The U.S. Geological Survey (USGS), in cooperation with the Town of Falmouth, used an existing groundwater flow model to simulate responses of the freshwater hydrologic system in Falmouth, Massachusetts to proposed wastewater-return-flow scenarios. The existing model is a steady-state, three-dimensional MODFLOW-2005 model of the Sagamore flow lens of the Cape Cod aquifer documented by Walter and others (2019). The existing model was updated with groundwater withdrawal and wastewater-return-flow data to represent average conditions for calendar years 2019 through 2023. The updated model was then used to simulate two wastewater-return-flow scenarios associated with the potential installation of an ocean outfall pipe in Falmouth, Massachusetts. This USGS data release contains the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20255066). Associated Scientific Investigations Report: -------------------------------------- Goldstein, K.M.F., and McCobb, T.D., 2025, Simulated hydrologic responses to proposed wastewater-return-flow scenarios in Falmouth, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2025-5066, 19 p., https://doi.org/10.3133/sir2025-5066. References: -------------------------------------- Walter, D.A., McCobb, T.D., and Fienen, M.N., 2019, Use of a numerical model to simulate the hydrologic system and transport of contaminants near Joint Base Cape Cod, Western Cape Cod, Massachusetts: U.S. Geological Survey Scientific Investigations Report 2019-5139, 98 p., https://doi.org/10.3133/sir20185139.