Application of the CMIP6 Approach for Determination of Climate Change Impact on Inflow to Malampuzha Reservoir, India

Abstract

Optimal operation of a reservoir is important for the efficient planning and management of water resources.  Inflow estimation into the reservoir is the basic information needed by a policy maker for the optimal planning of the reservoir operation.  Climate change has become a major cause for the changes in the hydrological phenomena.  An attempt was made to analyse the impact of climate change on Malampuzha reservoir inflow for the future using recent Shared Socioeconomic Pathways (SSP) scenarios.  Two SSP scenarios, SSP 245 and SSP 585 were considered for the evaluation of changes in the meteorological variables for the future period.  Rainfall-runoff modelling of the catchment area of the Malampuzha reservoir was done with IHACRES model for the period 2003-2022. The model performance was accepted in calibration (2003-2016) and validation (2017-2022) periods with R2 of 0.90 and 0.91 and RMSE 2.63 and 4.53 m3/s respectively.  The outputs of SSP245 and SSP585 scenarios were given to the developed runoff model to estimate the future inflow volume into Malampuzha reservoir for the period of 2023 to 2042. From the results, the change in monthly temperature varies from -0.88oC to 3.3oC and change in monthly precipitation varies from -0.64% to 1.73% which indicates a decrease in the inflow of water into the reservoir for future period by 2.6% and 9.3% than the base period (2003– 2022) for SSP245 and SSP585 scenarios, respectively.  The results of the study implies that better planning of the reservoir operation is needed for meeting the future demands.