DRERIP Ecosystem Conceptual Model: Fish Habitat Linkages

California Department of Fish and Wildlife (CDFW) | January 19th, 2008

The Delta Regional Ecosystem Restoration Implementation Plan (DRERIP) is one of four regional plans intended to guide the implementation of the CALFED Ecosystem Restorati

The Delta Regional Ecosystem Restoration Implementation Plan (DRERIP) is one of four regional plans intended to guide the implementation of the CALFED Ecosystem Restoration Program (ERP) element. The DRERIP will refine the planning foundation for the Delta, develop and refine specific restoration actions and provide project implementation guidance, program tracking, performance evaluation and adaptive management feedback specific to the Delta. The DRERIP Fish Habitat Linkage Model (FHL model) provides a roadmap for how the various conceptual models designed for the DRERIP process intertwine to define fish habitat and ultimately produce fish. The model identifies the key linkages between hydrology and numerous other components of fish habitat. The FHL model shows that hydrodynamics and water operations exert influences on fish recruitment by directly influencing transport fates, the water quality components of habitat, and some biotic interactions. The water quality components of habitat interact with structural components of habitat; their interaction affects the strength of biotic interactions (Peterson 2003). Because the FHL model is a generalized model serving as a template or road map, the relative importance of drivers and linkages, and their direction of impact (positive or negative), are not shown in the model diagram because they will depend on which species, contingent (sensu Secor 1999), or life stage is being evaluated. Additional general descriptions of the state of knowledge about these linkages are provided in the text boxes for each model component.

Dry Me a River: Ecological Effects of Drought in the Upper San Francisco Estuary

University of California, Davis (UC Davis) | May 24th, 2024

Ecological Limits of Hydrologic Alteration: Environmental Flows for Regional Water Management

U.S. Environmental Protection Agency (EPA) | March 20th, 2008

Worldwide, water conflicts are escalating as cities, industries, agriculture, and energy producers compete for limited freshwater supplies. At the same time, there is a g

Worldwide, water conflicts are escalating as cities, industries, agriculture, and energy producers compete for limited freshwater supplies. At the same time, there is a growing awareness of the need to maintain adequate freshwater flows in rivers, lakes, floodplains, aquifers, and estuaries to sustain biodiversity and the many benefits derived from the healthy, functioning ecosystems upon which local communities and economies depend. Efficient, integrated water resource management systems help  governments provide for growing human populations while protecting and restoring healthy freshwater ecosystems. The integration of ecological considerations into water management has been hampered by the difficulty, cost, and time required for determining environmental flows -- the quantity, timing, and quality of water flows required to sustain freshwater and estuarine ecosystems and the human livelihoods and well-being that depend on these ecosystems.  Environmental flow assessments scientifically evaluate tradeoffs between alteration of natural water flow patterns by humans and consequent changes in ecological health.

Ecosystem variability along the estuarine salinity gradient: Examples from long-term study of San Francisco Bay

Limnology and Oceanography (Wiley) | March 25th, 2017

The salinity gradient of estuaries plays a unique and fundamental role in structuring spatial patterns of physical properties, biota, and biogeochemical processes. We use

The salinity gradient of estuaries plays a unique and fundamental role in structuring spatial patterns of physical properties, biota, and biogeochemical processes. We use variability along the salinity gradient of San Francisco Bay to illustrate some lessons about the diversity of spatial structures in estuaries and their variability over time. Spatial patterns of dissolved constituents (e.g., silicate) can be linear or nonlinear, depending on the relative importance of river-ocean mixing and internal sinks (diatom uptake). Particles have different spatial patterns because they accumulate in estuarine turbidity maxima formed by the combination of sinking and estuarine circulation. Some constituents have weak or no mean spatial structure along the salinity gradient, reflecting spatially distributed sources along the estuary (nitrate) or atmospheric exchanges that buffer spatial variability of ecosystem metabolism (dissolved oxygen). The density difference between freshwater and seawater establishes stratification in estuaries stronger than the thermal stratification of lakes and oceans. Stratification is strongest around the center of the salinity gradient and when river discharge is high. Spatial distributions of motile organisms are shaped by species-specific adaptations to different salinity ranges (shrimp) and by behavioral responses to environmental variability (northern anchovy). Estuarine spatial patterns change over time scales of events (intrusions of upwelled ocean water), seasons (river inflow), years (annual weather anomalies), and between eras separated by ecosystem disturbances (a species introduction). Each of these lessons is a piece in the puzzle of how estuarine ecosystems are structured and how they differ from the river and ocean ecosystems they bridge.

Electrical Resistivity Investigation of Fluvial Geomorphology to Evaluate Potential Seepage Conduits to Agricultural Lands along the San Joaquin River, Merced County, California, 2012–13

U.S. Geological Survey (USGS) | ?

Increased flows in the San Joaquin River, part of the San Joaquin River Restoration Program, are designed to help restore fish populations. However, increased seepage los

Increased flows in the San Joaquin River, part of the San Joaquin River Restoration Program, are designed to help restore fish populations. However, increased seepage losses could result from these higher restoration flows, which could exacerbate existing drainage problems in neighboring agricultural lands and potentially damage crops. Channel deposits of abandoned river meanders that are hydraulically connected to the river could act as seepage conduits, allowing rapid and widespread water-table rise during restoration flows. There is a need to identify the geometry and properties of these channel deposits to assess their role in potential increased seepage effects and to evaluate management alternatives for reducing seepage. Electrical and electromagnetic surface geophysical methods have provided a reliable proxy for lithology in studies of fluvial and hyporheic systems where a sufficient electrical contrast exists between deposits of differing grain size. In this study, direct-current (DC) resistivity was used to measure subsurface resistivity to identify channel deposits and to map their subsurface geometry. The efficacy of this method was assessed by using DC resistivity surveys collected along a short reach of the San Joaquin River in Merced County, California, during the summers of 2012 and 2013, in conjunction with borings and associated measurements from a hydraulic profiling tool. Modeled DC resistivity data corresponded with data from analyses of core samples, hand-auger samples, a hydraulic profiling tool, and aerial photographs, confirming that DC resistivity was effective for differentiating between silty and sandy deposits in this setting. Modeled DC resistivity data provided detailed two-dimensional cross-sectional resistivity profiles to a depth of about 20 meters. The distribution of high-resistivity units in these profiles was used as a proxy for identifying areas of high hydraulic conductivity. Estimates of the cross-sectional area of channel deposits from DC resistivity pseudosections can provide critical input for groundwater-flow models designed to simulate river seepage and evaluate seepage-management alternatives.

Endangered Species Status for the San Francisco Bay-Delta Distinct Population Segment of the Longfin Smelt

U.S. Fish and Wildlife Service (FWS) | July 30th, 2024

We, the U.S. Fish and Wildlife Service (Service), determine endangered species status under the Endangered Species Act of 1973, as amended (Act), for the San Francisco Ba

We, the U.S. Fish and Wildlife Service (Service), determine endangered species status under the Endangered Species Act of 1973, as amended (Act), for the San Francisco Bay-Delta distinct population segment (DPS) of longfin smelt (Spirinchus thaleichthys), a fish species of the Pacific Coast. This rule extends the protections of the Act to this DPS and adds it to the List of Endangered and Threatened Wildlife.... This final rule is available on the internet at https://www.regulations.gov. Comments and materials we received on the proposed rule are available for public inspection at https://www.regulations.gov at Docket No. FWS-R8-ES-2022-0082. Availability of supporting materials: Supporting materials we used in preparing this rule, such as the species status assessment report, are available at https://www.regulations.gov at Docket No. FWS-R8-ES-2022-0082.

Environmental Water Account: Need for Legislative Definition and Oversight

Legislative Analyst's Office (LAO) | January 29th, 2001

We recommend that the Legislature hold oversight hearings to evaluate CALFED's proposal for the Environmental Water Account, implemented to acquire water for endangered s

We recommend that the Legislature hold oversight hearings to evaluate CALFED's proposal for the Environmental Water Account, implemented to acquire water for endangered species protection and recovery in the Bay-Delta region. There are many policy and implementation issues that the Legislature should consider before CALFED proceeds with the new program, including the program's costs, benefits, impacts, governance, and funding. Funding should be governed by the "beneficiary pays" principle.

Estimates of Natural and Unimpaired Flows for the Central Valley of California: Water Years 1922-2014 (draft)

California Department of Water Resources (DWR) | March 1st, 2016

Estimating regional water supplies that would have occurred absent human activities is a common practice in water resources planning. In this report, such theor

Estimating regional water supplies that would have occurred absent human activities is a common practice in water resources planning. In this report, such theoretical water supply estimates are referred to as “unimpaired” flow. Since 1980, the Department of Water Resources (Department) has periodically published estimates of Central Valley unimpaired flows. In spite of the Department’s previous attempts to distinguish between natural conditions and its calcula tion of theoretical unimpaired flows, unimpaired flow estimates have frequently been used as a surrogate measure of natural conditions, presumably because natural flow estimates were unavailable. A major objective of this report is to clarify the conceptua l differences between natural and unimpaired flows. In this report, the term “unimpaired” flow is used to describe a theoretically available water supply assuming existing river channel conditions in the absence of (1) storage regulation for water supply a nd hydropower purposes and (2) stream diversions for agricultural and municipal uses. Unimpaired flow estimates are theoretical in that such conditions have not occurred historically. In pristine watersheds which have undergone little land use change, unim paired flow estimates provide a fixed frame of reference to develop relationships between precipitation, runoff, and water supply based on long - term hydrologic records. For many years these relationships were based on the assumption of stationarity, i.e. that the past is a good indicator of the future. However, global warming now requires hydrologists and water resources managers to analyze non-stationary processes, requiring more sophisticated tools and techniques to quantify future water supplies. This report updates and extends the Department’s previous published estimates of unimpaired flows for 24 Central Valley sub-basins and the Delta. Monthly unimpaired flows are presented for water years 1922 - 2014.

Estuary News, October 2010

San Francisco Estuary Partnership (SFEP) | October 15th, 2010

Evaluating the hydrologic effects of the 2021–2022 Scott and Shasta irrigation curtailments using remote sensing and streamflow gages

Klamath Tribal Water Quality Consortium | September 11th, 2023

Key Points • Satellite remote sensing data indicated that curtailment orders in 2022 reduced consumptive water use (evapotranspiration, ETa) on agricultural lands i

Key Points • Satellite remote sensing data indicated that curtailment orders in 2022 reduced consumptive water use (evapotranspiration, ETa) on agricultural lands in Shasta Valley, but not Scott Valley. • Streamflow gage data indicate that flows in the Shasta River and some Scott River tributaries (Shackleford and French creeks) were substantially higher in summer 2022 than 2020 or 2021, but similar increases did not occur in the mainstem Scott River. • A likely major reason for the lack of Scott River flow increases was that groundwater use was allowed to continue under Local Cooperative Solutions (LCS) agreements in which water users agreed to reduce pumping by 30% from a prior year baseline. Despite abundant worldwide evidence that reducing consumptive use (i.e., evapotranspiration) is key to increasing environmental water, all LCS cropping and irrigation practices were given equal weight toward the 30% reduction, regardless of the effects on consumptive use. Pumping was not measured and compliance was primarily self-reported, with limited independent verification.