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Death Valley regional ground-water flow model calibration using optimal parameter estimation methods and geoscientific information systemsU.S. Geological Survey
ABSTRACT A steady-state, regional-scale, saturated ground-water flow model was constructed to evaluate potential regional ground-water flow in the vicinity of Yucca Mountain, Nevada. The model was limited to three layers to allow more convenient evaluation of the characteristics governing large-scale subsurface flow. Geoscientific information systems (GSIS) were used to characterize the complex surface and subsurface hydrogeologic conditions of the area, and this characterization was used to construct likely conceptual models of the flow system. A dominant characteristic of the system is that subsurface properties vary dramatically and rapidly, producing high contrasts and abrupt contacts. This, combined with the large scale of the model, make zonation the logical choice for representing the hydraulic-conductivity distribution. Different conceptual models were evaluated using sensitivity analysis and were tested by using nonlinear regression to determine parameter values that are optimal in that they provide the best match between the measured and simulated heads and flows. The different conceptual models were judged based both on the fit achieved to measured heads and spring flows, and the plausibility of the optimal parameter values. One of the conceptual models considered appears to represent the system most realistically, with any apparent model error probably caused by the coarse vertical and horizontal discretization.
mchill@usgs.gov Last Modified: August 14, 2000 |