San Joaquin River

River Floods Under Wetter Antecedent Conditions Deliver Coarser Sediment to the Coast

American Geophysical Union (AGU) | April 13th, 2025

Increasing hydrologic volatility—more extreme rain, and larger variations between wet and dry years—has become apparent in some regions, but few data exist to determi

Increasing hydrologic volatility—more extreme rain, and larger variations between wet and dry years—has become apparent in some regions, but few data exist to determine how intensifying hydrologic extremes affect sedimentary systems. Using uniquely high-resolution records of fluvial suspended sediment and coastal morphology, we quantify sedimentary responses from a steep, 357-km2 watershed in California under extreme wet and dry hydrologic conditions. In years with multiple 2- to 10-year floods, fluvial sediment coarsened significantly as the wet season progressed, with late-season floods delivering dominantly sand-sized material to the coast. Greater and coarser sediment supply under wetter antecedent conditions affected nearshore geomorphic evolution for 4–5 years. The watershed and coastal changes we documented point to an increasing role of sediment-related hazards (flooding and hillslope erosion) and resources (nearshore accretion) as wet seasons intensify.

River-Aquifer Interactions, Geologic Heterogeneity, and Low-Flow Management

U.S. Geological Survey (USGS) | ?

Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard mater

Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard materials beneath the river. Low flows are often important ecologically. Numerical simulations were used to assess how textural heterogeneity of an alluvial system influences river seepage and low flows. The Cosumnes River in California was used as a test case. Declining fall flows in the Cosumnes River have threatened Chinook salmon runs. A ground water–surface water model for the lower river basin was developed, which incorporates detailed geostatistical simulations of aquifer heterogeneity. Six different realizations of heterogeneity and a homogenous model were run for a 3-year period. Net annual seepage from the river was found to be similar among the models. However, spatial distribution of seepage along the channel, water table configuration and the level of local connection, and disconnection between the river and aquifer showed strong variations among the different heterogeneous models. Most importantly, the heterogeneous models suggest that river seepage losses can be reduced by local reconnections, even when the regional water table remains well below the riverbed. The percentage of river channel responsible for 50% of total river seepage ranged from 10% to 26% in the heterogeneous models as opposed to 23% in the homogeneous model. Differences in seepage between the models resulted in up to 13 d difference in the number of days the river was open for salmon migration during the critical fall months in one given year.

Rivers of California

Pacific Gas & Electric Company (PG&E) | July 1st, 1962

Root Creek Water District Groundwater Sustainability Agency Groundwater Sustainability Plan

Root Creek Water District | November 11th, 2019

Root Creek Water District Groundwater Sustainability Plan

Root Creek Water District | March 20th, 2023

Root Creek Water District Groundwater Sustainability Plan

Root Creek Water District | November 11th, 2019

The RCWDGSA covers almost 10,000 acres in southeast Madera County located southwest of the intersection of State Highway 41 and Avenue 12 along the banks of and just nort

The RCWDGSA covers almost 10,000 acres in southeast Madera County located southwest of the intersection of State Highway 41 and Avenue 12 along the banks of and just north of the San Joaquin River. In size, the GSA accounts for less than 3 percent of the land area within the Madera Basin. The District, which lies wholly within the GSA has recently contracted for surface water supplies from the Madera Irrigation District (MID) and the Wonderful Nut Orchards for up to 17,000 acre-feet (af) of surface water in a given year. The District has also recently completed the first phase of an agricultural conveyance and distribution system that has the ability to deliver surface water to approximately 2,500 acres of farmland. Since its completion, the system has delivered approximately 16,382af of surface water to date in the past three years.To accomplish these achievements the district has invested more than 12 million dollars. While large, the purchase and delivery of surface water supplies are crucial to the long-term groundwater sustainability of not only the District and the GSAbut also the region and the subbasin.

Ruling on Motions for Preliminary Injunction in Tulare Lake Basin Water Storage District v. California Department of Water Resources

Superior Court of California, County of Sacramento | June 20th, 2024

Sacramento and San Joaquin Basins Climate Impact Assessment

U.S. Bureau of Reclamation (USBR) | September 8th, 2014

Through West-Wide Climate Risk Assessments (WWCRAs) conducted under that program, Reclamation is conducting reconnaissance-level assessments of risks to water supplies an

Through West-Wide Climate Risk Assessments (WWCRAs) conducted under that program, Reclamation is conducting reconnaissance-level assessments of risks to water supplies and related resources in eight major Reclamation river basins in the Western United States. This report presents the results of the Sacramento and San Joaquin Climate Impact Assessment (SSJIA), which addresses impacts in two of these major basins in California. The SSJIA also includes the Tulare Lake Basin in the southern part of the Central Valley of California; part of the Trinity River watershed from which some water is diverted into the Central Valley; and a portion of California’s central coast region where Central Valley Project (CVP) and State Water Project (SWP) water supplies are delivered. The water supplies and demands analyzed in the SSJIA include CVP water users, SWP water users, and the other non-project water users in the study area. Included in the report is an overview of the current climate and hydrology of California’s Central Valley (Sacramento, San Joaquin and Tulare Lake Basins), an analysis of observed trends in temperature and precipitation over historical record, and a comparison of these trends to future water operation projections not considering climate change. The report then presents hydrologic projections developed from global climate models to evaluate the ways that projected climatic and hydrologic changes could impact water availability and management and water demands within the Sacramento, San Joaquin and Tulare Lake basins. The SSJIA analyzes potential impacts of climate change under a current trends projection of future urban growth considering the conversion of agricultural to urban land use and assuming the continuation of current crop types in the Central Valley. Finally, the SSJIA assesses risks to the eight major resource categories identified in the SWA by looking at a range of climate futures and attempting to book-end future uncertainties.

Sacramento and San Joaquin River Basins Comprehensive Study Technical Studies Documentation: Reservoir Operations Modeling - Existing Design Operations and Re-operation Analyses

U.S. Army Corps of Engineers (USACE) | December 1st, 2002

In response to extensive flooding and damages experienced in 1997, the United States Congress authorized the U.S. Army Corps of Engineers, Sacramento District (USACE) to

In response to extensive flooding and damages experienced in 1997, the United States Congress authorized the U.S. Army Corps of Engineers, Sacramento District (USACE) to provide a comprehensive analysis of the Sacramento and San Joaquin river basin flood management systems and to partner with the State of California to develop master plans for flood damage reduction. The USACE and the State Reclamation Board of California are leading this Comprehensive Study to improve flood management and integrate ecosystem restoration in the Sacramento and San Joaquin river basins. The authorization for the Comprehensive Study directed the development of hydrologic and hydraulic models for both river basins that will allow systematic evaluation. These models incorporate reservoir operations and flow along the major river systems to evaluate the performance of the flood management systems. The models can be used to assess the performance of the current systems or modified systems under a wide range of hydrologic conditions. This report documents the work conducted for the Sacramento and San Joaquin River Basins Comprehensive Study to develop reservoir operation models, specifically Phase II – Model Refinement and Simulation of both existing operational conditions and evaluation of flood management alternatives. The main product components of this effort include: HEC-5 Reservoir Operation Models for the Sacramento and San Joaquin River basins, which will include headwater and major flood management reservoirs. The first part of this document is limited to the use of reservoir models to identify and describe baseline conditions. It does not include the formulation or evaluation of flood management alternatives. The performance of modified flood management strategies is addressed within subsequent sections of this document. Future work will continue to use these models in the analysis of alternatives for reducing flood damages in California’s Central Valley.

Sacramento and San Joaquin Rivers Basin Study: Technical Report

U.S. Bureau of Reclamation (USBR) | March 8th, 2016

This Technical Report supplements the Sacramento and San Joaquin Basins Study Report (Summary Report) by providing greater detail on the technical approach employed in th

This Technical Report supplements the Sacramento and San Joaquin Basins Study Report (Summary Report) by providing greater detail on the technical approach employed in this analysis, including assumptions, methodologies and results not included in this Report. See the Summary Report for a discussion of the Basin Study program context (Section 1), basin settings (Section 2), and historic and projected climate (Section 2). Figure P-1 shows the geographic area included in the study. The Central Valley and regions that depend on the Sierra Nevada and Coast Range mountains for water have been facing rising demands for water from rapidly increasing populations, changes in land use, and growing urban, agricultural and environmental demands. These demands already exceed the capacity of the existing water management system to supply adequate water—especially in droughts like the one California is now experiencing. Future climate changes are likely to increase the challenges that have already occurred in the 20th century. This Basins Study builds on previous climate impact assessments and addresses both the potential impacts of climate and socioeconomic changes and explores how these challenges might be addressed (see Section 1. Introduction of the Summary Report).