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.

French Creek Flow Accounting Study

Scott River Water Trust | May 15th, 2020

The Scott River Water Trust (SRWT) has been working with adjudicated water-users in Scott Valley since 2007 to develop opportunities for stream flow enhancement through t

The Scott River Water Trust (SRWT) has been working with adjudicated water-users in Scott Valley since 2007 to develop opportunities for stream flow enhancement through temporary leases or long-term/permanent dedications of surface water rights. Under the seasonal Water Leasing Program, the SRWT contracts with voluntary agricultural producers to temporarily forbear all or part of their decreed water right(s) during the irrigation season in exchange for fair financial compensation. The purpose of the seasonal Water Leasing Program is to improve conditions for anadromous fish in priority stream reaches during critical life stages and time periods. The Siskiyou Resource Conservation District (SRCD) has been integrally involved with implementation of the seasonal Water Leasing Program since its inception and particularly with the monitoring component. Monitoring of seasonal transactions is generally limited to ensuring compliance with the lease terms and confirming stream response. However, in 2016 the SRWT proposed expanding the scope of effectiveness monitoring associated with the Water Leasing Program based on suggestions from Andrew Purkey and Rankin Holmes of the National Fish and Wildlife Foundation and their experience monitoring transactions in the Columbia River Basin (Holmes, et al., 2013). Under funding from the California Flow Restoration Accounting Fund managed by the National Fish and Wildlife Foundation, the SRWT contracted with the SRCD to explore several additional effectiveness monitoring techniques on French Creek including instream water level/discharge monitoring, wetted- perimeter analysis and alluvial connectivity surveillance. The purpose of this additional monitoring was to evaluate the applicability and effectiveness of these techniques to stream flow enhancement in Scott Valley and determine whether it would make sense for the SRWT adopt these practices into its programs. The specific components and objectives of the work completed on French Creek included: • Evaluate the instream effect of forbearance agreements performed by SRWT • Establish and maintain monitoring stations throughout French Creek to determine the downstream extent that returned water from various leases had on stream flow and temperature • Perform wetted perimeter analysis on French Creek to develop a relationship between instream flows and aquatic habitat conditions • Conduct periodic fisheries surveys through French Creek to evaluate the relative abundance of salmonids influenced by the transactions • Conduct periodic foot surveys through lower French Creek to establish the temporal and spatial connectivity to the Scott River This report summarizes the monitoring and analysis conducted by the SRCD during the 2018 and 2019 water leasing seasons under the French Creek Flow Accounting Study and provides conclusions related to the applicability of these methods to the SRWT.

From the Sierra to the Sea: The Ecological History of the San Francisco Bay-Delta Watershed

Bay Institute | January 1st, 1998

A vast watershed connects the mountain streams surrounding California’s Central Valley with San Francisco Bay and the ocean beyond. Over the course of the last two cent

A vast watershed connects the mountain streams surrounding California’s Central Valley with San Francisco Bay and the ocean beyond. Over the course of the last two centuries, much of the natural productivity, biodiversity and ecological integrity of the watershed has been destroyed by modifying the environment without fully understanding the long-term environmental consequences. Long the site of some of the nation’s most intensive conflicts over the use of land and water resources, this system is now emerging as the focus of one of the most ambitious ecological restoration efforts ever undertaken in the United States. This report was designed to provide a coherent and defensible ecological framework and information base for restoration. The need for such an historical, broad-scale perspective on system ecology stems from two fundamental principles of ecological restoration - the need to manage toward a natural template and to manage at ecosystem and landscape levels.

Frontiers in Ecology and the Environment: Alteration of streamflow magnitudes and potential ecological consequences: a multiregional assessment

Ecological Society of America (Wiley) | October 19th, 2010

Human impacts on watershed hydrology are widespread in the US, but the prevalence and severity of streamflow alteration and its potential ecological consequences have not

Human impacts on watershed hydrology are widespread in the US, but the prevalence and severity of streamflow alteration and its potential ecological consequences have not been quantified on a national scale. We assessed streamflow alteration at 2888 streamflow monitoring sites throughout the conterminous US. The magnitudes of mean annual (1980–2007) minimum and maximum streamflows were found to have been altered in 86% of assessed streams. The occurrence, type, and severity of streamflow alteration differed markedly between arid and wet climates. Biological assessments conducted on a subset of these streams showed that, relative to eight chemical and physical covariates, diminished flow magnitudes were the primary predictors of biological integrity for fish and macroinvertebrate communities. In addition, the likelihood of biological impairment doubled with increasing severity of diminished streamflows. Among streams with diminished flow magnitudes, increasingly common fish and macroinvertebrate taxa possessed traits characteristic of lake or pond habitats, including a preference for fine-grained substrates and slow-moving currents, as well as the ability to temporarily leave the aquatic environment.

Functional Flows in Modified Riverscapes: Hydrographs, Habitats and Opportunities

BioScience (Oxford University Press) | August 5th, 2015

Building on previous environmental flow discussions and a growing recognition that hydrogeomorphic processes are inherent in the ecological functionality and biodiversity

Building on previous environmental flow discussions and a growing recognition that hydrogeomorphic processes are inherent in the ecological functionality and biodiversity of riverscapes, we propose a functional-flows approach to managing heavily modified rivers. The approach focuses on retaining specific process-based components of the hydrograph, or functional flows, rather than attempting to mimic the full natural flow regime. Key functional components include wet-season initiation flows, peak magnitude flows, recession flows, dry-season low flows, and interannual variability. We illustrate the importance of each key functional flow using examples from western US rivers with seasonably predictable flow regimes. To maximize the functionality of these flows, connectivity to morphologically diverse overbank areas must be enhanced in both space and time, and consideration must be given to the sediment-transport regime. Finally, we provide guiding principles for developing functional flows or incorporating functional flows into existing environmental flow frameworks.

Gage Gap

Nature Conservancy | October 31st, 2018

Following a difficult five-year drought, California just had one of the wettest winters on record. The state is famous for its highly engineered water system, whi

Following a difficult five-year drought, California just had one of the wettest winters on record. The state is famous for its highly engineered water system, which moves millions of gallons of water from north to south and east to west. Thirty-nine million people and our $47 billion agricultural industry rely on that water, not to mention wildlife from the Sierra to the sea. And yet we have surprisingly little data about how much water is moving through our streams at any given time. There are over 3,600 locations in California where stream gages have been active at some point, but only 54% have been active recently. And even fewer of those provide the kind of rich, real-time reporting needed to manage what is arguably our state’s most precious and contentious resource.

Generalized Streamflow Relations of the San Bernardino and Eastern San Gabriel Mountains, California

U.S. Geological Survey (USGS) | October 19th, 1972

Going Beyond Low Flows: Streamflow Drought Deficit and Duration Illuminate Distinct Spatiotemporal Drought Patterns and Trends in the U.S. During the Last Century

American Geophysical Union (AGU) | August 30th, 2022

Streamflow drought is a recurring challenge, and understanding spatiotemporal patterns of past droughts is needed to manage future water resources. We examined regional p

Streamflow drought is a recurring challenge, and understanding spatiotemporal patterns of past droughts is needed to manage future water resources. We examined regional patterns in streamflow drought metrics and compared these metrics to low flow timing and magnitude using long-term daily records for 555 minimally disturbed watersheds. For each streamgage, we calculated streamflow drought duration (number of days) and deficit (flow volume below a specified threshold) for each climate year (April 1–March 31). We identified drought using five thresholds (2%–30%) and two approaches: variable thresholds with unique values for each day of the year, and a fixed threshold based on all period-of-record flows. We then analyzed drought trends using the Mann-Kendall test with persistence adjustment for 1921–2020, 1951–2020, and 1981–2020, and computed correlations between annual streamflow drought metrics and climate metrics using values from a monthly water balance model. Spatial patterns in drought metrics were consistent between variable and fixed approaches, though fixed threshold durations were typically longer and variable threshold deficits larger. High interannual variability in drought duration emerged in the central, interior west, and southwestern U.S., with high deficit variability in the interior west. Drought metrics were weakly correlated with low flow magnitude and timing, providing unique information. Drought duration and deficit increased in the southern and western U.S. for both 1951–2020 and 1981–2020, particularly using fixed thresholds, and paralleled trends in aridity. Projections of continued aridification for the southern and western U.S. may increase drought durations and deficits and intensify water availability impacts.

Gone with the flow

Bay Institute | August 1st, 2010

The Bay Institute's primer Gone with the Flow describes in plain language how runoff flowing from the mountain watersheds ringing California’s Central Valley provided c

The Bay Institute's primer Gone with the Flow describes in plain language how runoff flowing from the mountain watersheds ringing California’s Central Valley provided coldwater paradises for salmon returning to their native streams; turned lowland rivers and their floodplains into a rich source of food and shelter for young fish; mingled in the Delta’s complex maze of marshes and sloughs; and created a vast expanse of brackish water habitat essential for estuarine creatures in the upper reaches of San Francisco Bay. The primer also explains how the lack of access to most upland streams now forces migratory fish to cope with undesirable, often lethal flow conditions; how runoff in lowland rivers has been shifted from spring to summer, or even almost completely cut off in the San Joaquin basin, with disastrous consequences for the environment; how reverse flows in Delta channels kill hundreds of millions of aquatic organisms each year; and how the Bay is now in a permanent ecological drought because of the diversion of half its freshwater inflow.