The impacts of cold water releases on the East Branch

Those of us who have been around long enough to remember the abysmal releases of water from the Delaware System reservoirs prior to the implementation of the water releases legislation are mostly delighted with the new flow regimens. There are detractors off course, those that want more. That is another story, for another time and not for this column. But while the increased releases of water to these rivers provide suitable temperatures for trout year round, there are some interesting, negative side effects associated with the colder temperatures. The closer to the dams, the more profound those side effects are.

Over the last few years, anglers who ply the waters of the East Branch found an increase in filamentous green algae in the upper reaches of the river. Some thought that the algae were a function of nutrient loading, from dissolved phosphates and nitrates. Water chemistries and discussions with New York City Department of Environmental Protection (DEP) chemists proved that not to be the case. What then?

My research found there are species of filamentous green algae that thrive in cold-water environments. Such is the case with the upper reaches of the East Branch, where temperatures seldom reach 55°F, perfect for some species of algae. In addition, we found that the algae disappears by Shinhopple, further eliminating the theory of nutrient loading.

Another anomaly anglers found was an increase in the buildup of decomposing organic matter, mostly dead leaves along the bottom of slower pools. In some area, waders would find this stuff up to their knees, a potentially dangerous condition. Why all the glop?

The East Branch is a low gradient stream that is managed by the DEP as a controlled-flow tailwater. The goal is to provide enough void in the fall to prevent spill and flooding like that seen in 2006 and 2011. As a result, the Pepacton Reservoir did not spill enough to produce flows adequate to flush this material in 2014, 2015 and 2106. The reservoir did spill during the late winter and early spring of 2107, when flows were in the range of 4,000 cfs (cubic feet per second), high enough to remove much of the buildup.

Over many thousands of years, aquatic insect communities found in our rivers evolved to survive low and high flows, droughts, floods, icing and large fluctuations in water temperature. Enter man’s hand in manipulating flow through bottom releases of cold water and what happens? Rivers that once had low flows and high water temperatures during warmer months now are cold all year long.

That’s what has happened with the East Branch aquatic insect community. Let’s use Shinhopple as the break point and mayflies as the indicators. For those of you that fish above Shinhopple, these are the species of mayflies that will be found hatching: Quill Gordons, Hendrickson, Blue Quills, Pale Evening Duns, little Olives and Sulphur Duns. Below Shinhopple, anglers will find all of those species, plus March Browns, Grey Foxes, Green Drakes, Brown Drakes, Iysonichia, tiny tricos and a much larger variety of caddis flies. Why? The water temperatures in the East Branch above Shinhopple are too cold on a season-long basis for the species found below Shinhopple.

So it is legitimate to conclude that the upper East Branch has “devolved” when it comes to species diversity. But despite the fewer species in the upper river, anglers have the opportunity to fish all season long without the fear of high water temperatures found on Catskill freestone rivers. There are pluses and minuses with all controlled releases, and for the East Branch, the benefits outweigh the losses.

 

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