The State Water Board should focus on functional flows, not unimpaired flows, they say
In a letter to the State Water Resources Control Board, a broad group of Central Valley farmers have expressed concerns over the Board’s use of unimpaired flows in the proposals for phase 1 and 2 of the Bay Delta Water Quality Control Plan.
The State Water Board defines unimpaired flows as “runoff that would have occurred had water flow remained unaltered in rivers and streams instead of stored in reservoirs, imported, exported, or diverted.” In the Supplemental Environmental Document (SED) for phase 1 of the Bay Delta Quality Control Plan released in September of 2016, the Board has recommended that flows for the Stanislaus, Tuolumne, and Merced rivers be in the range of between 30-50% of unimpaired flow, with a starting point of 40%.
The farmers are strongly opposed to the use of unimpaired flows and say the approach, if implemented as proposed, would significantly impact their operations, the economies of farming communities, and groundwater resources, as well as the terrestrial and aquatic environment in the Central Valley. “This broad stroke metric is inconsistent with the search for progressive, collaborative, and balanced approaches that will improve ecosystems while providing security for communities that rely on reliable water supply for both agricultural and municipal and industrial uses,” they write.
Instead, the farmers are advocating a ‘functional flow’ approach where flows would specifically support fish and wildlife, but do so in a more water efficient and practical manner than unimpaired flow. The approach should also include non-flow measures such as habitat and floodplain restoration, they say. “The Central Valley is a significantly altered ecosystem with many stressors, including non-native and invasive species,” the letter states. “Any efforts to promote and protect specific native species must also address these significant stressors.”
Unimpaired flows versus functional flows: what is the difference? In an article summarizing the findings of a 2013 seminar sponsored by the Delta Science Program on the science of natural functional flows defined it as flows that are “designed to mimic key geomorphological and ecological processes that the natural flow regime provides, not necessarily to mimic the full natural flow regime.” These processes include peak magnitude flows, wet season initiation flows, spring recession flows, and dry season low flows.
The letter also points out that the SED as currently written assumes groundwater pumping will replace the reduction in surface water, which would eliminate the possibility of sustainable groundwater management without significantly reducing agricultural production and impacting local economies. “We ask that you revise your flow requirements to prevent conflict with SGMA and to incorporate groundwater recharge opportunities to promote both local and groundwater sustainability,” the letter states.
The letter also requests the study of possible canal improvements and additional surface storage to help provide ‘new’ water for functional flows, and that a range of alternative ways be analyzed that can achieve the same increase in fish population while lessening the significant effects of the project.
“We must employ the best available science in a collaborative and comprehensive way if we wish to benefit species recovery in our lifetimes,” the letter concludes.
To read the letter, click here.
For more information …
- Functional Flows in Modified Riverscapes: Hydrographs, Habitats and Opportunities, by Yarnell et al; journal article in BioScience
- Seminar explores the science of natural functional flows to the Delta, article by the Delta Science Program
Sign up for daily email service and you’ll never miss a post!
Sign up for daily emails and get all the Notebook’s aggregated and original water news content delivered to your email box by 9AM. Breaking news alerts, too. Sign me up!
