(This op-ed appeared on The Oregonian on July 12.)
The Fourth of July weekend saw the death of a dozen sockey salmon on the lower Deschutes River below the Pelton-Round Butte project.
According to Deschutes River Alliance, the temperature of water discharged from Pelton-Round Butte Dam complex have been increasing as the dam operators are drawing from the surface of the reservoir as the primary component of water being used to run turbines.
Read the post by the Alliance on the fish kill.
Damming a river may bring electric power, but it often comes at the price of high-quality food fisheries, experts say. When dams are proposed for power, flood control or irrigation, the often devastating impacts on fisheries in rivers and lakes are ignored or discounted.This report by the UN Environment Programme (UNEP) and the World Fish Centre warns that despite over 40 years of steady production globally, rapid environmental changes are occurring which challenge the viability of future fish stocks and a range of internationally- agreed development targets including the Millennium Development Goals.The report is available online at https://www.unep.org/pdf/Blue_Harvest.pdf
1. Seventy-two per cent of the Flathead River catchment (22,241 km^2) is federally designated and protected as wilderness or national park. Thus, the catchment remains one of the more pristine areas of its size in the temperate latitudes of the world.
2. Discharge in the downstream reaches of the river system outside the protected areas is regulated by three dams for flood control and hydropower production. These dams have blocked natural migration of native fish from Flathead Lake (496 km^2) and isolated populations in sub-catchments. Temperature and erratic flow fluctuations have altered phenologies of river zoobenthos and fish, and in dam tailwaters aquatic biodiversity is drastically reduced in comparison to unregulated segments.
3. Ecological problems caused by changing water quality conditions, altered land-use patterns and introductions of no-native biota are interactive with the impacts of stream and lake level regulation , thereby emphasizing the complexity of this river-lake ecosystem.
4. Mitigation of the effects of regulation is compromised by differing management priorities and regulatory mandates of County, State, Tribal, and Federal agencies responsible for natural resource management within the catchment. Moreover, economic and ecological interests outside the Flathead influence the way flows are regulated within the catchment.
5. The most pervasive influences of stream and lake regulation can be ameliorated by retrofitting the hypolimnial release dam with a selective depth outlet structure to allow temperature control, and by controlling changes in flow rates to create a more natural hydrograph in the tailwaters of the large dams. Allowing fish passage by construction of fish ladders is problematic because upstream passage will commingle native species that were isolated upstream by construction of the dams with non-native species that were introduced subsequently below the dams. Cascading food web interactions elicited by invasions of non-native biota may offset any advantage to native stocks gained by passage and/or augmentation with hatchery stocks.
6. Mitigation must be adaptive in the sense that unanticipated effects and interactions with other management objectives can be documented and alternative action can be implemented.
7. This case history of the effects of stream and lake level regulation, and the approaches to management reviewed in this paper, should serve as a lesson in river conservation.