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Ground Water and Aquifers

Background:

More than 50% of New Hampshire's population depends on groundwater supplies for drinking water. Groundwater particularly important during the dry periods when it is often the primary source of water for streams and rivers. Groundwater is found below the surface between particles of sands, silts and clays or in the cracks and fractures of bedrock. Aquifers are saturated zones in sediments, such as sand and gravel, and in fractured rock formations that receive, store and transmit water to wells and springs. Groundwater is recharged when rain and melting snow percolate down into the saturated zones. While groundwater quality in NH is generally good, groundwater is vulnerable to contaminatination from a variety of sources, e.g. chemical spills, leakage from landfills and underground storage tanks, septic systems, road salt, etc. Wellhead Protection Areas (WHPA) are the areas around a public water supply. The state's wellhead protection program enables municipal authorities, water suppliers and other local entities to delineate protection areas, identify potential contamination sources and actively manage land use in the WHPA. Increased impervious surfaces which reduce infiltration to groundwater and increase surface runoff can have a significant effect on recharge to groundwater supplies.

As the global, national, regional and local levels, ground water is the largest distributed store of fresh water and plays a central part in sustaining ecosystems and enabling human adaptation to climate variability and change. The strategic importance of ground water for water and food security will probably intensify under climate change as more frequent and intense climate extremes (droughts and floods) increase variability in precipitation, soil moisture and surface water. Protection of locally important aquifers by protecting the lands that overlie them is an important priority for maintaining adequate drinking water supplies into the future.

Basic NRI - What to Include:

Many of New Hampshire's reliable aquifers are found in deep, coarse-grained stratified drift deposits (sands and gravels), which were deposited by glacial meltwater at the time of deglaciation. The location and extent of these aquifers should be mapped along with transmissivity values which are available through GRANIT and GRANITVIew. See Sample Water Resources Map to view stratified drift aquifer information. Transmissivity is a measure of how much water can be transmitted horizontally in an aquifer. Higher transmissivity values indicate greater groundwater availability. Wellhead protection areas can also be shown on the map.

CLIMATE CHANGE As the world's largest distributed store of fresh water, ground water plays a central part in sustaining ecosystems and enabling human adaptation to climate variability and change. The strategic importance of ground water for global water and food security will probably intensify under climate change as more frequent and intense climate extremes (droughts and floods) increase variability in precipitation, soil moisture and surface water. The strategic importance of ground water for global water and food security will probably intensify under climate change as more frequent and intense climate extremes (droughts and floods) increase variability in precipitation, soil moisture and surface water.

Detailed Inventory Studies:

Favorable Gravel Well Analysisis (FGWA) is a technique developed by NH DES to help water suppliers and community planners take into account water quality and quantity constraints when analyzing stratified drift aquifer maps to review potential sites for new community wells. FGWA buffers out (based on state regulations) all potential and known contamination sources within an area underlain by stratified drift aquifersand takes into account potential well yield to show the actual areas that is potentially suitable for siting a community well. The FGWA mapped information also shows these sits in relation to existing conservation lands. Information about FGWA is housed on the website of the Society for the Protection of NH Forests, as part of a collaborative project between the Forest Society and NH DES. More information about FGWA can be found in the publication A Guide to Identifying Potentially Favorable Areas to Protect Future Municipal Wells in Stratified-Drift Aquifers.  The FGWA map on the Forest Society website is a PDF map of the entire state. To clip out the information for your community, increase the zoom of the Adobe PDF file to 200%. Using the sliding bars at the bottom and side of the page, move to the area where your community is located. Using the camera tool, click and drag your mouse over the area of interest. Copy the image into a Word or Powerpoint document. From there you can save it as a jpeg or png image. GIS users need to contact the NH DES GIS Coordinator  (kristen.svendsen@des.nh.gov or (603) 271-7483) to get the shapefiles for the FGWA data (the data is not available on GRANIT).
A Comprehensive Ground Water Resources Study can help a community interpret and understand their groundwater resources in more depth. By analyzing existing groundwater information (e.g. groundwater quality data, well locations and yields, etc.) and providing any additional necessary documentation, the comprehensive study can help to further identify areas where groundwater protection might be appropriate, look for potential conflicts between land use and groundwater protection, and address wellhead or groundwater protection plans. This type of assessment would require professional expertise.

Additional Resources:

NH DES Drinking Water and Groundwater Bureau (information about groundwater and ground water protection)
NH DES Water Supply Land Protection Grants
(funds to protect land around aquifers and other important drinking water sources)
Groundwater Protection for Municipalities
(NH DES)
Guide to Ground Water Protection  (NH DES)
Favorable Gravel Well Analysis Information and Map
(Forest Society)
New Hampshire Water Resources Primer provides information about the state’s water resources (including wetlands) and the challenges faced in sustainably managing them