The Water Forum Member Spotlight

The Lower American River Modified Flow Management Standard

The lower American River has many roles as a critical floodway. It is a habitat for fish and wildlife and a regional recreational parkway for residents. The American River is also a high-quality water source for the Sacramento region and irrigation water supply for California’s agricultural industry. Given the importance of the Lower American River as a regional and state asset, proper management of the River is critical. The recent drought highlighted issues with the existing flow requirements, and in conjunction with the continuing stress placed on the River by climate change, it is evident that existing flow requirements set by the 2006 Flow Management Standard do not sufficiently protect the fish population nor ensure a consistent water supply for the region. In response, the Sacramento Water Forum developed an update of the 2006 FMS known as the Lower American River Modified Flow Management Standard (Modified FMS) – the focus of this CRC Member Spotlight.


The Modified FMS, published in October 2015, is an update of the 2006 FMS. The motivation behind updating the Flow Management Standard was the need to address the variance in water conditions exacerbated by the recent drought and the increasing threat of climate change. The Lower American River is a valuable asset to the region and state as well as an important fish habitat. Flows established by the 2006 FMS don’t go far enough to support a healthy fish population nor do they ensure a consistent water supply for the region. Subsequently, the Modified FMS was developed with the goal of  protecting anadromous salmonids and preventing water shortages in the basin. The Modified FMS most notably varies from the 2006 FMS in the fact that it calls a modest level of carryover storage in Folsom Reservoir.  This added storage can be thought of as a drought reserve that helps guard against a bone-dry reservoir and helps improve water temperature conditions in the lower American River. In addition, the goals of the Modified FMS with regard to the River’s many roles are expanded to include:

  • Protecting anadromous salmonids
  • Preserving recreational and aesthetic values
  • Avoiding catastrophic water shortages in the basin
  • Contributing to the Delta’s ecological health downstream

The Modified Flow Management Standard has been modeled in comparison to the existing Flow Standard – the 2006 FMS, as well as the High Springs Flow approach which most closely mimics a natural unregulated hydrograph. In these comparisons, the each of the flow standards was modeled using an 82-year simulation with historical hydrologic conditions and 2030-level water demand. In the simulations, the Modified FMS outperformed the other flow standards. The model indicated that the Modified FMS would achieve the following:

  • Significantly lower water temperatures in the lower American River during the crucial rearing season for juvenile steelhead.
  • Provide more spawning habitat for fall-run Chinook salmon.
  • Provide better overall habitat conditions, particularly in the driest years.
  • Significantly improve water supply reliability in the American River basin by avoiding low reservoir levels.
  • Avoid redirected impacts to Sacramento River fisheries.
Future of the project

The latest version of the Modified Flow Management Standard (FMS) was submitted to the State Water Resources Control Board in November 2017 as part of a protest of the pending water right application for the Delta Tunnels, or WaterFix project.

Climate scientists predict that Northern California will be warmer and water conditions will be extreme – including more frequent droughts.  The Modified FMS and its inherently adaptive approach promises to provide the best protection for Sacramento’s ecosystem and water supply in the future.