A Stakeholder Elicitation-based Socio-hydrological Model of an Inter-basin Water Transfer Mega Project in Southern India

Abstract:

Inter-basin water transfer (IBT) is a supply side option to manage water scarcity, but has complex and uncertain social, environmental and economic impacts. Evaluating IBT megaprojects requires consideration of possible conflicts between donor and recipient basins, and uncertain future changes in climatic and socio-economic conditions. Socio-hydrological models allow quantitative coupling of social and hydrologic processes, which could be used to explore the complex decision context of IBT megaprojects. We develop a socio-hydrologic model for the Inchampalli-Nagarjuna Sagar (INS) IBT megaproject in Southern India (part of the National River Interlinking Project). The project connects two large monsoon dominated basins via a 200 Km long water transfer. Based on semi-structured interviews with potential stakeholders in the study area, we develop a causal loop diagram (CLD) that highlights the complex interconnections of human and water systems. The CLD informs the quantitative structure of the socio-hydrological model that integrates rainfall-runoff processes, reservoir water balance, command area water balance and consumer water usage patterns. The model is validated using historical data on relevant socio-hydrological variables and then used to evaluate the impact of the IBT megaproject under likely changes in climates as projected by five climate models under two RCPs (representative concentration pathways). Under wide-ranging projections, blue water withdrawal limits are frequently exceeded in the donor (recipient) basin in the presence (absence) of IBT. We also discover a rather complex impact on future groundwater storage with variation of 70% - 100% of the maximum groundwater storage in the donor and recipient basins, the nature of which varies considerably with choice of RCP and whether or not the IBT is present. We show how complex bi-directional interactions between water availability and consumers’ water demand affect the response of the socio-hydrologic system.