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

This water-level map represents general predevelopment conditions throughout the Middle Rio Grande Basin between Cochiti Lake and San Acacia, primarily in about the upper 300 feet of the saturated zone of the Santa Fe Group aquifer system. The water-level data used to complete this map were obtained from a variety of sources, including the USGS National Water Information System (NWIS) database, reports published by Federal and State agencies, and unpublished master’s theses from the University of New Mexico. In addition to water-level data for wells and springs, riverbed elevations of the Rio Grande and Jemez River were included in the data set used to construct the map. In the Albuquerque area, only water levels measured prior to 1961 were determined to be representative of predevelopment conditions and were included in the data set used to construct the map. Outside of the Albuquerque area, water levels measured during any year were included in the data set because development is sparse and ground-water withdrawals were assumed to be small enough to have only minimal effects on water levels.

Contouring of water levels for the map was done by hand (rather than by use of computer software), taking into consideration all water-level and riverbed-elevation data. Contour segments believed to have the largest potential for error are dashed, typically in areas where few data points were available or where the available data conflicted.

Hydraulic discontinuities, or large differences in water levels over short lateral distances, appear to occur in several areas. The discontinuities typically are located in the proximity of major faults near the basin margins and appear on the map as closely spaced or truncated contour lines. The apparent discontinuities across major faults likely are associated with large contrasts in hydraulic conductivity values between fault-juxtaposed geologic materials.