Pulse of the Delta 2012

San Francisco Estuary Institute (SFEI) | August 2nd, 2013

This second edition of the Pulse of the Delta includes the following sections: The KEY TOPIC article introduces this year’s theme, LINKING SCIENCE AND MANAGEMENT THR

This second edition of the Pulse of the Delta includes the following sections: The KEY TOPIC article introduces this year’s theme, LINKING SCIENCE AND MANAGEMENT THROUGH REGIONAL MONITORING (PAGE 6). The MANAGEMENT UPDATE section provides updates on Delta RMP development (PAGE 12) and the U.S. Environmental Protection Agency (EPA)’s Delta Clean Water Act evaluation (PAGE 18). It further provides an update on the development of Nutrient Numeric Endpoints for San Francisco Bay, due to the relevance of this topic to Delta stakeholders (PAGE 28). And as a new feature, the Management Update section now also provides a regulatory status update for pollutants of concern. This edition of the Pulse of the Delta introduces a NEW STATUS AND TRENDS section with updates on important monitoring results (PAGE 44) and leading indicators (PAGE 50) for the Delta. The STATUS AND TRENDS section was made possible thanks to significant contributions by the Interagency Ecological Program, U.S. Geological Survey, the Central Valley Regional Water Board, California Department of Fish and Game, California Department of Water Resources, and scientists at the UC Berkeley and San Francisco State University Romberg Tiburon Center. Two FEATURE ARTICLES provide an overview of recent research findings that could help wetland managers reduce the methylmercury problem and a glimpse into the future of the Interagency Ecological Program (IEP). One of the main challenges as ecosystem restoration efforts are moving forward will be the mercury problem. Large-scale restoration of wetland areas will be required to provide a sufficient amount of aquatic habitat for restoring the Delta ecosystem. At the same time, water quality managers will need to identify actions to protect people and wildlife from exposure to methylmercury that may originate from restored wetlands, due to a legacy of mercury contamination in Delta soils. Recently completed and ongoing studies in the Yolo Bypass provide new information on management options for controlling methylmercury production in wetlands and offsite transport (PAGE 66). IEP scientists have been monitoring and researching the San Francisco Estuary since 1970. Now the IEP has arrived at an important crossroads, and its future is being decided at the same time as environmental managers are determining what a desirable future ecosystem would look like, how it would function, and how it can be established (PAGE 76).

Pure Water Soquel Groundwater Model Simulation Results

Soquel Creek Water District | June 22nd, 2018

This technical memorandum discusses model simulation groundwater levels, groundwater budget, and particle tracking results to support the Environmental Impact Rep

This technical memorandum discusses model simulation groundwater levels, groundwater budget, and particle tracking results to support the Environmental Impact Report of the Pure Water Soquel project involving replenishment of advanced purified recycled water within Soquel Creek Water District’s (SqCWD’s) service area. Six model simulations have been run using the calibrated GSFLOW model for the Santa Cruz Mid- County Basin (the Basin) where SqCWD’s service area is located. These simulations have different pumping and active replenishment distributions, as follows: Two Projected Existing Conditions (No Project) simulations with SqCWD’spumping distribution reflecting future demand without additional replenishment at proposed recharge wells. Two Project simulations with SqCWD’s pumping distribution reflecting future demand and pumping re-distribution with the addition of replenishment at the Monterey and Cabrillo College Dr. sites (referred to as the Cabrillo-Monterey simulations). These simulations also represent potential replenishment at the Twin Lakes Church site instead of one of the two Cabrillo College Dr. sites. The Twin Lakes Church site is approximately 500-750 feet to the west of the Cabrillo College Dr. sites. Two Project simulations with the same pumping distribution as the Cabrillo- Monterey simulations, but with replenishment at the Monterey and Willowbrook sites (referred to as the Monterey-Willowbrook simulations).Simulation groundwater levels are evaluated for the following effects: Comparison of groundwater levels at coastal monitoring wells to protective elevations estimated to prevent seawater intrusion from further occurring in groundwater supply aquifers. Groundwater levels in the recharge wells to assess whether model results are consistent with estimated capacities for the well, recognizing that site specific testing will be needed to confirm recharge well capacities. Groundwater levels at nearby wells to evaluate effects on operation of those municipal, private, and institutional wells.Simulation groundwater budgets are evaluated for following effects: • Flows entering and leaving the Basin, including flows to and from groundwater in storage and flows offshore to prevent seawater intrusion. • Flows between groundwater and surface water. This memo does not include results for a Cumulative simulation. Information from the City of Santa Cruz to define its Aquifer Storage and Recovery project to be cumulative with Pure Water Soquel is not available or developed at this time. This memo includes results from particle tracking based on the above simulations performed to support the Salt and Nutrient Anti-degradation Study and permitting of the recharge wells. This involves particle tracking of simulated purified, replenishment water to evaluate the fate of the water as it travels in subsurface aquifers. Particle tracking is also used to evaluate travel times of purified, replenishment water, which requires refined analysis near the recharge wells. A scope to superimpose analytic element solutions for recharge and nearby extraction wells onto GSFLOW results to facilitate travel time calculations was approved by SqCWD Board December 18, 2017 and results should be forthcoming in July 2018.

Quality Assurance Program Plan for The Regional Monitoring Program for Water Quality in San Francisco Bay

San Francisco Estuary Institute (SFEI) | June 23rd, 2017

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) is managed and operated by the San Francisco Estuary Institute (SFEI). SFEI was founded as a

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) is managed and operated by the San Francisco Estuary Institute (SFEI). SFEI was founded as a non-profit organization in 1986 to foster the development of the scientific understanding needed to protect and enhance the San Francisco Estuary.

Quality Assurance Program Plan for The Regional Monitoring Program for Water Quality in San Francisco Bay

San Francisco Estuary Institute (SFEI) | December 16th, 2019

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) was created to provide long-term monitoring information on ecosystem health in the Bay. The i

The Regional Monitoring Program for Water Quality in San Francisco Bay (RMP) was created to provide long-term monitoring information on ecosystem health in the Bay. The impetus for the program development was a resolution by the San Francisco Bay Regional Water Board to require dischargers in the Bay Area regulated under the National Pollution Discharge Elimination System (NPDES) program to participate in regional monitoring. Contribution to the Program constitutes compliance with the requirement to participate. Elimination of certain permit requirements for individual permits offset the requirement for continued participation.  The RMP began as a pilot study in 1989 and has been collecting water, sediment, and biological tissue data since 1993. The Status and Trends component of the RMP routinely collects monitoring data on these environmental matrices. The San Francisco Bay Regional Water Quality Control Board (Water Board) uses Status and Trends data to assist in regulatory decision-making, such as for determining impairment (303(d)) listing, NPDES permit conditions, and estimating Total Maximum Daily Loads (TMDL) of various pollutants needed to protect ecosystem and human health. The data are also useful for monitoring and modeling the effectiveness of past and planned management actions.  The overarching goal of the program is to collect data and communicate information about water quality in San Francisco Bay to support management decisions. The RMP, in consultation with its stakeholders, the Technical Review Committee, and the Steering Committee refined the management questions in May 2008. 

Quality of Groundwater Used for Domestic Drinking-Water Supply in the Coachella Valley, 2020

U.S. Geological Survey (USGS) | January 13th, 2023

Quality of groundwater used for domestic supply in the eastern Sacramento Valley and adjacent foothills, California

U.S. Geological Survey (USGS) | November 1st, 2024

More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domes

More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domestic and small-system drinking-water supply wells in the eastern Sacramento Valley and adjacent foothills where more than 25,000 residents are estimated to use privately owned domestic wells. Study results show that inorganic and organic constituents in groundwater were present above regulatory (maximum contaminant level, MCL) benchmarks for public drinking-water quality in 8 and 3 percent, respectively, of the aquifer area used for domestic drinking-water supply. The only inorganic constituent detected above regulatory benchmarks was arsenic. The only organic constituent exceeding regulatory benchmarks was the fumigant 1,2,3-trichloropropane (1,2,3-TCP). Three additional organic constituents— the disinfection by-product chloroform, the gasoline oxygenate methyl tert-butyl ether (MTBE), and the solvent tetrachloroethene (PCE)—were detected at low concentrations below one-tenth of regulatory benchmarks in 34, 10, and 10 percent of domestic groundwater resources, respectively. Total dissolved solids (TDS), iron, and manganese exceeded non-regulatory aesthetic guidelines for drinking water in 5, 10, and 26 percent of domestic groundwater resources, respectively. Per- and polyfluoroalkyl substances (PFASs) were detected in 29 percent of domestic groundwater resources, with 5 percent exceeding the recently enacted (April 2024) U.S. Environmental Protection Agency MCLs. Total coliform and enterococci bacteria were detected in 13 and 8 percent of domestic groundwater resources, respectively. Redox sensitive constituents in this study included arsenic, manganese, nitrate, and iron. In the lower elevation portions of the eastern Sacramento Valley study area, reducing conditions in groundwater aquifers promote elevated arsenic, iron, and manganese, and conversely lower concentrations of nitrate. The presence of the volatile organic compound (VOC) 1,2,3-TCP was related to its past history in select agricultural land uses (on orchards or vineyards) in the Sacramento Valley; however, unlike in the San Joaquin Valley where orchards and vineyards are more common, its detection frequency was low (only detected in one well in this study). Chloroform was frequently detected in this study at low levels. Chloroform is a disinfection byproduct commonly found in domestic wells treated by shock chlorination. The solvent PCE is among the most frequently detected VOCs in groundwater, which is primarily related to its long history of use and its persistence in groundwater in oxic conditions. The gasoline oxygenate MTBE was a contaminant introduced to groundwater through atmospheric exchange when it was used as a fuel additive to decrease smog inducing emissions from vehicles. Its occurrence in groundwater at low levels is expected and makes it a potentially useful tracer of relatively recent recharge water being withdrawn from wells. The PFASs are anthropogenic chemicals with hundreds of uses, and they have been incorporated into many different products, processes, and applications worldwide. Like MTBE, the occurrence of PFASs in groundwater may be in part due to atmospheric exchange, but there are several other pathways that contribute PFASs to the environment.

Quality of groundwater used for domestic supply in the Gilroy-Hollister basin and surrounding areas, California, 2022

U.S. Geological Survey (USGS) | December 1st, 2025

More than 2 million Californians rely on groundwater from domestic wells for drinking-water supply. This report summarizes a 2022 California Groundwater Ambient Monitorin

More than 2 million Californians rely on groundwater from domestic wells for drinking-water supply. This report summarizes a 2022 California Groundwater Ambient Monitoring and Assessment Priority Basin Project (GAMA-PBP) water-quality survey of 33 domestic and small-system drinking-water supply wells in the Gilroy-Hollister Valley groundwater basin and the surrounding areas, where more than 20,000 residents are estimated to utilize privately owned domestic wells.

Quality of Groundwater Used for Domestic Supply in the Modesto, Turlock, and Merced Subbasins of the San Joaquin Valley, California

U.S. Geological Survey (USGS) | January 6th, 2023

More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domes

More than 2 million Californians rely on groundwater from privately owned domestic wells for drinking-water supply. This report summarizes a water-quality survey of domestic and small-system drinking-water supply wells in the Modesto, Turlock, and Merced subbasins of the San Joaquin Valley where more than 78,000 residents are estimated to use privately owned domestic wells. Results indicate that inorganic and organic constituents in groundwater were respectively present above regulatory (maximum contaminant level, MCL) benchmarks for public drinking-water quality in 37 percent and 9 percent of the aquifer area used for domestic drinking-water supplies (herein, “domestic groundwater resources”). The most prevalent inorganic constituents exceeding regulatory benchmarks were nitrate, uranium, and arsenic. The only organic constituents exceeding regulatory benchmarks were the fumigant constituents 1,2,3-trichloropropane (1,2,3-TCP) and 1,2-dibromo-3-chloropropane (DBCP), but the herbicides atrazine and simazine were detected at low concentrations below one-tenth of regulatory benchmarks in 30 percent of domestic groundwater resources. Total dissolved solids (TDS) and manganese exceeded aesthetic-based (secondary maximum contaminant level [SMCL]) benchmarks for drinking water in 3 percent and 13 percent of domestic groundwater resources, respectively. Per- and polyfluoroalkyl substances (PFAS) were detected in 23 percent of domestic groundwater resources, with 4 percent exceeding California state notification or response levels for specific compounds. Total coliform bacteria were detected in 20 percent of domestic groundwater resources. Elevated concentrations of nitrate, uranium, TDS, and pesticides (fumigant constituents and herbicides) are related to agricultural land use and were typically present at shallow depths up to 75 meters below land surface. Agriculturally derived constituents were detected in wells screened below the Corcoran Clay Member of the Tulare Formation (herein, “Corcoran Clay”) in the southeastern part of the study area, where the Corcoran Clay tends to be shallower and thinner than in areas to the northwest. Nitrate, uranium, and TDS were most prevalent in the northwest part of the study area proximal to the valley trough where soils are poorly drained and agricultural land uses are predominantly grain, alfalfa, and dairy farms. Pesticides tended to occur in groundwater below coarse-grained surficial deposits and within a northwest to southeast trending band along the eastern extent of the Corcoran Clay that typically demarcates the western extent of well-drained soils associated with perennial orchard crops. Elevated concentrations of arsenic tended to occur west of this band in reducing groundwater but also sometimes co-occurred with elevated nitrate in oxic groundwater, most likely because of geochemical conditions in agriculturally affected groundwater that can enhance the mobility of arsenic from aquifer sediments.

Quality of Groundwater Used for Domestic Supply in the Northern San Joaquin Valley, California

U.S. Geological Survey (USGS) | July 28th, 2021

 Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Moni

 Groundwater provides more than 40 percent of California’s drinking water. To protect this vital resource, the State of California created the Groundwater Ambient Monitoring and Assessment (GAMA) Program. The Priority Basin Project (PBP) of the GAMA Program provides a comprehensive assessment of the State’s groundwater quality and provides increased public access to groundwater-quality information. Private domestic and small-system drinking-water wells in the Northern San Joaquin Valley (NSJV) were the target for this assessment. These wells tend to pump water from shallower parts of alluvial aquifers compared to deeper, long-screened public-supply wells in the region. 

Quality of Groundwater Used for Public Supply in the Continental United States: A Comprehensive Assessment

American Chemical Society (ACS) | October 21st, 2022