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Relief for trout proposed

February 20, 2013

At a meeting of the Water Use and Resource Management Committee of the Upper Delaware Council (UDC) on February 19, Columbia Professor Emeretis Peter Kolesar of New York City and Eldred, and Jim Serio of Hancock presented a proposal to relieve thermal stress on trout in the coldwater fisheries of the Upper Delaware by releasing precisely targeted pulses from the reservoirs (see information box below for details).

The authors, supported by a coalition of environmental groups including Friends of the Upper Delaware and Trout Unlimited, are asking the UDC to support their appeal to have a pilot program in line with their proposal implemented in the flow management regime for the upcoming year starting June 1, 2013.

The reception at the meeting, which detailed the complex calculations that go into creating a a release program for the reservoirs, was favorable, and the committee voted unanimously to support and endorse the proposal.

In order to adopt the program, the authors and their supporters will need to convince the states of New York, Delaware, Pennsylvania New Jersey, and New Yok City, that it will not pose a threat to the NYC water supply nor to the supllies of any cities that get water from the Delaware River.

The Thermal Stress Relief Protocol: The Science

The problem:
The trout that form the mainstay of fishing tourism in the upper Main Stem of the Delaware River, considered to be the finest cold-water fishery in the East, can be devastated by high summertime water temperatures. While there is some dispute over the exact temperature that stresses trout, 75 degrees Fahrenheit is a conservative definition of “severe stress” that has been adopted by a coalition of conservation organizations.

Increasing cold-water releases from the New York City reservoirs, controlled by the 1954 Supreme Court Decree Parties (New York, Pennsylvania, New Jersey, Delaware and New York City) can reduce water temperatures downriver and thus provide relief. But since there are many stakeholders vying for Delaware water, and little has been known about how to efficiently protect the trout, efforts to relieve thermal stress have so far been sporadic at best.

Last summer, there were four thermal severe stress incidents at Lordville, NY on the upper Main Stem— currently the southern terminus of the year-round cold-water fishery. The worst of these lasted eight days. Though requested in all four cases, additional water was released only once—and apparently had the desired mitigating effect. The question is whether a way can be found to protect this economically important resource from thermal emergencies while still satisfying the needs of the other Delaware water stakeholders.

The proposed solution: Columbia Professor Emeritus Peter Kolesar of NYC and Eldred, NY and Jim Serio of Hancock, NY looked for a scientific way to measure the volume of reservoir releases that would be needed to avert thermal stress episodes on the Upper Delaware River, and to forecast when such events are likely. The result is the “Thermal Stress Relief Protocol,” which they claim can guide timely, accurate and highly efficient release decisions. To develop it, Kolesar and Serio used statistical modeling of historical data on river conditions and local meteorology, with three key parts:

• A statistical model showing that an increased release from the Cannonsville reservoir of 118 cubic feet per second would produce a one-degree Fahrenheit decline in water temperature at Lordville. It was derived by correlating water temperatures at Lordville with regional meteorological conditions on the same day and previous days, reservoir releases and other upstream conditions on the same day and previous days, and water flow and temperature at Lordville on previous days.

• A model predicting when future stress will occur at Lordville by correlating meteorological forecasts from the National Weather Service at Binghamton, NY,and current-day river conditions upstream.

• An analysis of historical thermal stress problems at Lordville, quantifying the problem in terms of the average number of stress days, highest number of stress days and worst stress days.

The first two models provide a scientific basis for predicting when thermal stress events are likely to occur, thus optimizing the likelihood that such requests will be made only when there is a real need, and for releasing targeted pulses no larger than required for the purpose, meaning no water is wasted. Applying estimates of water needed to relieve thermal stress from the first model to the historical data, the work shows that in past years there would have been more than enough water available to relieve most stress and still satisfy other stakeholders’ needs.

The authors, supported by a coalition of environmental organizations, have proposed that the Decree Parties implement their program on a pilot basis in the upcoming June 1, 2013 revision of the Delaware flow management plan.