Modeling the Physical Nexus across Water Supply, Wastewater Management and Hydropower Generation Sectors in River–Reservoir Systems

Abstract

Most water supply and hydropower generation is obtained from the river–reservoir system, and wastewater pollutants are also dumped into the system. Increasing water demand and consumption have caused the water supply, wastewater pollutant management and hydropower generation sectors to be interlinked and to reinforce each other in the system. A physical nexus across water supply, wastewater management and hydropower generation sectors for a river–reservoir system was developed based on the analytical water quality and hydropower generation equations. Considering the Jinghong hydropower reservoir, located in the middle and lower reaches of the Lancangjiang River Basin, as a case study, both the wastewater pollutant management target and water inflow from the upstream as the external and boundary conditions, were employed to establish the effects of the external and boundary conditions on the nexus. It was demonstrated that the nexus of water supply and hydropower generation sectors does not vary with the water quality indicators and its protection target, without the separation of environmental flow in hydropower generation flow. In addition, the amount of hydropower generation decreases with increasing water supply. However, the lapse rates of allowable wastewater pollutants–water supply differ based on the water inflow and the wastewater pollutant management sectors, while the efficiency of hydropower generation and the sensitivity of allowable wastewater pollutants per amount of water supply are considered to be unrelated to the water inflow and wastewater pollutant management target conditions. The quantitative nexus developed through the proposed equation not only contributes to a more complete understanding of the mechanism of cross-connections, but also in creation of specific water protection and utilization measures, which is also the focus of the water–energy nexus.