New Hampshire Geological Survey
Link to:New Hampshire Geological Survey Groundwater Information
NGWMN Contact:
Michael Howley
(603) 271-7332
michael.w.howley@des.nh.gov
The New Hampshire Geological Survey (NHGS) is a water-level data provider to the National Groundwater Monitoring Network (NGWMN). In the 1990's, NHGS acquired 12 wells from the USGS that had data going back to the late 1940's and early 1960's. Since then, NHGS groundwater monitoring has expanded to 32 well sites, all of which are being served to the NGWMN Portal. NHGS has been a part of the Network since 2016.
NHGS provides water-level data from the he Sand and gravel aquifers (glaciated regions) and the New England crystalline-rock aquifers.
NGWMN Projects:
2016 Round 1: 6/1/2016 to 5/31/2018
Initial project was to become a NGWMN data provider. A network of 29 trend water-level was added to the NGWMN.
Project provides persistent data services work, site information gap filling, and well maintenance. Persistent data service includes work to update existing web services. Site information updated from a GPS survey of the wells. Well integrity testing (slug tests) done at 17 wells.
Project provides persistent data services, fills gaps in site information, and performs well maintenance. Gap filling work focuses on two new wells which are being added to the network. This work will update construction information using an optical survey and will update the horizontal and vertical coordinates of the wells. Well maintenance work involves redevelopment pumping of 10 wells.
2019 Round 1: 7/15/2019 to 7/15/2021
Project is to add a new site to the NGWMN that will include gap filling and site maintenance at the new well. Maintenance work will also be performed at three other wells to replace protective casings to ensure the integrity of the wells. The project also provides persistent data service for the second year of the project.
Project is to provide persistent data services for two years to ensure that data continues to flow to the NGWMN Data Portal, and that sites and site information are up to date. They will do well maintenance at a site to protect the well from winter freezing. They will also drill three NGWMN replacement wells.
This project is to replace continuous water-level equipment at 20 wells and equip one additional well for continuous monitoring.
2022: 7/15/2022 to 7/14/2024
This project is to provide persistent data services for two years and to ensure that the metadata for Network sites are up to date. The NHDES will do borehole camera work to fill well construction data gaps at a well, replace surface casing at a well, pump 14 overburden wells for well integrity evaluation, drill a replacement well, and drill a new bedrock well to fill a gap in the NGWMN.
2023: 7/1/2023 to 6/30/2025
This project is to video log two wells, replace damaged casing at one well, replace the well cover on another well, pump ten wells, drill two new wells, and install continuous monitoring equipment at two existing wells.
NGWMN Presentations:
December 2016 presentation to SOGW
Site Selection and Classification
Site Selection
All 32 active monthly and continuous observation wells operated by the NHGS were selected for inclusion in the NGWMN. The wells represent both bedrock and shallow aquifers throughout the state. Eighteen of the selected wells are equipped with pressure transducers and provide daily data. The remaining sites are measured monthly.
Site Classification
The primary guiding principle for well selection and measurement that NHGS has consistently applied in managing the network has been that water levels recorded should be reflective of ambient groundwater conditions unaffected by anthropogenic or tidal influences. Based upon this initial criterion, our wells should fall within the NGWMN category of "Background" subnetwork monitoring. And, moreover, based on monitoring frequency, wells in the network are classified as "Trend" monitoring wells.
Many years have passed since the initial siting of most of the network wells, representing a period of time during which New Hampshire has experienced significant population growth and development. This development has the potential to influence groundwater levels in the vicinity of these sites. With this in mind, NHGS undertook an analysis of the location of each well using a Geographic Information Systems (GIS). We quantified and analyzed metrics for each well of land cover/land use, hydrologic modification (road and sewage/drainage infrastructure), topographic position (hypsometry and manual observations) and documented groundwater withdrawals. These results were used to rank each well as to the potential for anthropogenic impacts. From these rankings, we emphasized scrutiny of well hydrographs. Hydrographs of each well were plotted and used to aide in determinations of anthropogenic impact. Initially, the plots were reviewed to determine the seasonality of hydrograph response. When warranted by suspicious changes in each well hydrograph, additional analysis was performed by using correlation analysis with daily precipitation records from the closest weather station. This allowed potential discrimination of anthropogenic impacts versus impacts from evapotranspiration, earth tides and barometric fluxes. The results of this analysis indicated that all but three wells are acceptable for a "Background" subnetwork. The wells that are likely impacted by anthropogenic effects are the Concord bedrock wells, CVWB-01 and CVWB-02, and NAW-218. The Concord bedrock wells show a clear, periodic impact from drawdown of the groundwater table likely due to a pumping well in the vicinity. NAW-218 in Nashua, NH is located fairly close to a drinking water reservoir whose outlet is regulated by a dam. Unfortunately, only monthly hand level measurements are collected from NAW-218 which is not frequent enough to validate this assumption. Despite these short-comings, these wells continue to be useful in measuring groundwater conditions in these areas New Hampshire and can be classified as "Trend" monitoring Wells in a "Suspected Changes" subnetwork.
Data Collection Techniques
NHGS reviewed data collection methods and any Standard Operating Procedures currently and historically employed. We determined that the method we employ for using an electronic tape to measure groundwater levels is consistent with the United States Geological Survey (USGS) procedure found here. One item this comparison did elicit is the need for NHGS to calibrate and periodically (annually) compare our electronic tape devices.
We also determined that pressure transducer data logger data is also being collected consistent with the USGS procedure found here. This review did, however, highlight the need to document the logger condition during each monthly measurement and perform a field calibration, as necessary. Our current practice does not provide for immediate field calibration which is typically delayed until appropriately trained personnel can perform this operation. We are reconsidering this approach.
Data Management
NHGS uses the Consortium of Universities for the Advancement of Hydrologic Science, Inc. (CUAHSI) HydroServer data system to store and disseminate data (Maidment 2008). This system consists of several standardized pieces of software. The data store is a SQL Server instance with a schema specifically designed to store time series environmental data. The data store also provides for metadata and controlled vocabulary organization and is integrated with desktop software to load, analyze and qualify data. The system provides web services that allow access to time series data formatted in WaterML 1.1. Time series data will be provided to the NGWMN Portal using this web service. As of March 2017, all data systems are in place on production servers.
Most of NHGS wells have previously been part of the USGS Ground Water Site Inventory (GWSI) database. Therefore, NHGS obtained from GWSI monthly hand-measured data across the period of record for each well. NHGS did not heavily scrutinize these measurements as the data had already undergone USGS review.
An evaluation of hourly data from pressure transducer loggers from 18 wells was conducted. Data from these wells range back to 2011/2012 and had not been qualified in any meaningful way. Python scripts were created to review these data and eliminate obvious bad data, overlaps in record, confirm measurement time intervals (ensuring consistency of logger recording) and perform a comparison to corresponding monthly hand measurement values. Anomalous values from these analyses were flagged for review. If errors were found they were either retained in the record or removed. Records with significant departures from the monthly comparison hand level measurements were inspected individually, largely by plotting hydrographs. In a few cases, the hydrographs indicated a consistent but clear departure from the monthly measurements. In these instances a mathematical transformation was calculated for the hydrograph and if a 95% or greater r2 was achieved, the transformation was applied to the data.
Following qualification, data were loaded into SQL Server with all associated record and station level metadata. This effort highlighted the need to develop a written QA/QC standard operating procedure for handling data from the loggers and hand level measurements. These procedures will be used for qualifying and handling data going forward.
Other Agency Information
Information on the NHGS Groundwater Level Monitoring Program can be found at: https://www.des.nh.gov/organization/commissioner/gsu/gwlmp/index.htm
The New Hampshire groundwater monitoring network is used to address several critical issues in New Hampshire
- Drought indicators
- Climate change trends
- Basic data for ambient conditions