Optimal reservoir operation – A climate change adaptation strategy for Narmada basin in central India

The potential impacts of climate change on the water resources of the Narmada basin in central India has been investigated using the Soil and Water Assessment Tool (SWAT). The existing dams in the river basin have been incorporated in the model setups, calibration and validation. The COordinated Regional climate Downscaling EXperiment datasets for South-Asia (CORDEX-SA) at 0.5° × 0.5° resolution for four-time horizons, viz., 1970–05 (historical), 2006–40 (near-term), 2041–70 (mid-term) and 2071–99 (end-term) under Representative Concentration Pathways (RCP) scenarios, RCP4.5 and RCP8.5 has been used to investigate the changes in the future climate and simulation of future streamflow. The proposed dams have also been incorporated for modeling the future developmental scenarios. The scenario analysis based on the projected climate variables has led to the inference that the change in the precipitation pattern coupled with the warming trends, maybe contributing towards higher variability in water availability. A future scenario of lower water availability and higher water demands thus calls for optimal utilization of available water resources in the future, so that the higher water demands can be satisfied with lower anticipated future flows. Various alternatives were explored for devising adaptation strategies using the engineering/technical solutions in which the optimal water resources management approaches were explored using the simulation-only and the genetic algorithm based simulation–optimization approaches. The simulation–optimization framework based integrated reservoir operation of four reservoirs has led to better reservoir performance and the number of irrigation failures has decreased substantially from 92 to 12 during 2006–40, 86 to 22 during 2041–70 and 89 to 10 during 2071–99. The hydropower failures have also decreased considerably from 202 to 96 during 2006–40, 192 to 28 during 2041–70 and 179 to 67 during 2071–99 under the RCP8.5 scenario. There were no failures in meeting the domestic water supply and environment flow demands. This may be an important adaptation measure to address the issues of climate change impacts on the water resources in the future in the Narmada basin.