Hongze Lake is the fourth largest freshwater lake in China. In the lower reaches of Huaihe River in the west of Jiangsu Province, in the west of the central part of the North Jiangsu Plain, in Huaian and Suqian cities, it is the junction of the middle and lower reaches of the Huaihe River. Formerly known as shallow small lakes group, the ancient name of Fuling Lake, after the Han Dynasty, called Broken Putang, Sui called Hongzepu, the Tang Dynasty was originally named Hongze Lake. After 1128, the south of the Yellow River migrated to Surabaya via Huaiyin below the lower reaches of Huaihe. Huaihe lost its way into the sea, and the east of Xuyi kept its water.
Hongze Lake is a vast lake with abundant resources and a long history. It is not only a large reservoir and shipping hub in Huaihe River Basin, but also a production base for fisheries, special products and livestock products. It is known as "Sunrise Dou Jin".
Hongze Lake is a transitional zone between the warm temperate Huanghuaihai Plain and the middle and lower reaches of the North Subtropical Yangtze River. Due to the influence of monsoon climate, the precipitation of Hongze Lake is relatively abundant.
Hongze Lake is a super-water lake, and its area fluctuates greatly with water level. At the normal water level of 12.5 meters, the area is 2069 square kilometers and the volume is 3.127 billion cubic meters. It is the fourth largest freshwater lake in China. When the water level of the lake reaches 13.5 meters, the area of the lake area is 2231.9 square kilometers and the corresponding reservoir capacity is 5.295 billion cubic meters. At this time, the area of the lake area is basically the same as that of Taihu Lake, the third largest freshwater lake in China (the area of Taihu Lake is 2,388 square kilometers). When the water level is 17 meters, the flood control reservoir has a capacity of 13.5 billion cubic meters. The maximum water depth is 5 meters, and the average water depth is 1.5 meters. The elevation of the lake bottom is generally between 10 and 11 meters, and the lowest is about 7.5 meters. The elevation of the lake bottom is 4-8 meters higher than that of the eastern plain, so it is also called "suspended lake".
The highest water level in the history of Hongze Lake was 16.9 meters, which occurred in the first year of Qingxianfeng (1851). The water level of Hongze Lake rose sharply because of the breaking Dangshan of the Yellow River and the overflow of Liutang River to the east. The Liba (located on the South Bank of Sanhe sluice) was washed out. Since then, the Huaihe River has changed from sea-entry to river-entry. The lowest water level of Hongze Lake was 9.68 meters, which occurred in 1966.
The water quality of Hongze Lake belongs to the medium-eutrophic type. The main pollutants in Hongze Lake are organic matter, ammonia, phenol and total mercury. The average annual water temperature is 16.3 C, the highest water temperature is 28 C on September, and the lowest water temperature is 3 C on January. The freezing phenomenon occurs every year in Hongze Lake to varying degrees. Only when the strong cold air in the North passes through, the lake surface is frozen. The freezing of the whole lake generally occurs in the fish in the cold January-February. Cyprinidae is the dominant species, accounting for more than 50% of the total Lake species.
