The 2010 Delta Flow Criteria Report announced findings by the State Water Board that additional flow into and out of the Delta was needed to restore fisheries. The Report stated: “In order to preserve the attributes of a natural variable system to which native fish species are adapted, many of the criteria developed by the State Water Board are crafted as percentages of natural or unimpaired flows.”
CSPA strongly supports the percent-of-unimpaired approach to developing Delta flow requirements. However, figuring out how to actually implement this approach takes a lot of work. The State Board has not done much to advance understanding. Resource agencies have not consistently advocated for it. Other environmental and fishing groups have supported it as a principle, but have made little apparent effort to demonstrate its feasibility or evaluate the reservoir operations that it would require. And, of course, many irrigation districts and water agencies have hired talented modelers with the general intent of making a percent-of-unimpaired approach appear unreasonable.
License applicants in relicensings of three key Central Valley hydroelectric projects (Merced River Project, Don Pedro Project on the Tuolumne, and Yuba River Development Project) have developed daily operations models that allow careful analysis of how a percent-of-unimpaired approach could be implemented. CSPA’s hydropower advocate, with help from several engineers, has used these models to evaluate two of the systems: Merced River and Yuba River. In July, 2014 we posted the product of some of that work for the Merced River (“CSPA Proposes High Spring Flows on Merced River”). On September 24, 2014, CSPA made a presentation in the Yuba River Development relicensing discussing how conceptually a percent-of-unimpaired approach might be overlaid onto flows developed in the 2008 Yuba Accord to improve instream flow benefits both in the Yuba River and in the Delta downstream. Over the coming year, CSPA will be working on a similar analysis for the Tuolumne River.