Cabot Hydropower Station Fishway Hydraulic Model Study: Final Report


M Odeh
J Noreika




Prepared for NU/Northeast Generation Services Company and Connecticut River Atlantic Salmon Commission


adult, American shad, anadromous fish, Atlantic salmon, Connecticut River, design, design criteria, engineering, fish passage, hydraulic conditions, Hydropower, model studies, pool, pool and chute, salmon, shad, slope, spillway, upstream, weir


A hydraulic physical model, scale 1:6.4, of a straight section of Cabot Hydropower Station Fishway, Turners Falls, MA was constructed at the USGS - S.O. Conte Anadromous Fish Research Center (CAFRC). Weir modifications were evaluated and design criteria for the final alternative design were provided. The model study was performed in an effort to support an ongoing biological study plan at CAFRC. The study, 'Evaluation of passage performance of adult American shad at lower Connecticut River mainstem fish passage facilities,' is under the leadership of Dr. Alex Haro. The study evaluates passage of shad at the Vernon and Turners Falls (Cabot, Spillway, and Gatehouse) fishways. The final structural modifications to Cabot fishway weirs (numbers 125 thru 129) will consist of lowering the existing weir crest elevation by 2 feet and constructing a 2.5 feet wide chute (or ramp) starting at the weir and extending upstream into each pool. The remaining 2.5 feet of the existing weir width will be blocked to the flow. The chutes will be aligned on the south side-wall of the fishway; effectively converting the modified section to a 'pool & chute' fishway. This modification resembles existing pool and chute fishways in Maine and New Brunswick. The chutes will be installed at varying slopes to maintain the hydraulic conditions the same as in the existing fishway. Also, part of this modification will be to locate the open orifice below the chute in each pool. The Northeast Generation Services Co. (NU) will be responsible for detailed engineering design, construction, and operation of these modifications. The fishway flow discharge will remain the same as in prior years of operation; an estimated 32 cubic feet per second.

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