Role of Geological and Geophysical Data in Modeling a Southwestern Alluvial Basin

Abstract

ABSTRACTA parameter‐estimation technique based on existing hydrological, geophysical, and geological data was developed to approximate transmissivity values for use in a ground‐water flow model of the Animas Valley, southwest New Mexico. Complete Bouguer gravity anomaly maps together with seismic‐refraction profiles, geologic maps, geologic, geophysical, and drillers' logs, water levels, and pumping‐test data provide insight into the transmissivity of bolson deposits throughout the basin.The transmissivity distribution was primarily based on reported pumping and specific‐capacity tests in conjunction with complete Bouguer gravity anomaly maps and well log data. Reported transmissivity values were characterized by gravity values and well log data. In grid blocks lacking pumping and specific‐capacity tests, transmissivity values were assigned based on the relationship of gravity values and well log data within the grid block to gravity values and well log data within other grid blocks for which transmissivity values are available.A two‐dimensional, finite‐difference, ground‐water flow computer code was used to evaluate the effectiveness of the parameter‐estimation technique. Although the trial‐and‐error method of calibration was employed, the actual computer time necessary for model calibration was minimal. The conceptually straightforward approach for parameter estimation utilizing existing hydrological, geophysical, and geological data provides realistic parameter estimates.