I. Topography and precipitation characteristics around Hongze Lake in history

Historically, the Huaihe River entered the sea alone, and floods could be directly transported from the river to the estuary. However, due to the frequent capture of the Huaihe River by the Yellow River, the passage of the Huaihe River into the sea was blocked, and Hongze Lake in the middle reaches of the Huaihe River was formed, which had a far-reaching impact on the flood disaster and riverbed evolution in the middle reaches of the Huaihe River. Therefore, the terrain around Hongze Lake should be relatively flat in history, and the precipitation characteristics are seasonal precipitation, with more precipitation in summer and less precipitation in winter.

Second, expand knowledge.

1, Hongze Lake

Hongze Lake is located in the lower reaches of Huaihe River in the west of Jiangsu Province, on the west side of the central part of Subei Plain, in Huai 'an and Suqian.

Geographical location is 33 north latitude? 06′—33? 40', east longitude 1 18? 10′— 1 18? 52' is the junction of the middle and lower reaches of the Huaihe River. Originally a shallow lake group, it was called Fuling Lake in ancient times. After the Han Dynasty, it was called Broken Kettle Pond, which was called Hongzepu in Sui Dynasty and Hongzehu in Tang Dynasty. After 1 128, the Yellow River south migrated through Surabaya to seize the lower reaches of the Huaihe River and enter the waters below Huaiyin. The Huaihe River lost its access to the sea and stored water in the east of Xuyi, and the original small lake was expanded into Hongze Lake.

Zaoze Lake in Hong Ju has a vast surface, rich resources and a long history. It is not only a large reservoir and shipping hub in the Huaihe River basin, but also a production base for fisheries, specialties and livestock products. Known as the "sunrise for gold."

2. Causes of formation

There are three major factors for the formation of Hongze Lake: First, the depression formed by the crustal fracture is a natural factor for the formation of Hongze Lake, and the embryo began in a small lake before the Tang and Song Dynasties. There are mainly Fuling Lake, Pofu Creek, Mudun Lake and Wanjia Lake.

Second, the Yellow River's capture of Huai River is an objective factor that forms the embryonic form of Hongze Lake. In the fifth year of the Song Dynasty (A.D. 1 194), the Yellow River decided to take it, and it was divided into north and south branches on Liangshanpo. The south branch joins Surabaya and flows southward into the Huaihe River, which is the beginning of the diversion of the Yellow River. In the fifth year of Xianfeng in the Qing Dynasty (AD 1855), the Yellow River moved north and entered the sea from Lijin. The Yellow River occupied the Huaihe River for nearly 700 years.

Because the Yellow River is condescending, it flows into the Huaihe River, where Huanghuai meets, the flow increases and the water level rises, connecting small lakes and depressions such as Fuling Lake and Broken Kettle Pond into a lake.

Thirdly, the construction of high weir (Hongze Lake levee) is a man-made factor and a decisive factor for the complete formation of Hongze Lake.