Land surface modeling as a tool to explore sustainable irrigation practices in Mediterranean fruit orchards

Irrigation strongly influences land-atmosphere processes from regional to global scale. Therefore, an accurate representation of irrigation is crucial to understand these interactions and address water resources issues. While irrigation schemes are increasingly integrated into land surface models, their evaluation and further development remains challenging due to data limitations. This study assessed the representation of field-scale irrigation using the Community Land Model version 5 (CLM5) through comparison of observed and simulated soil moisture, transpiration and crop yield. Irrigation was simulated by (a) adjusting the current irrigation routine and (b) by implementing a novel irrigation data stream that allows to directly use observed irrigation amounts and schedules. In a following step, the effect of different irrigation scenarios at the regional scale was simulated by using this novel data stream. At the plot scale, the novel irrigation data stream performed better in representing observed SM dynamics compared to the current irrigation routine. Nonetheless, simplifications in crop and irrigation representation and uncertainty in the relation between water stress and yield currently limit the ability of CLM5 for field-scale irrigation scheduling. Still, the simulations revealed valuable insights into model performance that can inform and improve the modeling beyond the field scale. At regional scale, the simulations identified irrigation priorities and potential water savings. Furthermore, application of LSMs such as CLM5 can help to study the effects of irrigation beyond water availability, for example, on energy fluxes and climate, thus providing a powerful tool to assess the broader implications of irrigation at larger scale.