Groundwater provides cool and clean water that keeps the rivers and streams flowing during the summertime (baseflow). Groundwater is necessary for maintaining sufficient streamflow for aquatic life and recreation, as well as for supplying drinking water to most of the towns in the watershed. In New England, groundwater level is expected to respond more slowly to changes in precipitation than streamflow. It is the most comprehensive indicator of long-term drought conditions because of its slow reaction to precipitation dynamics.
This indicator is based on the average depth to groundwater at USGS monitoring well ACW-158 in Acton during August and September over the prior five summers. Although this is the only USGS monitoring well in the watershed, it is a good indicator of groundwater levels in the entire watershed’s glacial drift aquifers. The groundwater score is calculated based on comparisons with statistics from historic groundwater levels for this gage for the period of record starting in 1965.