Simulation of Ground-Water Flow And
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Simulation of Ground-Water Flow and Pumpage in Kings and Queens Counties, Long Island, New York Prepared in cooperation with the New York City Department of Environmental Protection QUEENS COUNTY KINGS COUNTY U.S. Geological Survey Water-Resources Investigations Report 98-4071 Simulation of Ground-Water Flow and Pumpage in Kings and Queens Counties, Long Island, New York By Paul E. Misut and Jack Monti, Jr. ____________________________________________________________ U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 98-4071 Prepared in cooperation with NEW YORK CITY DEPARTMENT OF ENVIRONMENTAL PROTECTION Coram, New York 1999 U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. Geological Survey Charles G. Groat, Director The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. ______________________________________________________________________ For additional information Copies of this report may be write to: purchased from: U.S. Geological Survey U.S. Geological Survey 2045 Route 112, Bldg. 4 Branch of Information Services Coram, NY 11727 Box 25286, Building 810 Denver, CO 80225-0286 ii CONTENTS Abstract............................................................................................................................................................................. 1 Introduction ...................................................................................................................................................................... 1 Purpose and scope .............................................................................................................................................. 3 Previous studies.................................................................................................................................................. 3 Acknowledgments.............................................................................................................................................. 3 Hydrogeology ................................................................................................................................................................... 4 Aquifers and confining units.............................................................................................................................. 4 Hydrologic conditions........................................................................................................................................ 4 Discharge ............................................................................................................................................. 5 Recharge .............................................................................................................................................. 5 Ground-water levels............................................................................................................................. 5 Simulation of ground-water flow ..................................................................................................................................... 9 Model discretization and geometry .................................................................................................................... 10 Boundary conditions .......................................................................................................................................... 13 Streams................................................................................................................................................. 13 Shoreline discharge boundary.............................................................................................................. 13 Saltwater-freshwater interface ............................................................................................................. 16 Subsea-discharge boundaries............................................................................................................... 16 Pumpage............................................................................................................................................... 17 Recharge .............................................................................................................................................. 17 Model calibration and sensitivity analysis ......................................................................................................... 17 Model water budgets .......................................................................................................................................... 23 Sustainability of 1991 pumpage......................................................................................................................... 24 Simulations of proposed pumping scenarios .................................................................................................................... 24 Placement of proposed wells.............................................................................................................................. 24 Results of simulations ........................................................................................................................................ 24 Periodic pumping under 1991 conditions (scenarios 1 and 2)............................................................. 24 Scenario 1 .............................................................................................................................. 30 Scenario 2 .............................................................................................................................. 30 Periodic pumping under “maximum aquifer storage” conditions (scenario 3) ................................... 30 Summary........................................................................................................................................................................... 31 References cited................................................................................................................................................................ 31 Appendix A: Locations and pumping rates of wells used in the Kings-Queens model ................................................... 39 Appendix B: Difference between simulated and measured water levels at selected wells .............................................. 40 FIGURES 1. Map showing location of vertical sections A-A´ and B-B´ in western Long Island, N.Y., and area supplied by ground water in 1997 ............................................................................................................................................ 2 2. Hydrogeologic sections A-A´ and B-B´ in Kings and Queens Counties, N.Y........................................................... 8 3. Maps showing ground-water levels in Kings and Queens Counties, N.Y., in March-April 1993: A. Water-table altitude in upper glacial aquifer......................................................................................................... 10 B. Potentiometric-surface altitude of Magothy and Jameco aquifers ........................................................................ 11 C. Potentiometric-surface altitude of Lloyd aquifer .................................................................................................. 12 4. Hydrograph showing water levels in upper glacial aquifer at observation well Q1249 showing effects of Jamaica Water Supply pumpage ................................................................................................................................ 13 5. Map showing west-central part of refined Kings-Queens ground-water flow-model grid and active area of layer 1 14 6. Diagrams showing model layering along hydrogeologic sections A-A´ and B-B´ in refined Kings-Queens ground-water flow model........................................................................................................................................... 15 iii FIGURES (continued) 7-10. Maps of western Long Island, N.Y., showing: 7. Locations of model stream cells used in revised Kings-Queens ground-water flow model ................................... 16 8. Locations of pumping wells in Kings and Queens Counties, N.Y., that are assumed to have been in operations during 1991 and are represented in refined Kings-Queens ground-water flow model.... 18 9. Percentage of surface area that is impervious in each cell of refined Kings-Queens ground-water flow model.... 19 10. Rates of recharge applied in simulation of 1990’s conditions in refined Kings-Queens ground-water flow model 20 11-14. Maps showing ground-water levels in Kings and Queens Counties, N.Y., indicated by refined model: 11. Simulated 1991 water levels in A. Layer 1 (water table) and B. Layer 2 (potentiometric surface of Jameco and upper Magothy aquifers).................................................................................................................................. 21 C. Layer 3 (potentiometric surface in basal part of Magothy aquifer) and D. Layer 4. (potentiometric surface in Lloyd aquifer........................................................................................................................................................... 22 12. Scenario 1—water levels in Kings and Queens Counties after 10 months of pumping totaling 30,000 million gallons (100 million gallons per day) in: A. Layer 1 (water table) and