AWWA WQTC52819

The Hemlocks multiple reservoir system provides water for a large distributionarea in southwestern Connecticut. This system consists of the Hemlocks Reservoir (the direct source), Aspetuck Reservoir, and Saugatuck Reservoir (a large, deep reservoir). The watershed drainage to Aspetuck and Hemlocks Reservoirs is soft water, while Saugatuck Reservoir and its watershed consist of hard water.This system provides an opportunity to study the interactions between hard and soft water systems. Water supply challenges included avoidance of phytoplanktonic blooms of Cyanobacteria, methylisoborneol and geosmin production by benthic Cyanobacteria mats, accumulation of anaerobic respiration products, and both ecological and water quality impacts of an unintentionally introduced population of land-locked alewife. This paper describes the various reservoir management approaches that have been taken to solve these problems in the Hemlocks system. These include deep water releases from the distribution and depth-selective releases from the storage reservoir, avoiding accumulation of iron and manganese, use of an artificial circulation system, and biomanipulation by fish stocking. Includes figures.