Beyond blue: An extended framework of blue water footprint accounting

The water use of societies results in multiple environmental and social impacts and is a fundamental component of sustainability. Correspondingly, water footprint studies have grown significantly in numbers over the last decade. However, these studies mostly account for the human appropriation of freshwater resources, while overlooking various alternative water resources. This paper responds to the growing need for a complete water footprint accounting and presents an extended framework of the blue water footprint, comprised of seven water types. A case study shows spatially-explicit and use-specific analysis of Israel's diverse water system. Israel's freshwater use accounts for only 40% of its total water use. Desalinated seawater and reused wastewater contribute 52% and 45% to the country's municipal and agricultural water use, respectively. The "original" blue water footprint assumes only freshwater use; thus, it overestimates the appropriation of natural water resources by humans. The extended blue water footprint accounts for seawater, brackish water, runoff, and reused wastewater along with surface water and fresh groundwater. It, therefore, estimates the human water use more accurately. Alternative water types' use has some adverse environmental and health impacts. These include high energy intensity due to desalination, soil salinization from brackish water irrigation, and human exposure to traces of pharmaceutical in drinking water due to treated wastewater irrigation. By acknowledging the water mix of different sectors and regions, the extended blue water footprint contributes to advancing a water-energy nexus analysis or accounting for various environmental and health impacts of water use.