Predictions of Land Use and Land Cover (LULC) and Runoff of the Teesta River Basin under Different Emission and Socioeconomic Scenarios

Abstract The Teesta basin, shared by Bangladesh and India, undergoes profound changes due to land use and land cover (LULC) dynamics combined with climate change, significantly impacting its water balance. This comprehensive study aims to analyze the combined effects of future LULC changes and climate change on basin runoff. Employing a cellular-automata model, we accurately predicted LULC for 2020 and projected scenarios for 2050 and 2080. We utilized the semi-distributed Soil Water Assessment Tool (SWAT) hydrological model for the base period (1995–2014) and two future periods: 2050s (2035–2064) and 2080s (2071–2100). SWAT model is forced by 8 General Circulation Models (GCMs) under two Socioeconomic Pathways (SSPs): SSP245 and SSP585. The study reveals notable LULC changes, with substantial increases in agricultural (0.49%) and settlement areas (1.67%) from 2000 to 2010, followed by changes from 2010 to 2020. The CA-Markov prediction indicates significant future increases in settlements and agricultural land by 2050 and 2080, coupled with reductions in forest, water, and snow cover. The calibrated and validated SWAT model effectively simulated discharge, yielding satisfactory results. Projected changes in discharge during the monsoon and winter periods were examined under different scenarios. Monsoon discharge is predicted to increase by 26–38% in the 2050s and 30–45% in the 2080s. Conversely, the winter/dry period may experience a decrease of 46–49% in the 2050s and 38% in the 2080s for SSP245 and SSP585 scenarios, respectively. Considering LULC changes to account, additional discharge increases during the monsoon are projected, with slight increases in the dry period during the 2050s and decreases during the 2080s. This study anticipates an increasing trend in peak flow during the monsoon and a declining trend in mean flow during winter without further upstream water control. Understanding and managing the combined effects of LULC changes and climate change on the hydrological dynamics of the basin is of utmost importance for sustainable water resource management in the region.