American River Basin Study

Final Report

The American River Basin Study (ARBS) was released in August 2022. To view the U.S. Bureau of Reclamation (USBR) press release, see American River Basin Study finds that increasing temperatures and changing precipitation will impact basin through rest of 21st century. For more information about the study, visit the USBR's ARBS webpage.

• Appendix A - Communication and Outreach Activities
• Appendix B - Development of Future Climate and Hydrology Scenarios
• Appendix C - CalSim 3 Upper American River Module Documentation
• Appendix D - Development of Urban and Agricultural Demands
• Appendix E - Adaptation Measure Preliminary Screening Results
• Appendix F - Draft Description of Adaptaion Portfolios
• Appendix G - Adaptation Portfolios Evaluation Results
• Appendix H - Lower American River Water Temperature Modeling Documentation and Results

Background

Water managers in the American River Basin continue to experience a growing imbalance between water demands and water supply due to a variety of factors, including population growth; increased regulatory requirements; changes in Central Valley Project (CVP) operations; inadequate infrastructure; and lack of interagency planning necessary to address emerging climate change conditions, and increasingly intense and more frequent extreme events (droughts and floods).

The U.S. Department of the Interior, Bureau of Reclamation (Reclamation) recently completed the Sacramento and San Joaquin Rivers Basin Study (SSJRBS) (March 2016). The SSJRBS forecasts the potential impacts of climate change on water supply, water quality and critical habitat within California’s Central Valley. The 60,000 square mile study area for the SSJRBS encompasses all main tributaries within the Central Valley as well as the Sacramento-San Joaquin Delta (Delta), the largest estuary on the west coast of North America. The SSJRBS outlines potential impacts over a range of possible future climate conditions on various natural resources and presents portfolios of broad adaptive strategies for consideration by water agencies and other interests.

The purpose of the American River Basin Study (ARBS or Study) is to refine and update the data, tools, analyses, and adaptation strategies in the SSJRBS for the American River Basin. Specifically, the ARBS will update the SSJRBS to reflect basin-specific, integrated water management strategies to improve regional water supply reliability within the American River Basin, while improving the Reclamation’s flexibility in operating Folsom Reservoir to meet flow and water quality standards and protect endangered fishery species in the lower American River.

The ARBS will present a holistic examination of water management practices to address significant recent changes in conditions and regulatory requirements related to the CVP and regional water management, including Biological Opinions for endangered fishery species protection, the State’s Sustainable Groundwater Management Act, and the science of climate change.

Basin Study Objectives

Under the “new normal” of a changing climate, the ARBS will improve the resolution of regional climate change data and develop regionally-specific mitigation and adaptation strategies, building on those identified in the SSJRBS. The ARBS will:

• Further refine an assessment of water supplies and demands for the American River Basin over the data developed for the SSJRBS.
• Address regional demand-supply imbalance and infrastructure deficiencies under the threat of climate change.
• Improve regional self-reliance and collaboration for sustainable water resources management and quality of life.
• Integrate regional water supply reliability with operational flexibility for Reclamation's Folsom Dam and Reservoir to help meet all authorized purposes of the CVP.
• Align regional water management strategies and planning efforts with those of Reclamation.

The ARBS will address the following specifically required Basin Study elements:

• Develop projections of future water supply and demand in the basin, including an assessment of risk to the water supply relating to climate change as defined in Section 9503(b)(2) of the SECURE Water Act.
• Analyze how existing water and power infrastructure and operations will perform in the face of changing water realities and other impact identified in Section 9503(b)(3) of the SECURE Water Act, including the ability to deliver water; hydroelectric power generation; recreation; fish and wildlife habitat; applicable species listed as endangered, threatened, or candidate species and/or designated critical habitat under the Endangered Species Act of 1973; water quality issues (including salinity levels); flow and water dependent ecological resiliency; and flood control and/or management.
• Develop appropriate adaptation and mitigation strategies to meet future water demands.
• Complete a trade-off analysis of the identified options, including an analysis of all options in terms of their relative cost, environmental impact, risk, stakeholder response, or other common attributes.

The ARBS will provide a unique opportunity to align the water management strategies and planning efforts of the region with those of Reclamation and the CVP, and Study Partners are committed to pursuing integrated water management solutions that benefit all parties.

Description of Study Area

The American River is one of four major tributaries to the Sacramento River. Figure 1-1 shows the Study Area - the American River Basin - that is bounded by the Bear River to the north, the Cosumnes River to the south, the Sierra Nevada mountain range to the east, and the Feather and Sacramento Rivers to the west. The Study Area encompasses two parts:

• American River Watershed - This watershed covers 2,140 square miles from Sacramento to the peaks of the northern Sierra Nevada mountains west of Lake Tahoe. Areas outside of the watershed that are served by Study Partners with American River water are also included in the Study Area.
• North and South Groundwater Subbasins - These two groundwater basins in the west side of the Study area are separated by the American River, and their eastern boundary represents the approximate edge of the alluvial basin, where little or no groundwater flows into or out of the groundwater basins from the Sierra Nevada basement rock. In addition to surface water from the American River, local water agencies use groundwater for their water supply needs.

Figure 1-1. American River Basin Study Area Map

Cost-Share Partners

Public and Stakeholder Participation

The ARBS will seek to be open and inclusive and to encourage diverse viewpoints. The Study Partners will be seeking broad stakeholder and public participation at key points during the ARBS development process. Stakeholders and interested members of the public can be notified of public meetings/workshops via the ARBS Web site, or elect to sign up for email notifications here. “Request to join ARBS Stakeholder distribution list.” Email distribution will be an important tool to keep interested stakeholders and the public informed on ARBS progress, timing of deliverables, and opportunities for input (e.g., public meetings/workshops).

In an effort to maximize public outreach, news/press releases will be developed and issued by the Study Partners at key points in the ARBS process, including:

• Initiation of ARBS development.
• Major ARBS milestones.
• Completion of the Draft ARBS Report.
• Completion of the Final ARBS Report.
• Notification of Public Meetings/Workshops.

The Study Partners intend to hold public meetings/workshops at key points during development of the ARBS for informational purposes and to solicit feedback/input. These meetings/workshops will be publicized with news/press releases, email notifications, Web site postings, targeted invitations, and/or other methods (as appropriate). If interested, please contact the Project Manager for the next Public Meeting.

Contact Information - Co-Study Managers