A Virtual Water Assessment Methodology for Cropping Pattern Investigation

Increasing freshwater demands have made allocation of water in water‐scarce regions especially severe in arid areas. To assist in allocating water, a virtual water assessment methodology is described to assess strategies of saving water by identifying products which would be better as imports rather than producing them. Virtual water quantities, including green and blue water for five major crops, are analyzed, utilizing the methodology, for the three regions of East, Mid and West in Gansu Province, Northwest China, over a nine‐year period from 2002 to 2010. Unit virtual water value as well as crop water use efficiencies are included, to determine if current cropping patterns are reasonable. Overall, the methodology encourages crops with lower water consumption, higher unit virtual water value, and crop water use efficiency. Estimates of potential virtual water flows reflect either the amount of virtual water which needs to be imported or the amount which can be exported. The results show that for different regions of Gansu, wheat and soy should be reduced in all three regions; cotton and corn can be increased in the West and Mid regions, respectively; potatoes can be a largely encouraged product throughout Gansu Province. Current cropping patterns in the three regions in the Province are therefore shown to be not optimal; changes in cropping patterns can be initiated, and water deficits can be balanced by virtual water transfers amongst the three regions as indicated by potential virtual water flows.