[Evaluation of agricultural drought in Luanhe River Basin based on the standardized soil moisture index.]

Drought is one of the main disasters causing agricultural production losses. Accurate and effective agricultural drought monitoring is of great significance to reduce agricultural production losses. In this study, the standardized soil moisture index for agricultural drought evaluation was established by using the historical time series of soil moisture. Based on the index, the temporal and spatial distribution of drought events in the Luanhe River Basin from 2002 to 2019 were analyzed, and the agricultural drought was quantitatively evaluated. The results showed that soil moisture of most grid units in the Luanhe River Basin obeyed normal distribution during the study period, and that the soil moisture of a few grid units obeyed generalized extreme distribution. The changes of drought and flood in each grid unit had good temporal consistency, that is, the changes of drought and flood was consistent. The changes of drought and flood in the middle of the basin was relatively significant, while the agricultural drought generally showed a trend of reduction. The spatial distribution of agricultural drought severity was not obvious. Relatively speaking, the drought characteristics (the frequency, duration and intensity of drought) were higher in the middle and northwest of the basin and lower in the southeast. The results could provide a reference for agricultural drought prediction and the formulation of drought prevention and mitigation measures in the Luanhe River Basin.