WATERSHED-SCALE HYDROLOGIC EFFECTS OF LARGE WILDFIRES IN THE SOUTHWESTERN USA

Recent increases in large wildfires in southwestern North America have been well documented and their effects at the point, hillslope, and small watershed scales have been extensively examined. However, less is known about the hydrologic effects of wildfires at the scale of large watersheds. In the Jemez watershed of northern New Mexico, we hypothesized that increased runoff and peak flows would be observed following two large wildfires that burned 150 km² in 2011 and 2013, respectively. To test this hypothesis we regressed peak snow water equivalent, precipitation, temperature, and presence of fire impacts against discharge metrics. In this way we assessed whether fire effects were associated with altered hydrologic response, after controlling for climatic effects. Counterintuitively we failed to uncover any effects of fire on total discharge or peak flows measured at the outlet of the Jemez watershed. However, after controlling for climate, low flows were significantly lower in fire-affected years than in years when no large wildfire occurred. These results suggest reduced groundwater recharge in headwaters in association with years impacted by large wildfires; however, further research is underway to better understand the mechanism and extent of watershed-scale hydrologic impacts of large wildfires.