Water release erosion

Lower-Esopus-Watershed-HZT+A flurry of high-volume water releases from the Ashokan Reservoir into the lower Esopus Creek caused the closing of the Marbletown Recreation Area for two weeks in early July, after a wet June raised the reservoir level higher than anticipated. Although no other major effects were reported downstream of the reservoir, the erosion in Marbletown emphasized concerns about the release protocols used by the New York City Department of Environmental Protection (DEP) as it moderates the storage of the city’s water supply.

When the agency began to use the release channel in 2013, controversy erupted over high flows of muddy water that impaired fish habitat, undermined banks, disturbed septic systems, and disrupted recreation in Hurley, Marbletown, Ulster, and Saugerties. The recent releases were less damaging because they were short-term and composed of clear water, but Mary McNamara of the Ashokan Release Working Group said the incident highlights the need for the New York State Department of Environmental Conservation (DEC) to get moving on its promised environmental impact study of the releases.

“The DEP is still operating with a temporary protocol that has not been given a good strong environmental review,” she explained. “At the moment, we’re waiting for the state to finalize the scope of studies for the review.”

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Complicating the issue is the new pattern of precipitation believed to result from climate change. “We just had the driest May on record in our area and the fourth wettest June,” said McNamara. “The weather patterns over the last four or five years are totally different from what was guiding the operation of reservoir for last 100 years.”

Adam Bosch, spokesperson for the DEP, said DEC regulations allow the reservoir to be maintained at 100 percent capacity from May 1 to July 1, to ensure a sufficient supply of drinking water for New York City and 70 smaller communities in the Hudson Valley. From July 1 to the second week of October, the reservoir ramps down to 90 percent as a flood prevention measure. After the region received double the expected rainfall in June, DEP met its state-mandated requirements by releasing high volumes of water starting July 1, raising the rate gradually from the usual trickle of 15 million gallons per day to a high of 600 million gallons per day for several days.

Marbletown supervisor Michael Warren said the recreation area had just been prepared for the community’s summer program for children when he was informed that the high-volume releases were beginning. The torrent of water washed away sand that had been delivered to the beaches, and the swimming area had to remain closed for the Fourth of July holiday and the following weekend, when the summer program was scheduled to open. “They could have been releasing more environmentally friendly amounts in May and June,” said Warren. “This is the third year in a row we’ve had this problem. It’s frustrating.”

 

Stream corridor stress

One study has already been completed, generating a 40-page report from the U.S. Geological Survey (USGS), commissioned and paid for by the DEP. It reports on the natural stream flow of the lower Esopus, including historical data from USGS stream gages, compared with the flow resulting from water releases over the last few years. “The stream is not functioning the way it’s supposed to,” said McNamara. “The report shows how stressful it is on the stream corridor when high unnatural flows are sustained over a long time. It does lead to stream bank erosion. It also shows how little water is flowing in the lower Esopus at other times, because of the reservoir.”

McNamara hopes that data from the USGS report and from the forthcoming DEC study will provide solid science to be used as a basis for fine-tuning a release protocol. However, the DEC has not informed the working group when the scope of study will be completed, and McNamara fears they will drag their heels unless pressured by the downstream communities. An inquiry about the timetable was directed to the DEC, but no response had been received by press time. Bosch of the DEP predicted the scope would be established within the next few months. “We want to try to gather the best scientific information we can,” said Bosch, “and make sure we get a release protocol that makes sense for the water supply and for the downstream concerns.”

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