SIMULATING GROUNDWATER-FLOW SYSTEMS IN BASINS HAVING SPARSE DATA AT FT. IRWIN NATIONAL TRAINING CENTER IN THE MOJAVE DESERT, CALIFORNIA

<span" roman"="Roman"" new="New">Where data are sparse, simulating groundwater-flow systems of basins is difficult. Groundwater models being developed for three basins (Nelson, Goldstone, and Superior) in the Fort Irwin National Training Center (NTC) highlight these challenges. The amount and types of data for each basin varies; however, none of the basins have sufficient data to adequately construct a model or constrain the model during calibration. For the groundwater model for Nelson Basin, which has the most hydrologic, geologic, and geophysical data, six parameter zones used to distribute hydraulic properties to 30 model layers were based on data from seven boreholes and from interpreted airborne electromagnetic (AEM) and aeromagnetic surveys. Initial hydraulic properties assigned to the parameter zones were derived from hydrologic testing at four wells and slug tests at three multiple-completion well sites. Several major mapped faults were included in the model and may be partial barriers to groundwater flow. Goldstone and Superior Basins have even less information than Nelson Basin. There are three boreholes each in Goldstone and Superior Basins having hydrologic and geologic data, and the AEM data are more regional in nature for both basins. Nonetheless, parameter zones for assigning hydraulic properties in the models will be based on these data. Initial hydraulic properties will be derived from hydrologic testing at one well each for Goldstone and Superior Basins and slug tests at two multiple-completion well sites in Goldstone basin. Several major mapped faults are included in the model of Goldstone Basin, which may compartmentalize groundwater flow. In Superior Basin, one major mapped fault is included in the model, and historical water-level data indicate it is a barrier to groundwater flow. Recharge to the three basins is relatively small and is estimated by using a water-balance model of watersheds. It is simulated as subsurface inflow from the areas upgradient to the basins (mountain-front recharge) and as infiltration of precipitation and any surface runoff. Groundwater discharge does not exist internally in the basins and what little recharge there is to the basins is simulated as subsurface outflow to adjacent basins.