Influence of irrigation water use efficiencies on the sustainability of irrigation: interrelations of irrigation efficiency, water availability and irrigated area at the global scale
Summary
Irrigation water use is crucial to sustain food production in the context of growing population and globalization, yet is one of the main drivers of water scarcity and increased competition between water users. This study evaluates the influence of irrigation water use efficiencies on the sustainability of irrigation by examining trends in irrigation water requirements. The PCR-GLOBWB model is run to simulate water availability and irrigation water demand over the historical period 1960-2010, using climate drivers from the CRU-TS 3.21 meteorological data set, and over the 21st century (2006-2099), using three climate projections from the HadGEM2-ES, the IPSL-CM5A-LR, and the GFDL-ESM2M global climate models. Irrigation water demand is estimated under a scenario of irrigation efficiency improvement based on future development of irrigation efficiency described by Fischer et al. [2007] and country-specific irrigation project efficiency compiled by Rohwer et al. [2007].
The results show that the global volume of irrigation water use significantly increased over the historical period, stabilizes around 2020, and slightly decreases until the end of the 21st century. Irrigated area expansion is the main driver of the significant increase in past irrigation water requirements. The results vary significantly over the 21st century, depending on the climate projection used. Our projections do not account for future irrigated area expansion due to the deficiency in qualitative and quantitative projections of land use change; hence results are mainly driver by climate variability (i.e., climate change).
The results indicate the necessity of pursuing irrigation water use efficiency improvement and that such development will play a large role to reduce the pressure of irrigation water use on water resources.