Spatio-temporal variability of global crop water requirement, during 1950-2020

Intensification of studies of the agricultural water requirement is a main challenge in a globalizedworld, where food production is pushed to meet the needs of a growing population and theinternational trade network requires large-scale planning policies. Agriculture is the human activitythat consumes most of the withdrawn freshwater and climate change can greatly influence theamount of irrigation required by crops. In recent years, the widespread availability of satelliteimages is providing an important contribution to water resources management, offering data athigh spatio-temporal resolution over an interestingly long period of time.This study deals with the temporal variability of global water requirement of the main crops, whichis assessed through a comprehensive model, driven by climate forcings, that estimates the dailycrop water requirement on a spatial resolution of 5 arc-min (or 0.0833°) from 1950 to 2020. Themodel computes a soil water balance using daily input data of precipitation andevapotranspiration, based on the high-resolution ERA5 reanalysis dataset from the ClimateChange Service of the Copernicus Program, which combines satellite information and groundmeasurements. The distribution of harvested areas and the length of crop development phasesare kept constant, to analyze the variability of crop water requirement strictly related to climateforcings, both in terms of precipitation (green water) and irrigation (blue water). The modelconsiders the separation between irrigated and rainfed areas, in order to provide a consistentspatial distribution of irrigation requirements. Examining the spatio-temporal variability of thecrop water requirement can support considerations on the effects of global warming in differentareas in the world.