Quantitative assessment of water quality in Upper Esopus Creek: fish, macroinvertebrates, periphyton, turbidity, and nutrients

Figure 1. Map of study sites in the Upper Esopus Creek watershed.

Background - The Esopus Creek is located in the Catskill Mountains of New York State and is part of the New York City (NYC) drinking water supply system. The basin was dammed in 1915 to form the Ashokan Reservoir splitting the creek into Upper (upstream of the reservoir) and Lower segments. The drainage area of Upper Esopus Creek, between the source (Winisook Lake) and the Ashokan Reservoir is approximately 192 mi2 (Figure 1). The Schoharie Reservoir, located 27 miles north of the Ashokan Reservoir, also supplies water to Upper Esopus Creek (and to the Ashokan Reservoir) via the Shandaken tunnel. Waters from the Schoharie watershed enter Upper Esopus Creek at the Shandaken portal and travel 18 km before entering the Ashokan Reservoir. The two reservoir’s account for approximately 40% of NYC’s mean annual water supply. The Upper Esopus Creek is also a world-class trout fishing and recreational stream. Waters from the portal have been the focus of controversy and legal action, however, because they are sometimes turbid and believed to negatively impact local trout populations and water quality. Primary sources of turbidity in the Schoharie and Ashokan watersheds are large deposits of eroding glacial clays along stream channels and hill slopes. Fine clay particles, when suspended in stream waters, can adversely affect growth and survival of fish and macroinvertebrates along with the health of their communities. The NYC watershed management plan also considers turbidity a source of water quality impairment because it is aesthetically unpleasing, reduces effectiveness of drinking water disinfection, and indicates the potential presence of bacteria and viruses.

Objectives - Primary objectives of the study are to,

• characterize current water quality and ecosystem conditions,
• define potential impacts effects of known and potential stressors (e.g., turbidity, suspended sediments, temperature, nutrient enrichment, Didymosphenia geminate), and
• compile information needed to assess management strategies intended to improve biological condition and water quality throughout the Upper Esopus Creek watershed and its major tributaries.

Approach - The US Geological Survey (USGS), New York State Department of Environmental Conservation (DEC), NYC Department of Environmental Protection (DEP), and Cornell Cooperative Extension of Ulster County are conducting a comprehensive study of biological resources (fish, macroinvertebrate, and periphyton communities), water quality (turbidity, suspended sediments, and nutrients), hydrology, and water temperature in the Upper Esopus Creek basin during the period 2009-12. Staff from the USGS, UCCC, and CCE are quantifying habitat and surveying fish communities at 18 to 20 study sites in the main stem Upper Esopus Creek and its major tributaries each summer during the study. The DEC and USGS are also conducting macroinvertebrate and periphyton community inventories at 20 main stem and tributary sites each during August, 2009-11. Staff from the USGS have installed and are operating stage/discharge and temperature sensors, automated water samplers, and data loggers at 10 to 13 main stem and tributary sites to characterize water quality (turbidity, suspended sediments, and nutrients), discharge, and water temperature. Comprehensive physical, chemical, and biological data will be compiled and evaluated to quantify the (a) current environmental or ecosystem conditions (b) normal variability in key ecosystem components (metrics), (c) relations between important metrics and environmental factors, (d) potential impairment of selected ecological metrics at sites located downstream of the portal, and (e) possible sources or causes for such impairment in the Upper Esopus Creek watershed. Results from the study will be summarized in one or more reports or peer-reviewed journal articles and will be available at the web site, http://ny.usgs.gov.