Water Availability Footprint Addressing Water Quality
The increasing issue of water quality degradation has affected the availability of water. The consideration of water quality is becoming more important for water minimisation. There is a need to integrate water quality into the current water assessment framework. This study tries to involve the water quality into the widely used water footprint assessment framework in order to quantify the water usability changes during the water use process. Based on water footprint concepts from international standard ISO 14046, water availability is further interpreted to emphasize the impact of water quality on the usability. An effective water availability footprint is defined as the quantitative and qualitative extent of a certain body of water which meets the needs of a certain purpose of water use. A water quality index is proposed to quantify the contribution of water quality on water availability, and two approaches of calculating water quality index are discussed, in order to explore the possibility of involving water quality into the water availability footprint assessment. Based on the definitions and framework, a case study is conducted to illustrate the features of this framework, and 3 outflows with different water quality are set to discuss the impact of different water quality profiles on the calculation of water availability footprint. It shows that water quality profiles can have a remarkable influence on the calculation. For the case with an outflow of F2-1, the water availability footprints with minimum water quality index, average water quality index and the volumetric water footprints as 1,600 m3, 1,277 m3, and 1,000 m3. This indicator can determine the consumptive water use and also quantify the exploitation of water quality. The involvement of water quality regarding multiple contaminants in water footprint assessment should be further investigated in future studies.