DRAFT Staff Report/Substitute Environmental Document in Support of Potential Updates to the Water Quality Control Plan for the San Francisco Bay/Sacramento-San Joaquin Delta Estuary for the Sacramento River and its Tributaries, Delta Eastside Tributaries, and Delta

California State Water Resources Control Board (SWRCB) | September 28th, 2023

DRERIP Ecosystem Conceptual Model: Delta smelt

California Department of Fish and Wildlife (CDFW) | October 22nd, 2010

This Conceptual Model is part of a suite of conceptual models which collectively articulate the current scientific understanding of important aspects of the Sacramento-Sa

This Conceptual Model is part of a suite of conceptual models which collectively articulate the current scientific understanding of important aspects of the Sacramento-San Joaquin River Delta ecosystem. The conceptual models are designed to aid in the identification and evaluation of ecosystem restoration actions in the Delta. These models are designed to structure scientific information such that it can be used to inform sound public policy. The Delta Conceptual Models include both ecosystem element models (including process, habitat, and stressor models) and species life history models. The models were prepared by teams of experts using common guidance documents developed to promote consistency in the format and terminology of the models http://www.delta.dfg.ca.gov/erpdeltaplan/science_process.asp . The Delta Conceptual Models are qualitative models which describe current understanding of how the system works. They are designed and intended to be used by experts to identify and evaluate potential restoration actions. They are not quantitative, numeric computer models that can be “run” to determine the effects of actions. Rather they are designed to facilitate informed discussions regarding expected outcomes resulting from restoration actions and the scientific basis for those expectations. The structure of many of the Delta Conceptual Models can serve as the basis for future development of quantitative models.

Effects Analysis for the Delta Smelt Fall Habitat Action in 2019

U.S. Bureau of Reclamation (USBR) | August 1st, 2019

Evaluation of Geohydrologic Framework, Recharge Estimates, and Ground-Water Flow of the Joshua Tree Area, San Bernardino County, California

U.S. Geological Survey (USGS) | February 7th, 2005

Ground water historically has been the sole source of water supply for the community of Joshua Tree in the Joshua Tree ground-water subbasin of the Morongo ground-water b

Ground water historically has been the sole source of water supply for the community of Joshua Tree in the Joshua Tree ground-water subbasin of the Morongo ground-water basin in the southern Mojave Desert. The Joshua Basin Water District (JBWD) supplies water to the community from the underlying Joshua Tree ground-water subbasin. The JBWD is concerned with the long-term sustainability of the underlying aquifer. To help meet future demands, the JBWD plans to construct production wells in the adjacent Copper Mountain ground-water subbasin. As growth continues in the desert, there may be a need to import water to supplement the available ground-water resources. In order to manage the ground-water resources and to identify future mitigating measures, a thorough understanding of the ground-water system is needed. The purpose of this study was threefold: (1) improve the understanding of the geohydrologic framework of the Joshua Tree and Copper Mountain ground-water subbasins, (2) determine the distribution and quantity of recharge using field and numerical techniques, and (3) develop a ground-water flow model that can be used to help manage the water resources of the region.

Evaluation of Surface-Water/Ground-Water Interactions in the Santa Clara River Valley, Ventura County, California

U.S. Geological Survey (USGS) | May 28th, 1999

The interactions of surface water and ground water along the Santa Clara River in Ventura County, California, were evaluated by analyzing river-discharge and water-qua

The interactions of surface water and ground water along the Santa Clara River in Ventura County, California, were evaluated by analyzing river-discharge and water-quality data and geohydrologic information collected by the U.S. Geological Survey between 1993 and 1995 for the Piru, Fillmore, and Santa Paula subbasins. Measurements of discharge and water quality were made at multiple locations along the Santa Clara River and its tributaries at eight different time periods during different releases from Lake Piru. Geologic, hydraulic, and water-quality data were collected from three new multiple-completion ground-water monitoring wells. These data, together with data collected as part of the U.S. Geological Survey Southern California Regional Aquifer-System Analysis (RASA) study, were analyzed in order to quantify rates and locations of ground-water recharge and discharge within the river, characterize the correlation of recharge and discharge rates with ground-water conditions and reservoir releases, and better characterize the three-dimensional ground-water flow system. Analysis of the data indicates that the largest amount of ground-water recharge from the river consistently occurs in the Piru subbasin. Some ground-water recharge from the river may occur in the upper part of the Fillmore subbasin. Increases in sulfate concentrations indicate that increases in flow at the lower ends of the Piru and Fillmore subbasins result from high-sulfate ground-water discharge. Increases in flow in the lower part of the Santa Paula subbasin are not accompanied by significant sulfate increases. Several sets of regressions indicate possible correlation between net flow changes in the river and depths to ground water and release rates from Lake Piru. These statistical relations may be of use for evaluating alternative Lake Piru release strategies. Data on the stable isotopes of hydrogen and oxygen from the ground-water monitoring wells that were installed as part of this investigation were used to distinguish between zones affected by recharge from the Santa Clara River and zones affected by recharge from local precipitation. Tritium data from a new multiple-completion monitoring site indicate that near the river in the upper Santa Paula subbasin, recent (post-1950) recharge water is not present at depths greater than about 350 feet below land surface. Water-level and lithologic data from the monitoring site indicate that the river and the Shallow aquifer have only limited hydraulic connection to the underlying aquifers at this location. Water-level data from the Shallow aquifer and from an in-stream drive point were used in an analytic model to estimate hydraulic properties governing stream-aquifer interactions in the upper Santa Paula subbasin. Hydraulic conductivities in all the USGS monitoring wells were estimated on the basis of slug tests.  

Facilitating Adaptive Management in California’s Sacramento–San Joaquin Delta

University of California, Davis (UC Davis) | July 1st, 2017

Uncertainties in understanding ecosystems increase the risk that management will fail to achieve desired results. Adaptive management is a structured, iterative applicati

Uncertainties in understanding ecosystems increase the risk that management will fail to achieve desired results. Adaptive management is a structured, iterative application of science-based knowledge to reduce uncertainties and build flexibility into decision-making. However, adaptive management is more easily planned than implemented, and it is only beginning to be applied in the California’s Sacramento–San Joaquin Delta. We draw from two assessments of adaptive management in the Delta and examples of its use elsewhere to suggest how the process can be facilitated. Although a highly structured adaptive-management process may not always be needed, several elements are essential. Adaptive management should begin by clearly identifying the problem, goals, and objectives; recognizing uncertainties; identifying decision points and alternative approaches; recognizing when adjustments are needed and having the flexibility to make them; and considering societal and political constraints. Model complexity should be matched to that of the system and management needs; experiments can help unravel causal relationships. Monitoring, analyses, and syntheses require comprehensive data-management systems. More frequent and organized communications among scientists, managers, stakeholders, and decision-makers are necessary. We propose the establishment of an “Adaptive Management Team” to coordinate efforts across the management spectrum of the Delta and to provide guidance and link individual projects to shared approaches and experiences. Reliable long-term support will be needed to assess results of management actions, adjust approaches where improvement is likely, and strive toward the legislated goals of enhancing the Delta ecosystem while also providing reliable water supplies to much of California, and doing both these things in a manner that protects values of the Delta as a place where people live and work. 

Final Value Planning Study Report for Through Delta Facility, Sacramento, California

California Department of Water Resources (DWR) | July 1st, 2007

Flow Augmentations Modify an Estuarine Prey Field

University of California, Davis (UC Davis) | June 15th, 2023

Flow Recommendations to the State Water Resources Control Board

California Department of Fish and Wildlife (CDFW) | May 22nd, 2008

Pursuant to Public Resouces Code (PRC) Section 10001, in the early 1980s, the Department of Fish and Game (DFG) in coordination with all regional DFG offices, identified

Pursuant to Public Resouces Code (PRC) Section 10001, in the early 1980s, the Department of Fish and Game (DFG) in coordination with all regional DFG offices, identified 21 streams and watercourses for which minimum flow levels needed to be established in order to assure the continued viability of stream-related fish and wildlife resources. Over approximately 20 years, DFG investigated the instream flow needs of these listed streams and watercourses.  The investigations included field studies, data analyses, and consultations with local, state, and federal agencies and interested individuals and organizations.  As a result of the investigations, DFG prepared instream flow recommendations for the listed streams. The attached transmittal summarizes the flow recommendations prepared by DFG pursuant to PRC 10000.  Submission of these recommendations to the State Water Resources Control Board (SWRCB) complies with PRC Section 10002. As will be evident upon review, the attached flow recommendations are intended to supplement, but not replace, current administrative records.  The attached flow recommendations should not be implemented by the SWRCB without further investigation and consideration of supporting information that would identify constraints or limitations that qualify each recommendation. In addition, as noted on each recommendation, some studies were done many years ago using early methods.  DFG has established an administrative file in the Water Branch that contains the resource documents cited in the flow recommendations.

Flows and Fishes in the Sacramento-San Joaquin Delta

Delta Stewardship Council (Delta Council) | August 1st, 2015

Record-low counts of Delta smelt at a time of persistent drought underscore the importance and challenges of managing freshwater flows for the benefit of fishes in the Sa

Record-low counts of Delta smelt at a time of persistent drought underscore the importance and challenges of managing freshwater flows for the benefit of fishes in the Sacramento-San Joaquin Delta while also meeting human demands for water. Understanding the effects of water flows on fishes is central to understanding how the Delta ecosystem functions and is key to achieving the state’s coequal goals of “providing a more reliable water supply for California and protecting, restoring and enhancing the Delta ecosystem … in a manner that protects and enhances … the values of Delta as an evolving place”. The economic, ecological, and social costs of scientific uncertainty in water management controversies are significant - and to some degree unavoidable. Scientific findings that relate fishes and flows increasingly guide decisions on how to manage flows for the well-being of threatened or endangered species in the Delta. Many studies – and management decisions – rely on correlations between water flows and fish populations. But the decisions warrant fuller understanding of precisely how the flows affect the fishes. Knowledge of these underlying mechanisms is likely to facilitate adaptive management by clarifying uncertainty and risk, by creating specific expectations for outcomes and by strengthening testable hypotheses. This report therefore recommends, first and foremost (there are other recommendations as well), redoubling effects to identify causes and effects concerning fishes and flows in the Delta.