Sacramento River

2022 Annual Review of the Construction and Operation of the State Water Project

California Water Commission (CWC) | January 18th, 2023

2022 Annual Water Supply and Demand Assessment Summary Report

California Department of Water Resources (DWR) | November 22nd, 2022

This summary report contains projected water shortage information at the urban water supplier level as well as regional and statewide analyses of water supply conditions

This summary report contains projected water shortage information at the urban water supplier level as well as regional and statewide analyses of water supply conditions and is intended to inform the State Water Resources Control Board (State Water Board). Additionally, the report includes information on water shortage response actions taken by urban water suppliers as a result of their Annual Water Supply and Demand Assessments (Annual Assessments), and urban water suppliers’ compliance statistics with respect to their Annual Water Shortage Assessment Report (Annual Shortage Report) submittals. The purpose of this Annual Water Supply and Demand Assessment Summary Report (Summary Report) is to fulfill the California Water Code (CWC) §10644(c)(1)(B) requirements and it is due on or before September 30, 2022, and every year thereafter. The full text of the CWC section regarding the Department of Water Resources’ (DWR) Summary Report to the State Water Board is presented below for reference.

2022 Drinking Water Needs Assessment

California State Water Resources Control Board (SWRCB) | April 30th, 2022

The Needs Assessment is comprised of Risk, Affordability, and Cost Assessment components. Enhancement of the 2022 Needs Assessment consisted of internal workgroup recomme

The Needs Assessment is comprised of Risk, Affordability, and Cost Assessment components. Enhancement of the 2022 Needs Assessment consisted of internal workgroup recommendations and a public workshop in February 2022, all of which were detailed in a publicly available white paper. The public feedback was incorporated into the final methodology and results. Three different water system types: public water systems, state small water systems and domestic wells, are analyzed within the 2022 Needs Assessment. Different methodologies were developed for these system types based on data availability and reliability.

2022 State Plan of Flood Control Descriptive Document

California Department of Water Resources (DWR) | February 28th, 2022

2023 Annual Water Supply and Demand Assessment Summary Report

California Department of Water Resources (DWR) | September 30th, 2023

This annual report summarizes the Department of Water Resources’ (DWR’s) review of Urban Water Suppliers’ Annual Water Shortage Assessment Reports (Annual Shortage

This annual report summarizes the Department of Water Resources’ (DWR’s) review of Urban Water Suppliers’ Annual Water Shortage Assessment Reports (Annual Shortage Reports) for the State Water Resources Control Board (State Water Board). As directed by the California Water Code (CWC) §10644(c)(1)(B), this summary report includes water shortage information at the supplier level, as well as regional and statewide analyses of water supply conditions.

2023 Drinking Water Needs Assessment

California State Water Resources Control Board (SWRCB) | April 30th, 2023

The Needs Assessment is comprised of four core components: the Failing Water System List (Failing list), the Risk Assessment, the Cost Assessment, and the Affordability A

The Needs Assessment is comprised of four core components: the Failing Water System List (Failing list), the Risk Assessment, the Cost Assessment, and the Affordability Assessment. Public input that the State Water Board received via workshops held in 2022 and February 2023 helped improve the 2023 Needs Assessment.

2023 Water Resilience Portfolio Progress Report

California Natural Resources Agency (CNRA) | October 31st, 2023

21st century California drought risk linked to model fidelity of the El Niño teleconnection

Nature Portfolio (Springer Nature) | September 3rd, 2018

Greenhouse gas-induced climate change is expected to lead to negative hydrological impacts for southwestern North America, including California (CA). This includes a decr

Greenhouse gas-induced climate change is expected to lead to negative hydrological impacts for southwestern North America, including California (CA). This includes a decrease in the amount and frequency of precipitation, reductions in Sierra snow pack, and an increase in evapotranspiration, all of which imply a decline in surface water availability, and an increase in drought and stress on water resources. However, a recent study showed the importance of tropical Pacific sea surface temperature (SST) warming and an El Niño Southern Oscillation (ENSO)-like teleconnection in driving an increase in CA precipitation through the 21st century, particularly during winter (DJF). Here, we extend this prior work and show wetter (drier) CA conditions, based on several drought metrics, are associated with an El Niño (La Niña)-like SST pattern. Models that better simulate the observed ENSO-CA precipitation teleconnection also better simulate the ENSO-CA drought relationships, and yield negligible change in the risk of 21st century CA drought, primarily due to wetting during winter. Seasonally, however, CA drought risk is projected to increase during the non-winter months, particularly in the models that poorly simulate the observed teleconnection. Thus, future projections of CA drought are dependent on model fidelity of the El Niño teleconnection. As opposed to focusing on adapting to less water, models that better simulate the teleconnection imply adaptation measures focused on smoothing seasonal differences for affected agricultural, terrestrial, and aquatic systems, as well as effectively capturing enhanced winter runoff.

A Bayesian approach to infer nitrogen loading rates from crop and land-use types surrounding private wells in the Central Valley, California

European Geosciences Union (EGU) | May 7th, 2018

This study is focused on nitrogen loading from a wide variety of crop and land-use types in the Central Valley, California, USA, an intensively farmed region with high�

This study is focused on nitrogen loading from a wide variety of crop and land-use types in the Central Valley, California, USA, an intensively farmed region with high agricultural crop diversity. Nitrogen loading rates for several crop types have been measured based on field-scale experiments, and recent research has calculated nitrogen loading rates for crops throughout the Central Valley based on a mass balance approach. However, research is lacking to infer nitrogen loading rates for the broad diversity of crop and land use types directly from groundwater nitrate measurements. Relating groundwater nitrate measurements to specific crops must account for the uncertainty about and multiplicity in contributing crops (and other land uses) to individual well measurements, and for the variability of nitrogen loading within farms and from farm to farm for the same crop type. In this study, we developed a Bayesian regression model that allowed us to estimate land-use-specific groundwater nitrogen loading rate probability distributions for 15 crop and land-use groups based on a database of recent nitrate measurements from 2149 private wells in the Central Valley. The water and natural, rice, and alfalfa and pasture groups had the lowest median estimated nitrogen loading rates, each with a median estimate below 5 kg N ha -1 yr -1. Confined animal feeding operations (dairies) and citrus and subtropical crops had the greatest median estimated nitrogen loading rates at approximately 269 and 65 kg N ha -1 yr-1, respectively. In general, our probability-based estimates compare favorably with previous direct measurements and with mass-balance-based estimates of nitrogen loading. Nitrogen mass-balance-based estimates are larger than our groundwater nitrate derived estimates for manured and non-manured forage, nuts, cotton, tree fruit, and rice crops. These discrepancies are thought to be due to groundwater age mixing, dilution from infiltrating river water, or denitrification between the time when nitrogen leaves the root zone (point of reference for mass-balance derived loading) and the time and location of groundwater measurement.

A Comparative Study for Estimating Crop Evapotranspiration in the Sacramento-San Joaquin Delta

University of California, Davis (UC Davis) | April 23rd, 2018

Consumptive water use by crops, often referred to as evapotranspiration (ET), is frequently the largest component of an agricultural region’s water balance. This study

Consumptive water use by crops, often referred to as evapotranspiration (ET), is frequently the largest component of an agricultural region’s water balance. This study investigates crop consumptive use in the Sacramento-San Joaquin Delta (“Delta”) of California using a comparative approach with several prominent methods for estimating crop ET, including estimates based on crop coefficients, water balances, energy balance using remote sensing, and field measurements. Click here to download full report and links to appendices