Planning for Future Water Supply Needs. Brandon Kernen NH Department of Environmental Services

Transcription

1 Planning for Future Water Supply Needs Brandon Kernen NH Department of Environmental Services &

2 Objectives 1)Legal Considerations 2)Methods to Assess Future Water Use 3)Methods to Assess Water Availability

3 Groundwater Quantity Management Questions Should municipalities be allowed to protect water quantity to a higher level (this is often done with water quality)? Should the state and municipalities ensure reasonably anticipated future water needs are protected? Can municipalities regulate groundwater withdrawals the State does not?

4 Existing Groundwater Management Approach in NH (statutory law) 1) Approve new land uses and associated consumptive withdrawals <57,600/day without assessing availability or viability 2) For new large groundwater withdrawals proactively ensure existing water users and resources are protected. Reduce permitted withdrawal volume in the future as needed to maintain public water supply needs. 3) Do nothing regarding the pre-1998 large groundwater withdrawals

5 Current Groundwater Regulation in NH NH Only Regulates No More than 7% of Groundwater Withdrawals Future water use needs are not considered when the state issues a large groundwater withdrawal permit 93% of the groundwater use in the state is not subject to regulation Predate the statute Below withdrawal threshold 60% of groundwater use in the state occurs at levels below the permitting threshold Neither the state or towns assess local well interference impacts for projects with new withdrawals that do not require a large groundwater withdrawal permit

6 Study Background Legislature conducted 9 regional public meetings to discuss how NH should regulate groundwater Developed a report with recommendations Conducted 4 additional regional public meetings to see if the recommendations were responsive to the public comments

7 Recommendation of a study Recognizing that land use planning and regulation at the municipal level ultimately affects how water resources are used, the subcommittee finds that there is a need to expand a municipality s role in groundwater management in New Hampshire in order to effectively evaluate proposed withdrawals in the context of long-term sustainability and public benefit.

8 Recommendation 1 Enable Municipalities to Regulate the Withdrawals the State Does Not (amend state law to enable this) Develop new land use regulations Well yield adequacy testing Water use availability and adverse impact studies The Groundwater Commission has developed model regulations to follow

9 Recommendation 2: Future Use State/Municipal Partnership Consumptive Water Use Capacity Plan Using Guidance developed by the State: 1) Estimate the capacity of a watershed 2) Estimate how much water is currently displaced through use from a small watershed 3) Estimate future use 4) Estimate the maximum amount of water that can be displaced in the future 5) The State reviews and approves the plan 6) Enable towns to make land use decisions in accordance with the plan (through a zoning overlay based on the plan) Ensures there is adequate water available for consumption on a reasonable planning horizon before approving proposed projects

10 Approach for Holistic Management of Groundwater Quantity Y GW Withdrawal > 57,600 gallons/day? N Existing and Future Water Needs Are Protected Consumptive Water Use Plan? Y N Existing Water Needs Are Protected Y Consumptive Water Use Plan? GW Withdrawal Land Use Regulation? Y N N Existing Water Needs Are Protected from Large Withdrawals Future and Existing Water Needs Are Protected from All Withdrawals Existing Water Needs Are Protected from All Withdrawals

11 What Data is Available to Estimate Water Use in New Hampshire?

12 Measured Water Use Data Available in New Hampshire Water use for all withdrawals, transfers and discharges that average over 20,000 gallons per day NPDES permitted discharges Public water supplies

13 Water Use that Needs to Be Estimated (not directly measured in NH) Domestic private wells Non domestic private wells extracting <20,000 gallons per day Wastewater discharges without a NPDES permit & <20,000 gallons per day

14 Tools to Estimate Water Use in New Hampshire - Methodology Methods for and estimates of 2003 Projected Water Use in the Seacoast Region, Southeastern NH (USGS OFR ) Methods for Estimating Withdrawal and Return Flow by Census Block for 2005 and 2020 for New Hampshire (USGS OFR )

15 Tools to Estimate Water Use in New Hampshire Data Tools Census Block Data (people, households, demographics) Water & sewer system distribution system coverage is GIS Population Projections Dun and Bradstreet Data (type, location and number of employees for businesses information must be purchased) Hydrography data and topographic maps to delineate watershed boundaries

16 Calculation of Consumptive Water Use Water Withdrawals Domestic Self Supplied Domestic Water System Withdrawals Non Domestic Water System Withdrawals Non Domestic Withdrawals Registered Withdrawals Water Returns Domestic On-site Non Domestic On-site - Registered = Discharges/Returns Non Registered Sewer System Returns Consumptive Use Data in red needs to be estimated

17 USGS OFR

18 OFR Estimating Water Use (non registered non domestic water use) Use Dun and Bradstreet Data to Identify Water Users Multiply water use by 0.90 to estimate return flow Determine if return flow goes to onsite or sewer discharges USGS

19 Estimating Water Use (non registered domestic water use) 1) Estimate number of people that obtain water from private wells and non registered public water systems and multiply by 75 gallons/person 2) Estimate that 84% of the water use is returned onsite or a sewer system Water use figures based on metered data as documented in USGS OFR

20

21

22 Estimating Future Water Use (options) Broad Brush Approach - Multiply increased water use by population projections/assume more water is extracted in the vicinity of existing sources Refined Approaches Utilize Regional Traffic Demand Models Utilize town Build Out Analysis which has been completed by regional planning commissions in some regions of the state. Analyze master plan and zoning and make development estimates

23 What Data is Available to Estimate Water Availability?

24 Available Data for Estimating Regional Availability Well construction reports dating back to 1984 (well yield trends, replaced wells, deepened wells) Watershed recharge and streamflow frequency estimation tool (USGS -des.nh.gov/organization/commissioner/pip/factsheets/geo/ documents/geo- 9.pdf Stratified Drift Aquifer Studies (USGS) Surficial Geology Mapping (USGS & NHGS) Seacoast Geologic Data Viewer (recharge, depth to bedrock, water use, well yield trend) - App/

25 Water Availability Concepts Aquifer Capacity Ensure withdrawals do not exceed the rate of recharge to aquifers on average and that adequate seasonal aquifer storage exists for high water use/low recharge periods (prevent long-term aquifer dewatering) Well Interference Ensure multiple pumping wells do not superimpose drawdowns unreasonably over one another. Watershed Capacity Ensure consumptive water uses do not adversely impact surface water baseflow (usually the limiting factor)

26 Question: How Much Water Do We Have? Answer: In most cases it depends on how much streamflow degradation is acceptable.

27 Methods to Estimate Streamflow Needs 1) Hydrological 2) Hydraulic Rating 3) Habitat Rating 4) Holistic

28 Hydrological Methods Used in the Northeast Amount of Water that Can Be Consumed: NHDES 4% of the Seasonal Q60 (flow that is exceeded 60% of the time) NJDEP 25% of the difference between median September flow and 7Q10 flow State of Rhode Island 50% of 7Q10 MADEP 7Q10 or 50% of August median flow

29 What do we need to do? Evaluate on a regional basis the amount of water that may be consumed Low-Flow Statistics Existing and projected withdrawals and returns Identify watershed capacity Withdrawals Returns Watershed Capacity

30

31

32

33 Pilot Groundwater Management Study See er_management_plan Identifies available water supply and future needs for the Bloody Brook Watershed.