Ground-water flow modeling to the Rincon and Mesilla Valley and adjacent areas, New Mexico, using U.S.G.S. modflow-96

Abstract

This thesis documents the results of the ground water modeling performed for the Rincon and Mesilla Valley, New Mexico. The model takes into consideration the hydrologic and geologic conditions, and internal and external boundary conditions of the subject area for various stress periods. The lateral extent and depth of the ground water system are defined by bedrock that has much smaller values of hydraulic conductivity than those of the flood plain alluvium and deposits of the Santa Fe Group. Hydraulic conductivity of the uppermost layer generally is about 15ft/day where the layer represents the Santa Fe Group and about 135 ft/day where the layer represents the flood-plain alluvium plus the upper part of the Santa Fe Group. Hydraulic conductivity of other layers ranges from about 15 ftlday for the upper part of the Santa Fe Group to 3 ft/ day for the lower part. Most flow into and out of the ground-water system occurs at or near land surface in the Valley and is the result of a complex interaction of the river, drains, canals, evapotranspiration, water withdrawals from the wells and a relatively small amount of recharge resulting from torrential surface runoff, mainly near the mountain fronts. A finite difference ground-water flow model of the basin consisting of 55 rows, 100 columns and 4 layers was used to simulate hydrologic conditions from 1915 to 1990. The model simulated ground-water flow to and from the Rio Grande and a series of drains that empties into the Rio Grande. Model-derived hydraulic heads and drain discharges were compared with measured values. The trend of the model derived results generally matches the trend of the measured values with some exceptions, which can be attributed to the lack of availability of hydrogeological data, especially for Rincon Valley and its adjacent areas.