2023 Early Hearing Detection & Intervention Conference

March 5-7, 2023 • Cincinnati, OH

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5/22/2018 | 3:00 PM - 3:15 PM | SMALL DAMS CAN HAVE LARGE THERMAL EFFECTS WITH NEGATIVE IMPLICATIONS FOR COLDWATER SPECIES | 310 A

SMALL DAMS CAN HAVE LARGE THERMAL EFFECTS WITH NEGATIVE IMPLICATIONS FOR COLDWATER SPECIES

The thermal impacts of the estimated 2 million dams in the U.S. are highly variable, even within geographic regions, such as the northeast. In a study of 30 small, low-head dams in Massachusetts, we found that while some dams had minimal effects on temperature, others imparted significant warming (>5 C) on downstream reaches, such that dams caused stream temperatures to exceed thermal maxima for coldwater species. In most cases, temperatures downstream of the dams did not immediately recover to upstream temperatures, and elevated temperatures persisted for large distances (0.35-4.78 km) downstream of the dam sites. Close-proximity dams on the same stream were shown to have additive warming effects, whereby the distance to thermal recovery from a dam was increased (up to 0.85 km) by the warming effect of a downstream dam. The collective warming from the high abundance of low-head dams may have shifted coldwater habitat to warmwater habitat and aided in fragmenting and isolating coldwater species in headwater streams. These results suggest that focused, watershed-scale restoration efforts may provide greater collective water quality and biotic improvements than piecemeal dam removals across the landscape.

Temperature
Restoration
Impairment

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Presenters/Authors

Peter Zaidel (), Massachusetts Cooperative Fish and Wildlife Research Unit, University of Massachusetts Amherst, pzaidel@umass.edu;