Blue, Green, and Grey Water Quantification Approaches: A Bibliometric and Literature Review

An array of methodologies to quantify blue, green, and grey water have emerged in recent years and are still evolving rapidly, as are efforts to come up with reliable indicators of human appropriation of freshwater resources. This study provides an overview of recent blue, green, and grey water quantification approaches by analyzing publications extracted from the Web of Science database utilizing the Network Analysis Interface for Literature Studies (NAILS) bibliometric analysis tool, covering the period 2000-2018. A steep increase in the number of blue, green, and grey water publications was observed from the year 2009, with the United States and China among the top contributing nations. Blue, green, and grey water quantification approaches used in the analyzed publications were broadly categorized into Water Footprint Assessment, Life Cycle Assessment, and Hybrid methodologies. The Water Footprint Network was the most influential hub in terms of providing the most productive and cited authors. "Water footprint" and "virtual water" were unsurprisingly the trendiest and most cited keywords associated with the sample of analyzed publications. The study provides important insights that are helpful in understanding the diversity of techniques that have been applied to quantify blue, green, and grey water in recent assessment studies.