Tulare Lake

Applying the Connectivity Approach: Groundwater management in California's Kings Basin

California Roundtable on Water and Food Supply (CRWFS) | March 27th, 2015

The California Roundtable on Water and Food Supply (CRWFS) studied the processes used in the Kings Groundwater Subbasin (Kings Basin) of California’s San Joaquin Valley

The California Roundtable on Water and Food Supply (CRWFS) studied the processes used in the Kings Groundwater Subbasin (Kings Basin) of California’s San Joaquin Valley to reveal strategies for advancing groundwater sustainability within the context of watershed-scale, integrated water management. This inquiry was guided by the principles of the “connectivity approach”: a framework developed by CRWFS for resource managers, land use planners and policymakers to discover the linkages, strengths, successes, potentials, and disconnects related to their particular resource stewardship issues. A key concept is connected benefits, which refers to achieving multiple benefits across resource and development sectors to respond to California’s increasing water management challenges.

Aquatic Life Study Final Report

San Joaquin Valley Drainage Authority | January 6th, 2016

Central Valley Salinity Alternatives for Long Term Sustainability (CV‐SALTS) is developing a comprehensive regulatory and programmatic approach to the management of sa

Central Valley Salinity Alternatives for Long Term Sustainability (CV‐SALTS) is developing a comprehensive regulatory and programmatic approach to the management of salt and nitrate in the Central Valley that is consistent with the State Recycled Water Policy (SRWP). This work is being carried out collaboratively with the Central Valley Regional Water Quality Control Board (Central Valley Water Board), the State Water Resources Control Board (State Water Board), the Central Valley Salinity Coalition and Stakeholders. As stated in the CV‐SALTS Strategy and Framework document, the strategy to fulfill the requirements of the SRWP is to adopt a Central Valley Salt and Nitrate Management Plan (SNMP) and revise the Basin Plans applicable to the Central Valley to facilitate implementation of the SNMP. This effort includes a technical review of the state of science with regards to the establishment of appropriate water quality objectives (WQO) to protect surface water beneficial uses. This Aquatic Life Study was undertaken to evaluate the technical basis for the establishment of salinity‐related WQOs to protect aquatic life in the Central Valley. The findings of this analysis will be considered by CV‐SALTS during development and adoption of the SNMP.

Arctic sea-ice loss drives a strong regional atmospheric response over the North Pacific and North Atlantic on decadal scales

Nature Portfolio (Springer Nature) | March 11th, 2025

Previous studies have suggested that Arctic sea-ice loss can have a profound influence on atmospheric circulation far away from the Arctic. However, there is litt

Previous studies have suggested that Arctic sea-ice loss can have a profound influence on atmospheric circulation far away from the Arctic. However, there is little scientific consensus on the features of these remote responses, with the opposite impacts reported. Here we present a multi-model analysis of the decadal climate response to Arctic sea-ice loss using state-of-the-art energy conserving methodologies to isolate the impacts of sea-ice decline. We observe weakening of the Aleutian Low and development of a geopotential ridge in the North Pacific, associated with drier winter conditions over the southwest United States. Over the Atlantic, a negative NAO-like response drives wetter winter conditions across the western Mediterranean. These decadal-scale impacts substantially differ from reported centennial-scale responses to Arctic sea-ice loss simulated using non-energy conserving methodologies. Factors such as the timescale of the response and methodologies used to isolate the impacts of disappearing sea-ice cover should be carefully considered when consolidating scientific understanding on the future impacts of changing Arctic.

Are Modern Droughts Unprecedented?

American Geophysical Union (AGU) | August 8th, 2026

Global drought variability of past centuries remains poorly understood due to sparse instrumental records and limited paleoclimate reconstructions. Yet, quantifying long-

Global drought variability of past centuries remains poorly understood due to sparse instrumental records and limited paleoclimate reconstructions. Yet, quantifying long-term forced and unforced variability is key for assessing the extremeness of modern (2000–2024) drought events. Here, we combine 20 ensemble members from a 600-year climate simulation (ModE-Sim, 1420–2009) and modern reanalysis data (ERA5-Land, 1950–2024) to place recent droughts in a multi-century context. Drought magnitude and timing are measured using the annual maximum potential cumulative water deficit (PCWD), which integrates atmospheric moisture demand and supply, the daily timing of precipitation events, snow melt, and radiation. We analyze the deviation of modern annual, multi-year mean, and 30-year extreme PCWD from alternative reference periods that sample forced and unforced variability to a variable extent. We find a strong decline in the number of regions with unprecedented modern (2000–2024) single-year and 25-year mean PCWD as the reference is extended into the past and with the additional consideration of unforced atmospheric variability. This is not the case for extreme droughts. 30-year extreme PCWD has increased beyond the range of variability of the last 600 years in over half of all regions globally. This suggests that drought extremes are intensifying more rapidly beyond the range experienced in the past than mean conditions. While individual droughts in the modern era may not appear unprecedented when viewed against a century-long record, the shift in their frequency distribution indicates a rising risk of damaging impacts and an increasing likelihood of droughts reaching unprecedented magnitudes in the near future.

Arsenic in California Drinking Water

Environmental Integrity Project | September 15th, 2016

More than three years after the U.S. Environmental Protection Agency found California in noncompliance with the federal Safe Drinking Water Act, 95 community water system

More than three years after the U.S. Environmental Protection Agency found California in noncompliance with the federal Safe Drinking Water Act, 95 community water systems in the state, serving more than 55,000 people, are still providing water with illegal levels of arsenic, according to an examination of state data for the last two years. Arsenic occurs naturally in the soil and groundwater in parts of California and is a known carcinogen that may also damage the developing brains of children and cause other health problems. Many of the people drinking excessive levels of arsenic are poor and/or Latino or African- American, with a cluster in the San Joaquin Valley. Nearly all have been exposed to excessive arsenic levels for at least five years and probably longer.

Assembly Bill 1337

State of California Office of Legislative Counsel | February 16th, 2023

Assembly Bill No. 2108, Chapter 347, An act to add Sections 189.7 and 13149.2 to the Water Code, relating to water

State of California Office of Legislative Counsel | September 16th, 2022

Assessing Causes and Consequences of Winter Surface Water Dynamics in California's Central Valley Using Satellite Remote Sensing

Wiley Online Library | June 3rd, 2025

California's Central Valley is increasingly vulnerable to winter floods. A comprehensive spatial baseline of flood extents is critical for inundation analyses that can en

California's Central Valley is increasingly vulnerable to winter floods. A comprehensive spatial baseline of flood extents is critical for inundation analyses that can enhance future flood predictions, but cloud cover has prevented the regular observation of surface water extents with optical satellite imagery. In this study, we leveraged the daily resolution of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data to create a continuous series of monthly Dynamic Surface Water Extent (DSWEmod) images across the Central Valley from January 2003 to January 2023. We used the timeseries to assess the climatic driving forces of winter (Oct–April) surface water variability at sub-basin and pixel scales. At the sub-basin scale, we evaluated the influences of winter precipitation, occurrence of atmospheric rivers, and antecedent soil moisture on monthly surface water extents and found that the greatest correspondence occurs in mid-winter (Dec–Feb); in contrast, non-precipitation drivers such as water management play a stronger role in autumn and spring. The pixel-level analysis identified the probabilities of precipitation-driven surface water occurrences in the Sacramento basin are highest along rivers, conveyance channels, and floodways, with higher probabilities under wetter antecedent soil moisture conditions. Precipitation-driven surface water occurrences are also common in leveed areas and outside flood boundaries designated by state and federal agencies where exposure of structures to inundation was larger in terms of their value. Finally, areas with more frequent precipitation-driven flooding have poor recharge potential but are commonly within 5 km of areas classified as having good potential. This study demonstrates a novel approach for exploring the utility of MODIS for understanding surface water dynamics in mid-winter, a period characterized by peak precipitation, flood risk, and surface water extent. This information can provide valuable insights for (1) assessing flood risks for infrastructure and populations, (2) identifying areas most suited to strategic water management investments to increase recharge, and (3) analyzing precipitation thresholds that trigger flooding to allow proactive water management strategies to minimize damage and maximize recharge.

Assessing Early Implementation of Urban Water Use Efficiency Requirements

Legislative Analyst's Office (LAO) | January 4th, 2024

Legislation approved in 2018 established a long‑term urban water use efficiency framework to “Make Conservation a California Way of Life.” This framework—which is

Legislation approved in 2018 established a long‑term urban water use efficiency framework to “Make Conservation a California Way of Life.” This framework—which is one component of the state’s overall water management strategy—creates new requirements for about 405 urban retail water suppliers that supply water to nearly 95 percent of state residents. This report responds to a requirement contained in the 2018 legislation for our office to assess implementation of the framework. (Our report is not able to address every aspect requested in the legislation due to framework implementation delays.)

Assessing potential effects of oil and gas development activities on groundwater quality near and overlying the Elk Hills and North Coles Levee Oil Fields, San Joaquin Valley, California

PLOS | August 5th, 2024