Impact of Wildfire-related Compound extreme events on hydrology - A case study of Simlipal National Park, India

In recent decades, the frequency of wildfire incidents has increased worldwide. These ecological disasters, often triggered by natural and/or anthropogenic factors, can have long-lasting effects on the hydrologic systems, ecosystems, environment, and biodiversity. They alter the land use conditions and thereby increase the chances of floods, soil and nutrient loss, and groundwater deficit. Wildfires are not uncommon in India, whose total forest cover exceeds 0.7 million km², about 21.67% of its total geographical area.  This study is motivated to identify the extreme events whose concurrence has led to forest fires in different parts of the Indian peninsula and to assess their impact on hydrological processes in river basins. The latter is demonstrated by analyzing a recent (Feb 2021) fire event in Simlipal National Park (Odisha). The park is a part of the UNESCO world network of biosphere reserves, and a major part of it lies in Budhabalanaga river basin. The wildfire event was preceded by a prolonged dry spell and a below-average monsoon in the year 2020. Two widely used hydrological models, SWAT (Soil Water Assessment Tool) and HEC-HMS are considered for simulating streamflows in the study area. The models are calibrated and validated using a variety of statistical performance measures. Furthermore, hydrological processes in the study area are simulated, corresponding to two different post-wildfire scenarios (optimistic and non-optimistic). A significant rise in streamflow is observed in both cases, indicating the possibility of flash floods in the downstream areas. It is concluded that the conjunctive use of models for wildfire prediction and hydrological simulation provides information to policize better fire risk mitigation strategies.