Tulare Lake

Inaction’s Economic Cost for California’s Water Supply Challenges

University of California, Davis (UC Davis) | May 14th, 2025

California’s water system is in for challenges in coming decades as climate, groundwater policy, and environmental regulations reduce availability and increase variabil

California’s water system is in for challenges in coming decades as climate, groundwater policy, and environmental regulations reduce availability and increase variability in water supplies for agricultural and urban uses. A previous report estimated 4 to 9 million acre-feet (maf) per year of unavoidable reductions in existing water supplies, 12% to 25% of today’s water use (Lund et al. 2024). This report estimates the economic costs of not responding to these reductions in water availability.

Inadequate Government-Led Water-Quality Monitoring Hinders Improvement Efforts in the Salton Sea

University of California, Los Angeles (UCLA) | September 4th, 2025

California’s largest inland body of water, the Salton Sea, has faced severe environmental degradation, leaving lasting impacts on surrounding desert communities. Situat

California’s largest inland body of water, the Salton Sea, has faced severe environmental degradation, leaving lasting impacts on surrounding desert communities. Situated between Riverside and Imperial counties, the lake has endured the effects of jurisdictional challenges, climate change, and unsustainable agricultural practices that have exacerbated nutrient pollution to levels surpassing those found in most lakes across the United States. Data collected over 16 years of quarterly government sampling and 12 months of high-frequency sampling—conducted collaboratively by local communities and the University of California, Los Angeles—consistently reveal high concentrations of nitrates and dangerously low oxygen levels in the water column. These nutrient-rich conditions create an environment conducive to hydrogen sulfide emissions, which persist around the Salton Sea at levels that exceed health standards and raise ongoing concerns within the community. The State of California and the federal government are contractually obligated to restore the Salton Sea. To address the water-quality issues and their consequences, we recommend a combination of environmental and economic remediation efforts aimed at improving the Salton Sea’s ecosystem and its resulting impact on nearby communities.

Incomplete Determination of the 2020 Groundwater Sustainability Plans Submitted for the San Joaquin Valley – Kern County Subbasin

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

Department management has reviewed the enclosed Staff Report, which recommends that the deficiencies identified should preclude approval of the Plan. Based on its review

Department management has reviewed the enclosed Staff Report, which recommends that the deficiencies identified should preclude approval of the Plan. Based on its review of the Staff Report, Department management is satisfied that staff have conducted a thorough evaluation and assessment of the Plan and concurs with, and hereby adopts, staff’s recommendation and all the corrective actions provided. The Department thus deems the Plan incomplete based on the Staff Report and the findings contained herein. A. The GSPs do not establish undesirable results that are consistent for the entire Subbasin. 1. While the Coordination Agreement presents Subbasin-wide undesirable results, the Subbasin’s fragmented approach towards establishing management criteria that define undesirable conditions in various parts of the Subbasin does not satisfy SGMA’s requirement to use same data and methodologies. B. The Subbasin’s chronic lowering of groundwater levels sustainable management criteria do not satisfy the requirements of SGMA and the GSP Regulations. 1. The GSPs relied on disparate methods to develop groundwater level minimum thresholds across the numerous GSPs and management areas. 2. The GSPs do not consistently and sufficiently document the effects of their selected minimum thresholds on beneficial uses and users in the Subbasin, nor explain how the minimum thresholds and measurable objectives that are set below historical lows will impact other applicable sustainability indicators, specifically water quality, land subsidence, and reduction of groundwater storage. C. The Subbasin’s land subsidence sustainable management criteria do not satisfy the requirements of SGMA and the GSP Regulations. 1. The Plan lacks a Subbasin-wide, coordinated approach to establishing land subsidence sustainable management criteria. 2. The GSPs and management areas that use their minimum thresholds for the chronic lowering of groundwater levels as proxy criteria for subsidence do not sufficiently demonstrate that groundwater levels (specifically groundwater levels below historical lows) are a reasonable proxy to avoid land subsidence that would substantially interfere with surface land uses.

Increasing water cycle extremes in California and in relation to ENSO cycle under global warming

Nature Portfolio (Springer Nature) | October 21st, 2015

Since the winter of 2013–2014, California has experienced its most severe drought in recorded history, causing statewide water stress, severe economic loss and

Since the winter of 2013–2014, California has experienced its most severe drought in recorded history, causing statewide water stress, severe economic loss and an extraordinary increase in wildfires. Identifying the effects of global warming on regional water cycle extremes, such as the ongoing drought in California, remains a challenge. Here we analyse large-ensemble and multi-model simulations that project the future of water cycle extremes in California as well as to understand those associations that pertain to changing climate oscillations under global warming. Both intense drought and excessive flooding are projected to increase by at least 50% towards the end of the twenty-first century; this projected increase in water cycle extremes is associated with a strengthened relation to El Niño and the Southern Oscillation (ENSO)—in particular, extreme El Niño and La Niña events that modulate California’s climate not only through its warm and cold phases but also its precursor patterns.

Influence of agricultural managed aquifer recharge on nitrate transport: The role of soil texture and flooding frequency

Soil Science Society of America (SSSA) | June 9th, 2021

Agricultural managed aquifer recharge (Ag-MAR) is a concept in which farmland is flooded during the winter using excess surface water to recharge the underlying groundwat

Agricultural managed aquifer recharge (Ag-MAR) is a concept in which farmland is flooded during the winter using excess surface water to recharge the underlying groundwater. In this study, we show how different recharge practices affect NO3− leaching and mineralization–denitrification processes in different soil systems. Two contrasting soil textures (sand and fine sandy loam) from the Central Valley, Califor- nia, were repeatedly flooded with 15 cm of water at varying time intervals in field and soil column experiments. Nitrogen species (NO3–, NH4+, total N), total C, dis- solved O2, and moisture content were measured throughout the experiments. Results show that when flooding occurs at longer intervals (every 1–2 wk), N mineralization increases, leading to an increase of mobile NO3− in the upper root zone and leach- ing of significant quantities of NO3− from both soil textures (137.3 ± 6.6% [sand] and 145.7 ± 5.8% [fine sandy loam] of initial residual soil NO3−) during subsequent flooding events. Laboratory mineralization incubations show that long flooding inter- vals promote mineralization and production of excess NO3− at rates of 0.11–3.93 mg N kg–1 wk–1 (sand) and 0.08–3.41 mg N kg–1 wk–1 (fine sandy loam). Decreasing the flooding frequency to 72 h reduces potential mineralization, decreasing the amount of NO3− leached during flooding events (31.7 ± 3.8% [sand] and 64.7 ± 10.4% [fine sandy loam] of initial residual soil NO3–). The results indicate that implementing recharge as repeated events over a long (multiple-week) time horizon might increase the total amount of NO3− potentially available for leaching to groundwater.

Information for the Future: The West Side San Joaquin Valley Project

West Side San Joaquin Valley Coordinating Council, University of California, Water Resources Center | September 1st, 1970

Information Needs for Water Markets: Fair and Effective Water Markets Require Adequate Measurement and Reporting of Diversion and Use

University of California, Berkeley (UC Berkeley) | November 14th, 2024

Interactions between urban water policy, residential irrigation, and plant & bird diversity in the Fresno-Clovis Metro Area

Nature Portfolio (Springer Nature) | August 11th, 2011

Ecological theory has begun to incorporate humans as part of coupled socio-ecological systems. Modern urban development provides an excellent laboratory to examine the in

Ecological theory has begun to incorporate humans as part of coupled socio-ecological systems. Modern urban development provides an excellent laboratory to examine the interplay among socio-ecological relationships. Urban land and water management decisions result from dynamic interactions between institutional, individual and ecological factors. Landscaping and irrigation at any particular residence, for example, is a product of geography, hydrology, soil, and other local environmental conditions, the homeowners’ cultural preferences, socioeconomic status, identity construction, neighborhood dynamics, as well as zoning laws, market conditions, city policies, and county/state/federal government regulations. Since land and water management are key determinants of habitat for other species, urban biodiversity is strongly driven by the outcome of interactions between these variables. This study addresses the significance of water as a key variable in the Fresno-Clovis Metropolitan Area (FCMA), shaping current patterns of landscape and water use, at a time when the city of Fresno is installing meters as a regulatory tool to conserve water. We combine data from a citizen science bird monitoring project, field surveys of trees, and mail surveys of residents to address interactions among key components of the urban socioecological system.

Introducing Time-Limited Permits to California’s Riparianism

University of California, Davis (UC Davis) | December 1st, 2023

Investigation on the Feasibility of Developing Uniformwater Recycling Criteria ror Direct Potable Reuse

California State Water Resources Control Board (SWRCB) | December 1st, 2016

The population of California is projected to increase from 38 million to 50 million by the year 2049. This population increase will have a dramatic impact on the water ne

The population of California is projected to increase from 38 million to 50 million by the year 2049. This population increase will have a dramatic impact on the water needs of the State. To address this increased water need, the State will take a variety of actions as outlined in the Governor’s California Water Action Plan, first released in 2014 and recently updated in 2016 (CA Natural Resources Agency, 2016). One component of that plan is to increase the use of recycled water. The State Water Board has set a mandate of increasing the use of recycled water by 200,000 acre-foot per year (AFY) by 2020 and an additional 300,000 AFY by 2030. Although the use of recycled water for non-potable uses such as agricultural and landscape irrigation is already well established and has been regulated for decades in California, increasing the use of recycled water for both non-potable uses as well as a source of potable water (“potable reuse”) is important for the State to be able to meet this mandate. For example, groundwater replenishment (groundwater recharge), which is an indirect form of potable reuse, has the capacity to reuse 200,000 acre-feet of recycled water a year via just eight projects throughout California. Accordingly, the State Water Board revised and adopted uniform water recycling criteria for groundwater replenishment in 2014 and is in the process of establishing uniform water recycling criteria for the augmentation of surface water reservoirs used as a source of drinking water supply, which is another form of indirect potable reuse.