Key Points :

Abstract

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, e.g. irrigation amounts and timing, and soil moisture (SM). This study assessed the representation of irrigation and its effect on crop yield in the Community Land Model version 5 (CLM5) through implementation of an irrigation data stream that allows to directly use observed irrigation data. Simulations were conducted at the point scale for two instrumented apple orchards using the CLM5 irrigation routine as well as the implemented data stream. Furthermore, irrigation requirements and the effect of deficit irrigation on crop yield and crop water use efficiency (CWUE) at the regional scale were simulated and discussed. The irrigation data stream performed better in representing observed SM dynamics compared to the standard irrigation routine that could be further improved by implementing more flexible irrigation schedules and irrigation efficiency. At the regional scale, simulated irrigation and yield showed a high sensitivity to climatic changes caused by the topographic gradient. While a 25 % reduction in irrigation had negligible negative effect on simulated yield and CWUE, a reduction of 50 % notably reduced both variables. These effects varied with climatic conditions, soil properties and timing of irrigation. These results showcase how CLM5 could be utilized for irrigation and water resources management.