A comprehensive approach to informing and monitoring results of stream management practices in the Upper Esopus Creek watershed

Elevated suspended-sediment and turbidity can negatively affect stream ecosystems in numerous ways, including degradation of aquatic habitat and decreased quality of water for drinking water supplies. The upper Esopus Creek supports a renowned trout fishery and is the primary tributary to the Ashokan Reservoir. The Ashokan Reservoir provides up to 40% of New York City's drinking water supply and is operated under a recurring Filtration Avoidance Determination issued by the NYS Department of Health. The upper Esopus Creek and its tributaries have elevated concentrations of suspended-sediment and turbidity values during large storms which can persist for days to weeks. A 10-year study is underway to determine source dynamics of suspended-sediment within the upper Esopus Creek watershed and monitor results of stream management practices targeted at reducing suspended-sediment concentrations and turbidity levels. This study includes extensive monitoring of discharge, suspended-sediment, and turbidity, and spans stream reach to reservoir watershed scales. Repeated mapping of stream channel geologic and geomorphic sediment sources, bank erosion monitoring, and sediment source fingerprinting (SSF) are being used to correlate watershed sediment dynamics to measured suspended-sediment and turbidity values and to inform stream management practices. Preliminary results indicate that (1) Stony Clove and Woodland Creeks are the largest sources of suspended-sediment and turbidity to the upper Esopus Creek watershed, (2) the highest turbidity values occur where fine-grained lacustrine material is in contact with the stream, (3) geologic sources of suspended-sediment varied across sites and through the hydrograph, and (4) Sediment and turbidity reduction projects have reduced suspended-sediment concentrations and turbidity values in the upper Esopus watershed for the streamflows monitored.