Evapotranspiration shed of agriculture: combining agro-hydrological estimates with atmospheric moisture dynamics

The increasing global demand for food, feed and flexible crops is exerting unprecedented pressure on the global hydrological cycle through landscape conversion and increasing irrigation demand, which altogether contribute to the alteration of land moisture recycling. This alteration influence evapotranspiration and precipitation patters through atmospheric flows. Atmospheric moisture flows connect sources of evapotranspiration to sinks of precipitation, from local to regional and continental scale, up to thousands of kilometres away. Terrestrial sources of evapotranspiration are crucial for global food production, regulating precipitation and climate patterns by redistributing water and latent heat. At the same time, the alteration of evapotranspiration dynamics from these sources is mainly driven by land-use conversion for pasture (cattle meat production), and feed crops (such as soy, and maize) and agricultural practises, such as irrigation.

Current crop water use assessments disregard these atmospheric moisture fluxes in redistributing evapotranspiration from agricultural parcels to precipitation in downwind areas. This understanding is particularly key to better assess the water-related implication of agricultural production. Addressing this research gap, this study aims to advance the understanding of how evapotranspiration from agricultural areas shape precipitation in other agricultural areas.

The agro-hydrological estimates for crop production were performed over the period 2008–2017 by means of the model waterCROP, which solves the daily soil water balance on a global 5 arc-minute grid, with global coverage for both irrigated and rainfed conditions.

These evapotranspiration estimates are then combined with atmospheric moisture connections by means of the RECON dataset (based on the UTrack Lagrangian moisture tracking model), a 4D matrix of annual moisture flow connections between any cell in the world at a spatial resolution of 0.5° including a globally closed water balance at annual scale. Each cultivated cell is linked to its blue and green evapotranspiration shed (i.e. the downwind area receiving precipitation from irrigated or rainfed crop production). Evapotranspiration sheds are finally classified according to their land use category to analyse potential synergies and trade-off between land and water use between the sites at the origin of evapotranspiration and others at the fate of precipitation. By characterizing these connections, this research sheds light on the hidden global links between cultivated land and downwind areas.