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

Abstract

The evaluation of climate change impacts on hydrology using Global Climate Models (GCM) and emission scenarios is incomplete, without quantifying the uncertainty associated with it. As the uncertainties play a significant role in such analysis, it is important to quantify them in order to develop productive management and decision-making capabilities. The objective of the present study is to model the GCM and scenario uncertainty in the Western Ghats (WG) region 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 0.25° resolution for 5 CMIP-5 GCMs CNRM, CCCMA, MPIMR, MPILR, and BNU for RCP 4.5 and 8.5 are used in the present study. The upper-middle and lower regions along with the elevation profile (lowland, midland, and ghats) of WG are chosen as a criterion for quantifying the uncertainty associated with GCM models and emission scenarios. Irrespective of the topography criteria, the uncertainty associated with GCM is found to be more significant than the scenario uncertainty. The GCM model shows a good correlation with the latitude profile in WG. The GCM MPILR and CCCMA have higher weightage in lower and middle regions as compared to the others while the GCM CNRM is less pronounced in the high elevation zones along the basin.