What is the cause of the drought? There was a severe drought in China's history. Can we learn from them?

Drought occurs when the evaporation of water vapor on the earth is greater than the supplementary amount, which makes the soil and plants short of water. The most famous drought in the history of China was in the late Ming Dynasty. Ten years and nine droughts. Because the imperial court was busy using troops, the maintenance of water conservancy facilities and disaster relief in various places were not in place, causing large-scale unrest. The significance of reference is that drought is not terrible, the most terrible thing is that in the absence of organization, adding chaos is the most terrible.