Sacramento River

Modeling the dynamic penetration depth of post-1950s water in unconfined aquifers using environmental tracers: Central Valley, California

Journal of Hydrology (Elsevier) | December 5th, 2022

The penetration depth of post-1950s recharge (D-1950) in aquifers is a marker that is frequently used to identify groundwater that is susceptible to anthropogenic contami

The penetration depth of post-1950s recharge (D-1950) in aquifers is a marker that is frequently used to identify groundwater that is susceptible to anthropogenic contamination. Here, we compute D-1950 values at wells, interpolate them in space, and project them across time to map the moving front of modern recharge in four dimensions in the Central Valley aquifer system, California, USA. Tracers of groundwater age (tritium, carbon-14, noble gases, sulfur hexafluoride, and chlorofluorocarbons) were collected at 650 wells spatially distributed throughout the Central Valley and were fit to a lumped-parameter model that assumes a logarithmic age-depth profile in the aquifer. For samples where tritium was present (>0.3 tritium units), the model was used to predict D-1950 at wells screened above or across the modern-premodern interface (n = 484). Wells with samples where tritium was absent (≤0.3 tritium units) were used to define the depth beyond which groundwater is completely premodern (n = 166). Predicted D-1950 values were below the depth of screen bottoms for wells where groundwater is completely modern, and above the depth of screen tops for wells where groundwater is completely premodern. The interpolated surface of D-1950 is dynamic, less prone to extreme values, and produces maps with lower interpolation errors due to a higher spatial density of wells than maps based on the depth of premodern groundwater. Between 2005 and 2025, D-1950 is expected to deepen by 11 and 12 m in the northern and southern parts of the Central Valley, respectively. Areas where D-1950 increases rapidly are likely to see increases in nitrate and other anthropogenic contaminants associated with the downward moving front of modern water.

Modeling the effect of habitat availability and quality on endangered winter-run Chinook salmon (Oncorhynchus tshawytscha) production in the Sacramento Valley

Ecological Modelling (Elsevier) | March 13th, 2021

Reconciliation between water uses and sustaining aquatic species populations requires an effort to identify and quantify essential habitat characteristics for ecosystem h

Reconciliation between water uses and sustaining aquatic species populations requires an effort to identify and quantify essential habitat characteristics for ecosystem health and valuation methods to predict ecosystem response to restoration actions. This process is particularly challenging for anadromous fish species such as California's Sacramento River winter-run Chinook salmon, due to their limited geographic range and diverse life history habitat requirements. Tools, such as life-cycle models, are needed to manage population dynamics and quantify the composite effects of processes across space and time. Nevertheless, complex institutions can hinder result interpretation and communication, and limit model use in decision-making. This paper focuses on the federally endangered and endemic Sacramento River winter-run Chinook (Oncorhynchus tshawytscha) by developing a Winter-Run Habitat-based Population Model (WRHAP). WRHAP is a conceptual, freshwater rearing stage model that includes alternative rearing habitats reported in the literature (e.g., floodplains, off-channel and tributaries), defines rules of habitat use based on instream conditions, and incorporates a juvenile growth module that combines bioenergetics modeling with empirical growth rates. Model outputs reasonably follow observed out-migration patterns and provide a realistic smolt size distribution arriving at the San Francisco Bay. This effort demonstrates the importance of currently “non-critical” habitats (as defined by the Endangered Species Act) for juvenile development, with floodplain habitat contributing to a quarter of out-migrating biomass (despite < 18% availability and <10% of total rearing days), and off-channel growth being one of the most sensitive parameters (explaining ~13% of average juvenile weight variance). The model shows the utility of a simple population model to explore relationships between habitat quality/quantity and juvenile development, and to assist water/environmental management and decision-making processes focused on species recovery.

Modernizing the system: California Water Fix finance and cost allocation (White paper #3)

Metropolitan Water District of Southern California (MWD) | August 10th, 2017

The third in a series of policy papers prepared for the consideration of Metropolitan’s Board of Directors in advance of planned summer meetings and decisions in fall 2

The third in a series of policy papers prepared for the consideration of Metropolitan’s Board of Directors in advance of planned summer meetings and decisions in fall 2017. Modernizing and improving California’s water system is essential for the reliable delivery of water supplies to much of the state. About 30 percent of the water that flows out of taps in Southern California homes and businesses comes from Northern California watersheds and flows through the Sacramento-San Joaquin Delta. But the Delta’s declining ecosystem and 1,100 miles of levees are increasingly vulnerable to earthquakes, flooding, saltwater intrusion, climate change and further environmental degradation. California WaterFix is the product of more than a decade of review, planning, rigorous scientific and environmental analysis and unprecedented public comment. This white paper provides information about the costs of the project, including adjustments of capital, mitigation and O&M costs to 2017 dollars. The financing plan is presented with financial assumptions and a range of financing scenarios. The cost allocation information covers Metropolitan’s anticipated financial commitment, an estimate of member agency wholesale rate impacts, and metrics to assess retail level impacts. Using this information and when compared to costs for other local supply alternatives, California WaterFix would provide a cost-effective supply for Southern California’s water portfolio.

Modernizing the system: California Water Fix Infrastructure (White paper #1)

Metropolitan Water District of Southern California (MWD) | July 3rd, 2017

The first in a series of three policy papers prepared for the consideration of Metropolitan Water District’s Board of Directors in advance of planned summer meetings an

The first in a series of three policy papers prepared for the consideration of Metropolitan Water District’s Board of Directors in advance of planned summer meetings and decisions in Fall 2017. Modernizing and improving California’s water system is essential for the reliable delivery of water supplies to much of the state. About 30 percent of the water that flows out of taps in Southern California homes and businesses comes from Northern California watersheds and flows through the Sacramento-San Joaquin Delta. But the Delta’s declining ecosystem and 1,100 miles of levees are increasingly vulnerable to earthquakes, flooding, saltwater intrusion, climate change and further environmental degradation. California WaterFix is the product of more than a decade of review, planning, and rigorous scientific and environmental analysis by water experts, engineers and conservationists, as well as unprecedented public comment. The proposed project will improve the security of our water system by fixing aging infrastructure and constructing new, state-of-the art facilities using innovative technologies and engineering practices. Significant planning work for the design and construction of the project has been performed by the state, water agencies, and construction and engineering firms, which have determined the project is buildable. Details of the project features, actions to address public comment, risk management, schedule projection and cost estimates are addressed in a new white paper and summarized below.

Modernizing the system: California Water Fix operations (White paper #2)

Metropolitan Water District of Southern California (MWD) | July 20th, 2017

The second in a series of three policy papers prepared for the consideration of Metropolitan’s Board of Directors in advance of planned summer meetings and decisions in

The second in a series of three policy papers prepared for the consideration of Metropolitan’s Board of Directors in advance of planned summer meetings and decisions in fall 2017. Modernizing and improving California’s water system are essential for the reliable delivery of water supplies to much of the state. About 30 percent of the water that flows out of taps in Southern California homes and businesses comes from Northern California watersheds and flows through the Sacramento-San Joaquin Delta. But the Delta’s declining ecosystem and 1,100 miles of levees are increasingly vulnerable to earthquakes, flooding, saltwater intrusion, climate change and further environmental degradation. California WaterFix is the product of more than a decade of review, planning, rigorous scientific and environmental analysis in collaboration with fishery agencies and an unprecedented level of public comment. Extensive analysis and work has been performed by state and federal water agencies and fish and wildlife agencies to determine conveyance system improvements and an operations framework to improve the direction of river flows in ways that will help native fish species, protect water supplies from climate change impacts and help restore the Delta ecosystem. Details of the proposed operations are addressed in Metropolitan’s second white paper and summarized below.

Mokelumne watershed avoided cost analysis: Why Sierra fuel treatments make economic sense

Sierra Nevada Conservancy | April 10th, 2014

High-severity wildfires in forests of California’s Sierra Nevada pose a serious threat to people and nature. Although proactive forest management can reduce the risk of

High-severity wildfires in forests of California’s Sierra Nevada pose a serious threat to people and nature. Although proactive forest management can reduce the risk of high-severity wildfire, the pace and scale of fuel treatments is insufficient, given the growing scope of the problem. Using the upper Mokelumne River watershed as a representative case, we sought to answer the following question: Does it make economic sense to increase investment in fuel treatments to reduce the risk of large, damaging wildfires? Our analysis suggests that the economic benefits of landscape- scale fuel-reduction treatments far outweigh the costs of wildfire. 

More state and local attention to financing can advance sustainable groundwater management

Berkeley Law Center for Law, Energy, & the Environment | April 12th, 2025

Mountain rock glaciers contain globally significant water stores

Nature Portfolio (Springer Nature) | February 12th, 2018

Glacier- and snowpack-derived meltwaters are threatened by climate change. Features such as rock glaciers (RGs) are climatically more resilient than glaciers and

Glacier- and snowpack-derived meltwaters are threatened by climate change. Features such as rock glaciers (RGs) are climatically more resilient than glaciers and potentially contain hydrologically valuable ice volumes. However, while the distribution and hydrological significance of glaciers is well studied, RGs have received comparatively little attention. Here, we present the first near-global RG database (RGDB) through an analysis of current inventories and this contains >73,000 RGs. Using the RGDB, we identify key data-deficient regions as research priorities (e.g., Central Asia). We provide the first approximation of near-global RG water volume equivalent and this is 83.72 ± 16.74 Gt. Excluding the Antarctic and Subantarctic, Greenland Periphery, and regions lacking data, we estimate a near-global RG to glacier water volume equivalent ratio of 1:456. Significant RG water stores occur in arid and semi-arid regions (e.g., South Asia East, 1:57). These results represent a first-order approximation. Uncertainty in the water storage estimates includes errors within the RGDB, inherent flaws in the meta-analysis methodology, and RG thickness estimation. Here, only errors associated with the assumption of RG ice content are quantified and overall uncertainty is likely larger than that quantified. We suggest that RG water stores will become increasingly important under future climate warming.

Multiple lines of evidence point to pesticides as stressors affecting invertebrate communities in small streams in five United States regions

Science of the Total Environment (Elsevier) | January 24th, 2024

Multiscale Assessment of Agricultural Consumptive Water Use in California's Central Valley

American Geophysical Union (AGU) | May 4th, 2021