Assessing the impacts of land use/land cover and climate change on surface runoff of a humid tropical river basin in Western Ghats, India

In this study, the impacts of changes in land use/ land cover (LULC) and climate on surface runoff are investigated in the Kadalundi river basin, Western Ghats, India. Land Change Modeller (LCM) was applied to project the future LULC scenarios in 2030 and 2050. Climate change scenarios of the future time period of near (2011-2040), mid (2041-2070), and far (2071-2099) were procured for Representative Concentration Pathway (RCP) 4.5 and 8.5 emission scenarios from five different general circulation models of coordinated regional downscaled experiment project. The 1988 and 2000 LULC were used for projection of 2014 LULC and validated with actual 2014 LULC. Further, 2000 and 2014 LULC were used for projection of 2030 LULC, and 2014 and 2030 LULC were used to project 2050 LULC. Changes in LULC from 2000 to 2050 are calculated using the transition matrix approach. The impacts of changes in LULC and climate on surface runoff are investigated by the Soil and Water Assessment Tool (SWAT) model. The results showed a decrease in forest and grassland and an increase in agriculture, and urban areas from 2000 to 2050, with an increase in the mean annual surface runoff. For climate change scenarios assessed, mean annual surface runoff in the near, mid, and far would be decreasing under both RCP 4.5 and 8.5 while RCP 8.5 showing more worse condition than RCP 4.5 in the future. The combined effects of changes in LULC and climate showed a decreasing trend in the surface runoff for the near and mid future. Furthermore, the projected results indicate that the surface runoff would be higher in both RCP scenarios during winter and summer; while the monsoon period largely demonstrates a reverse trend. The analysis of combined impacts reveals that the decreasing of surface runoff under RCP 4.5 and 8.5 would be higher in near compared to mid future.