DEC Releases Long Island Groundwater Sustainability Project Phase 1 Study Results

The New York State Department of Environmental Conservation (DEC), in collaboration with the United States Geological Survey's (USGS) New York Water Science Center, today announced the release of the Long Island Groundwater Sustainability Project (LIGWSP), the Island-wide groundwater model, and Phase 1 study and scenario results. Phase 1 focused on the aquifer system beneath Kings, Queens, and Nassau counties and provides valuable information about how the aquifer reacts under various scenarios, including sea level rise, drought, pumping, and more. 

"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."

"The results of this study will advance our scientific understanding of Long Island's groundwater-flow system," United States Geological Survey's New York Water Science Center Director Robert Breault said. "Through use of this knowledge, water suppliers and policymakers can better manage the Long Island aquifer system."

Long Island's sole source aquifers are used to supply water to more than 2.8 million New Yorkers. Factors such as over-pumping, population increase, pollutants, and climate change can stress the aquifer system and public water supply.

The Long Island Groundwater Sustainability Project is a multi-phase effort initiated in 2016 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 on Long Island. The study simulates changes in aquifer recharge, groundwater pumping, and sea-level position to determine the effects of these changes on water levels, streamflows, 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. Phase 1 results are available on the Groundwater Sustainability of the Long Island Aquifer System webpage.

Phase 1 major findings include:  

• location of the boundary between fresh and salty groundwater is most likely much closer to the coastline than previously thought;
• historical onshore saltwater intrusion in Kings and Queens counties has not receded, despite the cessation of groundwater withdrawals since the early 1990s;
• although saltwater intrusion remains a concern in certain localized areas of western Long Island, presently saltwater intrusion is not a significant concern for its overall water supply; and
• increases in aquifer recharge and sea level in response to climate change can increase water levels and stream flows, creating concerns for groundwater flooding of subterranean infrastructure in low-lying areas where the unsaturated zone is already thin.

Phase 2 of the study, which includes well drilling, data collection, and model recalibration for Suffolk County, is anticipated to be complete in 2025. Phase 3 will identify and fill data gaps identified during Phases 1 and 2 and will include long-term monitoring and modeling maintenance.

DEC anticipates more detailed analysis of the phase 1 scenario results and future phase 2 and 3 results will lead to more understanding of areas and issues of concern. 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.

Visit DEC's website for more information about the Long Island Well Program.

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