9706116 Smith Field sedimentological and hydrological studies of outcrop analogs for heterogeneous aquifers provide conceptualizations of heterogeneity unrealized by subsurface information and provide a means for assessing the validity and performance of popular stochastic models based on interpolation of well data. The approach, widely used for decades in the hydrocarbon industry, has seen little application to hydrological problems. Sedimentological studies of well-exposed rift-basin alluvium will be complemented by in-situ measurements of permeability, thus permitting designation of hydrofacies with defined hydraulic conductivity, shape, and boundaries that are linked with lithofacies whose distribution is related to depositional processes that formed the aquifer material. Outcrop data will be used to formulate a three-dimensional model of heterogeneity at the scale of typical subsurface-contaminant-migration scenarios. The study-site stratigraphy will also be simulated by geostatistical techniques using measured sections as conditioning data in much the same way as well data are used to condition subsurface models. The predictive ability of the simulation will be gauged by comparison to the outcrop data. The outcrop model will be subjected to flow simulations for varying scales (meters to tens of meters) of outcrop-defined heterogeneity to evaluate the quantity and type of data required for high-resolution prediction of flow paths and rates. The depositional environment selected for outcrop characterization is especially important for understanding aquifer heterogeneity in extensional basins of the southwestern United States, where studies to date have not adequately described the sedimentological characteristics that are of hydrogeological importance. The largest volume of clastic detritus deposited in asymmetric extensional basins is delivered from the hanging wall to the master fault. These alluvial-slope facies are the least well known deposits in rift basins. This projec t will produce the first outcrop analog for aquifer characteristics of alluvial-slope deposits by providing detailed three dimensional documentation of hydrofacies permeability, shape, and boundaries within an extraordinarily well exposed basin-fill sequence in the northern Rio Grande rift of New Mexico.
