Investigating the influence of future landuse and climate change on hydrological regime of a humid tropical river basin

Landuse landcover (LULC) and climate change have significant hydrological impacts, especially in humid tropical regions. Cautious planning and development based on early preparedness can result in LULC patterns that may improve the well-being of human beings and ecosystem. This demands significant knowledge related to the climatic and hydrological variables. In this study, the impact of future climate and LULC change of a humid tropical catchment Periyar river basin (PRB) in the Western Ghats, India, is investigated using the Soil and Water Assessment Tool (SWAT). The study critically evaluates the individual and combined impacts of LULC and climate change on water balance components including precipitation, surface runoff, evapotranspiration, soil water storage, percolation, base flow, and lateral flow. The future LULC maps are projected to 2030, 2050, 2075, and 2100 using the past data with the help of the Cellular Automata-Markov transition matrix. LULC change indicated an increased urbanization and cropland, whereas a decreased forests and plantations in future. For future climate change impact assessment, ensemble of five global circulation models with RCP 4.5 and RCP 8.5 scenarios is considered. The results suggest climate change impact is dominant over LULC change in the near (2011-2040) and mid (2041-2070) future, whereas vice-versa in the far (2071-2100) future. The quantitative assessment of spatial and temporal variation in hydrological components append insights to the hydrological processes. The results can further add value to studies related to irrigation requirement, groundwater recharge, crop water demand, soil permeability and integrated water resource management. Furthermore, the current modeling framework can be implemented in other humid tropical river basins to understand the hydrological regime changes aiming effective water resources and environmental management.