USGS Washington Water Science Center
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Hydrologists increasingly rely on computer watershed models to estimate ground-water recharge from precipitation on a regional scale. The model parameters used in simulations of recharge are various climatic, hydrologic, and physical characteristics of a watershed or stream basin. To date, the watershed models have not been evaluated to determine which model parameters are the dominant controls in determining ground-water recharge. Prior knowledge of the watershed-model parameters that control recharge estimates will help hydrologists focus on compiling the most relevant data in studies of regional ground-water recharge.
The USGS is comparing ground-water recharge estimates from previous studies using two watershed models - the Deep Percolation Model (DPM) and the Precipitation Runoff Modeling System (PRMS) - in the same humid Pacific Northwest basins and determining the sensitivity of recharge to the model parameters. Hydrologists are also evaluating the sensitivity of recharge to model parameters in three distinctly different humid regions in the United States to determine if there are regional differences across the United States in the sensitivity of ground-water recharge in humid-area basins to watershed-model parameters. Results of this work can help focus data-collection efforts in studies that require regional estimates of ground-water recharge, indicate which of the two models would be more applicable in what circumstances, and identifying regional differences in recharge processes.