North 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.

Drought Resilience Interagency and Partners Collaborative Progress Report (2026)

California Department of Water Resources (DWR) | March 16th, 2026

This report summarizes the 2025 activities and progress of the Drought Resilience Interagency and Partners (DRIP) Collaborative.

This report summarizes the 2025 activities and progress of the Drought Resilience Interagency and Partners (DRIP) Collaborative.

Droughts in California

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

EcoAtlas - Lake Tahoe Environmental Improvement Program: Tool Integration White Paper

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

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.

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.