Comments on the Scientific Basis for Implementation of Voluntary Agreements for the Sacramento River, Delta, and Tributaries

Delta Stewardship Council (Delta Council) | March 8th, 2023

Compliance with D-1641 San Joaquin River October Flow Requirements

California State Water Resources Control Board (SWRCB) | October 9th, 2023

Dam effects on bedload transport on the upper Santa Ana River, California, and implications for native fish habitat

River Research and Applications (Wiley) | May 23rd, 2019

Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known

Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known and common geomorphic responses to dams, such as bed armouring, the response downstream from any particular dam is dependent on local conditions. Herein, we investigate the response of the upper Santa Ana River in southern California, USA, to the construction of a large dam at the transition from mountains to valley, using calculations of bedload transport capacity on the mainstem below the dam and for major tributaries. Approximate sediment budgets were constructed for downstream reaches to estimate deposition and erosion rates for sand, gravel, and cobble particle sizes. Our results indicate that the classical response of bed armouring and erosion is likely limited to a short reach immediately below the dam. Farther downstream, though transport capacity is reduced by flow regulation by the dam, the channel reaches are likely to remain depositional but with reduced deposition rates. Persistent deposition, as opposed to erosion, is the result of the replenishment of flow and sediment supply by large downstream tributaries. In addition, the calculations indicate that the composition of the bed is unlikely to change substantially in downstream reaches. A Monte Carlo approach was employed to estimate the uncertainty in the sediment budget predictions. The impacts of the dam on the geomorphic character of the river downstream could have implications for native fish that rely on coarse substrate that supports their food base.

Decision on Petition for Rulemaking to Set Permanent Minimum Flows on the Shasta River

California State Water Resources Control Board (SWRCB) | February 16th, 2024

Decoupling outmigration from marine survival indicates outsized influence of streamflow on cohort success for California’s Chinook salmon populations

Canadian Journal of Fisheries and Aquatic Sciences (Canadian Science Publishing) | October 17th, 2018

Historically, marine survival estimates for salmon have been confounded with freshwater seaward migration (outmigration) survival. Telemetry studies have revealed low and

Historically, marine survival estimates for salmon have been confounded with freshwater seaward migration (outmigration) survival. Telemetry studies have revealed low and variable survival during outmigration, suggesting marine mortality may not be the primary source of variability in cohort size as previously believed. Using a novel combination of tagging technologies, survival during these two life stages was decoupled over 5 years for Sacramento River Chinook salmon (Oncorhynchus tshawytscha). Outmigration survival ranged from 2.6% to 17%, and marine survival ranged from 4.2% to 22.8%. Influential environmental drivers in both life stages were also compared with smolt-to-adult ratios (SAR) for three Chinook salmon populations over 20 years. Streamflow during outmigration had higher correlation with SAR (r2 > 0.34) than two marine productivity indices (r2 < 0.08). The few SAR estimates that were poorly predicted by flow occurred during years with the lowest marine productivity, suggesting most interannual SAR fluctuations are explained by outmigration survival, but abnormally poor marine conditions also reduce SAR. The outsized influence of flow on SAR provides managers with a powerful mitigation tool in a watershed where flow is tightly regulated.

Delta-Mendota Canal Recirculation Feasibility Study Plan Formulation Report

U.S. Bureau of Reclamation (USBR) | September 30th, 2010

The U.S. Department of the Interior, Bureau of Reclamation (Reclamation) is evaluating the feasibility of using recirculation strategies to improve water quality and flow

The U.S. Department of the Interior, Bureau of Reclamation (Reclamation) is evaluating the feasibility of using recirculation strategies to improve water quality and flow in the lower San Joaquin River (SJR). Specifically, Reclamation is evaluating the feasibility of the Delta-Mendota Canal (DMC) Recirculation Project (Project) in which water from the Sacramento–San Joaquin River Delta (Delta) would be recirculated through the Central Valley Project (CVP) pumping and conveyance facilities to the SJR upstream from Vernalis. The DMC, which is part of the CVP, would be the primary conveyance facility utilized. The DMC is 120-mile canal that begins at the C.W. “Bill” Jones Pumping Plant (Jones) and ends at Mendota Pool, near the town of Mendota. Jones pumps water from the Delta into the canal. Water would be released from the canal into either Newman Wasteway or Westley Wasteway and would flow back into SJR near its confluence with the Merced River (Newman Wasteway) or with the Tuolumne River (Westley Wasteway). The water would re-enter the Delta near the town of Vernalis. In 2004, Reclamation initiated the DMC Recirculation Project Feasibility Study (Study). The Study is authorized by the CALFED (California Federal Bay-Delta Program) Bay-Delta Authorization Act of 2004 (118 Stat. §§ 1681-1702.; Public Law 108-361) and a similar study is required by the State Water Resources Control Board (SWRCB) as part of Water Right Decision 1641 (D-1641). The purposes of the PFR are (1) to provide information on the existing and potential resources that may be affected by the Project and (2) to present the results of the evaluation of the alternative plans that were carried forward from the 2008 Initial Alternatives Information Report (IAIR). The alternative plans are compared and ranked and the next steps in the study are presented.

Depletion Requiremements in California’s Sustainable Groundwater Management Act

Environmental Defense Fund (EDF) | May 17th, 2018

Successful implementation of the Sustainable Groundwater Management Act (SGMA), including its provision to avoid signicant and unreasonable depletion of interconn

Successful implementation of the Sustainable Groundwater Management Act (SGMA), including its provision to avoid signicant and unreasonable depletion of interconnected surface water, is a high priority for the Environmental Defense Fund (EDF). The lack of established mechanisms for addressing depletions of interconnected surface water makes the implementation of this aspect of SGMA especially challenging. Accordingly, EDF offers recommendations to address the requirements of the law related to depletion of interconnected surface water, commonly referred to as “Undesirable Result No. 6” (UR #6). We believe that our proposed approach provides a reasonable balance among the con icting factors of rigor, cost, uncertainty, and enforceability that weigh on the implementation of this requirement. Our goal is to offer a pathway to achieve the fundamental and critical objective of UR#6 – preventing signi cant impacts to water users and ecosystems—in a way that is not unreasonably costly or unproductively burdensome on the Groundwater Sustainability Agencies (GSAs), water users, and state agencies who will bear most of the burden of complying with—or ensuring compliance with—SGMA.

Development of Flow Criteria for the Sacramento-San Joaquin Delta Ecosystem

California State Water Resources Control Board (SWRCB) | August 4th, 2010

Water Code section 85086 (See Appendix B), contained in the Delta Reform Act, was enacted as part of the comprehensive package of water legislation adopted in November 20

Water Code section 85086 (See Appendix B), contained in the Delta Reform Act, was enacted as part of the comprehensive package of water legislation adopted in November 2009. Water Code section 85086 requires the State Water Resources Control Board (State Water Board) to use the best available scientific information gathered as part of a public process conducted as an informational proceeding to develop new flow criteria for the Delta ecosystem to protect public trust resources. The purpose of the flow criteria is to inform planning decisions for the Delta Plan and the BDCP. The Legislature intended to establish an accelerated process to determine the instream flow needs of the Delta in order to facilitate the planning decisions required to meet the objectives of the Delta Plan. Accordingly, Water Code section 85086 requires the State Water Board to develop the flow criteria within nine months of enactment of the statute and to submit its flow criteria determinations to the Council within 30 days of their development. This report, required by Water Code section 85086(c) (2009 Delta Reform Act) in 2010, suggests the flows that would be needed in the Delta ecosystem if fishery protection was the sole purpose for which its waters were put to beneficial use. In keeping with the narrow focus of the legislation, this report only presents a technical assessment of flow and operational requirements to provide fishery protection under existing conditions.  

Development of Recommended Flow Targets to Support Biological Integrity Based on Regional Flow-ecology Relationships for Benthic Macroinvertebrates in Southern California Streams

Southern California Coastal Water Research Project | March 23rd, 2017

Changes to instream flow are known to be one of the major factors that affect the health of biological communities. Regulatory, monitoring, and management programs are in

Changes to instream flow are known to be one of the major factors that affect the health of biological communities. Regulatory, monitoring, and management programs are increasingly using biological community composition, particularly benthic invertebrates, as one measure of instream conditions, stormwater project performance, or regulatory compliance with NPDES or other requirements and regulations. Understanding the relationship between changes in flow and changes in benthic invertebrate communities is, therefore, critical to informing decisions about ecosystem vulnerability, causes of stream and watershed degradation, and priorities for future watershed management. There are many approaches to developing flow-ecology relationships that relate hydrologic change to responses in instream biological communities that can be used to establish management targets. The Ecological Limits of Hydrologic Alteration (ELOHA) framework (Poff et al. 2010) provides a way to assess the effect of flow alteration on the condition of biological communities (vs. individual taxa) on a regional basis. Consequently, it is a useful approach for setting targets across a wide range of geographies and stream types where comprehensive detailed site-specific investigations are not practical. The framework includes elements of stream classification, estimation of flow alteration and development of flow ecology relationships based on the response of biological communities to changes in flow.

Downstream Effects of Stormwater Management Basins

American Society of Civil Engineers (ASCE) | June 1st, 1979

Urbanization decreases the natural storage of a watershed, which changes the timing characteristics of the runoff. Stormwater management (SWM) basins are an attempt to pu

Urbanization decreases the natural storage of a watershed, which changes the timing characteristics of the runoff. Stormwater management (SWM) basins are an attempt to put the storage lost through development back into the runoff process. While SWM basins provide the proper volume of storage, they fail to return the timing characteristics to those that existed prior to development. The changes in storage and timing characteristics may have adverse effects on flow rates and bedload transport in downstream channel reaches. A study of a 2.12-sq mile watershed in Montgomery County, Md., showed that a SWM basin increased both peak flows and bedload transport rates in the channel downstream from the facility. This results from both the change in timing characteristics and the increased duration of bankfull flow. These results indicate that SWM policies must require evaluation of SWM plans on a regional basis and not just using on-site control criteria. Also, methods that can evaluate storage and timing changes must be used in the design of SWM facilities.