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A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA
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A hybrid machine learning model to predict and visualize nitrate concentration throughout the Central Valley aquifer, California, USA
Science of the Total Environment | June 9, 2017...
Summary
Intense demand forwater in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater resource....
Intense demand forwater in the Central Valley of California and related increases in groundwater nitrate concentration threaten the sustainability of the groundwater resource. To assess contamination risk in the region, we developed a hybrid, non-linear, machine learning model within a statistical learning framework to predict nitrate contamination of groundwater to depths of approximately 500m below ground surface.

A database of 145 predictor variables representing well characteristics, historical and current field and landscape-scale nitrogen mass balances, historical and current land use, oxidation/reduction conditions, groundwater flow, climate, soil characteristics, depth to groundwater, and groundwater age were assigned to over 6000 private supply and public supply wells measured previously for nitrate and located throughout the study area. The boosted regression tree (BRT) method was used to screen and rank variables to predict nitrate concentration at the depths of domestic and public well supplies.

The novel approach included as predictor variables outputs from existing physically based models of the Central Valley. The top five most important predictor variables included two oxidation/reduction variables (probability of manganese concentration to exceed 50 ppb and probability of dissolved oxygen concentration to be below 0.5 ppm), field-scale adjusted unsaturated zone nitrogen input for the 1975 time period, average difference between precipitation and evapotranspiration during the years 1971–2000, and 1992 total landscape nitrogen input.

Twenty-five variables were selected for the final model for log-transformed nitrate. In general, increasing probability of anoxic conditions and increasing precipitation relative to potential evapotranspiration had a corresponding decrease in nitrate concentration predictions.

Conversely, increasing 1975 unsaturated zone nitrogen leaching flux and 1992 total landscape nitrogen input had an increasing relative impact on nitrate predictions.

Three-dimensional visualization indicates that nitrate predictions depend on the probability of anoxic conditions and other factors, and that nitrate predictions generally decreased with increasing groundwater age.

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California Hydrogeologically Vulnerable Areas Map
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California Hydrogeologically Vulnerable Areas Map
California State Water Resources Control Board | January 31, 2012...
Summary
In response to Executive Order D-5-99, State Water Board staff created a map where published hydrogeologic information indicates soil or rock conditions that...
In response to Executive Order D-5-99, State Water Board staff created a map where published hydrogeologic information indicates soil or rock conditions that may be more vulnerable (or susceptible) to groundwater contamination: ”Hydrogeologically Vulnerable Areas.” The map was created due to groundwater concerns over releases of MTBE, primarily from leaking underground storage tank sites. However, areas that are vulnerable to MTBE may also be vulnerable to other contaminants released at the surface.

The map was created in 2000 using Department of Water Resources (DWR) and US Geological Survey publications. Data from these publications were used to identify areas where geologic conditions are more likely to allow recharge at rates substantially higher than in lower permeability or confined areas of the same groundwater basin.

The identified areas are associated by a metadata table (in the following pages) which identifies (1) DWR basin name and number, (2) published source of information (i.e., title, date, author, and appropriate page, figure, table, or plate number), and (3) specific criteria upon which the vulnerability category is based.

Groundwater resources underlying designated (i.e., published) recharge, rapid infiltration, or unconfined areas were considered categorically more vulnerable to potential contaminant releases than groundwater underlying areas of slower recharge, lower infiltration rates, or intervening low permeability deposits (i.e., confining layers).

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California Non-point Source Program Implementation Plan 2014 – 2020
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California Non-point Source Program Implementation Plan 2014 – 2020
California State Water Resources Control Board | August 5, 2015...
Summary
The 2014 - 2020 California Nonpoint Source (NPS) Program Implementation Plan (NPS Program Implementation Plan) describes how the State will be using its...
The 2014 - 2020 California Nonpoint Source (NPS) Program Implementation Plan (NPS Program Implementation Plan) describes how the State will be using its resources to effectively prevent NPS pollution from impacting surface water and groundwater in California. The vision for the CA NPS Program is to restore and protect the beneficial uses of the State’s waters through the reduction of NPS pollution and attaining water quality objectives.

This document serves as an update to the CA NPS Program Plan as approved by U.S. EPA and NOAA in 2000. As such, California will continue to implement a comprehensive statewide program working to implement management measures to address NPS pollution consistent with U.S. EPA and National Oceanic and Atmospheric Administration approval.

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Californians Without Safe Water and Sanitation
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Californians Without Safe Water and Sanitation
Department of Water Resources | October 30, 2014...
Summary
While most Californians enjoy access to safe drinking water and adequate sanitation, some residents live in communities or areas that do not have...
While most Californians enjoy access to safe drinking water and adequate sanitation, some residents live in communities or areas that do not have access to safe drinking water and/or adequate sanitation facilities. This report provides a framework for estimating the number of Californians that lack safe drinking water and/or adequate sanitation facilities. It also focuses on small (rural and urban) communities and tribal communities who often face similar challenges in accessing safe water and providing adequate sanitation.

These challenges include aging infrastructure, more stringent water quality standards, financial capacity, and the affordability of operation and maintenance costs associated with new treatment systems.

This report was prepared as part of the California Water Plan Update 2013 process and is an update to the 2005 Californians without Safe Water report. It continues the dialogue regarding Californians without safe drinking water and/or adequate sanitation facilities and includes 14 recommendations towards ensuring that all Californians have safe drinking water and adequate sanitation facilities. The report also highlights Governor Brown’s goal of ensuring that all Californians have access to safe drinking water, as specified by his signing of Assembly Bill (AB) 685 and the release of the California Water Action Plan that includes Action 7, “Provide Safe Water for All Communities.”

In recent years, there has been significant progress in heightening the awareness of the drinking water and sanitation problems facing small and disadvantaged communities in California, as evidenced by the numerous plans and reports on the issue. However, despite these efforts, there is still a lot of work to do to ensure that all Californians have access to safe drinking water and sanitation. In support of this effort, the report lists 14 recommendations that were developed with input from State agencies and public stakeholders.

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Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS)
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Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS)
Central Valley Salinity Coalition (CVSC) | January 19, 2017...
Summary
Elevated salinity and nitrates in surface water and groundwater are increasing problems affecting much of California, other western states, and arid regions throughout...
Elevated salinity and nitrates in surface water and groundwater are increasing problems affecting much of California, other western states, and arid regions throughout the world. In California, as surface and groundwater supplies become scarcer, and as wastewater streams become more concentrated, salinity and nitrate impairments are occurring with greater frequency and magnitude.

In 2006, the Central Valley Water Board, the State Water Board, and stakeholders began a joint effort to address salinity and nitrate problems in California’s Central Valley and adopt long-term solutions that will lead to enhanced water quality and economic sustainability. Central Valley Salinity Alternatives for Long-Term Sustainability (CV-SALTS) is a collaborative basin planning effort aimed at developing and implementing a comprehensive salinity and nitrate management program. The goal of CV-SALTS is to maintain a healthy environment and a good quality of life for all Californians by protecting our most essential and vulnerable resource: WATER.

In July 2008, the Central Valley Salinity Coalition (CVSC) was formed. CVSC represents stakeholder groups working with the Board in the CV-SALTS effort. Its purpose is to organize, facilitate and fund efforts needed to fulfill the goals of CV-SALTS. CVSC coordinates the meetings of the CV-SALTS committees, maintains an independent web site, and manages the projects originating from this effort. Information and materials regarding the stakeholder committees and other activity, including the meeting schedule, are posted on their website: www.cvsalinity.org.

The Final SNMP for Central Valley Water Board Consideration was completed in December 2016. The Central Valley Water Board staff plans to release this version of the SNMP and all of its supporting attachments in January 2017 for a comment period so that the public has the opportunity to review the SNMP documentation before a general information workshop is held with the Central Valley Water Board, currently planned for March 2017.

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Characterizing Nitrates in Central Coast Groundwater

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Characterizing Nitrates in Central Coast Groundwater
Central Coast Groundwater Coalition (CCGC) | April 1, 2016...
Summary
The Central Coast Groundwater Coalition (CCGC) is a third-party cooperative groundwater monitoring program that was established for landowners/operators in the Central Coast region...

The Central Coast Groundwater Coalition (CCGC) is a third-party cooperative groundwater monitoring program that was established for landowners/operators in the Central Coast region as an alternative to the individual groundwater monitoring program. The cooperative program collects and synthesizes groundwater monitoring data on behalf of its members to fulfill requirements of the Irrigated Lands Regulatory Program. The Central Coast Regional Water Quality Control Board required that the CCGC characterize groundwater quality in the uppermost aquifer and identify and evaluate groundwater used for drinking water purposes. Specifically, the focus was on evaluating the spatial distribution of nitrate concentrations in ground- water basins used for drinking water and provide statistically-based estimates of where groundwater nitrate concentrations are likely to be above the maximum contaminant level (MCL) for nitrate.

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Communities that rely on a contaminated groundwater source for drinking water
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Communities that rely on a contaminated groundwater source for drinking water
California State Water Resources Control Board | January 1, 2013...
Summary
AB 2222 (Caballero, Chapter 670, Statutes of 2008) requires the State Water Resources Control Board to submit a report to the Legislature that...
AB 2222 (Caballero, Chapter 670, Statutes of 2008) requires the State Water Resources Control Board to submit a report to the Legislature that identifies: 1) communities in California that rely on contaminated groundwater as a primary source of drinking water; 2) the principal contaminants and other constituents of concern; and 3) potential solutions and funding sources to clean up or treat groundwater or provide alternative water supplies.

A “community,” for the purposes of this report, is defined as a Community Public Water System (Health and Safety Code Section 116395). When this report refers to communities that rely on a contaminated groundwater source, it is referring to community public water systems that draw water from a contaminated groundwater source prior to any treatment. Over 95 percent of the 38 million Californians get their drinking water from a public water system. The findings in this report do not reflect private domestic wells or other unregulated water systems since the state does not require these groundwater users to sample their wells, and consequently a comprehensive database for these groundwater sources does not exist.

This report identifies 680 community water systems that, prior to any treatment, relied on a contaminated groundwater source during the most recent California Department of Public Health (CDPH) compliance cycle (2002-2010). It is important to note that, according to CDPH, over 98% of Californians on public water supply are served safe drinking water.

Although many water suppliers draw from contaminated groundwater sources, most suppliers are able to treat the water or blend it with cleaner supplies before serving it to the public. Consequently, when this report refers to communities that rely on contaminated groundwater, it is referring to community public water systems that draw water from one or more contaminated groundwater wells prior to any treatment or blending.

Some community water systems, however, cannot afford treatment or lack alternative water sources, and have served water that exceeds a public drinking water standard. Of the 680 community water systems that rely on a contaminated groundwater source, 265 have served water that exceeded a public drinking water standard during the most recent CDPH compliance cycle (2002-2010).

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Comparing Groundwater Quality in Public-Supply and Shallow Aquifers in the Monterey Bay and Salinas Valley Basins, California

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Comparing Groundwater Quality in Public-Supply and Shallow Aquifers in the Monterey Bay and Salinas Valley Basins, California
U.S. Geological Survey (USGS) | December 17, 2018...
Summary
Groundwater quality in the Monterey–Salinas Valley Public-Supply and Shallow Aquifer Systems was investigated by the GAMA-PBP. The Monterey–Salinas Valley Public-Supply Aquifer System study...

Groundwater quality in the Monterey–Salinas Valley Public-Supply and Shallow Aquifer Systems was investigated by the GAMA-PBP. The Monterey–Salinas Valley Public-Supply Aquifer System study unit (MS-PA) initially was assessed in 2005 (Kulongoski and Belitz, 2011). The Mon-terey–Salinas Valley Shallow Aquifer System study unit (MS-SA) was sampled in 2012–13 (Burton and Wright, 2018). The MS-PA and the MS-SA largely coincide areally; however, they represent different parts of the aquifer system vertically. The MS-PA examined deeper groundwater primarily used for public supply, whereas the MS-SA examined relatively shallow groundwater primarily used for domestic supply. The MS-SA was divided into four study areas. Three of these study areas combined (MS-SA3) were equivalent to the MS-PA study unit excluding a small sliver along the Carmel River. The fourth MS-SA study area, Highlands, is composed of the hills and mountains bordering the Salinas Valley.

The MS-PA and the MS-SA study units have warm, dry summers and cool, moist winters. The average annual rainfall is 331 millimeters (mm; 13 inches, in.) with average annual temperatures of14 degrees Celsius (57 degrees Fahrenheit) in Salinas. The study units are drained by three main rivers and their tributaries: the Salinas, Pajaro, and San Lorenzo Rivers.

Groundwater quality status and understanding assessments of the study units were based on data collected by the U.S. Geological Survey (USGS). In the MS-PA, additional inorganic data was obtained from the California State Water Resources Control BoardDivision of Drinking Water Public- Supply Well Water-Quality Database (Kulongoski and Belitz, 2011).

A grid-based method to select wells was applied in both study units, which allows for an estimation of the proportions of the aquifer system with constituents at low, moderate, or high concentrations relative to regulatory and non- regulatory benchmarks for drinking-water quality established by the U.S. Environmental Protection Agency (EPA) or California State Water Resources Control Board Division of Drinking Water. The grid-based method provides statistically unbiased results and permits comparison of those results to other GAMA Priority Basin Project study areas (Belitz and others, 2010).

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Data from Exploratory Sampling of Groundwater in Selected Oil and Gas Areas of Coastal Los Angeles County and Kern and Kings Counties in Southern San Joaquin Valley, 2014–15
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Data from Exploratory Sampling of Groundwater in Selected Oil and Gas Areas of Coastal Los Angeles County and Kern and Kings Counties in Southern San Joaquin Valley, 2014–15
U.S. Geological Survey (USGS) | December 9, 2016...
Summary
Exploratory sampling of groundwater in coastal Los Angeles County and Kern and Kings Counties of the southern San Joaquin Valley was done by...
Exploratory sampling of groundwater in coastal Los Angeles County and Kern and Kings Counties of the southern San Joaquin Valley was done by the U.S. Geological Survey from September 2014 through January 2015 as part of the California State Water Resources Control Board’s Water Quality in Areas of Oil and Gas Production Regional Groundwater Monitoring Program. The Regional Groundwater Monitoring Program was established in response to the California Senate Bill 4 of 2013 mandating that the California State Water Resources Control Board design and implement a groundwater-monitoring program to assess potential effects of well-stimulation treatments on groundwater resources in California. The U.S. Geological Survey is in cooperation with the California State Water Resources Control Board to collaboratively implement the Regional Groundwater Monitoring Program through the California Oil, Gas, and Groundwater Project.

Many researchers have documented the utility of different suites of chemical tracers for evaluating the effects of oil and gas development on groundwater quality. The purpose of this exploratory sampling effort was to determine whether tracers reported in the literature could be used effectively in California. This reconnaissance effort was not designed to assess the effects of oil and gas on groundwater quality in the sampled areas. A suite of water-quality indicators and geochemical tracers were sampled at groundwater sites in selected areas that have extensive oil and gas development. Groundwater samples were collected from a total of 51 wells, including 37 monitoring wells at 17 multiple-well monitoring sites in coastal Los Angeles County and 5 monitoring wells and 9 water-production wells in southern San Joaquin Valley, primarily in Kern and Kings Counties.

Groundwater samples were analyzed for field water-quality indicators; organic constituents, including volatile and semi-volatile organic compounds and dissolved organic carbon indicators; naturally present inorganic constituents, including trace elements, nutrients, major and minor ions, and iron species; naturally present stable and radioactive isotopes; dissolved noble gases; dissolved standard and hydrocarbon gases, ?13C of methane, ethane, and ?2H of methane. In total, 249 constituents and water-quality indicators were measured.

Four types of quality-control samples (blanks, replicates, matrix spikes, and surrogates spiked in environmental and blank samples) were collected at approximately 10 percent of the wells. The quality-control data were used to determine whether the groundwater-sample data were of sufficient quality for the measured analytes to be used as potential indicators of oil and gas effects. The data from the 51 groundwater samples and from the quality-control samples are presented in this report.

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Evaluation of Processes Affecting 1,2-Dibromo-3-Chloropropane (DBCP) Concentrations in Ground Water in the Eastern San Joaquin Valley, California: Analysis of Chemical Data and Ground-Water Flow and Transport Simulations
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Evaluation of Processes Affecting 1,2-Dibromo-3-Chloropropane (DBCP) Concentrations in Ground Water in the Eastern San Joaquin Valley, California: Analysis of Chemical Data and Ground-Water Flow and Transport Simulations
U.S. Geological Survey (USGS), University of California Davis | December 17, 1999...
Summary
Future use of the sole-source aquifer near Fresno in the eastern San Joaquin Valley, California, will depend, in part, on how long 1,2-dibromo-3-chloropropane...

Future use of the sole-source aquifer near Fresno in the eastern San Joaquin Valley, California, will depend, in part, on how long 1,2-dibromo-3-chloropropane (DBCP), an agricultural fumigant banned from use since the late 1970’s, persists at concentrations greater than the maximum contaminant level of 0.2 micrograms per liter (?g/L). Field data indicate that DBCP concentrations in ground water have decreased since the late 1970’s. Laboratory experiments by earlier investigators show that DBCP transformed to 2-bromoallyl alcohol (BAA) under conditions similar to in situ conditions, with an estimated half-life ranging from 6.1 (pH 7.8, 21.1 degrees Celsius) to 141 years (pH 7.0, 15 degrees Celsius). For this current study, a detailed hydrogeologic investigation was done to assess the relative importance of chemical transformation, dispersion, and ground-water pumping and reapplication of irrigation water in affecting DBCP concentrations.

Groundwater samples were collected from 20 monitoring wells installed along a 4.6- kilometer transect. DBCP concentrations in these samples ranged from less than the detection limit of 0.03 g/L to a maximum of 6.4 g/L. Results of chlorofluorocarbon (CFC) age dating indicate that DBCP occurs in water that ranges in age from about 2 to 41 years. The primary transformation product BAA, which was identified during previous laboratory studies, was not detected at or greater than 0.03 g/L in any of the 20 ground- water samples. The lack of detection of BAA indicates that transformation to BAA is insignificant relative to other processes controlling DBCP concentrations. Results from this current study indicate that the in situ hydrolysis half-life for DBCP to BAA is much greater than the laboratory-determined values.

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