Main hydrological characteristics of rivers in Chaohu Lake basin

Chaohu Lake water system mostly belongs to subtropical humid monsoon climate. The annual average temperature in this basin is 16℃, the extreme maximum temperature is 4 1.3℃, and the extreme minimum temperature is-15.7℃. The relative humidity is 76%. The average annual precipitation for many years is 1, 2 1.5mm, in which the precipitation from May to August in flood season accounts for 5 1% of the annual precipitation. The maximum annual precipitation 1986 mm occurs in 199 1 year; The minimum precipitation is 672 mm, which appears in 1978. The average annual runoff is 5.92 billion cubic meters, and 5 1% of the runoff is concentrated in the flood season from May to August.

Heavy rains mainly concentrate in the flood season from May to August, and the overall distribution law is that the south is big and the north is small. Except for the floods in the Yangtze River, the floods in the basin are caused by heavy rains. During the period of 1954, the whole basin was flooded and encountered the highest flood level in the history of the Yangtze River, resulting in the highest flood level in Chaohu Lake reaching 12.93. 199 1 year, there were two consecutive rainstorms with heavy rainfall and long duration, but the water level of the Yangtze River was relatively low, and the highest flood level in Chaohu Lake was 12.7438+0 meters. The highest flood level in history 1849 and 193 1 year.