A review of water footprint assessment for agricultural products

Water footprint (WF) is an indicator for both direct (domestic water use) and indirect (water required for industrial and agricultural production) water use of a consumer or producer.It has also been widely used in the analysis of global or regional virtual water trade.In the last decade, assessment of WF has been the focus of the footprint of rapid development.WF has three components (green, blue and grey water).This paper discussed a comprehensive review of the assessment of WF for agricultural products at different spatial scales, including global, regional and country scales.The main goal of the assessment of agricultural WF before 2008 was to determine global virtual water trade via agricultural products.However, the goal shifted to the rigorously quantification of three components for specific agricultural products and in specific geographical areas after 2009.As the assessment of WF has obvious spatial distribution characteristics, it was necessary to consider the influence of regional geographical characteristics, soil physical and chemical properties, climate change, as well as production technology and ecological toxicity of pollutants for building accurate, comprehensive and objective information on the WF of agricultural products.It was also necessary to take into account green water, blue water and gray water footprints for agricultural products in decision making on water resources management.This was because blue WF for agricultural products represented the direct consumption of freshwater resources, which was critical in decisions on international water trade market.The grey WF for agricultural products more clearly reflected the effect of agricultural production on the environment.In order to reach global or regional objectives on water resources conservation and sustainable utilization, not only the utilization efficiency of water resources in agricultural production needed improvement, but also the structure of agricultural production and both pattern and direction of virtual water trade for agricultural products needed adjustment.Furthermore, it was necessary to reduce waste of water resources in agricultural product cycle and food consumption.