American water utilities spend millions of dollars protecting and improving their source water to ensure the delivery of safe drinking water. Knowing the value of this green infrastructure helps communities and land managers better steward the watersheds we rely on and helps the Forest Service better engage with stakeholders in watershed protection. RMRS scientists partnered with the American Water Works Association (AWWA) to measure the effect of forest cover and development on water treatment costs.
The AWWA surveyed member utilities in highly forested regions of the United States that depend on surface water for most of their water supply. For each of the utilities in the dataset, the team mapped the watershed that delivers their raw water and measured land use characteristics like forest cover, development, and agricultural activities in the watershed.
The study found increasing forest cover is associated with lower levels of sediment at water intakes, and development and grazing are both associated with higher levels of sediment at water intakes. These findings are consistent with others in the literature that argue that one of the primary roles of forests and protected lands is to limit the presence of other land uses associated with poorer water quality. These improvements in water quality lead to real benefits to water users.
In the watersheds studied:
There was evidence of costs savings from both reduced sediment and reduced total organic carbon (TOC) in drinking water sources.
Increasing forest cover by 1 percent in the watershed decreases turbidity by about 3 percent.
Both development and grazing in the watershed increase turbidity. Increasing development by 1 percent in the watershed increases turbidity by about 3 percent.
Reducing sediment in the water by 1 percent reduces water treatment costs by 0.19 percent; reducing TOC in the water reduces water treatment costs by 0.46 percent.