Simulation of Crop Water Demand and Consumption Considering Irrigation Effects Based on Coupled Hydrology‐Crop Growth Model.

Hydrological models are widely used in regional drought assessments. Usually, the spatiotemporal development of droughts is evaluated only via drought indexes based on simulated soil moisture. However, the physiological status of crops is key to accurately assessing the effect of drought, and hydrological models either do not consider crop physiological status or oversimplify it. In addition, the effects of reservoirs, irrigation, and crop rotation are generally not considered. To overcome the oversimplification of crop and irrigation modules in hydrological models, the variable infiltration capacity (VIC) model was coupled with the Environmental Policy Integrated Climate model. Irrigation and reservoir modules were introduced into the coupled hydrology‐crop growth (CHC) model. The CHC model was built for the watershed upstream of Heilin hydrological station on the Qingkou River on the border of Jiangsu and Shandong Provinces, China. The model performance was compared with simulation results of the Soil and Water Assessment Tool and VIC, which showed that the CHC model was more accurate. The temporal variation of water consumption and demand of three crop rotations, namely spring peanuts, summer peanuts‐winter wheat, and summer corn‐winter wheat, in the study area was analyzed. Drought area data obtained from Junan County yearbooks were consistent with the simulated water deficit and drought index considering the effect of irrigation. Crop irrigation increased soil water content and evapotranspiration and decreased crop water deficit. Therefore, crop irrigation was considered in hydrological simulations. The CHC model reliably simulated crop water consumption, soil moisture, and drought index, and the model simulated data could be used as basic data for water resources management and drought mitigation measures. Plain Language Summary: Commonly used hydrological models oversimplify the simulation of crop growth. Some studies have coupled hydrological and crop models, but have several limitations, for example, the effects of reservoirs, irrigation, and crop rotation are not considered. Therefore, crop water consumption and drought events have not been accurately simulated. To overcome this limitation, this study coupled the variable infiltration capacity (VIC) and Environmental Policy Integrated Climate models with irrigation, reservoir, and gridded routing modules. The coupled hydrology and crop growth (CHC) model was developed, and the accuracy of the CHC simulation results was higher than that of the Soil and Water Assessment Tool and VIC simulation results. The temporal variation of crop water consumption and demand along the Qingkou River, China, were simulated. In summer, meteorological and soil water conditions cause the crop water demand to be minimum to correspond to maximum water consumption, which generated the maximum water deficit. The simulated water deficit and drought index considering irrigation effects were consistent with the drought area data obtained from Junan County yearbooks. Irrigation increased soil water content and crop evapotranspiration and decreased crop water deficit. This finding illustrated that crop irrigation effects should be considered in hydrological simulations. Results of this study can aid water resources management and agricultural drought assessment. Key Points: The CHC model was validated using the SWAT results, MODIS data, and drought event recordsIn summer, meteorological and soil water conditions cause the crop water demand to be minimum to correspond to maximum water consumptionIrrigation increases soil water content and crop water consumption, and should be considered in hydrological simulations [ABSTRACT FROM AUTHOR]