Changes in agricultural virtual water in Central Asia, 1992–2016

In recent years, flows of many rivers and lakes have become reduced in arid and semi-arid regions around the world. The most typical examples of this phenomenon occur in Central Asia, and the reduction of the Aral Sea area is closely related to agricultural water use. However, due to a lack of continuous data in Central Asia spanning many years, “virtual water” is used to evaluate changes in agricultural water use. Based on virtual water theory, 325 kinds of agricultural products in eight categories are selected as the research object, and changes in virtual water are calculated for Central Asia from 1992 to 2016. Results indicate that: (1) The average annual net export of agricultural virtual water (TVWNE) in Central Asia is about 9 billion m3, concentrated in Kazakhstan, whose annual TVWNE reaches 8.1 billion m3. (2) Since 2007, the TVWNE in Central Asia has dropped significantly, with a drop rate of 86%, while the total volume of agricultural virtual water has gradually increased since 1998. (3) The upstream and downstream countries in Central Asia have different characteristics in the change of virtual water quantity.