The effect of development in water-saving irrigation techniques on spatial-temporal variations in crop water footprint and benchmarking

Improved spatial and temporal resolutions in quantification enable the water footprint (WF) in crop production to be a comprehensive indicator of water consumption in agricultural water management. In general, existing literature focus on the impact of water-saving irrigation techniques on crop yield and water consumption during the growth period at sites or experimental units, few studies yet that explicitly addresses the effect of developments in water-saving irrigation techniques on large-scale WF accounting and benchmarking. Here, we fill this gap through a case study for wheat in China over 2000-2014, during which the micro-irrigated wheat area expanded 14 times. The green and blue WFs of China's wheat per year are estimated at a 5 arc-minute resolution. For irrigated wheat, we distinguish three irrigation techniques: furrow, sprinkler and micro-irrigation. The WF benchmarks by irrigation type are further estimated separately for arid and humid zones. Irrigation accounted for 70% of annual WF in China's wheat land, while furrow irrigation dominated the national total WF. The occupation by WF under micro-irrigation was the smallest but jumped by 14 times in quantity whereas that under sprinkler halved. China's average WF per ton of wheat under sprinkler irrigation was 21% higher than that under micro-irrigation in 2014. The 20th percentile WF benchmarks of wheat under micro-irrigation was 13% and 31% smaller than that under furrow and sprinkler irrigation, respectively, in arid zones. Meanwhile, high provincial heterogeneities in terms of WF under varied distribution of irrigation techniques were also shown. The study shows possibility and importance to account for developments of water-saving techniques in large-scale crop WF estimations.