Public Water Systems and populations receiving surface drinking water supply from National Forest System lands: 2nd edition

These data are a summary of Public Water Systems (PWS) and populations receiving surface drinking water supply from National Forest System (NFS) lands managed by the USDA Forest Service in the conterminous United States (CONUS). The PWS in these data include only those receiving some portion of their surface water supply from NFS lands, either through the intakes they manage or through water purchases from other PWS that receive some portion of their surface water supply from NFS lands. To generate these data, unique model input databases were created for each of the 172 NFS units in the CONUS and water supply from each NFS unit and other non-NFS lands were simulated and tracked through the river network using the Water Supply and Stress Index (WaSSI) model while including inter-basin transfers (IBTs). Water supply outputs were then linked to the Environmental Protection Agency’s Safe Drinking Water Information System (SDWIS) database of public surface drinking water intakes. When a PWS had more than one intake, the percentage of the total surface drinking water originating on the individual NFS unit for the public water system was calculated from the total available water and the total water from the individual NFS unit across all intakes for the public water system. In addition to results at the NFS unit level, Watershed Boundary Dataset (WBD) Watershed 12-digit Hydrologic Unit Code (HUC12) subwatersheds that contain NFS units and provide surface drinking water supply to PWSs are identified and summarized. Purchasing PWS in the SDWIS were included for those PWS that had an associated selling PWS with surface water intakes that received some portion of their water from NFS lands, and the purchasing PWSs did not have their own surface water intakes and therefore would already be in the database. Also included are results aggregated across all NFS units in each Forest Service Region.
The objectives of this analysis were to (1) estimate how much fresh surface water supply originates from NFS lands, and (2) estimate how many people and which communities receive this fresh surface water supply.
This data publication (second edition) was published on 03/31/2022 and supersedes that of https://doi.org/10.2737/RDS-2021-0098 (first edition). Changes to the original version include the following. The first edition included information on PWS intake facilities whose PWS-level primary water source was surface water or groundwater under the influence of surface water but whose facility-level water type was groundwater or groundwater purchased. Those facilities whose facility-level water type was groundwater or groundwater purchased were removed from this second edition. Secondly, this new edition includes three additional tables: All_NFS_Purchased.csv, FS_Region_Purchased.csv, and NFS_Unit_Purchased.csv. These tables provide additional information for those PWSs in the SDWIS that had an associated selling PWS with surface water intakes that received some portion of their water from NFS lands, and the purchasing PWSs did not have their own surface water intakes and therefore would already be in the database. On 07/22/2022 this second edition was updated to include two additional tables (NFS_Unit_HUC12.csv and NFS_Unit_HUC12_PWS.csv) that provide additional information about PWSs that receive surface drinking water supply from particular HUC12 subwatersheds containing NFS units. Also added were geospatial files containing the HUC12 subwatershed boundaries corresponding to those referenced in the new tables. On 09/20/2022 the metadata for this second edition was updated to include reference to the newly published General Technical Report by Liu et al. (2022). For more information about these data see Liu et al. (2022).