Quantifying the role of National Forest system lands in providing surface drinking water supply for the Southern United States
Forests and water are inextricably linked, and people are dependent on forested lands to provide clean, reliable water supplies for drinking and to support local economies. These water supplies are at risk of degradation from a growing population, continued conversion of forests to other land uses, and climate change. Given the variety of threats to surface water, it is important for forest managers to know how much of the drinking water supply originates in forests they manage and what populations and communities are served by that water. In this analysis, we used a hydrologic model, Water Supply Stress Index (WaSSI), and a database of surface water intakes to quantify the extent to which people depend on surface water from USDA Forest Service National Forest System (NFS) lands and State and private forest lands in the South. We computed the water yield for NFS lands in addition to other land cover types, and accumulated and tracked water from NFS and State and private forest lands through the river network. We then estimated the population served by water from NFS lands across the South using the U.S. Environmental Protection Agency’s Safe Drinking Water Act database of drinking water intakes. We estimated that NFS lands contributed 3.4 percent and State and private forest lands 32.4 percent of the approximately 900 million m3/year of total surface water supply in the region. Of the 6,724 public surface water intakes in the South, 1,541 intakes serving 19.0 million people receive some water from all NFS lands in and upstream of the 13 Southern States. Of the 1,541 intakes, 427 received more than 20 percent of their water from NFS lands and served 3.2 million people. Similarly, 6,188 intakes serving 48.7 million people receive some water from State and private forest lands. Of the 6,188 intakes, 3,143 received more than 20 percent of their water from State and private forest lands and served 29.0 million people. These results highlight the importance of southern forests in providing clean and dependable water supplies to downstream communities. While environmental and economic factors are likely to interact and cause changes in water availability and quality, forest conservation and proper management can help mitigate these effects.
National Forest System Drinking Water Supply Table (xls) 163 kb
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