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Peak and Ecological Flows: What’s in Store for Water Storage Projects in Oregon?

February 14, 2011

 In 2009, the Legislature required all new water storage projects funded with state dollars under House Bill 3369 to protect “peak and ecological flows.” The legislature left this term undefined, causing confusion and concern to potential funding applicants. To address these concerns, the Oregon Water Resources Department assembled a working group, the Ecological Flow Technical Advisory Group (EFTAG). The EFTAG is comprised of scientists that study environmental stream flows. The results of EFTAG’s efforts may be used by the Department to develop regulations.

In December 2010, EFTAG released a white paper on peak and ecological flows in an effort to provide guidance and possibly a framework for ensuing regulations. The white paper (1) defines peak and ecological flows, (2) describes common methods for determining these flows, and (3) provides recommendations for how these methods might be applicable in Oregon.

In its white paper, EFTAG describes peak and ecological flows. The concept behind peak and ecological flows is to have the high and low instream flows required to maintain habitat and perform ecosystem functions (e.g., mitigating water quality impairment). The paper describes “ecological flows” as “instream flows needed to sustain ecosystem functions that native fish and wildlife species require to survive and flourish.” EFTAG suggests that “peak flows” may refer to an Oregon Department of Fish and Wildlife guidance.  That guidance discusses methods for determining peak or elevated streamflows to meet fish and wildlife needs.

The EFTAG white paper describes in detail types of flows that serve various ecological functions.  It then describes the methods used to measure these flows, recognizing that different stream types may require different methods (e.g., a stream with floodplain will require a different type of flow to maintain habitat than a confined stream). The white paper does not discuss in any detail how flows or storage seasons vary by region or stream type nor how the methods should be adjusted to address these distinctions. 

EFTAG concluded that, in the interest of efficiency, the project scale should help determine the level of analysis of peak and ecological flows. The paper suggests a three-tiered approach, with increasing levels of scrutiny for higher impact projects and/or for projects on stream systems with greater sensitivity or value (e.g., those with endangered fish species). Tier 3 analyses would require significantly greater effort and cost than Tiers 1 or 2.

The EFTAG white paper suggests criteria for consideration in determining a project’s tier and notes that “[m]any of these choices would be based on societal concerns and balancing of issues.” Among the criteria that might be considered are the size of the project relative to the watershed, the degree of impact of other storage projects upstream and downstream, and a “rigorous ecological evaluation of the stream system’s overall ecological value in terms of listed species and other criteria.” The white paper provides little guidance in the way of how these factors will be weighed or what the target species may be. EFTAG suggests those determinations would be made based on a mixture of policy and science. 

EFTAG’s guidance leaves open many questions. The Department will undoubtedly need to further evaluate how peak and ecological flows should be analyzed and protected before it implements regulations. Questions that will need to be addressed include, among others, how criteria for evaluating flows will vary from region to region, what specific criteria will be evaluated to determine the tier a project falls within, and how cumulative impacts from other projects will be considered. While these issues may become less murky in time, the question remains whether applicants for new water supply projects will invest the time and money to perform these flow analyses or choose to forego state funding to avoid the regulatory burden.    

A final issue is whether peak and ecological flow projections will be extended beyond the limited reach of HB 3369, to projects other than state-funded storage projects. The white paper is focused on providing this analysis in relation to new water storage projects seeking state funding. That said, with water scarcity increasing and the on-going concern for protection of waterways and endangered salmonids, there is no telling what will evolve. 

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