South Lahontan

Drinking Water Notification Levels and Response Levels: An Overview

California State Water Resources Control Board (SWRCB) | February 6th, 2020

The Division of Drinking Water’s precursor, the Drinking Water Program of the California Department of Public Health (CDPH), and earlier, the California Department of H

The Division of Drinking Water’s precursor, the Drinking Water Program of the California Department of Public Health (CDPH), and earlier, the California Department of Health Services, CDHS, established health-based advisory levels, called “notification levels” (referred to as “action levels" through 2004), as needed since the early 1980s. These have been used to provide information to public water systems and others about certain non-regulated chemicals in drinking water that lack maximum contaminant levels (MCLs).  When chemicals are found at concentrations greater than these levels, certain requirement and recommendations apply.  Generally, notification levels have been established in response to actual contamination of drinking water supplies, e.g., perchlorate, which now has an MCL. However, notification levels for a number of chemicals were established in anticipation of possible contamination, such as from a hazardous waste site containing many pesticides (in the 1980s), or from a Superfund site (in the 2000s).  Chemicals for which notification levels are established may eventually be regulated by MCLs (through a formal regulatory process), depending on the extent of contamination, the levels observed, and the risk to human health. Most, however, have not proceeded to MCLs. Once established, a notification level generally stays in place, unless it is replaced by an MCL.On occasion, though, we have revised the numeric value of an individualnotification level to reflect new risk assessment information on the particularchemical. For some of the chemicals that had advisory levels established early on, if noMCL was adopted and the need for the notification level had passed, the advisory levelwas archived. Archived advisory levels may nevertheless be updated to reflect any newrisk information that may become available, and may be used as notification levels ifneeded. To date, of the 93 chemicals for which notification levels have been established; 40 now have MCLs. Of the remaining 53 chemicals, 29 are chemicals with current notification levels. 24 are chemicals with archived advisory levels (AALs). Note that following adoption of an MCL, the notification level is no longer used. For more about AALs and notification levels, go to: http://www.waterboards.ca.gov/drinking_water/certlic/drinkingwater/NotificationLevels.shtml. 

Drought less predictable under declining future snowpack

Nature Portfolio (Springer Nature) | April 20th, 2020

Mountain snowpack serves as an immense natural water reservoir, and knowledge of snow conditions helps predict seasonal water availability and offers critical ear

Mountain snowpack serves as an immense natural water reservoir, and knowledge of snow conditions helps predict seasonal water availability and offers critical early warning of hydrologic drought. This paradigm faces an impending challenge given consensus that a smaller fraction of future precipitation will fall as snow. Here, we apply downscaled hydrologic simulations from 28 climate model projections to show that by mid-century (2036–2065), 69% of historically snowmelt-dominated areas of the western United States see a decline in the ability of snow to predict seasonal drought, increasing to 83% by late century (2070–2099). Reduced predictability arises when peak snowpack approaches zero or because of decreased warm-season runoff efficiency. Changes in drought prediction skill show significant (P < 0.01) elevation dependence, with lower-elevation coastal areas most impacted by warming. Ancillary predictive information can only partially mitigate snow-based predictability losses to 65% of areas, underscoring the importance of declining future snowpack.

Drought Management and Climate Adaptation of Small, Self-Sufficient Drinking Water Systems in California

California Energy Commission (CEC) | August 15th, 2018

Examining human impacts, responses, and challenges to extreme climatic events can give insight into needed directions for climate adaptation to reduce future risks. This

Examining human impacts, responses, and challenges to extreme climatic events can give insight into needed directions for climate adaptation to reduce future risks. This study focuses on the 2012-2016 Drought in California, documenting how small self-sufficient drinking water systems were affected and challenged by, and responded to the extreme event.

Droughts in California

Public Policy Institute of California (PPIC) | April 1st, 2021

Economics of a State Water Resources Program

Legislative Analyst's Office (LAO) | July 9th, 1957

Effective at Any Scale: Watershed-based Decision Support Tools

San Francisco Estuary Institute (SFEI) | July 1st, 2016

EcoAtlas  tools apply the USEPA’s three-level wetland monitoring and assessment framework for wetland and stream protection in a variety of California watersheds, an

EcoAtlas  tools apply the USEPA’s three-level wetland monitoring and assessment framework for wetland and stream protection in a variety of California watersheds, and it can be adjusted to more generally support natural resource planning, assessment, monitoring, and reporting. EcoAtlas operationalizes the Wetland and Riparian Area Monitoring Plan (WRAMP) by enabling users to assess the abundance, distribution, diversity, and condition of wetlands in the landscape or watershed context.

Effective Implementation of the Public Trust Doctrine in California Water Resources Decision-Making: A View From the Bench

University of California, Berkeley (UC Berkeley) | April 12th, 2012

Forty years ago, in his seminal law review article on the public trust doctrine, Professor Joseph L. Sax suggested that “citizens seeking to develop a comprehen

Forty years ago, in his seminal law review article on the public trust doctrine, Professor Joseph L. Sax suggested that “citizens seeking to develop a comprehensive legal approach to resource management problems” could use the public trust doctrine to obtain “effective judicial intervention” where “legislative response and administrative action” had been inconsistent. Of course, water is one of the natural resources to which the public trust doctrine is, and always has been, particularly applicable. And yet, it was not until ten years after Professor Sax published his article that Professor Ralph W. Johnson first predicted an impending “collision” between “[t]he public trust doctrine and the appropriative water rights system . . . in the West.” The imminence of that collision — in California at least — was due in no small part to the National Audubon Society’s then-pending suit against the Department of Water and Power of the City of Los Angeles (“L.A. Water and Power”) to limit diversions from the streams feeding Mono Lake.  That suit, which was a prime example of the sort of public interest litigation Professor Sax had advocated in his article, led to the California Supreme Court’s seminal decision in National Audubon, in which the court announced that “[t]he state has an affirmative duty to take the public trust into account in the planning and allocation of water resources, and to protect the public trust uses whenever feasible.” Today, twenty-eight years after the decision in National Audubon and more than forty years after Professor Sax’s article, what have we learned about the use of the public trust doctrine in water resources decision-making in California? Has it been an effective tool for obtaining judicial intervention in the decision-making process, as Professor Sax suggested it could be? And, more importantly, is judicial intervention the best way to effectuate and protect public trust values in the state’s water resources? Those are some of the questions I seek to answer in this Article.

Effectiveness and Impacts of Dust Control Measures for Owens Lake

National Academy of Sciences (NAS) | March 3rd, 2020

During the 20th century, the city of Los Angeles diverted surface water flowing into Owens Lake for water supply, transforming the large, closed-basin, saline lake into

During the 20th century, the city of Los Angeles diverted surface water flowing into Owens Lake for water supply, transforming the large, closed-basin, saline lake into a small brine pool surrounded by dry playa. Under high winds, the exposed lakebed produced large amounts of airborne dust, resulting in the highest concentrations of airborne particulate matter with an aerodynamic diameter of 10 micrometers or less (PM10) in the United States. Since 2000, the Los Angeles Department of Water and Power (LADWP), at the direction of the Great Basin Unified Air Pollution Control District (District), has been constructing and implementing dust control measures (DCMs) on the dry lakebed, with the objective of meeting the U.S. Environmental Protection Agency (EPA) National Ambient Air Quality Standards (NAAQS) for PM10 and the PM10 standards set by the state of California. LADWP reported that it has spent $2.1 billion on dust control efforts as of May 2019 and that many of the DCMs require large amounts of water, energy, and maintenance to sustain their performance.1 Shallow flooding is, by far, the most widespread DCM, by surface area, that is applied at Owens Lake. Other DCMs, such as managed vegetation and gravel, are also applied over several areas on the lakebed, and a few small areas ordered for PM10 management are currently uncontrolled. On average since 2007, water use for dust control required 31 percent of LADWP’s fresh water supplies available at Owens Lake, 2 with a range of 17 to 51 percent. In 2014, a Stipulated Judgment agreed to by LADWP and the District3 ended litigation concerning dust control requirements and acknowledged the need “for additional effective DCMs that do not rely on water that can be substituted in areas currently under control or applied in areas ordered to be controlled.” The Judgment also acknowledged “the need to balance the requirements to control dust emissions and conserve water with the requirements to minimize impacts to cultural and biological resources.” As part of the Judgment, LADWP and the District agreed to contract with the National Academies of Sciences, Engineering, and Medicine to establish the Owens Lake Scientific Advisory Panel (OLSAP, or the panel) to provide ongoing advice on the reduction of PM10 in the Owens Valley. In addition, the Judgment intends the panel to foster communication and collaboration between the LADWP and the District within this context. The panel’s first task is to evaluate the effectiveness of alternative DCMs for their dust control and water use. The task includes consideration of the associated energy, environmental, and economic impacts and assessing the durability and reliability of such DCMs. In interpreting its task, the panel was informed by the definition of environment provided in the California Environmental Quality Act (CEQA), which encompasses impacts on land, air, water, minerals, flora, fauna, ambient noise, and objects of historical or aesthetic significance. The panel discussed key factors within the broad context of that definition with implications for dust management. The panel assessed 15 DCMs (see Box S-2) that represent a range of mitigation approaches that are either being applied at Owens Lake or at various stages of development. The panel’s evaluation criteria included reported PM10 control efficiency, water use, capital and operating costs, habitat value, protection of cultural resources, durability, reliability, and other factors. OVERALL CONCLUSIONS DCMs applied at Owens Lake during the past 20 years have significantly reduced PM10 concentrations in the Owens Valley, although further progress in controlling dust is needed to meet air quality standards. The panel evaluated 15 DCMs based on their potential effectiveness in reducing PM10 emissions, water use, and environmental impacts. Based on available data, none of the control measures has been documented to achieve mandated levels of dust control while substantially reducing water use (compared to shallow flooding) and consistently providing quality habitat, although some measures show promise with the need for additional research and testing. Progress toward these multiple goals, including protection of environmentally sensitive areas by reducing land disturbance from DCMs, can be more effectively achieved through a systems approach that considers outcomes over a large spatial scale and interactions among control measures. To inform these decisions, additional research is needed on individual and hybrid DCMs and on the landscape-scale effects of dust control configurations. Evaluation of operational performance of DCMs should be based on airborne PM10 measurements rather than surrogate measures, such as the percentage of a control area that must be covered by vegetation or surface water. Using a systems approach and evaluating DCM performance with PM10 measurements would promote innovative and hybrid strategies for dust control.

Effects of imported recharge on fluoride trends in groundwater used for public supply in California

Science of the Total Environment (Elsevier) | March 31st, 2022

Fluoride is a naturally occurring element in groundwater that supports bone and dental health at low concentrations but can cause health problems at elevated concentrati

Fluoride is a naturally occurring element in groundwater that supports bone and dental health at low concentrations but can cause health problems at elevated concentrations in drinking water. This study investigates spatial and temporal trends for fluoride concentrations in untreated groundwater from over 20,000 public supply wells in California. The presence of a significant temporal trend in fluoride concentrations in a well was assessed using the Mann-Kendall test and a spatial-weighting approach was used to identify the areal extent of the groundwater resources with significant trends. Less than 2% of the groundwater resources used for public supply in the state have concentrations above the California maximum contaminant level of 2 mg/L. Approximately 14% of the groundwater resource used for public supply show a significant recent trend (2000–2019), with decreasing trends occurring in 10%of the resource. Potential drivers for trends were evaluated in two of the areas in southern California with the greatest prevalence of trends but distinct climate and hydrogeological characteristics. Aquifers in the Mojave and Whitewater River watersheds, located in the desert region, and the Los Angeles Basin, located on the coast, have been replenished with imported and treated water over the last half century to maintain sustainable groundwater levels. The recharge of imported water with different chemistries has altered the geochemical conditions in the aquifers, driving changes in fluoride concentrations.

Effects of more extreme precipitation regimes on maximum seasonal snow water equivalent

American Geophysical Union (AGU) | October 31st, 2012

This study demonstrates how more extreme precipitation regimes (MEPR) under a changed climate might affect seasonal snow water resources.

This study demonstrates how more extreme precipitation regimes (MEPR) under a changed climate might affect seasonal snow water resources.