[photo: Drilling the East Kingston Bedrock Monitoring Well Site.]
Before 2009 the NHGS collected data from 22 wells installed mainly in the shallow, stratified drift aquifers in the state, and shared that data with the U.S. Geological Survey for posting on its web site. This small network of wells comprised the New Hampshire Groundwater Monitoring Network. Although 97 percent of all water wells in New Hampshire are drilled into crystalline bedrock, only one well in the network monitored this important statewide aquifer. Moreover, this bedrock well is only 102.7 feet deep, which is significantly less than the average depth of all bedrock wells in the state (mean total depth = 359.9 feet).
Thus the state of New Hampshire appropriated funds to expand the state's groundwater monitoring network to include additional bedrock wells. The network appropriation was only sufficient to install nine additional bedrock wells, so it was imperative that the state optimize the monitoring network design in order to collect meaningful information. New Hampshire is underlain by crystalline bedrock that is composed of 154 identified geologic formations. The state's Groundwater Well Inventory database currently has records for some 120,000 private and public wells, which includes well depth, yield, and aquifer type (bedrock or surficial) information. Histograms showing the relationship of yield as a function of depth, and the distribution of total depths, can vary considerably among rock types. However, this information, combined with GIS tools, census data, and the 1:250,000 state bedrock geologic map, made it possible to rank the most productive formations so they could be targeted for monitoring. The ranking was based on the formation area, number of wells, and population served.
To ensure long-term access to the well network infrastructure, and to locate wells in areas that are minimally impacted by groundwater use, NHGS installed the bedrock wells in state-owned or managed lands. The goal for this network is to monitor background, or non-stressed groundwater conditions, which are likely to occur in undeveloped lands such as parks. The bedrock wells were drilled in secluded locations as to not interfere with park activities or infrastructure. Some may be equipped with digital data loggers, but this equipment, for the most part, should be self-contained within the protective steel casing that encases the wells. The monitoring design includes installing a well nest (e.g., two wells at different depths installed in close proximity to each other) at each monitoring site. Each well would have screened intervals to collect water at elevations above and below the mean well depth specific to a formation in order to capture variation in water quality and water levels in the vertical dimension. NHGS anticipates minimal impact to any cooperating state lands managed by the Department of Resources and Economic Development. Moreover, the wells could be used as an outreach tool for Park interpretative programs in order to engage and educate the public on the importance of monitoring and managing the state's water resources.
For more information, please contact Rick Chormann at (603) 271-1975 or [email protected]