Abstract: Multi-source data of meteorology, disaster, crop, and soil in the cultivation areas of winter wheat in the Huang-Huai-Hai region from 1981 to 2020 were used to determine the water deficit indices at different development stages of winter wheat based on the reference crop evapotranspiration and water demand. Combined with the drought classification standard of winter wheat, the spatial-temporal variations of droughts in winter wheat in the Huang-Huai-Hai region were explored, which was of great significance for disaster prevention and reduction. The results showed that droughts in winter wheat from 1981 to 2020 existed obvious temporal and spatial variations in the Huang-Huai-Hai region. The areas affected by severe drought decreased, while the areas affected by moderate drought significantly increased. For the whole growth period of winter wheat, the most serious disaster during 1981-2020 was severe drought in the Huang-Huai-Hai region, followed by moderate drought, and finally light drought. The drought level gradually weakened from the north to the south in space, with a striped distribution. The winter wheat growing regions of 35°N northward and of 120°E eastward were basically suffered from serious drought all year round. For the growth period before winter, the most serious disaster during 1981-2020 was severe drought, followed by moderate drought and mild drought. The areas experiencing severe drought significantly decreased, while that affected by moderate drought significantly increased during the growth period before winter. For the overwintering period, the winter wheat during 1981-2020 in the Huang-Huai-Hai region suffered the extreme drought, followed by severe drought, and finally moderate drought. The areas affected by severe drought obviously decreased, while the areas affected by moderate drought increased during the overwintering period of winter wheat. For the period of regreening and heading, the droughts in winter wheat during 1981-2020 could be divided into four levels: mild drought, moderate drought, severe drought, and extreme drought. The areas with severe drought significantly decreased, while the areas with extreme drought significantly increased during the regreening and heading period of winter wheat. The droughts of winter wheat during the stage of grain filling and mature from 1981 to 2020 were mainly divided into three levels: no drought, mild drought, and moderate drought. The winter wheat areas with moderate drought were significantly decreased, while areas with mild drought increased during the stage of grain filling and mature.

Key words: Huang-Huai-Hai region, winter wheat, drought, crop water deficit index