Simulating Hydrologic Effects of Fire in a Small, Sub-alpine Watershed in New Mexico using AgES

Streamflow data before and after wildfire in a sub-alpine watershed in south-central New Mexico were used to calibrate a watershed model (AgES) for prefire and postfire conditions. Calibration results demonstrated that AgES adequately simulated both prefire and postfire hydrology in a mixed-conifer, high-gradient watershed. AgES accurately simulated the dramatic change in streamflow response to precipitation after fire, including a smaller threshold precipitation event to induce runoff. AgES closely simulated daily streamflow throughout the study period, with slight overestimation in the prefire period (Oct 2007 to Oct 2011, 1.3% bias, 0.91 Nash-Sutcliffe efficiency [NSE]) and slight underestimation in the postfire period (and postfire (Oct 2013 to Oct 2017, -6.7% bias, 0.62 NSE). Although each 4-year model period had nearly identical precipitation input values, annual runoff increased by 170% in the postfire scenario when compared to the prefire scenario. Appropriate soil and vegetation parameters were modified by the autocalibration process to represent the effects of fire: soil depression storage was increased, infiltration capacity was reduced, field capacity was reduced, and transpiration was reduced. AgES demonstrated skill in simulating daily streamflow response in sub-alpine watershed and in simulating the hydrologic response to fire.