Book Description

This document provides details of three research projects. First, a review was conducted on the hydrologic model, ParFlow v3.5.0, to provide information on ParFlow in a format that targets a broader community than a user manual or articles describing specific applications of the model. The history of ParFlow's development, core functionality, model equation discretization and solvers, parallel scaling and performance efficiency, and coupling capabilities of ParFlow with atmospheric, land surface, and subsurface models were discussed. The second project used ParFlow to simulate hydrogeologic conditions of the Walla Walla River Basin (WWRB), southeast Washington and northeast Oregon. Specifically, numerical simulations were performed to test the response of the unconfined aquifer system of the WWRB to supplemental managed aquifer recharge (MAR) scenarios, given a required minimum in-stream flows (ISFs) in the WWR over a 100-year period. The simulations indicated that maintaining minimum ISFs in the WWR and relocating some of the MAR sites downgradient could lead to balanced benefits to all users. The final research project focused on the creation of a three-dimensional groundwater flow model for the Pullman-Moscow Basin, north-central Idaho and southeastern Washington with MODFLOW-2005. The model was used to evaluate alternative water management scenarios to find long-term solutions to aquifer depletion. Model creation and calibration were done using existing hydrogeologic conditions and parameters estimated from previous studies in the basin, and suggestions of future updates to limit model assumptions and uncertainties were provided. Simulation results indicated that pumping less than 25 percent of historic rates (1983-2018) would stabilize/improve groundwater levels in Pullman and Moscow areas.