Risk-Informed Future Climate Scenario Development for the State Water Project Delivery Capability Report

California Department of Water Resources (DWR) | August 24th, 2023

This report introduces and documents an extensive effort undertaken by the California Department of Water Resources (DWR) to develop risk-informed future climate scenario

This report introduces and documents an extensive effort undertaken by the California Department of Water Resources (DWR) to develop risk-informed future climate scenarios for the State Water Project (SWP) Delivery Capability Report (DCR), a report issued by the SWP every two years. These reports present DWR’s analysis of the SWP system and planning information for users of SWP water. The analysis provides information about how climate change, regulatory, and operational considerations affect SWP delivery capability. Specifically, the report must provide “…under a range of hydrologic conditions, the then existing overall delivery capability of the project facilities and the allocation of that capacity to each contractor. The range of hydrologic conditions shall include the historic extended dry cycle and long-term average.” (Settlement Agreement 2003).

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.

SacPAS Fish Model: A model for emergence, migration and survival of Sacramento River salmon

Delta Stewardship Council (Delta Council) | November 1st, 2017

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 river basins: Procedures for hydrologic analysis

U.S. Army Corps of Engineers (USACE) | September 9th, 2008

The primary purpose of this document is to describe the methods and procedures we will use to complete the hydrologic analysis of the Sacramento and San Joaquin river b

The primary purpose of this document is to describe the methods and procedures we will use to complete the hydrologic analysis of the Sacramento and San Joaquin river basins. Specifically, we describe the required inputs, models, analysis, and anticipated results. This description will give the HAC an opportunity to review, in advance, the procedures for the hydrologic analysis. The secondary purpose of this paper is to initiate development of a project management plan (PMP) by outlining specific procedural tasks to be completed in the hydrologic analysis.

Salinas Valley Integrated Hydrologic and Reservoir Operations Models, Monterey and San Luis Obispo Counties, California

Monterey County Resources Agency (MCRA) | April 5th, 2025

To evaluate the challenging water management issues in the Salinas Valley, the U.S. Geological Survey, Monterey County Water Resource Agency, and the Salina

To evaluate the challenging water management issues in the Salinas Valley, the U.S. Geological Survey, Monterey County Water Resource Agency, and the Salinas Valley Basin Groundwater Sustainability Agency developed a comprehensive suite of models that represent the Salinas Valley Hydrogeologic system called the Salinas Valley System Model. The Salinas Valley Geologic Framework was developed to characterize the subsurface using various topographic and geologic data sources, including information on hydrogeologic units, their surfaces and extents, geologic structures, lithology, and elevations from borehole data and cross sections, as well as details on faults and existing models. The Salinas Valley Watershed Model simulates the entire Salinas River watershed. Monthly surface water inflows into the integrated hydrologic model domain were simulated using the Salinas Valley Watershed Model. The historical model uses historical climate data, water and land use data, and reservoir releases to simulate agricultural operations, including landscape water demands, diversions, and reclaimed wastewater. The operational model adds an embedded reservoir operations framework to the simulation of the historical model that allows specified operational rules to simulate reservoir releases and changes in reservoir storage. The operational model assumes current reservoir operations and constant land use, which differs from historical conditions. Thus, the operational model is a hypothetical baseline model that can be used by local water managers to evaluate and quantify potential benefits of water supply projects. Together, the geologic framework, watershed, historical, and operational models form a tool that can be used to simulate irrigated agriculture and associated reservoir operations of the integrated hydrologic system of the Salinas Valley.

Salt Tolerance of Crops in the Southern Sacramento-San Joaquin Delta

California State Water Resources Control Board (SWRCB) | January 5th, 2010

The purpose of this report is to research the scientific literature and provide the state of knowledge on subjects that impact crop productivity with saline irrigation wa

The purpose of this report is to research the scientific literature and provide the state of knowledge on subjects that impact crop productivity with saline irrigation water and analyze the existing information from the South Delta and quantify how the various factors influencing the use of saline water applies to conditions in the South Delta. There are five objectives for this study: One of the objectives of this study is the review of existing literature relating to the effect of salinity on a variety of irrigated crops under South Delta conditions, preparation of a comprehensive list of references, and a synopsis of findings from key references. A second objective is the review of the relative strengths and limitations of steady-state and transient models that have been used to determine the suitability of saline water for crop production. As part of this second objective, the strengths, limitations, and assumptions of each model when applied to field conditions are to be presented. The third objective involves the use of soil information to determine and describe the approximate area and nature of saline and drainage-impaired soils; an estimate of the effectiveness of local rainfall in reducing the irrigation requirement; and compiling and evaluating historical crop types, acreages, and evapotranspiration information. The fourth objective is to provide conclusions and recommendations to the State Water Resources Control Board based upon the literature, modeling, and data evaluation.  Among the conclusions and recommendations to be reported the following are considered paramount. (1) Identify significant gaps or uncertainties in the literature and recommend future studies to fill the gaps. (2) Using a steady-state model and appropriate data for the South Delta, estimate the leaching fraction required for salinity control for crops regularly grown on the drainage- and salinity-impaired soils of the South Delta. (3) Using the approach as in (2), recommend a salinity guideline that could provide full protection of the most salt sensitive crop currently grown or suitable to be grown on the drainage- and salinity- impaired soils. The final objective is to present the findings and recommendations in Sacramento to interested stakeholders and representatives of California state agencies.

Salton Sea Management Program Conceptual Project Implementation and Cost Estimates to Meet State Board Targets

California Natural Resources Agency (CNRA) | April 27th, 2017

The Salton Sea Management Program (SSMP) has developed a 10-year plan for Phase I that envisions a range of activities for habitat creation and dust management as

The Salton Sea Management Program (SSMP) has developed a 10-year plan for Phase I that envisions a range of activities for habitat creation and dust management as the Salton Sea recedes over 2018–2028. The California State Water Resources Control Board (SWRCB), through an order revising Order WRO 2002–0013, outlines annual and cumulative target areas for restoration through creation of habitat and dust suppression projects. These targets are defined for each year, ranging from a cumulative 500 acres by January 1, 2019, to a cumulative 29,800 acres by January 1, 2029, with a minimum 50 percent of the area being designated for fish and wildlife habitat projects. Areas around the sea are proposed for restoration projects, specifically at the southern end of the sea near the inflows of the Alamo and New rivers, and the northern end of the sea near the inflow of the Whitewater River. In a prior document (Salton Sea Management Plan Phase I: 10 Year Plan, March 2018), an overview of the project areas and activities was presented. This document presents a high-level plan for achieving the annual goals in the SWRCB order, by means of creation of wet habitat and dust control areas in different parts of the Salton Sea lakebed. This document identifies conceptual habitat ponds to be created, the associated wetted areas, and the additional dust control areas required to meet the order targets. For each of the conceptual project areas, there are estimates for berm lengths, heights, and needs for additional infrastructure, such as pumps and pipelines, causeways for equipment access, and levee extensions along river channels for flood protection of newly created habitat. Planned cross sections for the different types of linear structures are shown. Cost estimates are provided for each of the project areas over time to develop a total cost estimate. The conceptual habitat and dust control areas are based on the best current information on Salton Sea bathymetry, and demonstrate a reasonable path forward to attain the State Board order targets. The costs associated with these targets as presented in this document can be used for additional planning as part of the SSMP over the next decade. It is recognized that the actual footprints of individual projects may change in future years as better information becomes available on lakebed elevations, and relationships with other non-SSMP projects for habitat and dust control are better understood. These cost estimates are a refinement of estimates presented in the Salton Sea Management Plan Phase I: 10-Year Plan (March 2017). The cost estimates incorporate the best available cost information, and include the development of conceptual berm designs and supporting infrastructure, such as water diversions, pumps, and pipelines, and levees for river extensions. For these reasons, the cost estimate presented here supersedes the March 2017 estimate of $383 million for the 10-year implementation. But, all cost estimates at this stage are considered preliminary, and subject to revision as new field and construction data become available, and as designs are adjusted to best meet overall program needs. In the remainder of this document, two key topics are presented. In Chapter 2, there are estimates of the projected elevations of the Salton Sea over the 2018–2028 period, based on a hydrologic model of the sea. This is needed to allow estimation of exposed lakebed with the goal of constructing new habitat under dry conditions. Proposed conceptual project footprints, design and cost assumptions, and cost summaries are presented in Chapter 3.

Salton Sea Management Program Phase I: 10-Year Plan

California Natural Resources Agency (CNRA) | March 1st, 2017

Under the leadership of Governor Edmund G Brown Jr., the 2014 California Water Action Plan set forth a vision for California water management that balances statew

Under the leadership of Governor Edmund G Brown Jr., the 2014 California Water Action Plan set forth a vision for California water management that balances statewide water supply security with the protection of public, economic and ecological health. The Salton Sea offers a unique opportunity to preserve these values by leveraging a convergence of support from federal, state, and local stakeholders for a smaller and sustainable sea achieved through the projects outlined in this plan. The Salton Sea is California’s largest lake. Thirty-five miles long and 15 miles wide, the desert lake extends from the Coachella Valley into the Imperial Valley. Though saltier than the ocean, the Sea supports an abundance of fish, a food source for millions of migratory birds on the Pacific Flyway. Managing the Sea’s natural, agricultural, andmunicipal water inflows to maximize bird and fish habitat and minimize fine-particle air pollution will allow California to protect regional health, ecological wealth and a stable water supply. The Salton Sea formed in the Salton Trough in Imperial and Riverside counties. Much of the trough is below sea level and has a long history of periodic inundation from the shifting delta of the Colorado River or from infrequent storm events. The last Colorado River inundation of the area occurred in 1905 when an irrigation canal inlet gate failed and flooded much of the area. Since then, lake inflows have been primarily from agricultural activities in the area. Inflows from the New and Alamo rivers are primarily farm return flow water, although there is some inflow from Mexico, particularly during large precipitation events. Over the last several decades, water levels at the Salton Sea have declined and salinity concentrations have increased due to climate fluctuations, agricultural conservation measures, cropping practices and reduced inflows from Mexico. Recent water transfers from the Imperial Valley have further accelerated the rate of lake elevation decline and have increased the rate of salinity concentration. Declining lake levels threaten important bird habitat and pose public health risk due to particulate air pollution. Over the last 40 years numerous ideas and plans have been proposed by various entities to restore the Salton Sea. None have been implemented for a variety of reasons, including lack of a shared vision, funding constraints, and reduced inflows. In 2015, Governor Edmund G. Brown Jr. formed the Salton Sea Task Force with principle staff and members of various state agencies to identify short- and medium- term goals to respond to air quality and ecological threats at the Salton Sea. The Task Force developed actions for the Salton Sea that included: Develop and implement the Salton Sea Management Program through departments within the California Natural Resources and Environmental Protection Agencies Improve public outreach and local partnerships Accelerate project implementation and delivery Meet a short-term goal of 9,000 acres to 12,000 acres of dust suppression and habitat projects Establish a medium-term goal of 18,000 acres to 25,000 acres of dust suppression and habitat projects. The State’s Salton Sea Management Plan (SSMP) has several phases of development to protect air quality and ecosystem values at the Salton Sea. This draft technical memorandum prepared by the State of California outlines the SSMP’s first, 10-year phase (Phase I Plan). It will guide State and federal actions to meet the commitments outlined in the Memorandum of Understanding (MOU) executed on August 31, 2016, and amended on January 18, 2017 by the Department of Interior (DOI) and the California Natural Resource Agency (CNRA). The MOU, among other things, identified a goal of developing projects to protect or improve air quality, wildlife habitat, and water quality as necessary to minimize human health and ecosystem impact at the Salton Sea in the mid-term. While guided by the MOU, the SSMP is a longer-term process that has been developed and will be implemented by the State of California. This first phase of development has been planned to expedite construction of habitat and to suppress dust on areas of playa that have been or will be exposed at the Salton Sea by 2028. The Phase I Plan outlines the process for developing additional management measurements for the Salton Sea that will be implemented in later phases. The Phase I Plan also addresses the requirements of Assembly Bill 1095 (Garcia 2015) by including those projects deemed “shovel-ready projects” and including estimates of cost. Those projects include: Water backbone infrastructure, which will provide conveyance of river and Salton Sea water to air quality and habitat projects. SSMP air quality and habitat projects associated with the water backbone infrastructure The CNRA’s Phase I Species Conservation Habitat Project (saline impoundments along the southern shore to support fish and wildlife) Red Hill Bay Project, an effort of the U.S. Fish and Wildlife Service and Imperial Irrigation District to restore habitat on the southeastern shore. Torres-Martinez Wetland project, an effort of the Torres Martinez Desert Cahuilla Indians to build shallow wetlands along the northern edge of the Salton Sea. The Phase I Plan considers the implications of the 17-year drought on the Colorado River. The drought may force reductions of Colorado River water to the Lower Basin States, which in turn could impact inflows to the Salton Sea. The U.S. Bureau of Reclamation, seven Colorado River basin states and key principals of several water management agencies have been developing a Drought Contingency Plan (DCP) that includes implemented and proposed actions to address the potential water shortage. The Department of Interior Order No. 3344 - Actions to Address Effects of Historic Drought on Colorado River Water Supplies (DOI, January18, 2017) further outlines the details of the DCP. One component of the Phase I Plan is to evaluate the current hydrologic modeling for the Salton Sea and to include some of the proposed actions in the model to evaluate their potential impact to Salton Sea inflows.   As the Air Quality Planning and Implementation section of this document notes, the air quality mitigation will consist of measures to keep exposed playa wet or vegetated. A series of Best Available Control Measures (BACM) are being evaluated by the Quantification Settlement Agreement (QSA) Water Transfer mitigation program, which was created under a 2003 agricultural-to-urban water transfer agreement involving the State of California, the Imperial Irrigation District, Coachella Valley Water District, and the San Diego County Water Authority. The work of determining these best strategies will be paid for by the QSA Joint Powers Authority. The Phase I Plan involves coordination among Imperial Irrigation District, Imperial County Air Pollution Control District, South Coast Air Quality Management District and other agencies to ensure that the latest information about how lakebed exposure may affect air quality is included in the development of BACM pilot projects. In order to provide ample time for public input into this plan, the SSMP will schedule several regional workshops to solicit input from community members and stakeholders as well as provide necessary time for general public comment. This process will be announced via the program’s website. Associated documents: Salton Sea Management Program Conceptual Project Implementation and Cost Estimates to Meet State Board Targets, 4/27/2018 Appendix 1. Figures Appendix 2. Cost Projections Appendix 3. Ten-Year Phase I Plan Schedule Plan Spanish Translation: Programa de Gestión de Salton Sea Fase I: Plan de 10 Años *Plan appendices index from California Natural Resources Agency.

San Diego County Ecosystems: Ecological Impacts of Climate Change on a Biodiversity Hotspot

California Energy Commission (CEC) | August 27th, 2018

The diverse ecosystems, habitats, plants, and animals in the San Diego County region will be impacted by climatic shifts in multifold ways due to current and future vari

The diverse ecosystems, habitats, plants, and animals in the San Diego County region will be impacted by climatic shifts in multifold ways due to current and future variability, along with other factors including habitat loss and fragmentation, land use shifts, and changing fire regimes. While home to a major metropolitan area, San Diego County still hosts expanses of native and preserved habitats where management and conservation action could be greatly enhanced through science-based assessments and planning for climate change and increased climate variability. Projections of climate change in the region include warming by 4-9° F on average, and a 15-25% decrease in fall and spring precipitation with an increase in variability resulting in more frequent and intense droughts punctuated by increasingly rare yet extreme precipitation and flooding events. In addition, an increase in fire events and potential lessening of coastal marine influence may also affect San Diego’s ecosystems. Climate warming superimposed upon the pronounced spatially-varying temperature in the San Diego region will likely be associated with range shifts for many species resulting in novel community assemblages and biotic interactions and could create phenological mismatches. More frequent and intense heat waves may disproportionately affect younger age classes and reduce reproductive and survival rates of species sensitive to temperature extremes. With increasingly variable precipitation, drought may occur more frequently due to increased occurrence of dry days and could intensify because of warmer temperatures. Since drought disproportionately affects some species, these projected changes may cause structural changes to ecosystems. Santa Ana winds, occurring during increasingly dry fall months, would create ideal fire conditions. Coastal low clouds and fog along San Diego’s coast buffer this zone from the effects of warming and drying through shading and cooling. Although these marine stratus clouds will remain a presence, future changes in this phenomenon are uncertain. The spatial and temporal scales at which climate variations and change operate must be considered to build resilience into natural systems. Effective conservation actions will need to build on ongoing efforts focused on landscape-scale planning rather than more traditional single-species approaches. To carry this out will require cross-jurisdictional, multidisciplinary collaboration by scientists, policy-makers, planners, land managers, and the broader conservation community, which has a decades-long history of accomplishment in San Diego County.