California's Groundwater Update 2020 (Bulletin 118)

This zipped file includes 3 excel files and 2 ArcGIS shapefiles. Statewide_Production_WCRs_1977-2018.xlsx is a filtered summary of all production wells from the list of Well Completion Reports. This summary was cleaned up to only include wells with a known depth. Any well with an erroneous spatial location was removed from the analysis (read more about this in the Bulletin 118 Appendix C Methods and Assumptions). The Statewide_Production_WCRs_1977-2018.xlsx dataset was used to create Figures 3-6, 3-7, 3-8, 3-11, 3-12, 3-13, and 3-14, as well as Tables 3-19, 3-20, and 3-21. MTRS_with_Domestic_Well_Counts.xlsx is a summary of the MTRS_Domestic_Well_Counts.shp polygon shapefile. Polygon sections are only included if the domestic well count within each section is 1 or greater. MTRS_with_Irrigation_Well_Counts.xlsx is a summary of the MTRS_Irrigation_Well_Counts.shp polygon shapefile. Polygon sections are only included if the irrigation well count within each section is 1 or greater. These datasets were compiled using the Production Well information, but summarized by MTRS instead of by individual wells, to better show well density for Figures 3-9 and 3-10. MTRS = Meridian/Township/Range/Section

The CalGW Update 2020 — GW Level Monitoring Wells (2015–2018) dataset was compiled from groundwater-level monitoring program information from DWR’s California Statewide Groundwater Elevation Monitoring (CASGEM) and the U.S. Geological Survey’s (USGS’s) National Water Information System (NWIS). Privately collected and locally maintained groundwater-level data were not included in this report. Groundwater-level monitoring information represents data from those wells that were measured from January 1, 2015, through December 31, 2018, and have had data entered into DWR’s CASGEM or USGS’s NWIS online databases as of August 28, 2019. This dataset includes an excel spreadsheet and shapefile which were used to create Tables 5-1, 5-2, 5-3, 5-4, and 5-5, and Figures 5-1, 5-2, 5-3, 5-4, and 5-5.

The CalGW Update 2020 — GW Quality Monitoring Stations dataset is based on data accessed in the State Water Resources Control Board’s Groundwater Ambient Monitoring and Assessment (GAMA). The GAMA database was queried in July 2020 for all groundwater stations that fall within the boundaries of DWR’s hydrologic regions to create a statewide dataset of groundwater quality monitoring stations. This dataset includes an excel spreadsheet and shapefile, which were used to create Table 5-6, and Figure 5-6.

The CalGW Update 2020 — Land Subsidence Continuous Global Positioning System (CGPS) Stations dataset was created by merging information from two different sources that publicly host CGPS stations data. The two entities are the Scripts Orbit and Permanent Array Center (SOPAC) and Unavco, Inc. Active CGPS stations in California were queried from both sources and were combined to create a statewide layer. This dataset includes an excel spreadsheet and six shapefiles. These were used to create Table 5-7 and Figure 5-7.

The CalGW Update 2020 — Stream Gages in California dataset is based on the following publicly available sources: California Data Exchange Center, USGS’s Water Data website, and the National Weather Service’s Hydrometeorological Automated Data System. Each source was queried for all stream gages in California. The results from the three queries were combined into one comprehensive, statewide dataset in both excel and shapefile format. Some stream gage stations were found to be duplicated across one or more of these databases. In those cases, the station was reduced to a single record in the new dataset produced for CalGW Update 2020. This dataset was used to create Table 5-8 and Figure 5-8.

This zipped dataset includes an excel file and an ArcGIS shapefile for the Mann-Kendall Groundwater Level Trends between 1998 and 2018. This dataset was used to create Figure 6-5. Groundwater levels at selected wells were analyzed using the Mann-Kendall non-parametric test to determine whether a statistically significant trend (declining trend, no trend, or increasing trends in groundwater levels) was present during the specified time period. A 21-year analysis period (1998 through 2018) was selected. The data used came only from wells that have at least 10 years of data within the 1998–2018 time period. This period includes the dry periods of 2001–2002, 2007–2009, and 2012–2016; and wet periods of 1998–2000, 2005–2006, 2011, and 2017 that were as defined by water year types according to Sacramento River and San Joaquin River indices. If a statistically significant trend was observed, the Theil-Sen method was used to calculate the estimated slope of the trend line to quantify the decline or increase.

The CalGW Update 2020 - GW Level Change (2010-2018) dataset includes an excel spreadsheet and shapefile, which summarize the total groundwater level changes measured at groundwater monitoring wells statewide for the eight-year summary 2010-2018. This dataset was used in conjunction with the CalGW Update 2020 - GW Level Change (2015-2018) dataset to create Table 6-1. This dataset was also used to create Figure 6-7.

The CalGW Update 2020 - GW Level Change (2015-2018) dataset includes an excel spreadsheet and shapefile, which summarize the total groundwater level changes measured at groundwater monitoring wells statewide for the three-year summary 2015-2018. This dataset was used in conjunction with the CalGW Update 2020 - GW Level Change (2010-2018) dataset to create Table 6-1. This dataset was also used to create Figure 6-6.

The CalGW Update 2020 - Land Subsidence Vertical Displacement Points dataset summarizes the vertical displacement measured at continuous GPS sites. The vertical displacement (in feet) recorded at continuous GPS stations through December 31, 2018, shows the total vertical displacement for each station, from the individual record start dates until December 31, 2018. To filter out high frequency noise, a 31-day rolling average was applied to the timeseries data. The averaged vertical displacement between the individual record start dates until December 31, 2018, was calculated for each station. This shapefile was used along with InSAR data to create Figure 6-19.

The CalGW Update 2020 - Land Subsidence Vertical Displacement Polygon dataset is a shapefile based on the InSAR found at this open data link: https://gis.water.ca.gov/arcgisimg/rest/services/SAR/Vertical_Displacement_TRE_ALTAMIRA_v2019_Total_Since_20150613_20180601/ImageServer The raster layer for total subsidence from June 13, 2015, to June 1, 2018, was classified to 0.25-foot intervals and converted to a polygon layer. The resulting subsidence polygon layer was intersected with the hydrologic regions and the area was calculated for each subsidence interval and hydrologic region. This dataset is used to create Table 6-12.

The CalGW Update 2020 - GW Change in Storage (2006-2018) is a zip file containing 1 shapefile and 1 excel file. The shapefile, Reporting_Area_CV.shp, was used for the Bulletin 118 analysis for change in stored groundwater and shows the areas per Central Valley Hydrologic Region that are within a reporting area and outside of a reporting area. Reporting Area was found by creating a polygon around the extents of monitoring wells in DWR's Enterprise Water Management Database. The area in acres was force-calculated using the Shape_Area (in square meters) multiplied by 0.000247105, which is the square meters to acres conversion. This shapefile was used to create Figure 6-8 and Table 6-2. The excel file, Chap6_Statewide_Change_In_Storage, is a compiled dataset based on a series of queries from the DWR Enterprise Water Management Database. Annual changes in stored groundwater were estimated using annual spring groundwater level data from wells within the Central Valley. For each year from 2010 through 2018, an annual dataset of groundwater elevation points in the Central Valley was created. Using the annual spring groundwater level datasets, annual change-point datasets were created by calculating the difference in groundwater elevation at “like points” (wells measured during both monitoring periods) over each one-year time period. The calculated elevation difference at each of these monitoring points represents the total change in groundwater elevation that occurred between the two monitoring periods at that well. Eight change-point datasets were created, representing the groundwater level changes from 2010 to 2011, 2011 to 2012, 2012 to 2013, 2013 to 2014, 2014 to 2015, 2015 to 2016, 2016 to 2017, and 2017 to 2018. Each annual change-point dataset was then used to construct a triangulated irregular network “change surface” with GIS tools. Each change surface is an interpolated three-dimensional representation of the total volume of space between early and late groundwater elevation values for each time period analyzed. To obtain the change in stored groundwater estimates, the total volumes estimated from each annual change surface was multiplied by the low and high specific-yield values (0.07 and 0.17, respectively). This dataset was used to create Table 6-3, and Figures 6-9, 6-10, 6-11, and 6-12.

The CalGW Update 2020 - GW Quality Conditions (2009-2018) dataset assesses statewide groundwater conditions based on a query of the GAMA database (provided by the State Water Resources Control Board). The original query searched GAMA for the maximum groundwater quality sampling result for each chemical with an established maximum contaminant level (MCL) or secondary maximum contaminant level (SMCL) from January 1, 2009, through December 31, 2018. All stations tagged as monitoring wells for permitted discharge sites, active contaminant investigations, or active cleanup sites were omitted from the dataset. The final queried dataset included more than 5 million records, more than can fit into an Excel spreadsheet, so this dataset was created summarizing the top 5 chemicals. The top 5 chemicals were determined by the highest percentage of stations that recorded a maximum value above the MCL or SMCL. This dataset includes an excel spreadsheet and its associated shapefile. The summary includes the status of each measurement, which fall into one of three categories for each chemical with an established MCL or SMCL: High (maximum recorded value above the MCL or SMCL); Medium (maximum recorded value between half the MCL or SMCL and the MCL or SMCL); Low (maximum recorded values less than half of the MCL or SMCL). This dataset was used to create Tables 6-4, 6-5, 6-7, 6-8, 6-9, 6-10, and 6-11. This dataset was used to create Figures 6-13, 6-14, 6-15, 6-16, 6-17, and 6-18.

The CalGW Update 2020 – Depth to Groundwater (Spring 2018) dataset includes two shapefiles and one raster, which summarize the depth to groundwater in Spring 2018 using points, contours, and a raster. The dataset was queried from the DWR Enterprise Water Management Database. The query selected a single measurement closest to March 15 for each well based on all measurements collected from January 1, 2018, through May 31, 2018. Additional filtering eliminated measurements from wells with quality codes indicating pumping or flowing water. This dataset was used to create Figures 6-2 and 6-3.

The CalGW Update 2020 – Groundwater Elevation (Spring 2018) dataset includes a shapefile and a raster, which summarize the groundwater elevations in Spring 2018 using contours and a raster. The dataset was queried from the DWR Enterprise Water Management Database. The query selected a single measurement closest to March 15 for each well based on all measurements collected from January 1, 2018, through May 31, 2018. Additional filtering eliminated measurements from wells with quality codes indicating pumping or flowing water. This dataset was used to create Figure 6-4.