Shandaken Tunnel Outflow Turbidity and Temperature

Posted on: September 12th, 2013 by Leslie_Zucker

You may have noticed over recent weeks that Shandaken Tunnel outflows into the Esopus Creek have sustained higher turbidity levels than would normally be observed during dry summer conditions. According to NYC Department of Environmental Protection (DEP) officials, turbidity levels measured at the Schoharie intake have varied from 20-50 NTU in recent weeks, with temporary spikes up to double that amount during brief periods. As a result, the DEP has been operating the Tunnel at a reduced minimum flow of 97 MGD, with permission from the NYS Department of Environmental Conservation. DEP officials say the cause of elevated turbidity levels is currently unknown and they are investigating multiple possible causes. Turbidity levels are the same at the intake and outflow of the Tunnel, so investigations are focused on the Schoharie Reservoir and watershed. DEP has added additional monitoring buoys to track conditions in the Schoharie Reservoir, sent divers into the reservoir to ensure it was not the effect of fish activity, and performed an aerial inspection that found no visible problems from upstream tributaries. Also, DEP has initiated additional modeling to find and understand the root cause of the turbidity swings. At the same time, Tunnel releases have had a positive effect on water temperature in Esopus Creek. Until early August, daytime water temperatures at Coldbrook remained below the 72 degrees F needed to support trout populations.

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