Climatic Environment of Heshui River Basin

It belongs to the humid monsoon climate zone in the middle subtropical zone, with mild climate, abundant rainfall and sunshine. The climate in spring is warm, the temperature in summer is high, the weather is hot, and the autumn is very hot, especially in July and August. In late autumn, there is little rain in September and1October, and the climate is dry, so it is easy to be affected by typhoons in summer and autumn to produce rainstorm weather. Winter is wet and cold, sometimes cold air invades, the temperature drops below zero, but there is less rain and snow; Four distinct seasons, short winter and spring, long summer and autumn; The frost-free period is long.

The mountainous area of Luo Xiao in Heshui River Basin is one of the rainy areas in Jiangxi. Heavy rains are frequent, wide in scope and strong in intensity, which are easy to form large floods or extraordinarily large floods, causing great damage to industrial and agricultural production, people's lives and ecological environment. Generally, April-September is the flood season. About 70% of the floods occur in April-June of the main flood season, and a few occur in the flood season in early March and the autumn flood season in July, August and September. There are still floods in February and 10 in very few years. From the first year of the Western Jin Dynasty (A.D. 304) to A.D. 1645 1949, there were 122 times of catastrophic floods recorded in historical books, and it was recorded in historical books that "the river surged, the city collapsed and many people drowned." And "Yongxin and Luling are flooded, and people are hungry when they are old." And the record of "the Wo and Lu rivers are flooded, the water is soaring, the houses are tilted, the drifting people and animals are ignored, people are hungry at the age of 20, and people eat wild vegetables and Guanyin soil". After the founding of People's Republic of China (PRC), there were 3 floods1time, including 3 floods1time and 3 extraordinary floods. General floods occur once every 2-3 years, major floods occur once every 5-6 years, and catastrophic floods occur once every 20 years, such as 1962, 1982 and 2002, especially 1982, and the affected area is as high as 40,000 hectares. After July, the rainy season basically ended, and it entered the high temperature and little rain season. Rainfall drops sharply, temperature rises, humidity decreases, evaporation increases suddenly, and severe drought often occurs in summer and autumn. The earliest drought was recorded in the second year of Long 'an in the Eastern Jin Dynasty (AD 398). From then to 1949+0550, there were 94 extraordinary droughts recorded in historical materials. Historical records in previous dynasties recorded that "Jizhou County suffered from drought, with a rice bucket of 5,000 meters, and many people starved to death" and "Luling County suffered from drought, a hundred miles of bare land, great hunger, vines stripped away, hungry people had no food, people migrated, and the county town was stolen." And the record of "drought epidemic, cracked fields, fern roots dried up for people to eat wild vegetables, and hungry people were dying". After the founding of People's Republic of China (PRC), there were 19 drought years and 6 severe drought years, such as 1963, 1965, 1986 and 2003, and the affected areas were all nearly 60,000 hectares. "First-line flood, large-scale drought" is a remarkable feature of flood and drought disasters in Heshui basin.