Assessment of Dam Removal Impacts on the Klamath River
Although removing four dams on the Klamath River will have dramatic effects on the river ecosystem and may fundamentally alter riverine nutrient cycling downstream of the dams, our studies show that impacts of releasing the millions of tons of fine sediment stored behind the dams will be relatively short-lived and will not likely eradicate any species. For an overview, listen to Ethan Bell give a radio interview about the project.
Sediment transport simulations
In order to arrive at an optimum reservoir drawdown scenario, Stillwater Sciences used the DREAM-1 dynamic sediment transport model (Cui et al. 2006) to analyze multiple concurrent drawdown alternatives, including a variety of different drawdown start dates and drawdown rates. For more information, download the full Sediment Transport Technical Report.
Effects of sediment release on aquatic biota
Predictions of total suspended sediment and duration from the DREAM-1 modeling combined with Newcombe and Jensen’s (1996) “severity of ill effects indices” was used to assess possible impacts to selected key species. Based on this analysis, even under a worst case scenario, we expect populations of all focal species to recover in the long term; however, we recommend managers consider interim measures to ensure strong population recovery, including the protection of weak year classes, annual harvest management strategies, capture of adults or juveniles, increasing fall and spring instream flows, and improved habitat quality in tributaries. For more information, download the full Effects of Sediment Release on Aquatic Biota Technical Report. If you have questions about aquatics-related issues, contact Ethan Bell.
Water quality synthesis
Although sediment loads downstream of the dams will dramatically increase in the short term, we anticipate little to no impact from sediment-associated nutrients or contaminants on riverine biota. Long-term effects on temperature, nutrients, dissolved oxygen, pH, and turbidity are expected; however, most will likely benefit native aquatic species. As part of our analysis, we proposed ten conceptual study plans to address remaining water quality data gaps (including those related to climate change) and ultimately support informed decision-making regarding dam removal. For more information, download the full Water Quality Technical Report. If you have questions about water quality related issues, contact Maia Singer.
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While short-term impacts of removing four Klamath River dams are expected to be significant, our analyses suggest aquatic communities will rebound in the long-term.