In recent decades, the summer precipitation in eastern China has obvious characteristics of interdecadal north-south evolution. In the 1990s, the main rainy areas affecting China were located in the middle and lower reaches of the Yangtze River. At the beginning of 2 1 century, the rain belt went north to the Huaihe River Basin. The precipitation trend in the middle and lower reaches of the Yellow River has also increased significantly. Meteorologists predict that the probability of extreme precipitation events in the Huang-Huai-Hai region will increase in the future. In recent years, the rain belt in eastern China has gradually moved northward, and the precipitation in the middle and lower reaches of the Yangtze River and the southeast has decreased. During the cotton growing period, the eastern part of China may gradually change from "southern waterlogging and northern drought" to "southern drought and northern waterlogging". Therefore, under the condition of climate warming, the water resources in the Yellow River basin and the three major cotton areas in the northwest inland will increase, the available water for production will increase, the cotton planting area will further increase, and the yield potential under natural conditions will increase. However, the total amount of water resources in cotton areas in the Yangtze River Basin has not changed much, but the available water resources have decreased, the interannual variation of water resources has expanded, the probability of extreme precipitation events in summer has increased, the probability of short-term drought and flood in cotton production has increased, the natural conditions of cotton production have deteriorated, and the potential of total output and yield per unit area has decreased.
(Zhou Zhiguo)