Virtual water trade in the SADC region : a grid-based approach

In many areas in the world water is (becoming) a scarce resource. Therefore much research has been carried out on the alleviation of water stress or water quality. Most of these studies however focus only on water efficiency of production thereby neglecting the effects of consumption of commodities and virtual water flows related to trade. The water footprint concept considers these aspects and makes it possible to analyze the effects of (virtual) water allocation, trade and consumption on water scarcity more thoroughly. Also the concept makes a distinction between the types of water used: surface & ground waters (blue water), soil moisture and evaporated precipitation (green water), and polluted water (grey water). Virtual water refers to the actual volume of water that has been used to produce a commodity and that is virtually embedded in it: the so called water footprint. Most studies on water scarcity are conducted at the local, national or global level. Regional studies however are often lacking. The goal of this study is to extend the knowledge base for national and regional water management by applying the water footprint computation method of crops in a spatially-explicit way and by analyzing the impacts of water consumption and international virtual water trade on water scarcity. The approach is carried out on the Southern African Development Community (SADC) region, because it is one of the most water insecure regions of the world. The method to compute the water footprint of commodities is based on the approach of Hoekstra and Chapagain (2008). New in the approach, as used in this study, is that spatially explicit data (taking climatic variation in time and space into account) are used to compute the water footprint of crops. On top of that the actual crop evapotranspiration is used (instead of the maximum crop evapotranspiration) to determine the water footprint of crops, based on the water stress coefficient and a vertical soil water balance as described by Allen et al. (1998). Another improvement of this study is that grey water is taken into account. Seasonal variations in the water footprint of crops are still neglected. In this study water consumption of the SADC related to production and national consumption and virtual water trade of 22 crops (roughly 90% of total water consumption by crops), the 8 most reared animal categories and industry are taken into account. The time period analyzed is the period 1996-2005. The water footprints related to production of crops and livestock (products) are very high for most SADC countries compared with the global average water footprints. When the water footprints of crops in this study are compared with the study of Chapagain & Hoekstra (2004), this study gives much lower water footprint due to the improved approach. The water footprint related to industrial production of the SADC countries is very low except for Madagascar, Malawi, Zambia and Zimbabwe compared to the global average water footprints. Virtual water flows related to trade are very important for the SADC. The WF of consumption exists for 11.04% of virtual water imports related to imports of crops, livestock and industrial products. SADC's water footprint related to production exists for 8.69% of water consumed for producing export products. Especially agricultural products are traded between global regions and the SADC and vice versa; especially crop products. The SADC is a net water saver due to international virtual water flows related to trade and saves 7 Gm3/yr.The SADC is a net exporter of agricultural products to Western Europe, Eastern Europe, North Africa, Middle East and Central America, mainly coffee, sugar, cloves, cotton and cereals, bovine meat and bovine leather. SADC is net importing from South America, South East Asia, Central & South Asia, North America, Oceania and the Former Soviet Union, mainly cereals, sugar, cotton and oil crop products, bovine animals, bovine meat and live poultry. The SADC is a net importer of industrial products, imported mainly from Western Europe, North America, and Central & South Asia. The SADC is a net exporter of industrial products to North and Central Africa.Virtual w ater flow s related to intra SADC trade in crops, livestock and industrial products makes up 23.82% , 43.51% and 16.22% of total virtual w ater flow s related to trade in these products respectively. Intra SADC trade is dominated by South Africa and Zimbabwe