California Water Supply And Demand: Technical Report

Stockholm Environment Institute (SEI) | February 10th, 2011

The California Water Supply and Demand Model (CWSD) examines the ways in which California’s water supply and demand are likely to be affected by climate change; its pur

The California Water Supply and Demand Model (CWSD) examines the ways in which California’s water supply and demand are likely to be affected by climate change; its purpose is to serve as a base for quantifying these impacts in economic terms. California’s water future is modeled under conditions of no adaptation to climate change, and under several projected water use adaptation scenarios taken from the literature; climate change adaptation scenarios include water used for energy, the urban or residential sector, and agriculture. The main CWSD compares key categories of water inputs and outputs on a month-by-month basis to capture seasonality in water availability. A supplementary model allows for the main model’s beginning surface reservoir storage to result from water supply and demand interactions over a stylized previous 100 years. Three areas of water use are both especially critical and vulnerable to climatic change: the energy, agriculture, and urban sectors. In the energy module, water demand is a based on different scenarios of coal, nuclear and renewable power use, conservation technology, state population trends, and projected temperatures. In the agriculture module, crop and animal water use by county is a function of projected summer temperatures by county. In the urban module, residential, industrial/commercial, and public water use are based on projected levels of socio-economic growth.

California Wetland and Riparian Area Protection Policy Technical Memorandum No. 5: Stream Definition

San Francisco Estuary Institute (SFEI) | April 20th, 2016

With this memorandum, the Technical Advisory Team (TAT) recommends a definition of California streams to the Policy Development Team (PDT) of the State Water Quality Cont

With this memorandum, the Technical Advisory Team (TAT) recommends a definition of California streams to the Policy Development Team (PDT) of the State Water Quality Control Board (State Water Board) for its Wetland and Riparian Area Protection Policy (WRAPP). This memorandum does not recommend any process or procedure for identifying, delineating, or classifying streams, nor are such recommendations being planned by the TAT at this time. However, the TAT recommends that such processes and procedures should be developed in the future to support the WRAPP. The California Wetland Monitoring Workgroup (CWMW) is preparing recommendations for stream mapping as part of the recommending methodology of the California Aquatic Resource Inventory (CARI). 

California Winter Precipitation Change under Global Warming in the Coupled Model Intercomparison Project Phase 5 Ensemble

American Meteorological Society (AMS) | August 23rd, 2013

Projections of possible precipitation change in California under global warming have been subject to considerable uncertainty because California lies between the

Projections of possible precipitation change in California under global warming have been subject to considerable uncertainty because California lies between the region anticipated to undergo increases in precipitation at mid-to-high latitudes and regions of anticipated decrease in the subtropics. Evaluation of the large-scale model experiments for phase 5 of the Coupled Model Intercomparison Project (CMIP5) suggests a greater degree of agreement on the sign of the winter (December–February) precipitation change than in the previous such intercomparison, indicating a greater portion of California falling within the increased precipitation zone. While the resolution of global models should not be relied on for accurate depiction of topographic rainfall distribution within California, the precipitation changes depend substantially on large- scale shifts in the storm tracks arriving at the coast. Significant precipitation increases in the region arriving at the California coast are associated with an eastward extension of the region of strong Pacific jet stream, which appears to be a robust feature of the large-scale simulated changes. This suggests that effects of this jet extension in steering storm tracks toward the California coast constitute an important factor that should be assessed for impacts on incoming storm properties for high-resolution regional model assessments.

California's Area of Origin Laws

California State Water Resources Control Board (SWRCB) | April 8th, 2013

California’s Area of Origin Laws have long been in the background of the State’s major water issues. They were enacted 50-80 years ago, are written very generally, an

California’s Area of Origin Laws have long been in the background of the State’s major water issues. They were enacted 50-80 years ago, are written very generally, and have not been subject to a lot of interpretation by the courts. However, they remain a potential linchpin to resolving many of California’s most vexing water disputes. For that reason alone, the Area of Origin Laws are worthy of attention. It is the purpose of this report to: provide a brief description of the Area of Origin Laws, to discuss recent court cases that have discussed them, and to summarize the major principles embodied in the laws.

California's Central Valley Groundwater Wells Run Dry During Recent Drought

American Geophysical Union (AGU) | February 27th, 2020

Declining water tables are causing wells to run dry in California, but the prevalence and spatial distribution of wells that have run dry are not known beyond anecdotal a

Declining water tables are causing wells to run dry in California, but the prevalence and spatial distribution of wells that have run dry are not known beyond anecdotal and voluntary reports. Here, we apply a new, simple, and measurement‐driven method to calculate a localized water table; we show, for the first time using observations, that up to one‐in‐five wells now runs dry in California's Central Valley. The spatial distribution of wells identified as having dried up replicates hot spots of wells identified as having run dry in a voluntary reporting system, while also capturing impacts on groundwater wells that have not reportedly run dry. We assess the rates of drilling throughout the Central Valley and find, surprisingly, that domestic wells are being drilled deeper at a rate that exceeds agricultural wells across much of the central Central Valley. Because new groundwater wells are costly (i.e., $10,000 to $100,000), we suggest explicitly considering dry wells in groundwater sustainability planning to protect homes and farms from the loss of access to reliable water supplies in the future.

California's Flood Future: Recommendations for Managing the State's Flood Risk (Highlights)

California Department of Water Resources (DWR) | November 14th, 2013

California's Fourth Climate Change Assessment Statewide Summary Report

Governor's Office of Planning and Research (OPR) | August 27th, 2018

California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-

California’s Fourth Climate Change Assessment (Fourth Assessment) advances actionable science that serves the growing needs of state and local-level decision-makers from a variety of sectors. This cutting-edge research initiative is comprised of a wide-ranging body of technical reports, including rigorous, comprehensive climate change scenarios at a scale suitable for illuminating regional vulnerabilities and localized adaptation strategies in California; datasets and tools that improve integration of observed and projected knowledge about climate change into decision- making; and recommendations and information to directly inform vulnerability assessments and adaptation strategies for California’s energy sector, water resources and management, oceans and coasts, forests, wildfires, agriculture, biodiversity and habitat, and public health. In addition, these technical reports have been distilled into summary reports and a brochure, allowing the public and decision-makers to easily access relevant findings from the Fourth Assessment. Click here for key findings brochure

California's Future

Public Policy Institute of California (PPIC) | January 18th, 2018

Water management in California has always been challenging. The state’s variable climate is marked by long droughts and severe floods, with stark regional differences i

Water management in California has always been challenging. The state’s variable climate is marked by long droughts and severe floods, with stark regional differences in water availability and demand. California has adapted by building a vast network of storage and conveyance facilities to deliver water from the wetter parts of the state to population and farming centers in the Bay Area, the San Joaquin Valley, and Southern California. The Sacramento–San Joaquin Delta is a fragile link in the state’s water supply network, and a plan to address supply reliability, known as California WaterFix, faces many hurdles. California’s extensive network of dams is aging. Agricultural demand is becoming less flexible, as farmers are increasing tree crops (especially nuts), which must be watered every year. Conflicts are growing between human water use and water needed to support fish and other wildlife. And the latest cycle of droughts and floods provides a glimpse of an uncertain future under climate change. California’s water management challenges are complex, but they can be addressed. Solutions will involve difficult and sometimes costly trade-offs, as well as contentious legal and political changes.

California's Groundwater Conditions Semi-Annual Update: March 2023

California Department of Water Resources (DWR) | March 15th, 2023

These updates are part of the informational resources associated with DWR’s California’s Groundwater (Bulletin 118). This report uses groundwater data received electr

These updates are part of the informational resources associated with DWR’s California’s Groundwater (Bulletin 118). This report uses groundwater data received electronically by DWR as of February 15, 2022, through the conclusion of Water Year 2022, and the start of Water Year 2023.

California's Groundwater Conditions: Semi Annual Update May 2024, Spring Bulletin 118

California Department of Water Resources (DWR) | May 6th, 2024

In WY 2023, increased surface water supply led to a significant reduction in statewide groundwater extraction, amounting to a total annual extraction of 9.5 million acre-

In WY 2023, increased surface water supply led to a significant reduction in statewide groundwater extraction, amounting to a total annual extraction of 9.5 million acre-feet, a stark contrast to the 17 million acre-feet extracted in WY 2022.