Tyler D. Johnson, United States Geological Survey Kenneth Belitz, United States Geological Survey 2019 Raster Digital Data Set Reston, VA U.S. Geological Survey https://doi.org/10.5066/P9FSLU3B Tyler D. Johnson Kenneth Belitz Melissa A. Lombard 201910 publication Science of The Total Environment vol. 687 n/a Elsevier BV ppg. 1261-1273 https://doi.org/10.1016/j.scitotenv.2019.06.036 The 1990 census was the last nationally consistent survey of a home’s source of water, and has not been surveyed since. The associated larger work presents a method for projecting the population dependent on domestic wells for years after 1990, using information from the 1990 census along with population data from subsequent censuses. The method is based on the “domestic ratio” at the census block-group level, defined here as the number of households dependent on domestic wells divided by the total population. Analysis of 1990 data (>220,000 block-groups) indicates that the domestic ratio is a function of the household density. As household density increases, the domestic ratio decreases, once a household density threshold is met. The 1990 data were used to develop a relationship between household density and the domestic ratio. The fitted model, along with household density data from 2000 and 2010, was used to estimate domestic ratios for each decadal year. In turn, the number of households dependent on domestic wells was estimated at the block-group level for 2000 and 2010. High-resolution census-block population data were used to downscale and refine the spatial distribution of domestic-well usage and to convert the data into population numbers. The results are aggregated to 1km x 1km pixels and presented in two datasets for each decadal year: a BGM (Block Group Method) dataset and an REM (Road Enhanced Method) dataset. This dataset is an estimation of the location and population served by domestic wells in the contiguous United States for 2010. The purpose of this report is to provide datasets than can be used to estimate the location of domestic wells in the contiguous United States and the population being served for the year 2010. This dataset is a companion to the 1990 and 2000 datasets of the same topic. 20100101 20101231 ground condition Complete Not planned -127.8904 -65.3344 51.5819 22.8719 Alexandria Digital Library Feature Type Thesaurus census areas domestic well CDF cumulative distribution function data-binning private well water use USGS Thesaurus drinking water use USGS Metadata Identifier USGS:5c8c32afe4b093882452a025 Common geographic areas United States None. Please see 'Distribution Info' for details. None. Tyler Johnson PACIFIC REGION mailing and physical

4165 Spruance Road

San Diego CA 92101-0821 United States 619-225-6137 tyjohns@usgs.gov Environment as of Metadata Creation: Microsoft [Unknown] Version 6.2 (Build 9200) ; Esri ArcGIS 10.6.1 (Build 9270) Service Pack N/A (Build N/A) No formal attribute accuracy tests were conducted. No formal logical accuracy tests were conducted. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. A formal accuracy assessment of the horizontal positional information in the data set has not been conducted. This map product is most appropriately used for block-group sized or larger analysis. A formal accuracy assessment of the vertical positional information in the data set has either not been conducted, or is not applicable. Manson, S., Schroeder, J., Van Riper, D., and Ruggles, S. 2017 Vector Digital Data Set Minneapolis, MN National Historical Geographic Information System Manson, S., Schroeder, J., Van Riper, D., and Ruggles, S., 2017. IPUMS National Historical Geographic Information System: Version 12.0 [Database]. Minneapolis: University of Minnesota. 2017. http://doi.org/10.18128/D050.V12.0 http://doi.org/10.18128/D050.V12.0 Digital and/or Hardcopy Resources 19900101 19901231 ground condition Source Input 1 Source of water data from 1990 Census, block-groups, used for both the BGM and REM maps. Manson, S., Schroeder, J., Van Riper, D., and Ruggles, S. 2017 Vector Digital Data Set Minneapolis, MN National Historical Geographic Information System Manson, S., Schroeder, J., Van Riper, D., and Ruggles, S., 2017. IPUMS National Historical Geographic Information System: Version 12.0 [Database]. Minneapolis: University of Minnesota. 2017. http://doi.org/10.18128/D050.V12.0 http://doi.org/10.18128/D050.V12.0 Digital and/or Hardcopy Resources 20100101 20101231 ground condition Source Input 2 The data source provided the census-block scale polygons and the population data. Manson, S., Schroeder, J., Van Riper, D., and Ruggles, S. 2010 vector digital data Minneapolis, MN National Historical Geographic Information System Manson, S., Schroeder, J., Van Riper, D., and Ruggles, S., 2017. IPUMS National Historical Geographic Information System: Version 12.0 [Database]. Minneapolis: University of Minnesota. 2017. http://doi.org/10.18128/D050.V12.0 http://doi.org/10.18128/D050.V12.0 Digital and/or Hardcopy 20100101 20101231 publication date Source Input 3 Census block-group polygon boundaries for 2000. The Source Input 1 dataset consists of U.S. Census block-groups and associated data downloaded from the National Historical Geographic Information System (Manson et al. 2017) for use in a GIS. The data is from the 1990 Census Summary Tape File 3 tabular data joined to generalized block-group polygons using the “COMID”. The primary Census question used was question code H023 which asks for Source of Water. (http://www.census.gov/history/www/through_the_decades/index_of_questions/1990_housing.html) Possible responses to the survey question included: Public system or private company, individual well, or some other source. Individual wells included wells that were drilled or dug. The number of housing units using an individual well (drilled or dug) was the value used in this report. The ratio of households using domestic wells compared to other sources of water was calculated and termed the "domestic ratio". The domestic ratio (DR) was calculated for each block-group. The number of all households within a block-group divided by the area of the block-group was also calculated and termed the "household density" (HD). These two variables were analyzed and a relationship was built as outlined in the larger work citation. 20160205 Due to changes in census boundaries between years some considerations were necessary. Census boundaries change each decade: splitting, merging, or changing shape. No attempt was made to adjust the boundaries. Instead, the 1990 block-group polygons and the 2010 block-group polygons (Source Input 3) were merged together (“unioned” in GIS terminology) forming new polygons, appending all of their original HD and DR attributes. As a result, the polygons in the newly merged dataset will have three values each: a DR and HD for 1990 and a HD for 2010. Each polygon was then processed through an equation or the logic table independently to determine the resultant DR. See larger work citation for the equation and the logic table. Once a domestic ratio was estimated for each block-group or partial block-group, it was multiplied by the number of people in that block-group. See Process Step 3 20190215 Source Input 2 is the census-block data identifying population. The census-block data indicates whether a census block is populated or not based upon the 2001 decadal census. The data were downloaded from the National Historical Geographic Information System (Manson et al. 2017) for use in a GIS. A census block was considered populated if it contained population in the “Persons” field (source code NP1), or if it contained population in the “Households” field (source code NP3). The census-block data was used along with the estimated domestic ratio for 2000 (Process Step 2) to estimate population by multiplying the domestic ratio of a block-group by the population in the block-group. The total number of people being served by domestic wells within a block group were divided by the total number of 100 meter square pixels in the block-group. Due to shifting and changing census boundaries, census blocks can be split by two different block-groups and potentially different domestic ratios. Therefore, the mean pixel value was determined within each census block as an area-weighted average. The weighted average for each census block was then divided by the total number of pixels within the census block. This created a dataset where each pixel represents a population served by domestic wells. The results were aggregated to a pixel size of 1km by 1km and represent the number of people served by domestic wells per square km. 20190215 Raster Grid Cell 2904 4615 1 Albers Conical Equal Area 29.5 45.5 -96.0 23.0 0.0 0.0 row and column 1000.0 1000.0 meters North_American_Datum_1983 GRS 1980 6378137.0 298.2572221010042 Attribute Table Table containing attribute information associated with the data set. Producer defined Value The value represents the number of people served by domestic wells within each 1 km x 1 km pixel. U.S. Geological Survey 0 4782.49 number of individuals The entity and attribute information provided here describes the tabular data associated with the data set. Please review the detailed descriptions that are provided (the individual attribute descriptions) for information on the values that appear as fields/table entries of the data set. The entity and attribute information was generated by the individual and/or agency identified as the originator of the data set. Please review the rest of the metadata record for additional details and information. U.S. Geological Survey - ScienceBase U.S. Geological Survey - ScienceBase mailing and physical

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Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of these data, software, or related materials. The use of firm, trade, or brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. The names mentioned in this document may be trademarks or registered trademarks of their respective trademark owners. Raster Digital Data Set ArcGIS 10.5 ESRI File Geodatabase Raster This WinZip file contains the file geodatabase https://doi:10.5066/P9FSLU3B None. No fees are applicable for obtaining the data set. 20200826 Tyler Johnson U.S. Geological Survey Geographer mailing and physical

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San Diego CA 92101-0821 United States 619-225-6137 619-225-6101 tyjohns@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 local time