EVALUATION OF RECENT DROUGHTS IN NEW HAMPSHIRE USING HIGH-RESOLUTION SPATIAL AND TEMPORAL DATA FROM THE NEW HAMPSHIRE GROUNDWATER LEVEL MONITORING NETWORK

The New Hampshire Groundwater Level Monitoring Network (NH GWLMN), maintained by the New Hampshire Geological Survey, records variations in groundwater levels in 33 dedicated monitoring wells distributed throughout the State of New Hampshire. The purpose of the NH GWLMN is to evaluate the effects of meteorological drought on groundwater conditions and availability within New Hampshire and to evaluate the effects of longer-term climate trends on groundwater. The NH GWLMN serves as a critical resource to both New Hampshire Department of Environmental Services’ internal and statewide Drought Management Teams. Groundwater level data are recorded from 22 overburden wells and 11 bedrock wells located at 21 unique sites at either monthly or hourly frequency.

New Hampshire Geological Survey analyzed the timing and spatial patterns of groundwater level variations recorded in the NH GWLMN wells during three drought events that have occurred in New Hampshire during the last 10 years, namely during 2016-2017, 2020-2021, and 2022. Month-end groundwater level measurements were analyzed relative to the period of record monthly median statistics for each NH GWLMN well during the three drought events. Monthly groundwater level measurements were found to be at “low” (below lowest monthly median) to “below normal” (10th to 25th percentile) levels at most sites for one to three months prior to U.S. Drought Monitor designation of Moderate to Extreme drought (D1 to D3 Drought Conditions) for the same regions of New Hampshire. The geographic distribution of the NH GWLMN monitoring well sites throughout New Hampshire provided the U.S. Drought Monitor map contributors and other State and federal partners with timely, spatially dispersed information on groundwater level variations indicating the severity of hydrologic drought during these three drought events.