CAN CONJUNCTIVE USE OF SURFACE WATER AND GROUNDWATER RESOURCES REDUCE RELIANCE ON LARGE SCALE WATER TRANSFERS?

Infrastructure interventions such as inter-basin water transfers (IBWTs) provide one way to manage water scarcity in the presence of regional differences in water supply and demands. However, such large scale investments require consideration of preferences of mulitple stakeholders as well as changes in hydro-climatic and socio-economic conditions. Thus, it would be useful to explore alternatives that can complement IBWTs to increase performance and flexibility of the regional water resource system. Here, we investigate the role of groundwater development in reducing reliance on IBWTs for monsoon-dominated basins. We evaluate an IBWT scheme in southern India that proposes to transfer water from the Godavari basin to the Krishna basin - the Inchampalli-Nagarjuna Sagar (INS) project. We formulate a multi-objective decision problem to identifiy water transfer strategies for the INS-IBWT with and without conjunctive use of groundwater. Groundwater development in the command area of the recipient reservoir is simulated using an artificial recharge scheme. The objectives of the multi-objective optimization are related to demand satisfaction, reducing high flow exceedances downstream, and maintenance of minimum environmental flows. Two variants of the decision problem are used, one that includes an artificial recharge module coupled to the IBWT surface water balance model (recharge formulation) and another that does not (no-recharge formulation). Results show that the recharge formulation reduces the system level demand deficits by 50% across all the Pareto optimal strategies compared to the norecharge formulation. However, the suggested volume of transferred water does not reduce for the recharge formulation as artificial recharge helps in alleviating deficits that exist even in the presence of the INS-IBWT. Our analysis highlights that in cases where recipient basins face historically large demand deficits, groundwater development would not necessarily reducing the reliance on IBWTs and additional demand management alternatives would need consideration.