predevelopment water-level map of the Santa Fe Group aquifer system in the middle Rio Grande basin between Cochiti Lake and San Acacia, New Mexico

Because of its increasing population and limited water resources, the Middle Rio Grande Basin between Cochiti Lake and San Acacia, New Mexico, has recently become the subject of intense study. In particular, the U.S. Geological Survey (USGS) in cooperation with the City of Albuquerque has constructed a series of ground-water-flow models of the Tertiary and Quaternary basin-fill deposits of the Santa Fe Group aquifer system (Kernodle and Scott, 1986; Kernodle and others, 1987; Kernodle and others, 1995; Kernodle, 1998; Tiedeman and others, 1998). The ground-water-flow system also has been the focus of hydrochemical studies and other efforts intended largely to help develop an improved flow model. Among the information critical to a thorough understanding of the ground-water-flow system are water-level data that indicate the directions of ground-water flow and the magnitudes of hydraulic gradients in the aquifer prior to perturbation by substantial ground-water withdrawals (under predevelopment conditions).