Agricultural drought evaluation based on a soil moisture index coupled hydrological model in North China Plain

Global climate change has led to an increase in the number of drought events. Agricultural droughts, which are influenced by crops, climate, and soil, are complex and challenging to identify. This study proposed a new index, the available water content of the soil index, based on the soil reservoir theory, which focuses on soil water and considers both crops and soil structure. We constructed the MODCYCLE model to depict soil water dynamics and evaluate agricultural drought by using the available water content of the soil index in a typical North China Plain region. The results showed that the soil in the western and southern regions was relatively dry and that the soil in the eastern and northern regions was humid. Drought occurred owing to the increased water demand during the critical growth period of winter wheat. Irrigation alleviated the drought. When the AWCI is greater than 0.6 in early April, the degree of drought is relatively mild. When the AWCI is less than 0.4, it is very easy to experience severe drought in mid-April.The central and eastern regions were susceptible to drought after mid-April, and the western region experienced drought until late May. Varying soil moisture, particle composition, irrigation, and precipitation conditions influenced the evolution of the drought. Enhancing soil moisture and timely irrigation before the critical growth period of winter wheat effectively prevented severe droughts in the region. The results provide guidance for regional drought monitoring and forecasting, water resource management, and scientific irrigation, effectively ensuring food security.