Hudsonia staff and student intern set up eel traps at Annandale dam

Erik Kiviat, Hudsonia

Renewable energy generation is generally lighter on the environment than fossil fuel generation. However, all kinds of energy development have impacts, and, because renewable generation technologies are being rapidly developed and deployed, in place at a large scale, we need to better understand those impacts. In 2016-2017, under the NYSERDA grant to Bard College for a micro hydropower demonstration project on the Saw Kill, Hudsonia studied the flora and fauna of the lower Saw Kill to obtain “pre-case” data. Those data and resulting ideas will be used for comparison with conditions following turbine installation (“post-case”). We are focusing on those species that indicate conditions in the creek, and especially species that are of conservation concern.

Because commitments to locations and types of turbines had not been made when we did the original surveys, we studied the whole creek from Route 9G down to the tidal mouth in South Bay. We performed surveys of vascular (higher) plants, a rare plant called winged monkeyflower, bryophytes (mosses and liverworts), American eel, turtles, and birds. This spring and summer (2020), based on the results of the earlier work and the college’s decision to develop micro hydropower at a single existing dam in Annandale, and given the delays in development of the power project, we are repeating the vascular plant survey with a focus above and below the Annandale dam, re-checking the populations of the monkeyflower and a rare moss, trapping eels at the foot of the Annandale dam, surveying a bird (Louisiana waterthrush) and a turtle (wood turtle) of conservation concern, and continuing operation and improvement of an automated water quality monitoring station just above that dam. More details of these studies are in the report: Saw Kill Studies.

The water quality monitoring system was installed in 2019 just above the Annandale dam, and removed over the winter to avoid ice damage. The equipment has been reinstalled and samples a number of standard water variables at 15 minute intervals. Simpler equipment will be deployed below the dam to allow detection of changes due to the turbines that will be installed at the foot of the dam.

Eel trapping revealed a small number of large, but not yet mature, eels in the plunge pool at the foot of the dam. One eel may be a size record for the Saw Kill. The American eel has declined in recent decades throughout its geographic range on the East Coast.

Two mornings of Louisiana waterthrush survey detected one singing (territorial) male below the Lower Dam, where a male has sung almost annually since at least the 1970s. We did not find this species farther upstream.

The plant survey has begun. The seasonal development of winged monkeyflower was delayed this spring, as seems to have been true for many species, and deer have also been eating the plant. We plan to return (in August) for a better count of the monkeyflower stems for comparison with the original survey. Hudsonia botanists are examining the mosses on the bank where the rare species scimitar silk moss was found in 2017. We will also learn more about this species in August.

A wood turtle survey is scheduled for September 2020 when the turtles will be in the stream channel and easier to find. Years ago, this species was found near the Saw Kill at Bard, and in 2018 we found a population upstream of the college. Thus our concern about surveying for wood turtles in the wadeable reaches of the Saw Kill.

American eel, wood turtle, and Louisiana waterthrush are all Species of Greatest Conservation Need in New York. This designation includes species such as these that may become threatened or endangered if they do not receive adequate survey and conservation attention.

The results of all the 2020 Hudsonia studies will be reported in the fall. The surveys will be repeated in the first spring and summer following turbine installation in Annandale, hopefully in 2021.

Hudsonia studies this year are being conducted by Gretchen Stevens, Lea Stickle, Chris Graham, Susan Rogers, Jason Tesauro, and Emily White. The original surveys additionally involved Julia Palmer. Susan Williams and Ken Karol helped with critical plant identifications.


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