Characteristics of crop water footprint changes in five Central Asian countries from 1992 to 2017

This study analyzed the spatio-temporal characteristic of crop water footprint in five Central Asian countries from 1992 to 2017 using the crop water footprint as the assessment method, in order to reveal the structure of crop water footprint, and clarify the contribution of main crops that caused the change of water footprint in the five Central Asian countries. The results showed variation in the crop water footprints of these five Central Asian countries. From 1992 to 2017, changes in green water footprints were similar to those in their respective planting areas, and the overall trend was decreasing (-9.7×10⁹ m³). The overall blue water footprint also tended to decrease (-5.6×10⁹ m³). There were significant differences in the spatial distribution of crop water footprints in the five Central Asian countries. Kazakhstan had the highest green water footprint (average 49.6×10⁹ m³), much higher than the other four countries (average 3.6×10⁹ m³). Uzbekistan had the highest blue water footprint (average 15.3×10⁹ m³). From 1992 to 2017, the countries with the largest growth rates in the green and blue water footprints of crops were Turkmenistan (87.6%) and Kyrgyzstan (32.3%). The countries with the largest reduction rates in the green and blue water footprints were Kazakhstan (-20.7%) and Uzbekistan (-24.2%). The green water footprint of crops in Central Asia was mainly from cereals, and the blue water footprint was mainly from cereals and oil crops. The water footprint structure of cereals was mainly composed of wheat, rice, and corn, and the water footprint structure of oil crops was mainly composed of cotton. Kazakhstan had the largest reduction in green water footprint and accounted for most of crops with reduced green water footprint, barley (51.6%) and wheat (28.2%). Uzbekistan had the largest reduction in blue water footprint, with cotton (61.9%) contributing the most. The aim of this study was to examine the impact of crop yield on the virtual water content of crops and expand the virtual water content of dozens of crops in these five Central Asian countries. This avoids the shortcomings of inaccurate calculations of the long-term water footprint series in previous studies where the virtual water content remains unchanged. Research on the water footprint of crops in Central Asia revealed that the water footprint was declining, and the main crops causing the water footprint declines had been identified. These results can be used to optimize crop planting and water conservation in Central Asia.