Irrigation efficiency optimization at multiple stakeholders’ levels based on remote sensing data and energy water balance modelling

Abstract

The agricultural sector, the largest and least efficient water user, is facing important challenges in sustaining food production and careful water use. The objective of this study is to improve farm and irrigation district water use efficiency by developing an operational procedure for smart irrigation and optimizing the exact water use and relative water productivity. The SIM (smart irrigation monitoring and forecasting) optimization irrigation strategy, based on soil moisture (SM) and crop stress thresholds, was implemented in the Chiese (North Italy) and Capitanata (South Italy) Irrigation Consortia. The system is based on the energy–water balance model FEST-EWB (Flashflood Event-based Spatially distributed rainfall runoff Transformation Energy–Water Balance model), which was pixelwise calibrated with remotely sensed land surface temperature (LST), with mean areal absolute errors of approximately 3 °C, and then validated against local measured SM and latent heat flux (LE) with RMSE values of approximately 0.07 and 40 Wm−2, respectively. The effect of the optimization strategy was evaluated on the reductions in irrigation volume and on the different timing, from approximately 500 mm over the crop season in the Capitanata area to approximately 1000 mm in the Chiese district, as well as on cumulated drainage and ET fluxes. The irrigation water use efficiency (IWUE) indicator appears to be higher when applying the SIM strategy than when applying the traditional irrigation strategy: greater than 35% for the tomato fields in southern Italy and 80% for maize fields in northern Italy.