20 - Pinch Analysis for regional water scarcity assessment

Abstract

Water quality problems contribute significantly to water scarcity beyond water quantity shortages; this problem has not been well demonstrated in the previous studies. This study aims to redefine water scarcity in terms of water quality and quantity and proposes a Water Scarcity Pinch Analysis (WSPA) to quantify regional water scarcity. The WSPA is proposed based on the widely applied Water Pinch Analysis method. The quality of water sources and demands is specified by setting water quality categories from which a Staircase Grand Composite Curve (GCC) is constructed. After applying the Water Quality Cascade, the GCC provides the water quantity–quality target, which is the net deficit volume (m3) of water with a certain water quality (category). This target is defined as water scarcity. Water quality upgrading is applied to maximise the water use efficiency for various purposes by mixing water sources of varying quality. Three case studies are conducted to illustrate the implementation of the proposed method and investigate its performance. The results show that WSPA identifies both water quantity scarcity and scarcity caused by insufficient water quality or a water quality mismatch between sources and demands. WSPA also provides insights for water scarcity minimisation via Water Quality Cascade and upgrading. Conclusions and novel contributions are (1) WSPA enables water quality and quantity to be accounted for in water scarcity assessment and provides both quantity and quality targets for minimising regional water scarcity; (2) the WSPA applied at a macro level elevates the ratio-based water scarcity assessment from a single determination to an insight-based assessment that can guide regional water resource management; and (3) Water Quality Cascade and water quality upgrade via dilution can improve water use efficiency and reduce water scarcity.