Open-File Report 2006–1104
U.S. GEOLOGICAL SURVEY
Open-File Report 2006–1104
The Death Valley regional ground-water flow system (DVRFS) model domain encompasses about 100,000 km2 in Nevada and California and is bounded by latitudes 35°00’N and 38°15’N and by longitudes 115°00’W and 118°00’W (fig. 1). Belcher and others (2004), San Juan and others (2004), and Faunt and others (2004a, 2004b) documented the development of a conceptual understanding of the system hydrology and hydrogeology, and ultimately a transient ground-water simulation of the DVRFS. Faunt and others (2004a) and San Juan and others (2004) described the conceptualization of the system hydrology, natural ground-water discharge including evapotranspiration and springs, pumpage, ground-water recharge, and water levels (fig. 2). In particular, San Juan and others (2004) described model inputs and their sources, including the calculation of observations (water levels, flows at the model boundary, and natural discharge) and observation weights. These observations and the associated weights form the basis of the data used to calibrate and evaluate the transient numerical flow model.
The transient ground-water flow model of the DVRFS simulates steady-state conditions that represent predevelopment conditions followed by transient conditions from 1913 through 1998 (Faunt and others, 2004b). Recharge is constant at average annual values for the entire period of simulation; however, the simulated recharge varies spatially. Ground-water pumpage from 1913 to 1998 is a transient stress imposed using average annual values. Along some portions of the model boundary, constant-head boundary flows represent lateral flow from adjacent basins. Ground-water discharge from evapotranspiration and spring flow is simulated using head-dependent boundaries. DVRFS model input, output, and source code are available at the model archive link at URL: http://pubs.water.usgs.gov/sir20045205/ (accessed on December 22, 2005). A complete list and description of the archived model files are provided in the Appendix A (at back of report).
The DVRFS model uses the Ground-Water Flow Process of MODFLOW-2000 [which is similar to the capabilities of MODFLOW-96 (Harbaugh and McDonald, 1996)], as well as the Observation and Sensitivity-Analysis Processes of MODFLOW-2000 (Hill, 1990; Harbaugh and others, 2000; Hill and others, 2000). Subsequent to these publications, additional MODFLOW capabilities were developed and used in the DVRFS model including the Hydrogeologic-Unit Flow (HUF2) Package (Anderman and Hill, 2000, 2003) and the Multi-Node Well (MNW1) Package (Halford and Hanson, 2002). The HUF2 Package allows the modeler to translate the hydrogeologic framework into flow model layers by defining the geometry of the hydrogeologic units independently of the flow model layers. The MNW1 Package simulates pumping and injection for wells that penetrate multiple flow model layers.
This report provides the user of the DVRFS transient ground-water model a guide for conducting numerical simulations with the archived model using MODFLOW-2000 (Harbaugh and others, 2000; Hill and others, 2000). Both model input and output will be described for forward, sensitivity-analysis, and parameter estimation model simulations. Additionally, modification of the DVRFS transient ground-water model is discussed for two common uses of the DVRFS model: predictive pumping scenarios that extend beyond the end of the model simulation period (1998), and model simulations with only steady-state simulation. For both of these model modifications, the required editing of MODFLOW-2000 input, including observation files, is outlined with examples. This report is designed for users familiar with concepts associated with the Ground-Water Flow Process of MODFLOW-2000 [which is similar to the capabilities of MODFLOW-96 (Harbaugh and McDonald, 1996)] but perhaps less familiar with the Observation, Sensitivity-Analysis, and Parameter-Estimation Processes of MODFLOW-2000 (Hill, 1990; Harbaugh and others, 2000; Hill and others, 2000).
For more information about USGS activities in Nevada, visit the USGS Nevada Water Science Center home page.
U.S.
Department of the Interior | U.S. Geological
Survey
Persistent URL: http://pubs.water.usgs.gov/ofr20061104
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