Supplement to the 2007 Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead

U.S. Bureau of Reclamation (USBR) | May 6th, 2024

This ROD revises the 2007 Interim Guidelines for the near-term operation of Glen Canyon and Hoover Dams to address the potential for continued low-runoff conditions in th

This ROD revises the 2007 Interim Guidelines for the near-term operation of Glen Canyon and Hoover Dams to address the potential for continued low-runoff conditions in the Basin. Reclamation has concluded that the potential impacts of low-runoff conditions pose unacceptable risks to routine operations of Glen Canyon and Hoover Dams during the remainder of the interim period (through the end of the 2026 operating year) and that modified operating guidelines need to be expeditiously developed.

Synthesis of data and studies relating to Delta Smelt biology in the San Francisco Estuary, emphasizing water year 2017

Interagency Ecological Program (IEP) | November 1st, 2021

In the San Francisco Estuary (SFE), the effects of freshwater flow on the aquatic ecosystem have been studied extensively over the years and remains a contentious managem

In the San Francisco Estuary (SFE), the effects of freshwater flow on the aquatic ecosystem have been studied extensively over the years and remains a contentious management issue. It is especially contentious with regards to the Delta Smelt (Hypomesus transpacificus), a species endemic to the SFE that has been listed as threatened under the Federal Endangered Species Act and endangered by the State of California. Early studies of Delta Smelt distribution within the SFE suggested that Delta Smelt habitat is determined largely by freshwater flow; however, the exact mechanisms and processes producing such benefits remained unclear. In the summer of 2017, the Flow Alteration Management, Analysis, and Synthesis Team (FLOAT-MAST) was established to analyze, synthesize, and summarize the data collected from the various flow-related monitoring and special studies occurring in 2017(see Table Intro 4). This report will focus on the 2017 summer-fall status of Delta Smelt and its habitat following a record wet year. There has been a long-term decline in the abundance of Delta Smelt associated with a decline in other pelagic fishes. Investigators concluded that the decline has likely been caused by the interactive effects of several causes, including changes in both physical and biotic habitats, many of which are tied to amount and timing of freshwater flow. For this report, we formulated a number of basic predictions about the likely effects of high flows in 2017 on Delta Smelt and their habitat (Table 3). We use a qualitative weight of evidence approach to evaluate whether these predictions were supported by available data. Data sources included a variety of long-term monitoring surveys conducted by Interagency Ecological Program (IEP) agencies, as well as model outputs. Delta Smelt population, health, and life history metrics rarely responded as predicted. Water temperature appears to have a stronger effect on Delta Smelt growth rate and some metrics of life history diversity than outflow or X2 position. Other life history diversity attributes varied but did not appear to be driven by outflow or temperature. Health status was difficult to interpret. Low prevalence of lesions and improved nutritional condition during the drought was contradicted by declining overall population levels. Because of the sparse catches of Delta Smelt in the post-POD years, we consider the data insufficient to reach firm conclusions about the predictions concerning range and distribution of Delta Smelt, especially in the fall. The prediction of high survival was not supported. The 2017 Delta Smelt year class began with poor recruitment in spring of 2017 and below average survival for spring to summer and summer to fall. Thus, low production and low survival led to low abundance of all life stages. During the fall to winter period survival improved, yet the resulting adults were low in number. Foraging success of the fish captured, as measured by stomach fullness, was high for juveniles and adults in 2017 relative to recent years associated with the higher densities of common zooplankton prey that occurred in 2017.

Synthesis of Studies in the Fall Low-Salinity Zone of the San Francisco Estuary, September–December 2011

U.S. Geological Survey (USGS) | July 14th, 2014

In fall 2011, a large-scale investigation (fall low-salinity habitat investigation) was implemented by the Bureau of Reclamation in cooperation with the Interagency Ecolo

In fall 2011, a large-scale investigation (fall low-salinity habitat investigation) was implemented by the Bureau of Reclamation in cooperation with the Interagency Ecological Program to explore hypotheses about the ecological role of low-salinity habitat in the San Francisco Estuary—specifically, hypotheses about the importance of fall low-salinity habitat to the biology of delta smelt Hypomesus transpacificus, a species endemic to the San Francisco Estuary and listed as threatened or endangered under federal and state endangered species legislation. The Interagency Ecological Program is a consortium of 10 agencies that work together to develop a better understanding of the ecology of the Estuary and the effects of the State Water Project and Federal Central Valley Project operations on the physical, chemical, and biological conditions of the San Francisco Estuary. The fall low-salinity habitat investigation constitutes one of the actions stipulated in the Reasonable and Prudent Alternative issued with the 2008 Biological Opinion of the U.S. Fish and Wildlife Service, which called for adaptive management of fall Sacramento-San Joaquin Delta outflow following “wet” and “above normal” water years to alleviate jeopardy to delta smelt and adverse modification of delta smelt critical habitat. The basic hypothesis of the adaptive management of fall low-salinity habitat is that greater outflows move the low-salinity zone (salinity 1–6), an important component of delta smelt habitat, westward and that moving the low-salinity zone westward of its position in the fall of recent years will benefit delta smelt, although the specific mechanisms providing such benefit are uncertain. An adaptive management plan was prepared to guide implementation of the adaptive management of fall low-salinity habitat and to reduce uncertainty. This report has three major objectives: •To provide a summary of the results from the first year of coordinated fall low-salinity habitat studies and monitoring. •To provide a synthesis of the results of the fall low-salinity habitat studies and other ongoing research and monitoring, to determine if the available information supports the hypotheses behind the adaptive management of fall low-salinity habitat as set forth in the adaptive management plan. •To begin to put the results from the fall low-salinity habitat studies into context within the larger body of knowledge regarding the San Francisco Estuary and, in particular, the upper San Francisco Estuary, including the Sacramento-San Joaquin Delta, Suisun Bay, and associated embayments.

System Reoperation Study, Phase 1: Plan of Study

California Department of Water Resources (DWR) | June 16th, 2011

System reoperation is generally defined as changing the operational and management procedures of existing water system facilities to obtain water resources related benefi

System reoperation is generally defined as changing the operational and management procedures of existing water system facilities to obtain water resources related benefits. Reoperation is considered an alternative to constructing major new facilities, although it may consist of physical modification of existing facilities. The specifics associated with a system reoperation strategy will vary among water purveyors depending upon the complexity of their system and their interest in participating in local and or interregional efforts. There may be opportunity to reoperate portions of California’s statewide water system to yield increased water resources related benefits. This opportunity was recently recognized by the State Legislature in Senate Bill X2 1 (SB X2 1) (Perata, 2008 – Water Code Section 83002.5), which mandated and allocated resources for “planning and feasibility studies to identify potential options for the reoperation of the state's flood protection and water supply systems that will optimize the use of existing facilities and groundwater storage capacity.” Specifically, SB X2 1 stipulated that “the studies shall incorporate appropriate climate change strategies and be designed to determine the potential to achieve the following objectives: (I) Integration of flood protection and water supply systems to increase water supply reliability and flood protection, improve water quality, and provide for ecosystem protection and restoration. (II) Reoperation of existing reservoirs, flood facilities, and other water facilities in conjunction with groundwater storage to improve water supply reliability, flood hazard reduction, and ecosystem protection and to reduce groundwater overdraft. (III) Promotion of more effective groundwater management and protection and greater integration of groundwater and surface water resource uses. (IV) Improvement of existing water conveyance systems to increase water supply reliability, improve water quality, expand flood protection, and protect and restore ecosystems. RELATED DOCUMENTS: System Reoperation Study, Phase 2: Strategy Formulation and Refinement System Reoperation Study, Phase 2: Appendix A: Forecast?Based Operations Analysis System Reoperation Study, Phase 2: Appendix B: Tradeoff Analysis System Reoperation Study, Phase 3 Report: Assessment of Reoperation Strategies System Reoperation, Phase 3: Appendix C: State Water Project and Central Valley Project Integrated Operations Analysis System Reoperation, Phase 3 Appendix D: Ecosystem Evaluation

System Reoperation Study, Phase 2: Appendix A: Forecast-Based Operations Analysis

California Department of Water Resources (DWR) | January 29th, 2014

The System Reoperation Study (“Reoperation Study”) is investigating changes in operations and other strategies that may result in improved system performance in terms

The System Reoperation Study (“Reoperation Study”) is investigating changes in operations and other strategies that may result in improved system performance in terms of additional water supply, flood hazard reduction, and ecosystem protection and restoration. It is recognized that existing reservoir operations are typically based on meeting all or some of these three objectives. As such, the Reoperation Study focuses on modifications to existing operations and expansion of these benefits. The Reoperation Study team has developed several reoperation components to evaluate at select river/reservoir systems to quantify benefits and improve understanding of the trade-offs involved. MBK Engineers is providing technical, strategic, and coordination support for the Reoperation Study.  An analysis of Forecast-Based Operation (F-BO) is part of that support. The following report summarizes this effort. F-BO can be applied to any reservoir with a traditional water supply and flood control space allocation paradigm. The incorporation of weather forecasts allows for greater flexibility in the management of the reservoir’s space (flood control versus conservation) and inherently increases the opportunities for gaining additional water supply and flood control benefits through its implementation. System reoperation is informed by historical flood patterns and utilizes records of inflow, outflow, and storage in the reservoirs to develop modified rules for flood releases. Changes to historical operations of the reservoirs is expected to reveal potential for additional water supply storage. With improvements to many of the reservoir facilities, such as increased release capacity, operations are no longer required to be as conservative as they once were. By reducing outflow and allowing an increase in water storage, significant improvements in water supply can be achieved. However, care must be taken so that sufficient water can still be evacuated in the event of a significant forecasted flood. RELATED DOCUMENTS: System Reoperation Study, Phase 1: Plan of Study System Reoperation Study, Phase 2: Strategy Formulation and Refinement System Reoperation Study, Phase 2: Appendix A: Forecast?Based Operations Analysis System Reoperation Study, Phase 2: Appendix B: Tradeoff Analysis System Reoperation Study, Phase 3 Report: Assessment of Reoperation Strategies System Reoperation, Phase 3: Appendix C: State Water Project and Central Valley Project Integrated Operations Analysis System Reoperation, Phase 3 Appendix D: Ecosystem Evaluation

System Reoperation Study, Phase 2: Appendix B: Tradeoff Analysis

California Department of Water Resources (DWR) | March 3rd, 2014

The System Reoperation Study is designed to identify potential options for the reoperation of the state’s flood control and water supply systems to meet the following o

The System Reoperation Study is designed to identify potential options for the reoperation of the state’s flood control and water supply systems to meet the following objectives: Water supply reliability Flood hazard reduction Ecosystem protection and restoration Reoperation options include integration of flood control and water supply systems, effective conjunctive management, and improvements to existing water conveyance systems. This phase of the analysis focuses on integration of flood control enhancing water supply systems and expanded conjunctive management with existing conveyance systems. An analysis was designed and performed with the goal of identifying potential reoperation options and to improve understanding of existing system constraints. The analysis is referred to as the tradeoff analysis in recognition of the fact that the existing flood control/water supply system is highly integrated and currently operated to meet water supply, flood control, and ecosystem purposes. Current system operations are complex and frequently constrained by flood control and ecosystem requirements and water rights and contracts for the beneficial use of water. Therefore, reoperation options designed to meet one of the three objectives of the System Reoperation Study frequently create tradeoffs with the other objectives. For example, reductions in required reservoir space for flood control may improve water supply reliability but increase risk of flood damage. The tradeoff analysis is a reconnaissance-level study designed to help illustrate how operational changes designed for one purpose can affect other objectives. Because the existing reservoir and conveyance system is highly integrated and constrained, changes in operation for one purpose create tradeoffs with other purposes. A reconnaissance-level study can help identify these tradeoffs, some of which may be unexpected or unintended, and thereby help guide refinement of more promising options. Model simulations performed in the tradeoff analysis are not refined for the purpose of quantifying benefits or impacts, but rather are intended to illustrate how operational changes in one area affect other areas. For example, how Central Valley Project (CVP) operations can affect State Water Project (SWP) operations, and vice versa. RELATED DOCUMENTS: System Reoperation Study, Phase 1: Plan of Study System Reoperation Study, Phase 2: Strategy Formulation and Refinement System Reoperation Study, Phase 2: Appendix A: Forecast?Based Operations Analysis System Reoperation Study, Phase 2: Appendix B: Tradeoff Analysis System Reoperation Study, Phase 3 Report: Assessment of Reoperation Strategies System Reoperation, Phase 3: Appendix C: State Water Project and Central Valley Project Integrated Operations Analysis System Reoperation, Phase 3 Appendix D: Ecosystem Evaluation

System Reoperation Study, Phase 2: Strategy Formulation and Refinement

California Department of Water Resources (DWR) | March 3rd, 2014

The California Department of Water Resources (DWR) is conducting a system reoperation study (SRS) in cooperation with other State and federal agencies, local water distri

The California Department of Water Resources (DWR) is conducting a system reoperation study (SRS) in cooperation with other State and federal agencies, local water districts, groundwater managers, and other stakeholders, to identify potential strategies for reoperation of the statewide flood protection and water supply systems. The opportunity to reoperate portions of California’s statewide water system to yield increased water resources-related benefits was recognized by the State Legislature in Senate Bill X2 1 (SB X2 1) (Perata, 2008 – Water Code Section 83002.5). California’s statewide water system is comprised of a multitude of local, state, and federal projects. These projects include facilities such as dams and reservoirs, hydropower plants, canals, and water diversion structures. Many of these facilities were developed in the early to mid-20th century, and were not designed, constructed, or operated as an integrated water supply and flood management system. Over time, operations of the two largest water supply projects, the State Water Project (SWP), operated by DWR and the Central Valley Project (CVP), operated by the U.S. Department of the Interior’s Bureau of Reclamation (Reclamation), have been integrated to a certain degree. California’s water supply and flood management infrastructure is physically interconnected to the extent that it is technically feasible to move water around the system from Trinity County in the north to Imperial County in the south. However, the management of the water system is not as well integrated as it could be. The underlying logic of the SRS is that California can do much more with its existing water infrastructure by taking advantage of the physical interconnections (and enhancing them) while also operating the system in a coordinated manner to optimize the benefits. The current focus of the SRS is the Central Valley because this region has the highest integration of water supply and flood management facilities. Additionally, the greatest potential for ecosystem restoration through infrastructure reoperation is found in the Central Valley because the existing infrastructure has had a profound effect on aquatic ecosystems. RELATED DOCUMENTS: System Reoperation Study, Phase 1: Plan of Study System Reoperation Study, Phase 2: Strategy Formulation and Refinement System Reoperation Study, Phase 2: Appendix A: Forecast?Based Operations Analysis System Reoperation Study, Phase 2: Appendix B: Tradeoff Analysis System Reoperation Study, Phase 3 Report: Assessment of Reoperation Strategies System Reoperation, Phase 3: Appendix C: State Water Project and Central Valley Project Integrated Operations Analysis System Reoperation, Phase 3 Appendix D: Ecosystem Evaluation

System Reoperation Study, Phase 3 Report: Assessment of Reoperation Strategies

California Department of Water Resources (DWR) | August 21st, 2017

The California Department of Water Resources (DWR) is conducting a System Reoperation Study (SRS) in cooperation with other State and federal agencies, local water distri

The California Department of Water Resources (DWR) is conducting a System Reoperation Study (SRS) in cooperation with other State and federal agencies, local water districts, groundwater managers, and other stakeholders, to identify potential strategies for reoperation of the statewide flood protection and water supply systems. The opportunity to reoperate portions of California’s statewide water system to yield increased water resources-related benefits was recognized by the State Legislature in Senate Bill X2 1 (SB X2 1) (Perata 2008). In support of the legislative objectives, DWR developed the SRS to identify viable reoperation strategies and understand how integrated management can: • Improve the reliability of municipal and irrigation water supply. • Reduce flood hazards. • Restore and protect ecosystems. • Buffer the hydrologic variations expected from climate change. • Improve water quality. California’s statewide water system is composed of a multitude of local, State, and federal projects. These projects include dams and reservoirs, hydropower plants, canals, and water diversion structures. Many of these facilities were developed in the early to mid-20th century, and were not designed, constructed, or operated as an integrated water supply and flood management system. Over time, operations of the two largest water supply projects, the State Water Project (SWP), operated by DWR, and the Central Valley Project (CVP), operated by the U.S. Department of the Interior’s Bureau of Reclamation (Reclamation), have been integrated to a certain degree. California’s water supply and flood management infrastructure is physically interconnected to the extent that it is technically feasible to move water around the system, from Trinity County in the north to Imperial County in the south. However, the management of the water system is not as well integrated as it could be. The underlying logic of the SRS is that California can do much more with its existing water infrastructure by taking advantage of the physical interconnections (and enhancing them) while also operating the system in a coordinated manner to optimize the benefits. The current focus of the SRS is the Central Valley, because this region has the highest integration of water supply and flood management facilities. Additionally, the greatest potential for ecosystem restoration through infrastructure reoperation is found in the Central Valley, because the existing infrastructure has had a profound effect on aquatic ecosystems. Figure ES-1 shows the location of the Central Valley and the study area for the SRS. Figure 1-1 also shows major features of the CVP and SWP. RELATED DOCUMENTS: System Reoperation Study, Phase 1: Plan of Study System Reoperation Study, Phase 2: Strategy Formulation and Refinement System Reoperation Study, Phase 2: Appendix A: Forecast?Based Operations Analysis System Reoperation Study, Phase 2: Appendix B: Tradeoff Analysis System Reoperation Study, Phase 3 Report: Assessment of Reoperation Strategies System Reoperation, Phase 3: Appendix C: State Water Project and Central Valley Project Integrated Operations Analysis System Reoperation, Phase 3 Appendix D: Ecosystem Evaluation

System Reoperation, Phase 3: Appendix C: State Water Project and Central Valley Project Integrated Operations Analysis

California Department of Water Resources (DWR) | August 21st, 2017

The California Department of Water Resources (DWR) is conducting a system reoperation study (SRS) in cooperation with other state and federal agencies, local water distri

The California Department of Water Resources (DWR) is conducting a system reoperation study (SRS) in cooperation with other state and federal agencies, local water districts, groundwater managers, and other stakeholders to identify potential strategies for reoperation of the statewide flood protection and water supply systems. The opportunity to reoperate portions of California’s statewide water system to yield increased water resources–related benefits was recognized by the State Legislature in Senate Bill (SB) X2 1 (Perata, 2008 – Water Code Section 83002.5). In support of the legislative objectives, DWR developed the SRS to identify viable reoperation strategies and understand how integrated management can: • Improve the reliability of municipal and irrigation water supply • Reduce flood hazards • Restore and protect ecosystem function and habitat conditions • Buffer the hydrologic variations expected from climate change • Improve water quality A component of the SRS is to evaluate how operational improvements of the state and federal water Projects in California may increase water supply and enhance ecosystem function and habitat. The Central Valley Project (CVP) generally has more storage and less conveyance flexibility; the opposite is generally true for the State Water Project (SWP). The SWP and CVP are operated by DWR and the U.S. Bureau of Reclamation (Reclamation), respectively. The operation of the two Projects is coordinated in accordance with the 1986 Coordinated Operating Agreement and other agreements. Though the operation is coordinated, the SWP and CVP are operating as two distinct units. They each have different contractual obligations and operating constraints. Operational improvements using strengths and assets of both Projects may result in improved operational efficiency and help achieve goals of the SRS. The purpose of this effort is to assess potential benefits of operating the SWP and CVP as a single, integrated Project. RELATED DOCUMENTS: System Reoperation Study, Phase 1: Plan of Study System Reoperation Study, Phase 2: Strategy Formulation and Refinement System Reoperation Study, Phase 2: Appendix A: Forecast?Based Operations Analysis System Reoperation Study, Phase 2: Appendix B: Tradeoff Analysis System Reoperation Study, Phase 3 Report: Assessment of Reoperation Strategies System Reoperation, Phase 3: Appendix C: State Water Project and Central Valley Project Integrated Operations Analysis System Reoperation, Phase 3 Appendix D: Ecosystem Evaluation

Systematic Screening of Dams for Environmental Flow Assessment and Implementation

Oxford University Press (OUP) | November 30th, 2014