More Flow Doesn’t Equal More Fish

Existing state and federal water supply restrictions in the Delta have increasingly reduced supplies available to urban and agricultural users to make more water available for fish and the environment.

A recent analysis by the Southern California Water Committee quantified environmental water restrictions using Department of Water Resources’ (DWR) CALSIM II model. The analysis shows that current environmental flows requirements provide, on average, about 1.3 million acre-feet of additional water for the ecosystem. The modeling estimates that D-1641 (enacted by the state in 1999 and amended in 2000) increases environmental flows by 300,000 acre-feet on average, and the Biological Opinions (BiOps) issued by the federal government (2008 and 2009) for delta smelt and salmonid species requires an additional one million acre-feet.

Over the past 16 years these increased environmental flows have come at significant economic cost to residents, workers, farms, and businesses dependent on the Delta for their water supplies. Given these significant costs, it is important to understand the benefits, if any, the current increased flow regimes have provided to species.

The following analysis show abundance trend data for Endangered Species Act protected fish in the Delta from 2000-present.

As the charts illustrate, the increased flows mandated by state and federal regulations have provided no measurable benefit to endangered fish species. In fact, the data clearly documents that each of the endangered species state and federal regulators are trying to protect have continued to decline during the period of increased flows.

Featured photo provided by Hakai Magazine