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

•The frequency of extreme events including droughts and floods are projected to increase in future time horizons.•The future climate variability may likely affect the water supply–demand pattern in the basin.•The proposed new water resources development projects will be beneficial in storing the flows during high intensity rainfall events to be utilised later during intervening periods of dry spells and droughts.•Integrated operation of the existing and proposed reservoirs using genetic algorithm based simulation-optimisation framework improved the overall system performance and can be considered as a climate change adaptation tool. 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 dec