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Recent Scientific Contributions by the U.S. Geological Survey in the San Francisco Bay and Sacramento–San Joaquin Delta Estuary

Fact Sheet 2025-3058
By:  and 
https://doi.org/10.3133/fs20253058

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Introduction 

The San Francisco Bay and Sacramento–San Joaquin Delta Estuary (hereafter, Bay-Delta) is the largest estuary on the West Coast of the United States. The Bay- Delta covers more than 1,600 square miles and drains a watershed of more than 75,000 square miles, which is greater than 40 percent of California. The region surrounding the Bay- Delta is home to about 10 million people, and its habitats (fig. 1) support more than 800 plant and animal species. The waterways of the Bay- Delta are the central hub of California’s extensive freshwater delivery system, supplying water to more than 27 million Californians and 4 million acres of farmland in the Central Valley.

The U.S. Geological Survey (USGS) is the primary science agency of the U.S. Department of the Interior, providing a broad range of Earth, water, biological, and mapping data and expertise to inform natural resource management across the country. This fact sheet focuses on research conducted by the USGS in the Bay- Delta region, mostly within the past 5 years. The fact sheet is organized across five major themes: water flow and water quality, fish and wildlife, wetland restoration, invasive species, and hazards. In each of these areas, the USGS works closely with Federal, State, and local agencies; academia; and non- governmental organizations to provide objective, evidence-based science. The data and knowledge gained from USGS research and monitoring are publicly available and are routinely used by agencies, including the U.S. Bureau of Reclamation, U.S. Army Corps of Engineers, U.S. Fish and Wildlife Service, California Department of Water Resources, California Department of Fish and Wildlife, California State Water Resources Control Board, Delta Stewardship Council, and many additional organizations and stakeholders to inform management of the Bay- Delta region and its resources.

Plain Language Summary

The U.S. Geological Survey (USGS) is the primary science agency of the U.S. Department of the Interior. In the San Francisco Bay and Sacramento–San Joaquin Delta Estuary (Bay-Delta) of California, the USGS plays a unique role in providing scientific leadership because of its broad research and monitoring capabilities, innovative methodologies for data collection and analysis, and dedication to objective and credible science. This fact sheet provides a summary of recent USGS projects across the Bay-Delta organized under five major research themes: water flow and water quality, fish and wildlife, wetland restoration, invasive species, and hazards. A key component of USGS research is close collaboration with State and Federal partners, academia, and non-governmental organizations to accomplish its goals. The research and partnerships described in this fact sheet are critical to the management of the complex natural resource issues across the Bay-Delta region of California.

Suggested Citation

Drexler, J.Z., and Weltzin, J.F., 2026, Recent scientific contributions by the U.S. Geological Survey in the San Francisco Bay and Sacramento–San Joaquin Delta Estuary: U.S. Geological Survey Fact Sheet 2025–3058, 6 p., https://doi.org/10.3133/fs20253058.

ISSN: 2327-6932 (online)

Study Area

Table of Contents

  • Introduction
  • U.S. Geological Survey Role
  • Water Flow and Water Quality
  • Wetland Restoration
  • Invasive Species
  • Hazards
  • Conclusions
  • Reference Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Recent scientific contributions by the U.S. Geological Survey in the San Francisco Bay and Sacramento–San Joaquin Delta Estuary
Series title Fact Sheet
Series number 2025-3058
DOI 10.3133/fs20253058
Publication Date January 26, 2026
Year Published 2026
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) California Water Science Center
Description 6 p.
Country United States
State California
Other Geospatial Sacramento–San Joaquin Delta Estuary, San Francisco Bay
Online Only (Y/N) Y
Additional publication details