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MODFLOW-NWT groundwater model used for simulating a potential future pumping scenario and forecasting associated groundwater-level changes in the Hualapai Valley, Northwestern Arizona.

January 13, 2022

A numerical groundwater flow model of the Hualapai Valley Basin, using MODFLOW-NWT, was developed to assist water-resource managers in understanding the potential effects of projected groundwater withdrawals on groundwater levels in the basin. Hualapai Valley Basin is a broad, internally drained, intermountain desert basin in Mohave County, northwestern Arizona. Basin-fill aquifers are the primary groundwater source for many desert communities, and the residents, commerce, and agriculture in and near to the Hualapai Valley Basin must rely on such groundwater to meet water needs. As in many parts of the western United States, population growth in this part of Arizona is substantial. From 2000 to 2018 the population of the City of Kingman, Arizona, grew from 20,069 to 30,314, an increase of 51 percent, whereas the population of Mohave County grew from 155,062 to 209,550, an increase of 35 percent. Water managers in Mohave County have raised concern about the potential for future groundwater development and additional stresses on the groundwater system in the Hualapai Valley Basin. In particular, the City of Kingman, Ariz., water supply is primarily groundwater withdrawn from the Kingman subbasin of the Hualapai Valley Basin, northeast of the city. The potential effects of future water development on the City of Kingman well field have become a top concern to regional water-resource managers. To address these concerns the Hualapai Valley Hydrologic Model (HVHM) simulates the hydrologic system for the years 1935 through 2219, including future withdrawal scenarios that simulate large-scale agricultural expansion with and without enhanced groundwater recharge from potential new infiltration basin projects. HVHM is a highly parameterized model (75,586 adjustable parameters) capable of simulating grid-scale variability in aquifer properties (for example, conductivity, specific yield, and specific storage) and system stresses (for instance, natural recharge and groundwater withdrawals). System stresses were partially adopted from a previously-published groundwater model (Tillman and others, 2013). Parameter estimation and uncertainty quantification were performed using an iterative ensemble smoother software (PESTPP-IES) to produce an ensemble of models fit to historical data. Two future scenarios were simulated with a subset of the posterior parameter ensemble comprising the 40 best-fit realizations. In scenario 1, future pumping was simulated to increase linearly from 2019 through 2029 and then held constant through 2219. Scenario 2 includes the same specified future pumping, but also simulates enhanced recharge at proposed infiltration basins throughout the Kingman subbasin beginning in 2019. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (