Helium isotope studies in the Mojave Desert, California: implications for groundwater chronology and regional seismicity

Chemical Geology (Elsevier) | November 7th, 2003

Hexavalent Chromium Maximum Contaminant Level (MCL) Standardized Regulatory Impact Assessment (SRIA)

California State Water Resources Control Board (SWRCB) | May 4th, 2023

The Division of Drinking Water (DDW) of the State Water Resources Control Board (State Water Board) is responsible for adopting drinking water standards. Primary drinking

The Division of Drinking Water (DDW) of the State Water Resources Control Board (State Water Board) is responsible for adopting drinking water standards. Primary drinking water standards, as defined in section 116275 of the California Safe Drinking Water Act (Health & Safety Code (HSC), div. 104, pt. 12, ch. 4, section 116270 et seq.), must be set in accordance with the requirements of HSC 116365. The purpose of the proposed regulation addressed in this Standardized Regulatory Impact Assessment (SRIA) is to adopt a primary drinking water standard for hexavalent chromium in drinking water consisting of a maximum contaminant level (MCL) and pertinent monitoring and reporting requirements. Consistent with title 1 of the California Code of Regulations (CCR), section 2003(a), the economic impact method used for the assessment was the Regional Input-Output Modeling System (RIMS II) developed by the U.S. Bureau of Economic Analysis (BEA).

High organofluorine concentrations in municipal wastewater affect downstream drinking water supplies for millions of Americans

National Academy of Sciences (NAS) | January 6th, 2025

Historical Fresh Water and Salinity Conditions in the Western Sacramento-San Joaquin Delta and Suisun Bay

Contra Costa Water District (CCWD) | February 23rd, 2010

The watershed of the Sacramento–San Joaquin Delta (Delta) provides drinking water to more than 23 million Californians as well as irrigation water for millions of acres

The watershed of the Sacramento–San Joaquin Delta (Delta) provides drinking water to more than 23 million Californians as well as irrigation water for millions of acres of agriculture in the Central Valley. The Delta itself is a complex estuarine ecosystem, with populations of many native species now in serious decline. The Delta estuary as we know it began to form about 6,000 years ago, following the end of the last ice age. Because the estuary is connected to the Pacific Ocean through San Francisco Bay, seawater intrusion causes the salinity of Suisun Bay and the Delta to vary depending on hydrological conditions. This seawater intrusion into the Delta affects estuarine species as well as drinking water and irrigation water supplies. Successful restoration of the Delta ecosystem requires an understanding of the conditions under which native species evolved. Contra Costa Water District’s report on “Historical Fresh Water and Salinity Conditions in the Western Sacramento-San Joaquin Delta and Suisun Bay” presents a detailed review of more than 100 years of studies, monitoring data, scientific reports, and modeling analyses that establish an historical record of the salinity conditions in the Western Delta and Suisun Bay.

Historical Seawater Intrusion Map Pressure 180-Foot Aquifer - 500 mg/L or Greater Chloride Areas

Monterey County Water Resources Agency (MCWRA) | April 11th, 2018

History and Sources of Co-Occurring Pesticides in an Abstraction Well Unraveled by Age Distributions of Depth-Specific Groundwater Samples

American Chemical Society (ACS) | November 24th, 2019

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse sources and different contaminants may have different sources even in a single groundwater well, making these questions complicated to answer. Age dating of groundwater has been used to reconstruct contaminant travel times to wells; however, critics have highlighted that groundwater flow is often complex with mixing of groundwater of different ages. In drinking water wells, where water is typically abstracted from a large depth interval, such mixing is even more problematic. We present a way to overcome some of the obstacles in identifying the source and age of contaminants in drinking water wells by combining depth-specific sampling with age tracer modeling, particle tracking simulations, geological characterization, and contaminant properties. This multitool approach was applied to a drinking water well, where bentazon and dichlorprop contamination was found to have different pollutant sources and release histories, even though both pesticides can be associated with the same land use. Bentazon was derived from recent application to a golf course, while dichlorprop was derived from agricultural use more than 30 years ago. The advantages, limitations, and pitfalls of the proposed course of action are then further discussed.

History and Sources of Co-Occurring Pesticides in an Abstraction Well Unraveled by Age Distributions of Depth-Specific Groundwater Samples

American Chemical Society (ACS) | November 24th, 2019

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse

When groundwater-based drinking water supply becomes contaminated, the timing and source of contamination are obvious questions. However, contaminants often have diffuse sources and different contaminants may have different sources even in a single groundwater well, making these questions complicated to answer. Age dating of groundwater has been used to reconstruct contaminant travel times to wells; however, critics have highlighted that groundwater flow is often complex with mixing of groundwater of different ages. In drinking water wells, where water is typically abstracted from a large depth interval, such mixing is even more problematic. We present a way to overcome some of the obstacles in identifying the source and age of contaminants in drinking water wells by combining depth-specific sampling with age tracer modeling, particle tracking simulations, geological characterization, and contaminant properties. This multitool approach was applied to a drinking water well, where bentazon and dichlorprop contamination was found to have different pollutant sources and release histories, even though both pesticides can be associated with the same land use. Bentazon was derived from recent application to a golf course, while dichlorprop was derived from agricultural use more than 30 years ago. The advantages, limitations, and pitfalls of the proposed course of action are then further discussed.

Hoopa Valley Tribe Water Quality Plan

Hoopa Valley Tribal Environmental Protection Agency | February 14th, 2008

The Hoopa Valley Tribal Council pursuant to Title 37 of the Hoopa Tribal Code has assigned the primary responsibility for the protection and enhancement of water quality

The Hoopa Valley Tribal Council pursuant to Title 37 of the Hoopa Tribal Code has assigned the primary responsibility for the protection and enhancement of water quality on the Hoopa Valley Indian Reservation to the Riparian Review Committee (RRC). The RRC along with the Hoopa Valley Tribal Environmental Protection Agency provides Reservation-wide coordination of the water quality control program by developing, reviewing and recommending for Tribal approval Reservation wide policies and plans for the implementation of Tribal and Federal law. This Water Quality Control Plan recognizes the unique characteristics of each watershed with regard to natural water quality, existing, potential, and historical beneficial uses, and water quality problems. The goal of this plan is to provide a definitive program of actions designed to preserve and enhance water quality on the Reservation, and to protect the beneficial uses of water for the next 10 years to 20 years. The plan is concerned with all factors and activities that might affect water quality. However, the plan emphasizes actions to be taken by the Riparian Review Committee, the Hoopa Valley Tribal Fisheries, Forestry, Public Utility Departments, and Tribal Environmental Protection Agency, as they have responsibility for maintaining water quality on the Reservation. The Water Quality Control Plan (WQCP) is comprehensive in scope. The WQCP describes the Hoopa Valley Reservation waters, the quality and quantity issues, and the existing, potential and historical beneficial uses of the Reservation’s waters. The plan also prescribes criteria for the protection of the Reservation waters and includes plans and policies that describe the basis for the management of water quality and protection of human health. The Hoopa Valley Tribe has recognized authority for setting water quality standards for its Reservation waters, including both the Trinity and Klamath Rivers (U.S. EPA, 2002). Included in the plan are specific criteria that apply to the Lower Klamath River on the Hoopa Valley Reservation (Figure 1.1).

How freeing rivers can help California ease flood risks and revive ecosystems

Los Angeles Times | February 20th, 2024

Natural floodplains — the lush green lands along rivers that historically flooded, retained water, and nourished life in the heart of the valley — were mostly drained

Natural floodplains — the lush green lands along rivers that historically flooded, retained water, and nourished life in the heart of the valley — were mostly drained and converted to farmland generations ago as the state’s waters were dammed and diverted. Today, an effort to bring back some of those floodplains is flourishing at the 2,100-acre Dos Rios Ranch Preserve near Modesto, where workers years ago planted native trees on retired farm fields and removed berms to create space for water to spread out again.

Human Impacts Dominate Global Loss of Lake Ecosystem Resilience

American Geophysical Union (AGU) | June 5th, 2024