Fractured Bedrock Aquifers as Early Indicators of Ground Water Response to Climate

Recent findings suggest that climate change will lead to modifications in the timing and nature of precipitation, giving rise to an altered hydrologic cycle. The amount and timing of precipitation has potential implications for ground water as it affects the total amount of water available as contributions to streamflow, ground water, lake levels, and the timing of peak and low flows as extreme events.  Ground water flow and storage, often viewed as static reservoirs, are dynamic and continually changing in response to human and climatic stress.  The response of the subsurface hydrology to decadal climate and longer-term climate change to date has been investigated via site specific analyses, modeling studies, and proxy analysis.  Here present a first instrumental long-term regional compilation and analysis of the water table response to the last 60 years of climate in New England.  Ground water trends are calculated as normalized anomalies, and analyzed with respect to regional compiled precipitation, temperature, and streamflow. Anomalies in ground water levels are investigated for wells in surficial glacially-derived sediments and the underlying fractured crystalline bedrock.  The time-series display decadal patterns with ground water levels being more variable and lagging that of precipitation and streamflow pointing to site specific and non-linear response to changes in climate.   Fractured bedrock systems display larger amplitude variations and are quick to integrate short-term climate variability compared to surficial materials.  Thus, fracture bedrock wells may be good indicators of change over 1-2 year periods compared to surficial wells.