Release Channel Activation – Managing Water Quality in New York’s Reservoirs
The Ashokan Release Channel is a concrete canal, constructed in the early 1900s during construction of the Ashokan Reservoir and is used to convey water — currently up to 600 million gallons per day — in a controlled manner from the reservoir through the upper and lower gate chambers to the Old Esopus Creek, which runs in a southeasterly direction through the SUNY Ashokan Field Campus to the Lower Esopus Creek.
Release Channel Releases
The Ashokan Release Channel has the ability to reduce turbidity levels following storms and be used proactively to create a void to help accept flows from an impending storm or when seasonal runoff is expected to be high.
In October 2011, DEP and New York State Department of Environmental Conservation announced a new interim protocol for operating the Ashokan Reservoir that will, for the first time ever, create target reservoir elevations during certain months of the year. The new protocol will help reduce flooding and help protect the drinking water of approximately eight million New York City residents and the roughly 160,000 residents of towns that rely on the Catskill Aqueduct such as New Paltz and High Falls in Ulster County, and New Windsor and Cornwall in Orange County. The agreement provides for a 10% void in the reservoir from October 15 to March 15; an average of a 5% void from March 15 to May 1 and from July 1 to September 1. The interim protocol also guarantees minimum water releases throughout the year – 10 MGD in summer and 15 MGD in winter. The summer time release will be a benefit to river recreation at a time when the lower Esopus Creek usually becomes somewhat stagnant and warm.
To read the entire protocol, click here:
Its operation has a number benefits: it helps protect water quality by minimizing the potential for spilling high turbidity water from the West Basin into the East Basin (where the intake to the Catskill Aqueduct is located, which supplies nearly half of the drinking water needs of nearly nine million New Yorkers); it lessens the need for alum treatment; and it helps to mitigate flooding conditions below the reservoir. The Release Channel can be operated until the turbidity condition improves, with higher flows resulting in a shorter duration of operation, while at the same time balancing operations against the ability to refill Ashokan Reservoir by June 1st for the start of drawdown.
To protect infrastructure immediately downstream, Release Channel operations are managed in cooperation with the SUNY Ashokan Field Campus. Releases are monitored daily both electronically and by direct observation. The Release Channel It is not activated when the lower Esopus has the potential to flood.
This new protocol is made possible because of DEP’s multi-million dollar investment in our new Operations Support Tool (OST), a high-tech computer application which allows DEP to better predict reservoir-specific water storage levels, quality, and inflows, which gives us a level of certainty that was not previously possible about when it is safe to release water without unnecessarily depleting New York’s water supply.
Catskill watershed streams can contribute elevated turbidity following high rainfall and/or snowmelt events. This turbidity is caused primarily by naturally occurring clay particles being suspended in the water. The clay particles make the water cloudy or less transparent, and can give the water a brownish appearance. Turbid water is of particular concern in a drinking water supply. Not only is the cloudy water less appealing to consumers but the particles can interfere with the disinfection process. For this reason, levels of turbidity in drinking water supplies are highly regulated by both state and federal government and rigorously monitored. DEP currently monitors turbidity at over 1,400 locations in the watershed and distribution system.