CDM DEM-Office of Water Resources EOEA - Nashua River Basin Team Hydrologic Assessment Nashua River Watershed March 2002 2.5 2.0 1.5 1.0 0.5 0.0 JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC 60 50 Wastewater Flow Existing Flow 40 Virgin Flow 30 20 10 0 River River Brook RIVER River 2 NORTH Stillwater Stillwater Reservoir Nissitissit Nissitissit NASHUA Wachusett Wachusett Quinapoxet James Brook James Mulpus Brook Mulpus Catacoonamug Catacoonamug Contents Introduction 1.1 General ...................................................................................................................... 1-1 1.2 Watershed Description............................................................................................ 1-1 1.3 Overview of Assessment......................................................................................... 1-2 Background Information 2.1 General ...................................................................................................................... 2-1 2.2 Community Land Areas ......................................................................................... 2-1 2.3 Surficial Geology and Aquifer Delineations ........................................................ 2-1 2.4 Water Supplies ......................................................................................................... 2-4 2.5 Wastewater Discharges......................................................................................... 2-26 2.6 Population............................................................................................................... 2-29 2.7 Streamflow.............................................................................................................. 2-32 Water Supply Needs 3.1 General ...................................................................................................................... 3-1 3.2 Watershed Communities ........................................................................................ 3-1 3.3 Water Service Areas................................................................................................. 3-1 3.4 Forecasted Population Growth .............................................................................. 3-3 3.4.1 Methodology................................................................................................. 3-3 3.4.2 Current Populations and Future Projections ........................................... 3-5 3.5 Water Needs Projections......................................................................................... 3-5 3.5.1 Methodologies.............................................................................................. 3-5 3.5.2 Comparison and Summary of Water Need Projections ....................... 3-12 3.5.3 Non-Community Water Supply Needs .................................................. 3-14 3.5.4 MWRA and Worcester Needs.................................................................. 3-14 3.6 Water Conversation Assessment ......................................................................... 3-14 3.6.1 Water Conservation Standards ................................................................ 3-14 3.6.2 DEM Water Conservation Plan for Public Water Suppliers ................ 3-15 3.6.3 Review of Public Water Suppliers ........................................................... 3-17 3.6.4 Screening Methodology ............................................................................ 3-17 3.6.5 Results of WCP Review............................................................................. 3-17 3.6.6 Recommendations...................................................................................... 3-19 Water Supplies at Risk ) i 10821-26411 RT.REPORT Hydrologic Assessment of the Nashua River Watershed Table of Contents 4.1 General ...................................................................................................................... 4-1 4.2 Methodology ............................................................................................................ 4-1 4.2.1 MCP Site Coverage...................................................................................... 4-2 4.2.2 Solid Waste Site Coverage .......................................................................... 4-2 4.2.3 Public Water Supply Coverage.................................................................. 4-3 4.3 Evaluation Methodology ........................................................................................ 4-4 4.3.1 Criteria for Evaluating Potential Risk for Public Water Supplies......... 4-4 4.4 Findings..................................................................................................................... 4-6 4.4.1 Public Water Supplies ................................................................................. 4-6 4.4.2 MCP Sites ...................................................................................................... 4-6 4.4.3 Solid Waste Facilities................................................................................. 4-11 4.4.4 Supplies Potentially at Risk ...................................................................... 4-11 Wastewater Discharges 5.1 General ...................................................................................................................... 5-1 5.2 Watershed Communities ........................................................................................ 5-1 5.3 Present Service Areas.............................................................................................. 5-1 5.4 Planned Service Areas............................................................................................. 5-3 5.5 Existing Wastewater Discharges............................................................................ 5-3 5.6 Future Wastewater Discharges .............................................................................. 5-5 Subarea Inflow/Outflow Analysis 6.1 General ...................................................................................................................... 6-1 6.2 Subareas ....................................................................................................................6-1 6.3 Inflow/Outflow Methodology............................................................................... 6-1 6.4 Existing Inflow/Outflow ...................................................................................... 6-17 6.4.1 Average Annual 2000 ................................................................................ 6-17 6.4.2 August 2000................................................................................................ 6-26 6.5 Projected Future Inflow/Outflow ....................................................................... 6-28 6.5.1 2020 Annual ................................................................................................ 6-28 6.5.2 August 2020................................................................................................ 6-35 Virgin Flow Analysis 7.1 General ...................................................................................................................... 7-1 7.2 Methodology ............................................................................................................ 7-1 7.3 Subarea Flows........................................................................................................... 7-4 7.4 Aquifer Yields........................................................................................................... 7-4 Subarea Flow and Stream Flow Changes 8.1 General ...................................................................................................................... 8-1 ) ii 10821-26411 RT.REPORT Hydrologic Assessment of the Nashua River Watershed Table of Contents 8.2 Methodology ............................................................................................................ 8-1 8.3 Subarea Flow Impacts ............................................................................................. 8-3 8.3.1 7Q10 and Average August Flows........................................................... 8-3 8.3.2 Average Annual and Average Winter Flows ....................................... 8-6 8.4 Stream Flow Changes.............................................................................................. 8-6 8.5 Flow Stressed Systems .......................................................................................... 8-13 Findings and Recommendations 9.1 General ...................................................................................................................... 9-1 9.2 Water Supplies ......................................................................................................... 9-1 9.3 Wastewater Discharges........................................................................................... 9-2 9.4 Inflow/Outflow Analysis ....................................................................................... 9-2 9.5 Subarea Flow and Stream Flow ............................................................................. 9-4 9.6 Recommendations ................................................................................................... 9-5 Appendix A Appendix B ) iii 10821-26411 RT.REPORT Hydrologic Assessment of the Nashua River Watershed Table of Contents Tables Table 2-1 Communities in the Nashua River Basin....................................................