Stream Flow in the Willimantic River Watershed
The amount of stream flow can be impacted by natural events such as floods and droughts. The flow is also affected by water withdrawals from the river (surface water) or from sand and gravel aquifers underlying the river corridor (ground water).
Ground Water Withdrawals
Currently, the University of Connecticut Storrs campus and the Town of Tolland have wells in aquifers next to the main stem river. After droughts in the 2005-2010 period, stream flow standards were determined for the University wells, and conservation measures are required if the flow falls below an adequate level for a specified period of time. Ct. DEEP regulates these and other consumptive water diversions through permitted or registered (as of right) conditions.
Surface Water Withdrawals
Several reservoirs in the watershed provide water for industrial use and for public water supply systems. In 2011, regulations were approved by the Connecticut General Assembly for minimum outflows below reservoir dams. These regulations require releases that insure adequate stream flow below dams to maintain aquatic life. Ct. Department of Energy & Environmental Protection (DEEP) will establish flow standards, starting with the Thames River Basin, which includes the Willimantic River. The first phase of this project classified sections of waterbodies below dams. Since there are few dams in the Willimantic River watershed, most of the river and its tributaries are listed as Class 1 (free flowing stream) and support native aquatic life. Ct. DEEP issues updates about the standards and stream flow classifications and a map with information about the 18 classification factors analyzed for a particular stream of interest.
Floods and droughts can cause the river's water levels to rise and fall dramatically. For a perspective on extreme events, note these Flood Facts. Hurricane Irene's rains in August, 2011, caused a high flow of 3,035 cubic feet per second (cfs) past the Coventry, Ct. USGS stream gauge. The highest flow in recent memory was 12,400 cfs in October, 2005 (following a serious drought) when the river's level rose to just under many bridges. In comparison, the September, 1938 Hurricane's peak flow was 15,500 cfs. Since records have been kept, the all-time high flow was 24,200 cfs in August, 1955 (following the back-to-back named hurricanes Connie and Diane), when many bridges along the river were washed out.