Modelling Post-Fire Hydrologic Recovery in Snow Dominated Catchments in Colorado’s San Juan Mountains

Abstract:

Wildfires act as extreme disturbances to hydrologic systems with both immediate and long-term consequences. As wildfires increase in duration and frequency in the western U.S., water managers need predictive tools that appropriately represent the dynamic hydrologic environment to plan for current and future water needs. This study evaluates three paired catchment systems in Colorado’s San Juan Mountains located in and around burn scars from the West Fork Fire Complex (2013) and the 416 Fire (2018). A combination of ground-based observations, reanalysis data, and remotely sensed products are used to close surface water budgets for these systems and to calibrate and validate a monthly water balance model (MWBM) during post-fire years. Catchments from two different burn scars are evaluated to better understand both immediate post-fire effects (1-2 years) and longer-term recovery (6+ years) following burn. Preliminary results suggest that the most extreme water budget changes occur in the first few years after a burn event, followed by a period of slower recovery as vegetation is reestablished. To capture this recovery process in the MWBM, we also develop dynamic parameters for the MWBM for the study catchments by scaling selected parameters against MODIS-based vegetation products. By developing dynamic parameter sets, we hope to improve the skill of the MWBM in representing both short and longer-term post-fire recovery. Our methodology may be transferable to other burned catchments or modelling efforts that seek to represent changes following a hydrologic disturbance. Ultimately, understanding how hydrologic systems recover after extreme disturbances, like wildfire, may help water managers narrow the “cone of uncertainty” associated with water resource scenario planning.