Analysis of  Uncertainty Due to Climate Change Using REA Approach in Different Rivers of Western Ghats, South India

The appraisal of climate change impacts on river hydrology using different Global Climate Models (GCM) and emission scenarios is incomplete, without quantifying the uncertainty associated with it. It is critical to quantify those uncertainties in order to develop beneficial managerial capabilities. The objective of the present study is to model the GCM and scenario uncertainty in Western Ghats (WG) river basins of South India using Reliability Ensemble Average (REA) for the estimation of stream flows. The analysis is carried out grid wise, for monsoon (JJAS) rainfall in near future (2011-2040). The statistically downscaled (kernel regression) rainfall data at 0.25o resolution for three CMIP-6 GCMs CNRM, CCCMA and MPILR for SSP2 4.5 and SSP5 8.5 are used in the present study. The river basins Netravati, (upper region), Kadalundi (middle region) and Manimala (lower region) in different elevation profile (lowland, midland and ghats) of WG are chosen as a criterion for quantifying the uncertainty associated with GCM models and emission scenarios. The uncertainty associated with GCM is found to be more significant than the scenario uncertainty in this region. The GCM model shows good correlation with the latitude profile in WG. The GCM MPILR have higher weightage in lower and middle region as compared to the others while the GCM CNRM is less pronounced in the high elevation zones along the basin.Keywords: Climate Change, Variable Infiltration Capacity Model, Uncertainty, REA approach.