An integrated modeling approach for the design and planning of inter-basin water transfer under climate change conditions

The spatiotemporal variability of water resources has necessitated the adoption of inter-basin water transfer (IBT) as a feasible option to achieve equitable water distribution. This study aims to assess the feasibility of IBT under the influence of uncertainties of future climate and demand changes with a robust approach to arrive at a feasible volume of water transfer across watersheds while accounting for increasing demands, climate change, and environmental flow concerns. The proposed Pamba-Achankovil-Vaippar (PAV) link between the states of Kerala and Tamil Nadu, located in the southern portion of peninsular India, has been taken up as the study area. This study proposes an integrated modeling approach and an assessment of flow health and sustainability of water transfer under RCP 4.5 and 8.5 climate scenarios for future demand changes under four developmental scenarios to estimate possible transferrable amounts of water. The amount of water transfer obtained shows that the reliability in meeting the donor basin demands while transferring the water at 50% and 75% dependability levels varied with different water usage and climate scenarios. An average sustainability index value of 0.45, 0.55, and 0.40 was estimated for most of the future period during normal, excess, and deficient southwest monsoon years, and a slight reduction was due to IBT. The results demonstrate that the robust integrated approach developed in this study effectively determines the percentage of demand met in the donor basins and assesses the amount of sustainable water transfer possible under both the supply and demand side uncertainties without adversely affecting the hydrological flow health.