New Mexico Geological Society Annual Spring Meeting — Abstracts

A planned project by the City of Santa Fe and the United States Forest Service to thin a portion of the Pecos Wilderness Area in the upper Santa Fe municipal watershed involves prescribed fire by aerial ignition in the absence of mechanical treatments. These burn treatments are an attempt to decrease fuel loads that could lead to dangerous wildfires and also to increase soil water availability per tree. Careful study and monitoring of the impacts of the prescribed burns on water quality and quantity are planned during the course of the treatments. Watershed-scale response to these relatively new treatment methods are currently understudied. Pyrogenic carbon (PyC), a form of black carbon, is a byproduct of forest fires formed from the incomplete combustion of organic matter. It encompasses the carbonaceous component of fire-derived materials such as char, soot, and ash. PyC is studied due to its effect on contaminant transport, water quality, and the global carbon cycle. PyC has the ability to adsorb heavy metal contaminants, and can alter the transport and sequestration of these contaminants in post fire storms. Fires can also reduce understory vegetation and surface roughness, and may enhance hydrophobicity in burned soils. These short-term effects have the potential to increase water yields and change storm water runoff timing. We are monitoring dissolved and suspended total and organic carbon throughout the project, along with dissolved trace metals in the surface water of the Santa Fe River before, after, and during the upstream burn treatments. Also, we are analyzing the impacts of the treatments on water yield using stream flow gauge records. Current results are an analysis of the first year of baseline data ahead of the prescribed burn. All dissolved analytes were found in low or trace amounts or were not detected. Dissolved elements reflect the basin lithology mineral constituents, and decline in concentration during spring runoff. Dissolved carbon increased during the rising limb of snowmelt as it was first flushed through the system, but then declines through the spring and summer.