Assessment of Fire Effect on Water Balance Components under Different Land Uses in Central Zagros Rangelands, Iran

Fire occurrence may lead to a significant impact in many terrestrial ecosystems. This basin scale study attempted to evaluate the effects of fire on the water balance components in the Central Zagros, Iran in 2019. Two modeling frameworks including WetSpass-M spatial model and Bayesian Belief Networks were used to investigate the effect of fire on the amount of runoff, groundwater recharge and evapotranspiration. The first part of the study was water balance simulation at a monthly scale. In addition, the Bayesian belief networks were applied to explore and understand key issues effect on water balance after the fire. Calibration and validation of the WetSpass-M model were performed without considering the effect of fire (2000-2014) and then, the model was run again for the fire scenario by reducing manning roughness coefficient and increasing the θ coefficient. Subsequently, the water balance components of each class, i.e. sparse forest, sparse, semi- dense and dense rangelands were calculated. The percentage of changes in the water balance components was used for comparison. Calibration and validation were performed before finalizing the simulation. A Nash-Sutcliff coefficient of 0.61 and 0.58 was obtained during the calibration and validation, respectively. The analysis of the water balance components results depicted that fire had increased the amount of runoff (13.5%) and it has reduced the amount of groundwater recharge (2.52%) and reduced the amount of actual evaporation (4.45%). The highest increase in runoff belonged to the sparse forest (15.8%), followed by dense (14.5%), semi- dense (13.7%) and sparse rangelands (12.5%), respectively. The results showed that runoff acts as the major factor affecting soil water balance (50.36%) followed by land use (10.49%), and infiltration (10.12%).