The awareness of the impact that obsolete dams have on stream ecosystems is becoming widely recognized. Many dams inhibit fish migratory patterns, retain nutrients and sediment within the reservoir, and alter water temperature regimes below the dam. Fish and invertebrate populations are highly dependent on their aquatic habitats to supply necessary nutrients, space, and water quality in order to carry out biological processes. For this project, we evaluated the impact that a small, defunct dam is having on the stream communities by altering temperature regime. We deployed temperature loggers at multiple locations above and below the dam and analyzed the thermal data across multiple months including the warmest point of the year (July/August 2018). We compared the seasonal patterns in water temperature to the fish and invertebrate communities that we sampled in fall 2018.
Results/Conclusions
This study found that in the warmer months of summer, the temperature below the dam was nearly 10°F warmer than the temperature found in free flowing sections above the reservoir. We found lower fish density, including lower trout density, below the dam along with differences in the invertebrate communities. Our study provides evidence to support recent efforts to remove the dam, which would allow downstream locations to return to normal thermal regime and reconnect the stream communities.