This page includes brief descriptions for each data layer that appears in Your Water Data and is available for interaction and visualization in The Drinking Water Tool. Where available, spatial data (shapefiles) and metadata are available for download as (.zip) files. If using any data layers or related information for analysis or reporting, please cite according to each layer’s guidelines.
This shapefile contains a feature class with polygons that represent 353 Groundwater Sustainability Agencies (GSA) formed under the Sustainable Groundwater Management Act (SGMA). The GSA boundaries were downloaded from the Department of Water Resources’ GSA MapService (August 7, 2023). Multiple spatial analyses were undertaken to populate the fields you see in the summary data table of the Drinking Water Tool. To estimate a count of each entity per GSA, the following fields were spatially joined to the GSA boundaries: domestic wells locations, public supply well locations, public and state small water systems, and severely disadvantaged and disadvantaged census places (see metadata for more details).
The drought scenario results for Central Valley domestic wells were aggregated to GSAs (see Gailey 2020). This information is viewable in the Drinking Water Tool in the summary table and in the Groundwater Supply – Drought Scenarios section. Results from all scenarios are included in this download. Note that for the drought analysis results at the GSA level, there may be only partial data support for some areas. To evaluate this consideration, review the area covered by the Alluvial Boundary found in the Other Boundaries section.
Download the GSA Shapefile and GSA Metadata
This shapefile contains a feature class with polygons that represent the 58 counties in California. Multiple spatial analyses were undertaken to populate the fields you see in the summary data table of the Drinking Water Tool. Information on the number of domestic wells and population reliant on domestic wells is based on data from Rempel & Pace et al. (2023). To estimate a count of each entity per county the following fields were spatially joined to the county boundaries, public supply well locations, water systems, severely disadvantaged and disadvantaged census places. We also included race/ethnicity, and median household income data based on the 2017-2021 American Community Survey 5-Year Estimates.
The drought scenario results for Central Valley domestic wells were aggregated to counties (see Gailey 2020). This information is viewable both in the summary data table and as a layer in Groundwater Supply. Results from all scenarios are available for download as part of this shapefile. Note that for the drought analysis results at the county level, there may be only partial data support for some areas. To evaluate this consideration, review the area covered by the Alluvial Boundary found in the Other Boundaries section.
Download the County Shapefile and County Metadata
This shapefile contains a feature class with polygons that represent spatial geography for 4,035 public water systems (PWSs) and state small water systems (SSWSs) in California (state small water systems have fewer than 5-14 service connections and a different regulatory framework). Data for 2,917 boundaries were accessed from the California State Water Resources Control Board (Water Board) and processed by Cal EPA’s Office of Environmental Health Hazard Assessment for CalEnviroScreeen (CES) 4.0. The remaining 1,271 boundaries were accessed from the Monterey County Department of Public Health and processed by the Water Equity Science Shop.
Statewide Boundaries originating from the Water Board include community water systems (CWSs) – 15 or more service connections or serving 25 or more people, and State Small Water Systems (SSWSs). We integrated regional water system boundaries provided by Monterey County, a dataset unique to Monterey County that includes SSWSs; Local Small Water Systems (LSWSs) – 2-4 service connections; Transient non-community (TNC) and Non-transient non-community (NTNC) water systems (e.g., parks and schools, respectively); and boundaries for public water systems that are monitored by Monterey County, the Local Primacy Agency (LPA). Boundaries were cleaned and integrated into a single layer. NTNC and TNC systems were excluded in the statewide dataset but retained in Monterey County.
Each water system includes demographic data from the US Census Bureau’s American Community Survey 2017-2021 5-year estimates for race/ethnicity, median household income, and disadvantaged community status (DAC). Demographic data was originally downloaded at the block group level and aggregated to water systems using areal apportionment. The Demographics section below explains the variables in greater detail.
This layer is available as an interactive layer with summary information for each system in the data table and as a standalone reference layer, which can be found under Groundwater Users – Public and State Small Water Systems.
Characteristics for each water system available in this layer are the result of several different research efforts. The metadata file documents the methodology and data source for each characteristic. Only certain water system characteristics are available for download, as indicated in the metadata file. The drought scenario results are only available for small community water systems, those serving fewer than 10,000 people, in the Central Valley (see Gailey 2020).
Download the Shapefile and Metadata
If using for analysis or reporting, please cite the Community Water System Boundary dataset as:
Pace, C., Fisher, E., Subramanian, A. Cushing, L., Morello-Frosch, R. (2023). Water system boundaries version 2.0, Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop.
This shapefile represents approximate point locations for 1,329 state small water systems (SSWSs) in California. SSWSs serve 5-14 service connections. This dataset was developed by the California State Water Board as an intermediate step toward compliance with Senate Bill 200 (SB 200) which requires the collection of water quality data for SSWS and domestic wells. Read more about the timeline and progress of SB 200 here. Data was downloaded from the California State Water Board Clearinghouse in October 2022.
Download the State Small Water System Point Locations Metadata
This shapefile contains a feature class with point data that represent the locations for all municipal or public supply wells from the Department of Water Resources’ Online System for Well Completion Reports (OSWCR). This shapefile contains points for 7,158 public supply wells with spatial reference, selected from the OSWCR system by Dr. Rob Gailey, based on a downloaded .csv file of well completion reports (WCRs) (Nov. 16, 2018). Latitude and longitude coordinates supplied in the .csv file were used to plot public supply WCRs as points (see Gailey 2020).
Download the Public Supply Well Locations Shapefile and Metadata (.zip)
If using for analysis or reporting, please cite the public supply well location dataset as:
Gailey, R. (2019) Public Supply Well Locations. CWC Drinking Water Tool.
This shapefile contains a feature class with polygons that represent domestic well areas. This layer combines multiple data sources to identify domestic well areas at the Public Land Survey System (PLSS) section level: 1) domestic well locations, 2) block and block group geography from the 2020 census, 3) high-resolution population estimates from Depsky et al., 2022, 3) public and state small water system boundaries, and 4) residential parcels and building footprints. Domestic well location data came from the Department of Water Resources’ Online System for Well Completion Reports (OSWCR) dataset for wells drilled between 1970 to 2021. Well locations were refined using a multi-method approach to match wells to residential parcels (although this location data is unavailable for download due to privacy issues, the unprocessed data may be accessed through OSWCR).
PLSS section grids (approximately 1×1 mile grid squares) are the underlying geographic units used to define areas served by domestic wells. A domestic well area is defined as a portion of a PLSS section that has at least one domestic well, intersects with a populated census block (2020), and has a residential population based on Depsky et al., 2022 . Domestic well areas can overlap with areas also served by a public or state small water system. Please consult the complete methodology described in Rempel & Pace et al., 2023.
Two key attributes of this layer, as displayed are:
Download the Shapefile and Metadata
If using for analysis or reporting, please cite the domestic well area dataset as:
Rempel, J.*, C. Pace*, L. Cushing, R. Morello-Frosch. (2023). Domestic Well Areas Version 2.0. Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley. *Designates shared co-first authorship.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop
This shapefile contains a feature class with polygons that show water quality values for arsenic, nitrates, hexavalent chromium, and 1,2,3-Trichloropropane (TCP). These four contaminants were selected due to their acute or carcinogenic health effects. Water quality data were assigned from two sources; data processed for 2,918 public and state small water systems included in CalEnviroScreen (CES) 4.0, and data for 1,271 public and state small water systems collected and shared by the Monterey Department of Public Health. Processing steps vary between the sources based on data availability.
Water quality data for the 2,918 water systems from the California Office of Environmental Health Hazard Assessment’s (OEHHA) CalEnviroScreeen (CES) 4.0 dataset received water quality estimates representing the 9-year system average for water delivered to the customer from 2011 to 2019. To calculate water quality estimates, OEHHA accessed and processed monitoring data from the State Water Resources Control Board (SWRCB) Water Quality Monitoring (WQM) database. “Active treated” samples were primarily evaluated, as these represent water delivered to the consumer. Delivered water could include sources sampled post-treatment or sampled from “untreated” sources. Approximately 3% of the data came from “raw” water samples because the systems had no treated or untreated source classifications. Complete methods used in CES 4.0 are available from OEHHA (CES 4.0, 2021). The drinking water contaminant data is available for download from OEHHA for public and state small water systems (CES Indicator – Downloads).
The 1,271 water systems from the Monterey County Department of Public Health received annual maximum measured water quality for each year from 2015-2020, and the overall maximum measured concentration between 2015-2020. 1,2,3-TCP data was not available for Monterey county. This dataset includes public water systems and state small water systems.
Only certain water source characteristics are available for download, as indicated in the Public and State Small Water System layer metadata file.
Water quality data for Public and State Small Water Systems in Monterey, CA, is available for download from the Monterey County Department of Public Health.
Download the Metadata
If using for analysis or reporting, please cite the water quality dataset as:
Pace, C., Fisher, E., Subramanian, A. Cushing, L., Morello-Frosch, R. (2023). Water system boundaries version 2.0, Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop.
This shapefile contains a feature class with polygons that represent the Public Land Survey System (PLSS) sections (approximately 1×1 mile grid squares) and populated areas with domestic wells, as well as water quality values assigned to PLSS sections of the Domestic Well Areas in California. It was generated by the Water Equity Science Shop (WESS) research team using water quality values provided by the State Water Resources Control Board and developed for the Safe and Affordable Funding for Equity and Resilience (SAFER) Program’s 2022 Aquifer Risk Map. This dataset was used to assign contaminant concentrations for arsenic (As), nitrate as nitrogen (N), 1,2,3-trichloropropane (1,2,3-TCP), and hexavalent chromium (Cr[VI]) to populated PLSS sections. These four contaminants were selected due to their acute or carcinogenic health effects. Future iterations of this tool will include data on additional high priority contaminants. The Aquifer Risk Map utilized data from the State Water Resources Control Board’s Groundwater Ambient Monitoring & Assessment (GAMA) dataset, a groundwater information system that integrates water quality data from various sources.
Complete methodology is available in the GAMA Needs Assessment White Paper “Methodology to estimate groundwater quality assessed by domestic wells” and is available from the SWRCB (Aquifer Risk Map, 2022). In brief, existing groundwater quality data in the GAMA Groundwater Information System was filtered by time and depth to better represent domestic well water quality. The water quality estimation layer consists of a twenty-year average detection level per Public Land PLSS section per chemical.
The groundwater contaminant data is available for download from the Aquifer Risk Map.
Handling non-detects: Results reported as “non-detects” in this dataset were assigned a value equal to the detection limit at the time the sample was collected. If the sample had no associated reporting limit, the closest earlier measurement with a known reporting limit was assigned (GAMA Needs Assessment, 2020).
Download the Domestic Well Areas Metadata
If using for analysis or reporting, please cite the water quality dataset as:
Methodology notes for the 2022 Aquifer Risk Map created in support of SB 200 to help prioritize SAFER funding for domestic wells and state small water systems at risk for water quality issues.
The Drinking Water Threats section of the tool includes information on per- and polyfluoroalkyl substances (PFAS) detections in well water, PFAS sources, superfund sites, pesticide use, and oil and gas wells. PFAS sources include airports certified to use PFAS-containing substances, military sites, some superfund sites, chrome-plating facilities, wastewater treatment facilities, landfills, and refineries and terminals. The threats listed in this section have been identified by their ability to release harmful substances – such as PFAS, nitrates, heavy metals, various pesticides, pathogens, etc. – into the environment with the potential to contaminate groundwater. Given that these facilities and activities can release multiple contaminants simultaneously, it is probable that exposures to chemical mixtures will occur. Cumulative exposures to drinking water contaminants can result in short-term and long-term adverse health impacts, including gastrointestinal illnesses, effects on the nervous, reproductive and developmental systems, and cancer.
This shapefile contains data extracted and refined from California’s State Water Resources Control Board (SWRCB) GeoTracker PFAS map. The data have been aggregated to a shapefile of 2,256 points representing locations where per- and polyfluoroalkyl substances (PFAS) were measured or detected in drinking water wells that supply public water systems. SWRCB’s data collection began in 2019 with an order for water systems near airports with fire training areas and municipal solid waste landfills to collect data. This shapefile represents locations where water sampling results were collected, where PFAS were detected at any concentration above the detection limit (DL) for any PFAS, and a subset of samples that exceed one or more of the EPA proposed maximum contaminant levels (MCLs).
Download the PFAS Detections Shapefile and Metadata
If using for analysis or reporting, please cite the airport dataset as:
Karasaki, S., Pace, C., Cushing, L., Morello-Frosch, R. (2023). PFAS detections in water samples. Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop
The shapefiles listed below indicate the locations and boundaries of several types of facilities known to have current or historical use and storage of materials containing per- and polyfluoroalkyl substances (PFAS). These facilities include P-139 certified airports (i.e. airports certified to use aqueous film-forming foam (AFFF) that contains PFAS), military sites, superfund sites, chrome-plating facilities, wastewater treatment facilities, landfills, and refineries and bulk terminals. These sites are considered PFAS sources because they may release PFAS into the surrounding water, soil, and air. See the sections below for further information on each PFAS Source.
This shapefile contains 36 polygons representing boundaries of public airports in California that may be a potential source of PFAS contamination due to permitted use of PFAS-containing aqueous film-forming foam (AFFF). Airports equipped to use this foam are required to have Part 139 certification (P-139) by the Federal Aviation Agency (FAA). Airports with both current and historical (2014 – 2022) P-139 certification are considered potential PFAS sources. Other contaminants released by airports include volatile organic compounds (VOCs) and petroleum hydrocarbons. Part 139 Certified Airport boundaries were downloaded from the California Department of Transportation (Caltrans) and we identified airports with P-139 Certification using Bureau of Transportation data. For more detailed information on how this dataset was assembled, download the metadata.
Download the P-139 Airports Shapefile and Metadata
If using for analysis or reporting, please cite the airport dataset as:
Karasaki, S., Pace, C., Cushing, L., Morello-Frosch, R. (2023). Airports permitted to use aqueous film-forming foam (AFFF). Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop
This shapefile contains 78 polygons representing boundaries of military installations, ranges, and training areas (MIRTA) in California. Military sites are considered sources of PFAS due to their continued use of PFAS-containing aqueous film-forming foam which is commonly used during training exercises and emergency situations. Military sites also release other kinds of contamination, including heavy metals and radiation. Data for Military Installations, Ranges, and Training Areas (MIRTA) boundaries was accessed from data.gov. Detailed information on how this dataset was assembled, cleaned, and processed is available in the metadata.
Download the MIRTA Shapefile and Metadata
If using for analysis or reporting, please cite the MIRTA dataset as:
Karasaki, S., Pace, C., Cushing, L., Morello-Frosch, R. (2023). Military Installations Ranges and Training Areas (MIRTA). Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop
This shapefile contains polygons that represent Public Land Survey System (PLSS) sections (approximately 1×1 mile grid squares) where 271 chrome-plating facilities are located within California. Chrome plating is the process of coating a metal object with a thin, protective layer of chromium to reduce wear and tear. Since the 1950s, PFAS have been used in the chrome-plating industry to act as a mist and fume suppressant. Wastewater from these facilities has been shown to contain high levels of PFAS and other harmful chemicals including volatile organic compounds (VOCs) and heavy metals. See this factsheet for more information on the use of PFAS in the metal-plating industry. Spatial data for chrome-plating facilities was accessed from the State Water Resources Control Board’s (SWRCB) online data portal. These sources are a subset of the facilities that received investigative orders from the SWRCB between 2019 and 2021 (here are links to a timeline of California agencies’ actions on PFAS, and more detailed information on the investigative orders).
Download the Additional PFAS sources Shapefile and Metadata (Includes Chrome Plating Facilities)
This shapefile contains polygons that represent Public Land Survey System (PLSS) sections (approximately 1×1 mile grid squares) where 270 wastewater treatment facilities are located within California. Wastewater treatment facilities receive wastewater contaminated with PFAS and other toxic substances from residential, commercial, and industrial sources. After treatment, the remaining waste – or effluent – is released into the environment, oftentimes still containing high levels of PFAS. Additionally, PFAS may contaminate biosolids which may then be applied to agricultural fields as fertilizer. See this website for more information on PFAS in wastewater treatment facilities. Other chemicals of concern from wastewater treatment facilities include other organic compounds, volatile organic compounds (VOCs), inorganic compounds, disinfection by-products, pharmaceuticals, and personal-care products. Spatial data for wastewater treatment facilities was accessed from the State Water Resources Control Board’s (SWRCB) online data portal. These sources are a subset of the facilities that received investigative orders from the SWRCB between 2019 and 2021 (here are links to a timeline of California agencies’ actions on PFAS, and more detailed information on the investigative orders).
Download the Additional PFAS sources Shapefile and Metadata (Includes Wastewater Treatment Facilities)
This shapefile contains polygons that represent Public Land Survey System (PLSS) sections (approximately 1×1 mile grid squares) where 205 landfills are located within California. Landfills are the final destination for many PFAS-containing products – like furniture, textiles, and carpeting – that have reached the end of their life-cycle. As these products break down, PFAS may be released into the environment through landfill discharge (leachate), surface runoff, and evaporation. For more information on PFAS and landfills, read this article. Landfills may also release other harmful organic compounds, volatile organic compounds (VOCs), heavy metals, pharmaceuticals, and personal-care products. Spatial data for Landfills was accessed from the State Water Resources Control Board’s (SWRCB) online data portal. These sources are a subset of the facilities that received investigative orders from the SWRCB between 2019 and 2021 (here are links to a timeline of California agencies’ actions on PFAS, and more detailed information on the investigative orders).
Download the Additional PFAS sources Shapefile and Metadata (Includes Landfills)
This shapefile contains polygons that represent Public Land Survey System (PLSS) sections (approximately 1×1 mile grid squares) where 155 refineries and bulk terminals are located within California. The use of PFAS in the operations of bulk fuel storage terminals and refineries is varied. PFAS is used in fire-fighting foam for fire suppression, fire training, and flammable vapor suppression. PFAS is also used in bulk fuel storage tanks as a protective floating layer on the surface to reduce evaporation loss. Read this article for more information on PFAS in refineries and bulk terminals. Refineries and terminals may also release other harmful organic compounds and volatile organic compounds (VOCs). Spatial data for Refineries and Bulk Terminals was accessed from the State Water Resources Control Board’s (SWRCB) online data portal. These sources are a subset of the facilities that received investigative orders from the SWRCB between 2019 and 2021 (here are links to a timeline of California agencies’ actions on PFAS, and more detailed information on the investigative orders).
For more detailed information on how the Additional PFAS Sources dataset was assembled, download the metadata.
Download the Additional PFAS sources Shapefile and Metadata (Includes Refineries and Terminals)
If using for analysis or reporting, please cite the airport dataset as:
Karasaki, S., Pace, C., Cushing, L., Morello-Frosch, R. (2023). Additional PFAS Sources: Chrome-Plating Facilities, Wastewater treatment facilities, Landfills, and Refineries and Terminals. Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop
This shapefile contains 100 polygons representing Superfund Site boundaries in California. Superfund Site boundaries represent the footprint of a whole site, defined as the sum of all operable units (OUs) and the current understanding of the full extent of contamination. Superfund sites are locations with high levels of toxic contamination, including PFAS, heavy metals, asbestos, dioxin, and radiation. Contamination is caused by improper management of hazardous materials used in manufacturing facilities, processing plants, landfills, mining sites, and other industrial sites. Depending on the toxins present, living within close proximity to a Superfund site can have adverse health effects on mental health, infant mortality, water and food-borne illness, and cancer. A subset of Superfund sites where PFAS has been detected were identified using data from EPA and these sites are flagged in the Drinking Water Tool. Boundaries for the U.S. EPA Superfund Sites were accessed from data.gov. Detailed information on how this dataset was assembled, cleaned, and processed is available in the metadata.
Download the Superfund Site Shapefile and Metadata
If using for analysis or reporting, please cite the airport dataset as:
Pace, C., Karasaki, S., Cushing, L., Morello-Frosch, R. (2023). Superfund Sites in California. Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop
This shapefile contains a feature class with 61,756 polygons that represent the Public Land Survey System (PLSS) sections (approximately 1×1 mile grid squares), populated areas with domestic wells, and estimates of agricultural pesticide use. Annual and total pounds of pesticide active ingredients applied in sections of the Domestic Well Areas in California are reported. Pesticide use data was accessed for 2011 to 2019 from the California Department of Pesticide Regulation’s (DPR) Pesticide Use Reporting (PUR) Program database and filtered for 166 active ingredients that pose a threat to groundwater quality. A pesticide was considered a drinking water threat if it was already being routinely monitored in well water by the DPR, was previously detected in groundwater, or had a high soil mobility rating, indicating that it is likely to move through soil and contaminate groundwater. The classes of pesticides most commonly detected in groundwater include organophosphates, organochlorines, and triazines. Exposures to pesticides in drinking water can have varied adverse health effects which depend on the type of chemical, its concentration, and duration of exposure. Repeated exposures to low levels of pesticides commonly found in drinking water can result in birth defects, damage to the nervous system, and cancer. Future iterations of this tool will include data on measured concentrations of pesticides in well water.
Download the Pesticides Use Shapefile and Metadata
If using for analysis or reporting, please cite the pesticide use dataset as:
Libenson, A., Pace, C., Cushing, L., Morello-Frosch, R. (2023). Pesticide Application in California, 2011-2019. Drinking Water Tool metadata, prepared by the Water Equity Science Shop, UC Berkeley.
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop
This shapefile contains point data for 58,085 active oil and gas wells in California. We accessed a Statewide dataset of oil and gas wells from the California Department of Conservation, California Geologic Energy Management Division (CalGEM). We selected oil and gas operations in California between 1898 and 2021 (n=241,254) and sub-selected active wells (n=58,085). Oil and gas activities may lead to groundwater contamination through various pathways including surface spills, fracking, improper management or disposal of wastewater, and deteriorating or improper construction of wells. These conditions can result in the release of PFAS, other harmful organic compounds, volatile organic compounds (VOCs), and dissolved solids into well water. Research has shown that residents living within close proximity to oil and gas wells are more likely to experience adverse health effects such as birth defects, cardiovascular disease, impaired lung function, anxiety and depression (Gonzales, 2023).
Download the Oil and Gas Wells Metadata
If using for analysis or reporting, please cite the oil and gas wells dataset as:
All Wells Dataset, GIS Mapping, (2021). California Department of Conservation, California Geologic Energy Management Division (CalGEM), https://www.conservation.ca.gov/calgem/maps/Pages/GISMapping2.aspx,
Contact: Clare Pace, Ph.D., MPH, cpace@berkeley.edu, UC Berkeley, Environmental Science Policy and Management, Water Equity Science Shop
Concentrated animal feeding operations (CAFOs) are industrial-sized agricultural facilities that contain a large amount of animals within a small space. CAFOs produce massive quantities of animal sewage containing disease-causing pathogens, chemicals (e.g. nitrates), pharmaceuticals, heavy metals, and other pollutants that contaminate the surrounding environment. Hazardous gasses – including ammonia, hydrogen sulfide, and methane – and particulate matter are also released into the air surrounding CAFOs. Negative human health impacts can result from contaminated water supplies, hazardous air pollution or diseases spread from CAFOs. Nitrates are especially concerning for drinking water quality as exposure to high levels can cause harm to the respiratory and reproductive system, kidney, spleen, and thyroid. Nitrates are also particularly harmful to infants.
A drought scenario in this tool is a scenario of groundwater level decline that is based on observations from the 2012 to 2016 drought. Groundwater level declines for each scenario were based on a scaled version of the 2012 to 2016 drought. These scaling factors (0.5, 0.75 and 1.0) reflect the Drought Scenarios of 50%, 75% and 100%. The drought scenario analysis considers how declining groundwater elevations might reduce well production potential as well as what mitigation measures might be required to maintain supplies. Selecting between these scenarios communicates the estimated impacts and costs on either domestic or small water system wells (<10,000 people served) in the Central Valley. The starting groundwater levels for the analysis are fall 2014, and the 2012 to 2016 drought groundwater levels were defined by fall 2011 (pre-drought) and fall 2016 (late drought) levels. Please consult this analysis’s report for more information: Gailey 2020.
Impact and cost calculations were performed for each Public Land Survey System section (approximately 1×1 mile grid square) where information is available for both a well’s depth and groundwater levels during the 2012 to 2016 drought. This set of data layers are feature classes with polygons that represent domestic wells at the section level or a small community water system. For small community water systems, results are aggregated to the community water system’s boundary or service area. The results for both public supply wells and domestic wells are defined as follows:
Note: When interpreting aggregated impacts for groundwater sustainability agencies and counties, there may be only partial data support for some areas and blank values indicate there was no data available for analysis. No designation is made to indicate partial data support. Results for several counties are incomplete given the spatial boundary (Alluvial Basin) of the analysis undertaken: Alameda, Contra Costa, El Dorado, Mariposa, Napa, San Benito, San Luis Obispo, and Tuolumne. Please consult this analysis’s report for more information: Gailey 2020.
Download the Shapefile and Metadata for all Drought Scenarios: (DomesticWells.zip | WaterSystems.zip )
Download Results Table (.xlsx)
If downloading or using for analysis or reporting, please cite as:
Gailey, R. (2020) California Supply Well Impact Analysis for Drinking Water Vulnerability Webtool.
Demographic information is available for three census geographies: places, tracts, and block groups. Places include incorporated places, which are legal entities like cities, and census-designated places, which are statistical entities created by the Census for unincorporated communities with settled concentrations of population that are identifiable by name but not located within an incorporated place. Census tracts and block groups are geographic entities within a county: census tracts generally have 1,000 to 8,000 people but aim to have around 4,000 people. Census block groups are a statistical division of tracts, and typically have 600 to 3,000 people. For each geography, layers show estimated 5-Year Averages from the American Community Survey of the US Census (ACS) (2017-2021). The ACS includes estimates of social and economic characteristics for people living in housing units and group quarters. Available information from the ACS includes median household income, disadvantaged community status (DAC), and race.
If using for analysis or reporting, please cite the demographic dataset as:
U.S. Census Bureau, 2017-2021 American Community Survey 5-Year Estimates.
The median household income (MHI) values are the estimated 5-year averages from the American Community Survey of the US Census. Income data is collected annually from a sample of census block groups and combined as a period estimate to describe the average characteristics of the population/housing units over the data collection period. The MHI income is defined as the MHI in the past 12 months (in 2021 inflation-adjusted dollars) (see Table B19013).
In California, a disadvantaged community (DAC) is one with an average median household income (MHI) of less than 80% of California’s overall MHI. A severely disadvantaged community (SDAC) is one with an average MHI of less than 60% of California’s overall MHI (California Public Resources Code). This layer shows both DAC and SDACs, based on the 2021 American Community Survey of the US Census 5-year data. In 2021, the statewide MHI was $84,097. The calculated DAC threshold is $67,278 and the calculated SDAC threshold is $50,458. In the California Water Data Tool, census geographies with MHIs below $67,278 are labeled DACs and MHIs below $50,458 are labeled SDACs. Any census geographies with incomes above these thresholds, or with missing data, do not appear.
The California Water Data Tool uses race/ethnicity variables included in the 2021 American Community Survey (ACS) 5-year average (see Table B03002). Data is based on respondents’ self-identified ethnicity and race. Each category is shown as a percent of the total population for each census geography. In the shapefiles available for download, each race/ethnicity category includes a population count, percent of that geography’s total population, and ACS’s margin of error calculations. ACS definitions of race/ethnicity categories are displayed as follows:
Download shapefiles: (Places.zip| Tract.zip| BlockGroup.zip)
The boundary of California’s 80 state assembly districts, based on boundary lines published by the California Redistricting Commission (Data Source).
The boundary of California’s 40 state senate districts, based on boundary lines published by the California Redistricting Commission (Data Source).
The alluvial boundary defines the extent of the alluvial deposits in California’s Central Valley including the Sacramento, San Joaquin, and Tulare Lake groundwater basins as defined by California’s Department of Water Resources Bulletin 118 (Data Source). The alluvial boundary in the California Water Data Tool indicates the geographic extent of the drought scenario analysis for domestic wells and small community water systems in the Central Valley.
Through a State Water Board order, basin plan management zones are required to provide free well testing to households in their service area to determine if their well has nitrate contamination levels above the legal limit of 10 mg/L (milligrams per liter).(Data Source). Currently, the Central Valley Water Board has begun to implement programs to control nitrate levels in 6 of the highest priority groundwater basins. Active management zones in California’s Central Valley include the Valley Water Collaborative, Chowchilla Management Zone, Kings Water Alliance, Kaweah Water Foundation, and Tule Basin Management.
California’s groundwater basins are defined and characterized by the Department of Water Resources’ Bulletin 118 (B118), the official publication on the occurrence and nature of groundwater statewide. Since the Sustainable Groundwater Management Act (SGMA) was passed, Bulletin 118 also provides Groundwater Sustainability Agencies with key information: Critical Conditions of Overdraft, Basin Boundaries, and Basin Priority (see Bulletin 118). The California Water Data Tool visualizes Bulletin 118 groundwater basin priority results from the Department of Water Resources’ basin prioritization process and critically overdrafted basins.
This layer shows the 515 groundwater basins in the state of California; visualized by the SGMA basin prioritization levels (December 2019). Basin prioritization is a process of classifying the State’s 515 groundwater basins (as identified in Bulletin 118) into one of four categories high-, medium-, low-, or very low-priority based on components identified in the Water Code. SGMA requires medium- and high-priority basins to develop groundwater sustainability agencies (GSAs), develop groundwater sustainability plans (GSPs) and manage groundwater for long-term sustainability.
This layer shows the 21 groundwater basins that have been categorized as critically overdrafted of the 515 groundwater basins in the state of California (December 2019). Groundwater basin overdraft happens if the average annual amount of water extracted exceeds the long-term average annual supply of water to the basin. Consequences of overdraft can include seawater intrusion, land subsidence, groundwater depletion, and/or chronic lowering of groundwater levels. In response to SGMA, DWR evaluated California’s groundwater basins for conditions of critical overdraft in 2015 with information available from the SGMA Dataviewer.
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