The U.S. Forest Service released a new report that quantifies the role of national forest system lands (NFS) and other forested lands in providing the surface drinking water supply in the conterminous United States (CONUS). While 89% of the forested lands in the 11 western states are owned by the federal government, most of the forested land in the east is privately owned—for example, in the South 90% of forested land is owned by state and local governments, corporations, families, and other private entities. The report looks not just at direct water flows from these forested lands but also includes estimates of interbasin transfers to assess the contribution of water originating on forested lands to public drinking water supplies more accurately. This is the first national-scale study to account for interbasin transfers in the linkage between water originating on NFS and other forested lands and the public water systems (PWSs) and populations they serve

“This study provides a systematic accounting of NFS and other forested lands for surface drinking water supply,” the authors write. “Our results can aid water resource and forest managers in developing integrated watershed management plans at a time when climate change, population growth, and land development threaten water supplies.”

Although NFS and other forested lands make up 28.7% of the total CONUS land area, they provide 46.0 percent of the surface water supply. About 125.5 million people, or 38.9 percent of the total population in the CONUS in 2017, derived more than 10% of their surface drinking water supply from NFS and other forested lands from the intakes managed by their public water systems (PWSs), including those receiving water through interbasin transfers. Around 83.1 million people, or 25.7% of the total population in the CONUS, receive the majority (>50%) of their surface drinking water supply from NFS and other forested lands. In addition to those populations receiving surface drinking water supply from their local public surface drinking water intakes, 38.3 million people were served by PWSs that purchased surface drinking water from other PWSs deriving >10 percent of their surface drinking water supply from NFS and other forested lands.