19 DECEMBER 2024 WorldWide Drilling Resource® Long Island’s Groundwater Sustainability Project Adapted from Information by USGS and DEC The U.S. Geological Survey (USGS) has partnered with the New York State Department of Environmental Conservation (DEC) to conduct a comprehensive study of the Long Island aquifer system, which supplies water to more than 2.8 million New Yorkers. The project is a multiphase effort to develop a comprehensive state-of-the-art 3D groundwater model to understand Long Island’s sole source aquifer, help make informed, scientifically driven water use decisions, and bolster water supply sustainability and resiliency. The study simulates changes in aquifer recharge, groundwater pumping, and sea level position to determine the effects of these changes on water levels, streamflow, and saltwater intrusion from 1900 to present, and can be used to simulate the aquifer system’s response to various hydrologic stresses in the future. The approach for this investigation consisted of three main components. The hydrogeologic framework component provided updated hydrostratigraphic surfaces and unit extents, building upon the last regional framework update of the aquifer system. As part of this update, a network of new groundwater wells were installed at about 25 locations in the Lloyd and Magothy aquifers throughout the Island to fill in substantial data gaps. During and after completion of the newly drilled wells, lithologic core samples were collected and analyzed to improve the understanding of the hydrogeologic framework. Borehole-geophysical logging techniques were also used to provide additional information on the geology, as well as aquifer salinity, as part of the saltwater-interface mapping component of the investigation. The saltwater-interface mapping component used borehole-geophysical logs collected at existing and newly installed wells and surface-geophysical soundings using time-domain electromagnetic technology. This effort will build upon earlier studies conducted at a much coarser scale throughout the Northern Atlantic Coastal Plain aquifer system. The final model was used to simulate various scenarios, including changes in groundwater withdrawals, aquifer recharge management, and climate change. DEC will use this tool to predict the outcomes of various water withdrawal management strategies. Based on current and future model scenario outcomes, DEC will work with partners to develop policies and best management practices to protect Long Island’s groundwater resources. “Protecting Long Island’s sole source aquifer is critical, and this comprehensive science-driven modeling is an important tool for DEC and water supply stakeholders to manage this precious water resource effectively and efficiently,” DEC Interim Commissioner Sean Mahar said. “DEC looks forward to continuing this collaborative effort with U.S. Geological Survey to identify challenges and advance actions to ensure clean drinking water supplies for the long term.” Sediment core sample from the Magothy aquifer at 800 feet below land surface during the drilling of a well. Photos courtesy of USGS. Time-domain electromagnetic survey collected by a USGS scientist in Queens County, New York. WTR
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