Spatial and temporal patterns of global crop water footprints
Oleksandr Mialyk is a PhD student in the Department Multidisciplinary Water Management. (Co)Promotors are prof.dr.ir. M. Berger, dr.ir. M.J. Booij and dr.ir. J.F. Schyns from the Faculty of Engingeering Technology.
Crop production is responsible for most of humanity’s water consumption. In some regions, the consumption levels already exceed sustainable limits putting local water security and ecosystems at risk. Thus, one of the grand challenges of the next decades is to satisfy growing global crop demand while minimising water consumption.
One way to assess the water consumption and productivity of a crop is to use the consumptive Water Footprint (WF). It measures green and blue water volumes consumed to produce a particular crop. Green water refers to the evapotranspiration of water from precipitation and blue water refers to the evapotranspiration from irrigation or shallow groundwater via capillary rise. The first comprehensive crop WF dataset was produced more than a decade ago and covered around 150 individual crops averaged for the year 2000. This dataset provided a basis for numerous studies on a wide range of topics, including agricultural water management, environmental economics, water footprint and life cycle assessments. Later, it was projected over the 1961–2016 period using a fast-track approach, which succeeded in providing historical coverage but also propagated the limitations and uncertainties from the original dataset.
This thesis aims to produce and analyse a new WF dataset covering 175 individual crops over the 1990–2019 period. These new estimates are based on fresh simulations using state-of-the-art input data, methods, and a global gridded crop model. The latter is developed from FAO’s process-based crop model AquaCrop with additional implemented features, such as the ability to run at the 10 x 10 km scale, trace green and blue water fluxes in the soil, and simulate perennial crops. The accompanying analysis of spatial and temporal patterns provides new insights into the crop WF evolution over the last decades. For example, it demonstrates that most of the crops experienced large water-productivity gains as crop yields improved and cultivation centred around more productive areas. Also, it shows that these gains were insufficient to stop the global water consumption for crop production from increasing, mainly across the tropics. This raises multiple concerns regarding already existing (and expected in the future) environmental and socio-economic water-related issues. Therefore, more efforts should be dedicated towards more water-sustainable agrifood systems.
