Sacramento River

Dispersion and Stratification Dynamics in the Upper Sacramento River Deep Water Ship Channel

University of California, Davis (UC Davis) | December 1st, 2021

Hydrodynamics control the movement of water and material within and among habitats, where time-scales of mixing can exert bottom-up regulatory effects on aquatic ecosyste

Hydrodynamics control the movement of water and material within and among habitats, where time-scales of mixing can exert bottom-up regulatory effects on aquatic ecosystems through their influence on primary production. The San Francisco Estuary (estuary) is a low-productivity ecosystem, which is in part responsible for constraining higher trophic levels, including fishes. Many research and habitat-restoration efforts trying to increase primary production have been conducted, including, as described here, a whole-ecosystem nutrient addition experiment where calcium nitrate was applied in the Sacramento River Deep Water Ship Channel (DWSC) to see if phytoplankton production could be increased and exported out of the DWSC. As an integral part of this experiment, we investigated the physical mechanisms that control mixing, and how these mechanisms affect the strength and duration of thermal stratification, which we revealed as critical for controlling phytoplankton dynamics in the relatively turbid upper DWSC. Analysis of a suite of mixing mechanisms and time-scales show that both tidal currents and wind control mixing rates and stratification dynamics in the DWSC. Longitudinal and vertical dispersion increased during periods of high wind, during which wind speed influenced dispersion more than tidal currents. Thermal stratification developed most days, which slowed vertical mixing but was rapidly broken down by wind-induced mixing. Stratification rarely persisted for longer than 24 hours, limiting phytoplankton production in the study area. The interaction between physical mechanisms that control mixing rates, mediate stratification dynamics, and ultimately limit primary production in the DWSC may be useful in informing habitat restoration elsewhere in the Delta and in other turbid aquatic environments.

Dissolved Oxygen in South San Francisco Bay: Variability, Important Processes, and Implications for Understanding Fish Habitat

San Francisco Estuary Institute (SFEI) | October 30th, 2018

Dissolved oxygen (DO) is a key water quality parameter that is related to nutrient enrichment in estuaries around the world. In 2017-2018, the San Francisco Estuary Inst

Dissolved oxygen (DO) is a key water quality parameter that is related to nutrient enrichment in estuaries around the world. In 2017-2018, the San Francisco Estuary Institute (SFEI) launched a study to investigate the potential effects of low-DO on habitat quality in Lower South Bay (LSB) to inform decisions about nutrient regulation. The goal of the study was to understand where and when regions of LSB provide adequate DO to support resident fish species. The study approach involved convening a team of experts to advise on methods, analyzing high frequency DO measurements from seven mooring stations in LSB, and partnering with researchers from UC Davis to interpret several years of monthly fish abundance data in LSB relative to DO and other factors.

Distribution of Lakes in the United States

Scientific American | June 12th, 1880

There are numerous lacustrine basins to be found in the States bordering the Pacific Ocean. As in other regions of the globe, their distribution is determined by the co

There are numerous lacustrine basins to be found in the States bordering the Pacific Ocean. As in other regions of the globe, their distribution is determined by the configuration of land, or, more specifically, by the forms of the great hydrographic basins in the interior of the continent; hence some general idea of the topography of the western portions of the United States is an essential preliminary.

Ditching Our Innocence: The Clean Water Act in the Age of the Anthropocene

Lewis & Clark College | May 10th, 2018

Humanity has entered the Age of the Anthropocene, a geologic era marked by the emergence of human activity as the single most dominant influence on Earth’s environment.

Humanity has entered the Age of the Anthropocene, a geologic era marked by the emergence of human activity as the single most dominant influence on Earth’s environment. Every ecosystem shows signs of anthropogenic influence, and the environments we experience everyday are often shaped almost entirely by human actions and decisions. The new discipline of reconciliation ecology recognizes this reality and suggests that we must manage the new habitats we create in order to protect species diversity and ecosystem services. But the 2015 rule defining the jurisdiction of the Clean Water Act explicitly excludes many manmade environments, including many artificial lakes, farm ponds, reflecting pools, and most ditches, treating these landscape features as faux nature somehow unworthy of protection. This treatment is a marked departure from past Environmental Protection Agency and U.S. Army Corps of Engineers practices, which allowed for consideration of such places on a case-by-case basis. This departure finds no support in the Supreme Court precedent leading up to the new rule and seems to be based entirely on a shortsighted view of these places as somehow unimportant to protecting the waters of the United States. Based on the law and science surrounding ditches, we conclude that such places merit protection under the Clean Water Act.

Divergent effects of climate change on future groundwater availability in key mid-latitude aquifers

Nature Portfolio (Springer Nature) | July 24th, 2020

Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater stora

Groundwater provides critical freshwater supply, particularly in dry regions where surface water availability is limited. Climate change impacts on GWS (groundwater storage) could affect the sustainability of freshwater resources. Here, we used a fully-coupled climate model to investigate GWS changes over seven critical aquifers identified as significantly distressed by satellite observations. We assessed the potential climate-driven impacts on GWS changes throughout the 21st century under the business-as-usual scenario (RCP8.5). Results show that the climate-driven impacts on GWS changes do not necessarily reflect the long-term trend in precipitation; instead, the trend may result from enhancement of evapotranspiration, and reduction in snowmelt, which collectively lead to divergent responses of GWS changes across different aquifers. Finally, we compare the climate-driven and anthropogenic pumping impacts. The reduction in GWS is mainly due to the combined impacts of over-pumping and climate effects; however, the contribution of pumping could easily far exceed the natural replenishment.

Diverse stakeholders create collaborative, multilevel basin governance for groundwater sustainability

California Agriculture (UCANR) | March 13th, 2018

The Sustainable Groundwater Management Act (SGMA) is introducing significant changes in the way groundwater is governed for agricultural use. It requires the format

The Sustainable Groundwater Management Act (SGMA) is introducing significant changes in the way groundwater is governed for agricultural use. It requires the formation of groundwater sustainability agencies (GSAs) to manage groundwater basins for sustainability with the engagement of all users. That presents opportunities for collaboration, as well as challenges, particularly in basins with large numbers of agricultural water users who have longstanding private pumping rights. The GSA formation process has resulted in the creation of multiple GSAs in many such basins, particularly in the Central Valley. In case studies of three basins, we examine agricultural stakeholders' concerns about SGMA, and how these are being addressed in collaborative approaches to groundwater basin governance. We find that many water districts and private pumpers share a strong interest in maintaining local autonomy, but they have distinct concerns and different options for forming and participating in GSAs. Multilevel collaborative governance structures may help meet SGMA's requirements for broad stakeholder engagement, our studies suggest, while also addressing concerns about autonomy and including agricultural water users in decision-making.

Domestic well vulnerability to drought duration and unsustainable groundwater management in California's Central Valley

Environmental Research Letters (IOP) | March 18th, 2020

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and th

Millions of Californians access drinking water via domestic wells, which are vulnerable to drought and unsustainable groundwater management. Groundwater overdraft and the possibility of longer drought duration under climate change threatens domestic well reliability, yet we lack tools to assess the impact of such events. Here, we leverage 943,469 well completion reports and 20 years of groundwater elevation data to develop a spatially-explicit domestic well failure model covering California’s Central Valley. Our model successfully reproduces the spatial distribution of observed domestic well failures during the severe 2012–2016 drought (n=2027). Next, the impact of longer drought duration (5–8years) on domestic well failure is evaluated, indicating that if the 2012–2016 drought would have continued into a 6 to 8 year long drought, a total of 4037–5460 to 6538–8056 wells would fail. The same drought duration scenarios with an intervening wet winter in 2017 lead to an average of 498 and 738 fewer well failures. Additionally, we map vulnerable wells at high failure risk and find that they align with clusters of predicted well failures. Lastly, we evaluate how the timing and implementation of different projected groundwater management regimes impact groundwater levels and thus domestic well failure. When historic overdraft persists until 2040, domestic well failures range from 5966 to 10 466 (depending on the historic period considered). When sustainability is achieved progressively between 2020 and 2040, well failures range from 3677 to 6943, and from 1516 to 2513 when groundwater is not allowed to decline after 2020.

Draft finding of no significant impact, 2-Gates Fish Protection Demonstration Project.

U.S. Bureau of Reclamation (USBR) | November 13th, 2009

The proposed Demonstration Project is a 5-year experiment to validate a new delta smelt behavioral model and study the effects of modifying flows in the Sacramento-San Jo

The proposed Demonstration Project is a 5-year experiment to validate a new delta smelt behavioral model and study the effects of modifying flows in the Sacramento-San Joaquin Delta (Delta) to protect delta smelt and other sensitive aquatic species from entrainment in Central Valley Project (CVP) and State Water Project (SWP) export pumps. Research suggests that the pre-spawning migration of adult delta smelt is tied to sediment/suspended particles in the water (turbidity). Temporary gates would be placed across Old River and Connection Slough in the central Delta and operated from December to March to keep turbid water away from the CVP and SWP export pumps, thus keeping adult delta smelt away from the pumps, and in March and June to prevent larvae and juvenile delta smelt from being entrained by the export pumps.

Draft Monitoring Special Study Plan

California State Water Resources Control Board (SWRCB) | August 15th, 2022

Delta Estuary (Bay–Delta Plan), as amended through 2006, the State Water Resources Control Board (State Water Board) set salinity objectives for the interior southern D

Delta Estuary (Bay–Delta Plan), as amended through 2006, the State Water Resources Control Board (State Water Board) set salinity objectives for the interior southern Delta. In Water Right Decision 1641 (D-1641), as part of the implementation of the 1995 Bay–Delta Plan, the California Department of Water Resources (DWR) and U.S. Bureau of Reclamation (Reclamation) were assigned partial responsibility for meeting these objectives, including maintaining Specific Conductance (EC) levels at three monitoring stations (Interagency Stations No. C-6, C-8, and P-12) in the interior southern Delta waterways (Figure 3-1)1. In 2018, the State Water Board adopted amendments to the Bay–Delta Plan. Per the 2018 Bay-Delta Plan amendments, DWR and Reclamation are working to develop a Monitoring Special Study (MSS). This document serves as the study plan for the MSS and identifies three goals, consistent with section B(1)(iv) of the 2018 Bay–Delta Plan. Since early 2021, using best-science practices, DWR and Reclamation have been soliciting input from participating agencies and working with State Water Board staff to design technical studies to accomplish the following goals. 1) Characterize the spatial and temporal distribution and associated dynamics of water level, flow, and salinity conditions in the southern Delta waterways. 2) Identify the extent of low- or null-flow conditions and any associated concentration of local salt discharges. 3) Inform the development of a Long-Term Monitoring and Reporting Plan that will: a. Assess attainment of the salinity objective in the interior southern Delta; and b. Include long-term monitoring and reporting protocols, including specific compliance monitoring locations in, or monitoring protocols for, the three river segments that comprise the interior southern Delta salinity compliance locations.

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