Tulare Lake

The Rebirth of California Fish & Game Code Section 5937: Water for Fish

University of California, Davis (UC Davis) | July 1st, 2012

Swarms of living creatures will live wherever the river flows. There will be large numbers of fish, because this water flows there and makes the salt water fresh; so wh

Swarms of living creatures will live wherever the river flows. There will be large numbers of fish, because this water flows there and makes the salt water fresh; so where the river flows everything will live. Fishermen will stand along the shore; from En Gedi to En Eglaim there will be places for spreading nets. In an average year, California receives inflows and imports of water totaling around 200 million acre-feet,2 enough water to cover the entire state twenty-three inches deep. But California is a state of spatial and temporal water extremes. Spatially, precipitation varies wildly: Death Valley in the Southeast averages less than three inches per year, yet the northwestern corner of the state averages over 140 inches per year. More than 70% of California’s stream flow originates north of Sacramento, but more than 80% of the water is used south of Sacramento. Temporally, precipitation varies both seasonally and annually. California’s wet season typically runs from October or November to April or May, with little or no precipitation during the growing season, from May to September.7 Annual rainfalls of 40% or more below average and 36% or more above average each typically occur once every six to seven years.  To balance these extremes, over 1,300 dams store water across the state, supplying water for urban, industrial, and agricultural uses. While these uses sustain a tremendous part of California’s economy, they also come at high, often unappreciated costs. Fish also need water, so dams that alter water flows for human benefits may also have marked negative impacts on fish.

The Relationship between California Rainfall and ENSO Events

American Meteorological Society (AMS) | November 1st, 1989

This paper examines the annual rainfall over California during 11 ENSO events within the period 1950 to 1982. During six of these, unusually wet conditions prevailed thro

This paper examines the annual rainfall over California during 11 ENSO events within the period 1950 to 1982. During six of these, unusually wet conditions prevailed throughout California; conditions were near normal during five events; and in one extreme drought occurred statewide. A comparison with the ENSO classification scheme of Fu et al, based on SST patterns in the Pacific, shows an excellent correspondence. Type 1 years, with large positive temperature anomalies east of the date line and lasting well into winter, are invariably events that enhance California rainfall. Normal years coincide with Type 2 ENSO events (moderate warming over a broad sector); the dry year is the sole Type 3 year, with weak anomalies confined to the eastern Pacific. This study also shows that the response to ENSO is regionally specific. Although throughout the state most years with extremely wet conditions are ENSO years, the tendency for an ENSO event to increase rainfall is greatest in Southern California, where 9 of 11 events produced above-normal rainfall and 8 of the 10 wettest years was an ENSO year. The pattern is more complex in central California; there ENSO years are almost invariably ones with highly abnormal rainfall, but they may be either wet or dry. The areas least influenced by ENSO are the Sierra Nevada and Northern California. The reasons for the geographical pattern of response become apparent when the seasonality and causes of rainfall in the various regions are evaluated.

The State Water Project Delivery Capability Report 2023 Addendum - Impacts of Subsidence

California Department of Water Resources (DWR) | May 7th, 2025

The purpose of this addendum is to show how ongoing subsidence effects on the California Aqueduct will impact operation of the State Water Project (SWP). The addendum pro

The purpose of this addendum is to show how ongoing subsidence effects on the California Aqueduct will impact operation of the State Water Project (SWP). The addendum provides information to SWP water users about a potential range of water delivery impacts over the next 20 years if no corrective action is taken to address the subsidence effects. However, the California Department of Water Resources (DWR) is committed to restore the conveyance capacity of the California Aqueduct and has an engineering plan for near-term fixes. DWR is also working with its partners to secure additional funding sources for this work. DWR is confident that the California Aqueduct capacity will be restored and the SWP will not see the impacts outlined in this addendum. Thus, long-term water supply planning activities by water users should rely on the potential future SWP allocation results presented in the 2023 Delivery Capability Report (DCR 2023) released in 2024.

The Struggle for Water Justice in California’s San Joaquin Valley: A Focus on Disadvantaged Unincorporated Communities

University of California, Davis (UC Davis) | February 1st, 2018

In California, lack of access to clean, safe, and affordable water is a threat to public health and well-being, and violates the state’s newly codified Human Ri

In California, lack of access to clean, safe, and affordable water is a threat to public health and well-being, and violates the state’s newly codified Human Right to Water (HRTW). In low-income communities located outside city boundaries (otherwise known as disadvantaged unincorporated communities or DUCs), drinking water is often unsafe to drink. In many such localities, drinking water is contaminated by industrial by-products (usually associated with agriculture, oil and gas production, transportation, and manufacturing) and compromised by inadequate wastewater treatment and disposal systems, as well as naturally occurring toxic substances like arsenic and uranium. Many DUC residents in the San Joaquin Valley pay a triple penalty to obtain safe water: they bear the health costs of unsafe drinking water; they purchase that unsafe water at high costs; and they must also purchase “substitute” water—typically expensive bottled water—for drinking and cooking purposes. Lack of access to clean, safe and affordable drinking water has a racial and ethnic component: the vast majority of the valley’s DUC residents are people of color who also face cumulative impacts from environmental contamination brought on by proximity to air pollution, pesticides, toxic facilities and waste disposal. Without city governments to directly represent their interests and provide essential services, residents of these DUCs have been systematically deprived of access to important means of democratic governance (Anderson 2008). California’s San Joaquin Valley is the source of much of the state and the nation’s agricultural wealth. Yet it is also a region where poverty persists amidst prosperity (Taylor and Mar n 1998). Many of the region’s DUC residents hold low-wage and dangerous jobs, and confront severe and cumulative environmental contamination of their air, water, and land (London, Huang, Zagofsky 2011). The well-being of the nearly 350,000 residents living in 450 DUCs throughout San Joaquin Valley is therefore an important environmental health, and social justice issue that demands urgent attention by policy makers, public agencies and advocates. Over the past two decades, community leaders, advocates, and policymakers have pursued a range of strategies to address unsafe drinking water in the valley’s DUCs and elsewhere in California. For example, in 2004, resident advocates won a case against the City of Modesto in 2003 for its systematic exclusion from city services of communities of color living in nearby DUCs (Molina 2014). In 2011, Senate Bill (SB) 244 required cities and counties to address the infrastructure needs of California DUCs in land use and municipal service plans, and in annexation decisions. In 2012, an HRTW policy was passed in response to massive community mobilization. Known as Assembly Bill (AB) 685, and signed by Governor Jerry Brown, it codified that every human being has a right to safe, clean, affordable, and accessible water to meet basic human needs, and required state agencies to consider this right when establishing policies and regulations. A 2013 report by the Community Equity Initiative (led by PolicyLink, California Rural Legal Assistance Inc., and California Rural Legal Assistance Foundation) developed a sophisticated analysis of the conditions of DUCs in the San Joaquin Valley. California Unincorporated: Mapping Disadvantaged Communities in the San Joaquin Valley (Flegal et al. 2013) put DUCs on the map by using a new methodology to identify these communities, and to highlight the need for new policies and funding mechanisms to address the significant challenges they face. This report, and the dedicated work of water justice advocates, have greatly increased public awareness of water inequality in DUCs. This has helped direct new public funding to improve water infrastructure, and encouraged collaborative solutions among interest groups that historically have been in conflict with each other. However, all parties agree that much more needs to be done to understand the complex issues facing DUCs, and to provide their residents with safe and affordable drinking water. Our report analyzes this situation in detail, and offers several recommendations to inform policy and advocacy on how to improve water access to these communities. To do so, we have used maps of DUCs, CWSs, and State Small Water Systems (SSWSs), as well as water quality reports, demographic data, and expert interviews. Together, these sources have helped us highlight gaps in the provision of safe and a ordable drinking water. Our main conclusion is that California’s legislature, regulatory agencies, and water suppliers need to undertake more concerted and well-resourced efforts to ensure that the HRTW is ensured for all of the San Joaquin Valley’s residents.

The Sustainable Groundwater Management Act challenges the diversity of California farms

California Agriculture (UCANR) | November 16th, 2016

California’s agricultural sector, a major groundwater user, finds itself in the midst of the implementation of the Sustainable Groundwater Management Act (SGMA). The la

California’s agricultural sector, a major groundwater user, finds itself in the midst of the implementation of the Sustainable Groundwater Management Act (SGMA). The law mandates the formation of local groundwater sustainability agencies (GSAs) and adoption of groundwater sustainability plans (GSPs) for all overdrafted groundwater basins across the state by 2020. Each GSA will be unique, with its own governance structures and rules, including the size and composition of the governing board, mechanisms for representing different interests, opportunities for stakeholders to participate, and rules concerning the allocation of pumping “rights” and the use of economic instruments, such as pumping permits, pumping taxes or tiered pricing, to incentivize pumping curtailments (DWR 2016). This new water management landscape may threaten the diversity of the state’s farming operations.

The tradeoff between water savings and salinization prevention in dryland irrigation

Advances in Water Resources (Elsevier) | December 7th, 2023

Soil salinization is a global phenomenon that affects large tracts of arid farmland worldwide. It contributes to the loss of soil fertility, declining yields, and – in

Soil salinization is a global phenomenon that affects large tracts of arid farmland worldwide. It contributes to the loss of soil fertility, declining yields, and – in the most severe cases – land unsuitability for cultivation. Irrigation water applications are both the main cause of and the solution to, anthropogenic (or ‘secondary’) salinization because salt typically enters the soil column as dissolved in irrigation water and leaves it through excess water applications (e.g., leaching). Excess leaching, which places additional water costs in areas affected by water scarcity, can be achieved with different irrigation techniques and practices. Here, by complementing a process-based crop water model with a salt balance of the shallow soil, we investigate the tradeoff between root zone salinization and water conservation to limit withdrawals from the water source. We evaluate how such a tradeoff is achieved under different irrigation technology and excess leaching practices. Considering as a case study the cultivation of tomatoes in Egypt, we find that drip and furrow irrigation allows for better control of salt accumulation, thus preventing crop exposure to salt stress. Drip irrigation achieves this goal with minimal water applications because it maintains the soil wetter. Thus, the (rare) rainfall events find more suitable conditions to drain the excess moisture. Conversely, by using more irrigation water (and ‘less efficiently’), furrow irrigation allows for higher rates of soil drainage and salt leaching. The irrigation schedule typically adopted with sprinkler irrigation allows for soil drying, thus limiting the ability of rainfall events to drain the soil and leach its salts. Collectively, these results highlight the key role of irrigation technology and practices in the management of secondary salinity in dryland agriculture. Specifically, there is a tradeoff between minimizing water use and preventing salt accumulation in the root zone. Drip irrigation exhibits the co-benefit of achieving both goals, while furrow irrigation limits soil salinity at the cost of requiring greater volumes of applied irrigation water.

The Untapped Potential of California’s Urban Water Supply: Water Efficiency, Water Reuse, and Stormwater Capture

Pacific Institute | April 12th, 2022

In this assessment, we quantify the potential for a range of water strategies in urbanized parts of California to both reduce inefficient and wasteful water uses and expa

In this assessment, we quantify the potential for a range of water strategies in urbanized parts of California to both reduce inefficient and wasteful water uses and expand local water supplies. This assessment finds that urban water-use efficiency improvements could reduce statewide urban water use by 2.0 million to 3.1 million acre-feet per year (AFY). The reuse potential of municipal wastewater is 1.8 million to 2.1 million AFY, and the stormwater capture potential is 580,000 AFY in a dry year to as much as 3.0 million AFY in a wet year. Previous assessments have shown that these efficiency and supply options are more cost effective than traditional – and increasingly hard to implement – options to expand supply. Programs to tap this potential would tremendously help solve California’s long-standing water problems.

The Water Districts of California

Association of California Water Agencies (ACWA) | April 1st, 1979

The West Wide Drought Tracker: Drought Monitoring at Fine Spatial Scales

American Meteorological Society (AMS) | September 1st, 2017

 The western United States has seen increases in population and water use over the past century. Total water use has remained relatively unchanged over the past several

 The western United States has seen increases in population and water use over the past century. Total water use has remained relatively unchanged over the past several decades due to water conservation efforts. However, water scarcity has become more acute across much of this semiarid region during recent decades due to long-term declines in water storage juxtaposed with the region’s notable hydroclimatic variability. Observed declines in mountain snowpack and increases in atmospheric demands tied to long-term warming trends have further exacerbated water scarcity and increased the importance of monitoring efforts given the array of social, economic, and ecosystem sectors dependent upon the already stressed water supply. The recent severe drought in California and protracted drought across much of the southwestern United States over the past couple decades have prompted demand for accessible drought decision-making information at appropriate spatial scales across the western United States. 

Thousands of domestic and public supply wells face failure despite groundwater sustainability reform in California’s Central Valley

Nature Portfolio (Springer Nature) | September 8th, 2023