Rainfall Scenario in Future over Cauvery Basin in India

A study was undertaken for developing rainfall scenarios using the ensemble of all 16 different Global Climate Model outputs for A1b scenario for mid (2040–2069) and end (2070–2099) century. For the analysis, the entire Cauvery basin was demarcated into five smaller basins viz., Basin 1 (Upper Cauvery upto Mettur reservoir), Basin 2 (Bhavani basin from Mettur to Upper Anicut), Basin 3 (Amaravathy basin), Basin 4 (Upper Anicut to Grand Anicut) and Basin 5 (Downstream of Grand Anicut, including lower Anicut and the delta region). From the 16 Global Climate Model ensemble outputs, rainfall in the mid century is expected to increase in the SWM months starting from May through December in the order of 1 to 36% (Basin 1), 3 to 21% (Basin 2), 1 to 17% (Basin 3), 3 to 22% (Basin 4) and 4 to 22% (Basin 5). The same trend is expected in the end century with different magnitude. The South West Monsoon (JJAS) and post-monsoon rainfall (ONDJ) is expected to increase towards mid and end century whereas not much change is expected in the pre-monsoon rainfall in the future. Annual rainfall is expected to be 21, 11 and 7% more during mid century compared to the baseline (1981–2000) in the upper Cauvery (Basin 1), mid Cauvery (Basin 2, 3 and 4) and delta region (Basin 5) respectively. The rainfall would be higher by 33, 15 and 10% than the current quantity in the upper Cauvery, mid Cauvery and delta region respectively during end century. These results could contribute to the development of policies for future agricultural water management.Keywords: Cauvery Basin, Climate Model Ensemble, Rainfall.