Projects by Discipline / Environmental Science

Impact Study of Wildfire in the Santa Fe Watershed

 The Santa Fe River watershed is located east of Santa Fe, New Mexico, in the Pecos Wilderness. The watershed contains the city’s two reservoirs and provides about 40 percent of the city's drinking water supply. Closed to public access in 1932, the watershed is mostly uninhabited and encompasses approximately 17,000 acres of dense ponderosa pine, spruce, and fir forests.

The Cerro Grande fire in 2000 was a wake-up call to officials from the U.S. Forest Service and the City of Santa Fe. They were concerned about the potential consequences of a wildfire within the Santa Fe municipal watershed and troubled by the unmanaged forest conditions there. If a fire swept the watershed, the resulting loss of vegetation could lead to flooding.  Public safety issues were primary, but flooding would also carry soil and other debris to the city’s water supply reservoirs, affecting their water quality and storage capacity.

 Hydrosphere was hired by the U.S. Forest Service to analyze the impacts to water quality, runoff volumes, erosion and sedimentation from a variety of forest thinning methods over different locations in the watershed. A “no-action” scenario was also included in the analysis, which looked at the consequences of a stand-replacement wildfire in the watershed.

• Hydrosphere's role in the project included:
• Rainfall/runoff modeling for thinned, disturbed and burned areas
• Water quality assessment
• Identification of areas where erosive soils and potentially high fire intensity coincide
• Investigation of changes in flow regime over time after a stand replacement fire
• Erosion and sedimentation analysis
• Flood plain mapping
• Analysis of reservoir operations and impacts

Our analysis showed that due to biomass combustion, hydrophobic soils and an apparent trend for greater storm intensity over burned areas immediately after a fire, peak flows in the Santa Fe River would likely increase three orders of magnitude the first year after a catastrophic wildfire. Sediment yields would also dramatically increase during the first year. For instance, one scenario suggested that sediment yields averaging 15 percent of burned mineral soil to a depth of 4 cm would be moved out of the basin and into the city’s reservoirs.

The analysis results were presented in an Environmental Impact Statement (EIS) prepared by the Forest Service as part of a watershed management plan. With the approval of the EIS, the Forest Service is now in the process of implementing forest management activities to reduce fuel loads, which in turn will reduce the risk of an uncontrolled wildfire in the watershed.  

Read more about Hydrosphere's wildfire services.