Modified Flow Management Standard

Implementing the right flow regime within the lower American River is one of the most critical elements—and perhaps the biggest challenge—in implementing the historic Water Forum Agreement.

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Implementing the Right Flow Regime for the Lower American River

The Sacramento Water Forum adopted the most recent update to the Modified Flow Management Standard (Modified FMS) for the lower American River in October 2015.  The goals for the modified standards include protecting anadromous salmonids, preserving recreational and aesthetic values, avoiding catastrophic water shortages in the basin and contributing to the Delta’s ecological health downstream. After 20 years of study and refinement, the Water Forum strongly believes that this standard represents the best path forward for protecting these local resources without re-directing negative impacts to other regions.

Adaptive mechanisms set the Water Forum Flow Standard apart from those developed for other California waterways.  With American River water conditions varying from year to year, it is imperative that Flow Standard flows and temperature targets are recomputed every season.

The Modified FMS performs exceedingly well compared with other approaches. Specifically, the Modified FMS will:

  • Significantly lower water temperatures in the lower American River during the crucial rearing season for juvenile steelhead.
  • Provide better overall habitat conditions, particularly in the driest years. Under the Modified FMS, flows never drop below 500 cubic feet per second (cfs) and only rarely drop to 800 cfs, under conditions modeled in the simulation.
  • Significantly improve water supply reliability in the American River basin by avoiding low reservoir levels.
  • Avoid redirected impacts to Sacramento River fisheries.

Establishing a Flow Standard as a Priority 

Beginning in 2000, the Water Forum worked jointly with state and federal agencies for 5 years to develop a rigorous, science-based flow management standard. The key to this work was an improved understanding of the definition of healthy conditions for fish. Many experts said that water temperature is equally, if not more important, than flows for improving conditions for lower American River fish. This work resulted in a 2006 proposed standard that specified minimum releases from Folsom and Nimbus Dams and a new approach to managing water temperatures.

The 2006 FMS is a set of measures that includes minimum release requirements and water temperature objectives, oversight by an interagency workgroup called the American River Group, and monitoring and evaluation. Unlike other flow standards, the 2006 FMS uses a sliding scale for minimum flow releases, and water temperature targets that balance available water supplies with achievable objectives to preserve wildlife and biological functions within the river.

The 2009 Biological Opinion and recent drought impacts led to the development of a better approach: the Modified Flow Management Standard that builds upon and improves the 2006 FMS.

Modified Flow Management Standard (Modified FMS)

Using complex computer models, the Water Forum’s technical team developed an improved approach to managing flows of the lower American River.  Our analytical pursuit was guided by three objectives:

  1. Improve conditions for fish in the lower American River;
  2. Reduce the risk of dead pool conditions in Folsom Reservoir; and
  3. Avoid redirected impacts to Sacramento River salmonids.

We determined that carryover storage protection in Folsom Reservoir will provide both improved temperature conditions for lower American River salmonids and help avoid Folsom dead pool conditions.  However, we also learned that storage protections at Folsom Reservoir could create temperature problems for the Sacramento River.  After conducting and review hundreds of modeling runs, our team found a “sweet spot” condition that meets all three of our objectives.

In other words, we could generate greater benefits for the American River basin (for both fish and water supplies) but at the expense of creating redirected impacts to Sacramento River fisheries.

The resulting approach is embodied in the Modified FMS, which includes updated minimum flow curves, minimum storage requirements for end-of-December and end-of-May, and annual temperature planning requirements.

Flow Management Standard (FMS)