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Donald A. Walter

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In 2016, the United States Geological Survey (USGS) began development of a regional-scale numerical model of the Long Island aquifer system, as part of the National Water Quality Assessment (NAWQA) Program. The three-dimensional groundwater-flow model was developed to evaluate 1) responses of the hydrologic system to changes in natural and anthropogenic hydraulic stresses 2) the subsurface distribution of groundwater age, and 3) the regional-scale distribution of groundwater travel times and the source of water to fresh surface waters and coastal receiving waters. The model also provides the groundwater flow components used to define model boundaries for possible inset models used for local-scale analyses. Unconsolidated...
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The U.S. Geological Survey, in cooperation with the Air Force Civil Engineer Center, developed a numerical, steady-state regional model, using MODFLOW-2005, to evaluate current (2010) conditions and the potential effects of future (2030) groundwater withdrawals on water levels, streamflows, hydraulic gradients, and advective transport near the Joint Base Cape Cod (JBCC). Two numerical models were used in this analysis. An existing two-dimensional (one layer) model (termed the “coast model”), developed as part of a previous investigation of the potential effects of sea-level rise on the Cape Cod aquifer system (https://doi.org/10.3133/sir20165058), simulates the position of the freshwater/saltwater interface by using...
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