This is the 2022 version of the Aquifer Risk Map. The 2021 version of the Aquifer Risk Map is available here.This aquifer risk map is developed to fulfill requirements of SB-200 and is intended to help prioritize areas where domestic wells and state small water systems may be accessing raw source groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the risk map is to be made available to the public and is to be updated annually starting January 1, 2021. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding. This is the final 2022 map based upon feedback received from the 2021 map. A summary of methodology updates to the 2022 map can be found here.This map displays raw source groundwater quality risk per square mile section. The water quality data is based on depth-filtered, declustered water quality results from public and domestic supply wells. The process used to create this map is described in the 2022 Aquifer Risk Map Methodology document. Data processing scripts are available on GitHub. Download/export links are provided in this app under the Data Download widget.This draft version was last updated December 1, 2021. Water quality risk: This layer contains summarized water quality risk per square mile section and well point. The section water quality risk is determined by analyzing the long-tern (20-year) section average and the maximum recent (within 5 years) result for all sampled contaminants. These values are compared to the MCL and sections with values above the MCL are “high risk”, sections with values within 80%-100% of the MCL are “medium risk” and sections with values below 80% of the MCL are “low risk”. The specific contaminants above or close to the MCL are listed as well. The water quality data is based on depth-filtered, de-clustered water quality results from public and domestic supply wells.Individual contaminants: This layer shows de-clustered water quality data for arsenic, nitrate, 1,2,3-trichloropropane, uranium, and hexavalent chromium per square mile section. Domestic Well Density: This layer shows the count of domestic well records per square mile. The domestic well density per square mile is based on well completion report data from the Department of Water Resources Online System for Well Completion Reports, with records drilled prior to 1970 removed and records of “destruction” removed.State Small Water Systems: This layer displays point locations for state small water systems based on location data from the Division of Drinking Water.Public Water System Boundaries: This layer displays the approximate service boundaries for public water systems based on location data from the Division of Drinking Water.Reference layers: This layer contains several reference boundaries, including boundaries of CV-SALTS basins with their priority status, Groundwater Sustainability Agency boundaries, census block group boundaries, county boundaries, and groundwater unit boundaries. ArcGIS Web Application

This data was acquired from the Integrated Water Resources Information System (IWRIS), hosted by the California Department of Water Resources (DWR). The Bulletin 118 Groundwater Basins shapefile was downloaded, projected to the CCS83 Zone 5 (ftUS) Map projection and clipped to the Los Angeles County Boundary for internal Los Angeles County use. Please also visit information on Bulletin 118.Supplemental Information:Stormwater Engineering, a Division of the Los Angeles County Department of Public Works, maintains a list of its spreading grounds.The California Department of Water Resources has information on statewide issues.The California Geoportal offers statewide GIS data.

There are 487 onshore oil and gas fields in California encompassing 3,392 square miles of aggregated area. The California State Water Resources Control Board (State Water Board) initiated a Regional Monitoring Program (RMP) in July 2015, intended to determine where and to what degree groundwater quality may be at potential risk to contamination related to oil and gas development activities including well stimulation, well integrity issues, produced water ponds, and underground injection. The first step in monitoring groundwater in and near oil and gas fields is to prioritize the 487 fields using consistent statewide analysis of available data that indicate potential risk of groundwater to oil and gas development. There were limited existing data on potential groundwater risk factors available for oil and gas fields across the state. During 2014-2016, the U.S. Geological Survey (USGS) extracted and compiled data from various sources, including the California Division of Oil, Gas, and Geothermal Resources (DOGGR) and the Department of Water Resources (DWR). Geospatial data from the DOGGR were used in the prioritization analysis. Dataset include geospatial data for 222,637 petroleum wells, administrative boundaries for 514 oil, gas, and geothermal fields, and boundaries for DOGGR's 6 juristictional districts. The data were downloaded from DOGGR's Geographic Information System (GIS) Mapping website at http://www.conservation.ca.gov/dog/maps. The DOGGR GIS Mapping website is periodally updated, and the datasets downloaded by the U.S. Geological Survey in 2014 may no longer be available on the DOGGR website.

The aquifer risk map is being developed to fulfill requirements of SB-200 and is intended to help prioritize areas where domestic wells and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the risk map is to be made available to the public and is to be updated annually starting January 1, 2021. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding.Methodology for the draft aquifer risk map available for download.Water quality risk: This layer contains summarized water quality risk per census block group, square mile section, and well point. The overall census block group water quality risk is based on four risk factors (the count of chemicals with a long-term average (20 year) or recent result (within 2 years) above the MCL, the count of chemicals with a long-term average (20 year) or recent result (within 2 years) within 80% of the MCL, the average magnitude or results above the MCL, and the percent area with chemicals above the MCL or within 80% of the MCL). The specific chemicals that contribute to these risk factors are listed as well. Higher values for each individual risk factor contribute to a higher overall score. The scores are converted to percentiles to normalize the results. The water quality data is based on depth-filtered, declustered water quality results from public and domestic supply wells, collected following a similar methodology as the Domestic Well Needs Assessment White Paper. This layer also displays the total estimated count of domestic wells per census block group, based on the Department of Water Resources Online System for Well Completion Reports, and the total estimated count of domestic well user population, based on the United States Geological Survey Road-Enhanced Methodology (Johnson and Belitz, 2019). To provide comments or feedback on this map, please email SAFER@waterboards.ca.gov or Emily.Houlihan@Waterboards.ca.gov. Individual chemicals: This layer shows declustered water quality data for arsenic, nitrate, 1,2,3-trichloropropane, uranium, and hexavalent chromium per square mile section. The intent of the aquifer risk map is to help prioritize areas where domestic well users and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL) and will be updated annually starting January 1, 2021. The section water quality data is based on depth-filtered water quality results from public and domestic supply wells, collected following a similar methodology as the Domestic Well Needs Assessment White Paper. This layer contains the long-term average (20 years) as well as the count of recent results (within 2 years) above the MCL, between 80% - 100% of the MCL, and below 80% of the MCL for each square mile section. Drinking water users: This layer shows the locations of state small water systems and domestic well density. The state small water system locations were collected by the Rural Community Assistance Corporation. The locations are approximate and may not exactly represent well locations or service boundaries. The domestic well density per square mile is based on well completion report data from the Department of Water Resources Online System for Well Completion Reports. This layer also contains the public water system boundaries (available on the State Water Board REST endpoint) for reference.Reference layers: This layer contains several reference boundaries, including boundaries of CV-SALTS basins with their priority status, Groundwater Sustainability Agency boundaries, census block group boundaries, county boundaries, and groundwater unit boundaries.

There are 487 onshore oil and gas fields in California encompassing 3,392 square miles of aggregated area. The California State Water Resources Control Board (State Water Board) initiated a Regional Monitoring Program (RMP) in July 2015, intended to determine where and to what degree groundwater quality may be at potential risk to contamination related to oil and gas development activities including well stimulation, well integrity issues, produced water ponds, and underground injection. The first step in monitoring groundwater in and near oil and gas fields is to prioritize the 487 fields using consistent statewide analysis of available data that indicate potential risk of groundwater to oil and gas development. There were limited existing data on potential groundwater risk factors available for oil and gas fields across the state. During 2014-2016, the U.S. Geological Survey (USGS) extracted and compiled data from various sources, including the California Division of Oil, Gas, and Geothermal Resources (DOGGR) and the California Department of Water Resources (DWR). During 2014-2016, the depth to top of perforated intervals and depth to base of freshwater for oil and gas production wells in California were extracted from well records maintained by the DOGGR. Well records including geophysical logs, well history, well completion reports, and correspondences were viewed on DOGGR's Well Finder website at https://maps.conservation.ca.gov/doggr/wellfinder/. This digital dataset contains 3,505 records for production wells, of which 2,964 wells have a recorded depth to top of perforated intervals and 1,494 wells have a recorded depth to base of freshwater. Wells were attributed with American Petroleum Institute (API) numbers, oil and gas field, and well location, well status and type, and nearest oil and gas field for wells that plotted outside field boundaries using the DOGGR All Wells geospatial data included in this data release. Wells were attributed with land surface elevations using the California National Elevation Dataset. Due to limited time and resources to analyze well records for the most recent well configuration, wells spatially distributed throughout the state and accounting for about 2 percent of the more than 185,000 production wells (new, active, idle, or plugged well status) were attributed with depth data.

See feature layer here.The aquifer risk map is being developed to fulfill requirements of SB-200 and is intended to help prioritize areas where domestic wells and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the risk map is to be made available to the public and is to be updated annually starting January 1, 2021. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding.Methodology for the draft aquifer risk map available for download.This layer shows domestic well density. The domestic well density per square mile is based on well completion report data from the Department of Water Resources Online System for Well Completion Reports, excluding wells drilled prior to 1970.

The Aquifer Risk Map Web Tool contains all archived maps, including this 2023 Aquifer Risk Map.The Aquifer Risk Map is developed to fulfill requirements of SB-200 (Monning, 2019) and is intended to help prioritize areas where domestic wells and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the map is made available to the public and updated annually starting January 1, 2021. This web map is part of the 2023 Aquifer Risk Map. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding.

This web map includes the following layers:Water Quality Risk: water quality risk estimates per square mile section for all contaminants with an MCL. Water quality risk is listed as “high” (average or recent concentration in section is above MCL for one or more contaminants), “medium” (average or recent concentration in section is between 80% - 100% of MCL for one or more contaminants), “low” (average or recent concentration in section is less than 80% of MCL for all measured contaminants) or “unknown” (no water quality data available in section).Individual Contaminant Risk: water quality risk estimates for nitrate, arsenic, 1,2,3-trichloropropane, hexavalent chromium, and uranium per square mile section.State Small Water Systems (DDW): state small water systems (5-14 connections) location from the Division of Drinking Water joined with water quality risk section estimates from the 2023 Aquifer Risk Map.Domestic Well Records (OSWCR): the approximate count and location of domestic well completion reports submitted to the Department of Water Resources. This is used as a proxy to identify domestic well locations.Public Water System Boundaries (DDW): the approximate boundaries of public drinking water systems, from the Division of Drinking Water. For reference only.Census Areas: Census block groups and census tract boundaries containing demographic information from the 2021 American Community Survey (B19013 Median Household Income and B03002 race/ethnicity) joined with summarized water quality risk estimates from the 2023 Aquifer Risk Map (count of high risk domestic wells and state small water systems per census area).Reference Boundaries: Various geographic boundaries including counties, basins, GSA’s, CV-SALTS basin prioritization status, Disadvantaged Community (DAC) status, and legislative boundaries. For reference only.CalEnviroScreen 4.0: CalEnviroScreen scores from OEHHA. For reference only.Groundwater Level Percentiles (DWR): Groundwater depth in various monitoring wells compared to the historic average at that well. For reference only.

The water quality risk is based on depth-filtered, de-clustered water quality results from public and domestic supply wells. The methodology used to determine water quality risk is outlined here. For more information about the SAFER program, please email SAFER@waterboards.ca.gov. For technical questions or feedback on the map please email GAMA@waterboards.ca.gov.

This is the feature layer. The map image layer is available here.The aquifer risk map is being developed to fulfill requirements of SB-200 and is intended to help prioritize areas where domestic wells and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the risk map is to be made available to the public and is to be updated annually starting January 1, 2021. This layer is part of the 2022 Aquifer Risk Map. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding.This layer displays data available at the census block group level. Water quality risk data from the 2022 Aquifer Risk Map is summarized by block group by displaying the number of domestic wells and state small water systems per block group in "high-risk" areas. Drought risk scores for rural/self-supplied communities from the Department of Water Resources are displayed (drought risk scores range from 0-100, with 100 representing the highest drought risk and 0 representing the lowest drought risk). Demographic information including Median Household Income (from 2018 ACS) and race/ethnicity data per block group is also displayed.

The Aquifer Risk Map is developed to fulfill requirements of SB-200 (Monning, 2019) and is intended to help prioritize areas where domestic wells and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the map is made available to the public and updated annually starting January 1, 2021. This layer is part of the 2023 Aquifer Risk Map. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding.This layer contains summarized water quality risk per square mile section for nitrate.The water quality risk is based on depth-filtered, de-clustered water quality results from public and domestic supply wells. To provide comments or feedback on this map, please email SAFER@waterboards.ca.gov or Emily.Houlihan@Waterboards.ca.gov.

The Aquifer Risk Map is developed to fulfill requirements of SB-200 (Monning, 2019) and is intended to help prioritize areas where domestic wells and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the map is made available to the public and updated annually starting January 1, 2021. This layer is part of the 2023 Aquifer Risk Map. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding.

This layer displays the approximate location of state small water systems (location data accessed October 2022 from the Division of Drinking Water) joined with water quality risk estimates from the 2023 Aquifer Risk Map.

The water quality risk is based on depth-filtered, de-clustered water quality results from public and domestic supply wells. To provide comments or feedback on this map, please email SAFER@waterboards.ca.gov or GAMA@Waterboards.ca.gov.

This study, completed by the U.S. Geological Survey (USGS) in cooperation with the Pennsylvania Department of Conservation and Natural Resources, Bureau of Topographic and Geologic Survey (T&GS), provides estimates of ground-water recharge for watersheds throughout Pennsylvania computed by use of two automated streamflow-hydrograph-analysis methods--PART and RORA. The PART computer program uses a hydrograph-separation technique to divide the streamflow hydrograph into components of direct runoff and base flow. Base flow can be a useful approximation of recharge if losses and interbasin transfers of ground water are minimal. The RORA computer program uses a recession-curve displacement technique to estimate ground-water recharge from each storm period indicated on the streamflow hydrograph.

Recharge estimates were made using streamflow records collected during 1885-2001 from 197 active and inactive streamflow-gaging stations in Pennsylvania where streamflow is relatively unaffected by regulation. Estimates of mean-annual recharge in Pennsylvania computed by the use of PART ranged from 5.8 to 26.6 inches; estimates from RORA ranged from 7.7 to 29.3 inches. Estimates from the RORA program were about 2 inches greater than those derived from the PART program.

Mean-monthly recharge was computed from the RORA program and was reported as a percentage of mean-annual recharge. On the basis of this analysis, the major ground-water recharge period in Pennsylvania typically is November through May; the greatest monthly recharge typically occurs in March.

[Summary provided by the USGS.]

The aquifer risk map is being developed to fulfill requirements of SB-200 and is intended to help prioritize areas where domestic wells and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the risk map is to be made available to the public and is to be updated annually starting January 1, 2021. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding.This layer contains several reference boundaries, including:California County boundariesCensus Tract boundaries with Disadvantaged Community Status (based on Median Household Income)California Assembly District boundariesCalifornia Senate District boundariesCalifornia Regional Water Board boundariesCV-SALTS priority groundwater basinsGroundwater Sustainability Agency boundariesGroundwater Unit boundaries

This layer was created for use in the Aquifer Risk Map to provide summarized water quality risk data for domestic wells and state small water systems per census area (tract and block group). For more detailed descriptions of all data layers within the Aquifer Risk Map, refer to the Aquifer Risk Map Web Map page.This layer contains census block group and tract boundaries joined with:-2021 ACS Median Household Income (table B19013 column 001E - estimates only)-2021 ACS Race/Ethnicity data (table B03002 multiple columns - estimates only)-2023 Aquifer Risk Map count of total and high risk domestic wells and state small water systems per census area

This is the map image layer. The feature layer is available here.The aquifer risk map is being developed to fulfill requirements of SB-200 and is intended to help prioritize areas where domestic wells and state small water systems may be accessing groundwater that does not meet primary drinking water standards (maximum contaminant level or MCL). In accordance with SB-200, the risk map is to be made available to the public and is to be updated annually starting January 1, 2021. This layer is part of the 2022 Aquifer Risk Map. The Fund Expenditure Plan states the risk map will be used by Water Boards staff to help prioritize areas for available SAFER funding.This layer shows domestic well density. The domestic well density per square mile is based on "domestic" well completion records from the Department of Water Resources Online System for Well Completion Reports, excluding records with a drilling date prior to 1970 and excluding records labeled as "destruction".