Simulation of Ground-Water Flow and Chemistry to Evaluate Water-Management Alternatives in Kings and Queens Counties, New York

 

Water-management alternatives being considered for New York City involve aquifer storage and recovery, or ASR. An ASR system may store surplus water in an aquifer, then later recover this water in times of short supply. The success of an ASR system depends on the quantity and quality of water that can be withdrawn during recovery phases, which are influenced by hydrogeologic, microbiological, and geochemical factors. Mixing surface waters with ambient ground waters within a deep confined aquifer may cause freshwater/saltwater interface movement, clay swelling, mineral dissolution, new patterns of bacterial growth, and other hydrogeologic consequences. In 2005, data were collected at Tottenville, Staten Island, where a well was drilled through the unconsolidated deposits and into the underlying bedrock. Geophysical surveys and continuous geologic cores were collected from the borehole and archived. A suite of analyses are being conducted which include pore water extraction, carbon content, mineral identification, and bacteria identification. Deep confined water-bearing zones at Tottenville may correlate with units on Long Island and in New Jersey. In 2006, data on the Magothy and Lloyd aquifers on Long Island were collected at three drilling sites operated by the Nassau County Department of Public Works in southwest Nassau County. 

 

To evaluate the potential for ASR, computer models are being developed to simulate the complex interplay of hydrogeologic structures, flow boundaries, aqueous chemical reactions, mineral dissolution and precipitation, ion exchange, and geochemical reaction kinetics.