Enhancement and validation of a state-of-the-art global hydrological model H08 (v.bio1) to simulate second-generation herbaceous bioenergy crop yield

Abstract. The bioenergy crop yield is a critical determinant of the bioenergy potential for various stringent climate change mitigation scenarios. Currently, the bioenergy crop yield is usually determined from a limited number of simulations. However, reliable yield simulation remains a challenge at the global scale. Here, through parameter calibration and algorithm improvement, we enhanced a state-of-the-art global hydrological model (H08) to simulate the bioenergy yield from dedicated the herbaceous bioenergy crops Miscanthus and switchgrass. Site-specific evaluations showed that the enhanced H08 had the ability to simulate yield for both Miscanthus and switchgrass, with the calibrated yields being well within the ranges of the observed yield. Independent country-specific evaluations further confirmed the performance of the enhanced H08. Using this improved model, we found that unconstrained irrigation more than doubled the yield of the rainfed condition, but reduced the water use efficiency (WUE) by 29 % globally. With irrigation, the yield in dry climate zones can exceed the rainfed yields in tropical climate zones. Nevertheless, due to the low water consumption in tropical areas, the highest WUE was found in tropical climate zones, regardless of whether the crop was irrigated.