Souhegan River Water Management Plan
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NHDES-R-WD-11-15 Souhegan River Water Management Plan 30 August 2013 This Page Intentionally Blank NHDES-R-WD-11-15 Souhegan River Water Management Plan Prepared by Watershed Management Bureau NH Department of Environmental Services With contractor assistance from Normandeau Associates, Inc., University of New Hampshire, and Rushing Rivers Institute Thomas S. Burack Commissioner Vicki Quiram Assistant Commissioner Harry T. Stewart. P. E., Director Water Division 30 August 2013 This Page Intentionally Blank Table of Contents Page EXECUTIVE SUMMARY ............................................................................. viii SOUHEGAN RIVER WATER MANAGEMENT PLAN .............................. 1 I. INTRODUCTION ..................................................................................... 1 A. Definition of Protected Instream Flows and Identification of Protected Entities .................2 B. Natural Flow Paradigm .........................................................................................................3 C. Protected Flow Assessment for Flow-Dependent, Instream Public Uses .............................3 D. Souhegan River Protected Instream Flows ...........................................................................4 1. Protected Flows for the Upper and Lower Souhegan River .............................................4 2. Protected Instream Flow for Human Uses ........................................................................4 3. Protected Instream Flows for Fish and Aquatic Life ........................................................5 4. Protected Instream Flows for Riparian Wildlife and Vegetation......................................9 II. SOUHEGAN RIVER WATER MANAGEMENT PLAN ................... 11 A. Souhegan River Water Management Planning Area ...........................................................11 1. Watershed Description ....................................................................................................13 2. Designated River Description .........................................................................................13 B. Individuals Affected by the Water Management Plan ........................................................14 1. Affected Water Users ......................................................................................................14 2. Affected Dam Owners ....................................................................................................17 C. Is There a Present Need for Management of the Souhegan River Instream Flows? ...........19 1. Aggregate water use versus standards for stream flow ...................................................19 2. Water use versus the protected instream flows ...............................................................20 3. Water use and population trends .....................................................................................21 4. Impervious Surface and Other Watershed Conditions ....................................................22 D. Are the Souhegan River Instream Protected Flows Manageable? ......................................22 1. Management of Water Use .............................................................................................22 2. Management by Releasing Stored Water from Impoundments ......................................22 3. Deficit Flow Analysis .......................................................................................................23 Lower Souhegan River .....................................................................................................24 Upper Souhegan River .....................................................................................................25 4. Certain Bioperiods and Common Flows Will Not be Actively Managed ......................26 5. Relief Flow Release Rates By Bioperiod..........................................................................27 6. Effects of Relief Flows on Impoundment Levels .............................................................27 1. De Minimis Amount ........................................................................................................32 2. Conservation Plan Strategy .............................................................................................32 3. Water Use Plan Strategy .................................................................................................33 4. Dam Management Plan Strategy ....................................................................................33 Relief Flows Applied to Catastrophic Conditions ............................................................33 Relief Flow Volumes Calculated ......................................................................................34 Relief Flows Applied ........................................................................................................34 Sources of Relief Flow ......................................................................................................35 Other Dam Management Strategies .................................................................................35 5. Strategy for Management of Other Protected Instream Flow Criteria ............................35 iii 6. Strategy for Ensuring Continued Flow Variability .........................................................36 F. Application of Components of the Souhegan River Water Management Plan ...................36 1. Conservation Plans..........................................................................................................36 Agriculture ........................................................................................................................37 Aquaculture ......................................................................................................................37 Bottled Water ....................................................................................................................37 Hydroelectric Power ........................................................................................................37 Industrial ..........................................................................................................................38 Irrigation ..........................................................................................................................38 Remediation ......................................................................................................................39 Water Supplies ..................................................................................................................39 2. Water Use Plan ..............................................................................................................41 Agriculture ........................................................................................................................41 Aquaculture ......................................................................................................................41 Bottled Water ....................................................................................................................42 Hydroelectric Power ........................................................................................................42 Industrial ..........................................................................................................................43 Irrigation ..........................................................................................................................44 Amherst Country Club/Ponemah Green Family Golf Center ..........................................45 Souhegan Woods Golf Club .............................................................................................45 Remediation ......................................................................................................................46 Water Supplies ..................................................................................................................47 Greenville Water Works ...................................................................................................47 Pennichuck Water – Souhegan Woods Community Water Supply ...................................48 Milford Water Works ........................................................................................................49 Wilton Water Works .........................................................................................................49 3. Dam Management Plan ...................................................................................................51 Flood Control ...................................................................................................................52 Hydroelectric Power ........................................................................................................55 Recreation ........................................................................................................................55 Water Supply ....................................................................................................................56 G. Financial Assistance ............................................................................................................57 H. Water Management Plan Implementation ...........................................................................57 1. Dam Management Plan Implementation ........................................................................58 2. Management