Science Center Objects

Hydrologists increasingly rely on computer watershed models to estimate groundwater 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 groundwater 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 groundwater recharge.

The USGS is comparing groundwater 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. 

9722-ARK - Evaluating Recharge Parameter Sensitivities in the Deep Percolation Model and the Precipitation-Runoff Modeling System

Problem - To estimate ground-water recharge on a regional scale, hydrologists will increasingly need to rely on distributed models to obtain those estimates. To date, these models have not been evaluated to determine which model parameters are the dominant controls in determining ground-water recharge. In this study, the parameter sensitivity to ground-water recharge will be determined for Deep Percolation Model (DPM) and Precipitation Runoff Modeling System (PRMS). Prior knowledge of the watershed-model parameters that control recharge estimates will help hydrologists focus on the compilation of the most relevant data in studies of regional ground-water recharge. Parameter sensitivities will be determined using UCODE (Poeter and Hill, 1998).

Objectives - The general objective of this study is to determine which model parameters in DPM and PRMS are the dominant controls in determining ground-water recharge. The following tasks are needed to complete the investigation:

  1. Compare ground-water recharge estimates that were obtained in previous studies in the Pacific Northwest using DPM and PRMS in the same humid-area basins,
  2. Determine the sensitivity of ground-water recharge in the Pacific Northwest basins to model parameters, and
  3. 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.

Relevance and Benefits - The DPM and PRMS have both been used to estimate recharge but no comprehensive study has been completed that examines how the two models respond to parameter values or in what circumstances one model would have greater applicability. Results of this work would strengthen future recharge studies completed with either the DPM or MMS by focusing data collection efforts in studies that require regional estimates of ground-water recharge and identifying regional differences in recharge processes.

Approach - Existing DPM and PRMS recharge estimates for two basins in the Pacific Northwest will be compared and the ground-water recharge estimates will be evaluated. The study will include an evaluation of the two models in each basin by examining the sensitivity of ground-water recharge to the DPM and PRMS parameters. Three existing MMS studies from three distinctly different humid regions of the United States will then be chosen to perform a similar evaluation of the UCODE diagnostic statistics as described above. This evaluation will identify by region the model parameters that are most important for determining ground-water recharge, and it will also compare and contrast the hydrologic system responses to those parameters.