MODFLOW-NWT model used to evaluate the groundwater availability of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho

A three-dimensional groundwater flow model (MODFLOW-NWT) of the Columbia Plateau Regional aquifer (CPRAS) in Washington, Oregon, and Idaho was developed to provide an integrated understanding of the hydrologic system to implement effective water-resource management strategies. The U.S. Geological Survey (USGS) Groundwater Resources Program assessed the groundwater availability as part of a national study of regional systems (https://pubs.usgs.gov/circ/1323/). The CPRAS assessment includes the status of groundwater resources, how these resources have changed over time, and development and application of tools to estimate system responses to stresses from future uses and climate variability and change. A major product of this assessment is a numerical groundwater-flow model of the system. Two models were constructed to simulate groundwater flow in the CPRAS: a steady-state predevelopment model representing conditions before large-scale pumping and irrigation altered the system, and a transient model representing the period 1900–2007. Construction of the model, development and calibration of the steady-state and transient simulations, as well as, a commingling scenario, is documented in the Scientific Investigations Report 2014-5127 (https://doi.org/10.3133/sir20145127). Two additional scenarios were completed and documented in the U.S. Geological Survey Professional Paper 1817 (https://doi.org/10.3133/pp1817). One scenario represents long-term equilibrium under 2007 conditions and the other modified the equilibrium conditions to account for potential increased pumpage under projected temperature increases with climate change. The model is a useful tool for investigating water supply, water demand, management strategies, groundwater-surface water exchanges, and potential effects of changing climate on the hydrologic system. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation reports: U.S. Geological Survey Professional Paper 1817 (https://doi.org/10.3133/pp1817) and the modeling report that documents the construction and calibration of the model, Scientific Investigations Report 2014-5127 (https://doi.org/10.3133/sir20145127).