What is the general cause of flood in Huaihe River Basin?

Generally, it is formed by long meiyu period and large-scale continuous rainstorm.

Heavy rains and floods in the Huaihe River basin are concentrated in the flood season from June to September, and mainly occur in Huainan mountainous area in June. It can occur in the whole basin in July; In August, it mostly appears in Funiu Mountain area in the west and Yimeng Mountain area in the northeast, and typhoon rainstorm often occurs in the eastern coastal areas affected by typhoons.

The rainstorm in the basin decreased in September. Generally, from mid-June to early July, the south of Huaihe River enters the rainy season, which usually lasts for 15-20 days and lasts for one and a half months.

The average annual runoff of Huaihe River Basin is 6.21100 million cubic meters, of which Huaihe River System is 45.3 billion cubic meters and Yishu Sishui River System is168 million cubic meters. The average annual runoff depth in Huaihe River Basin is about 23 1mm, including 238mm in Huaihe River System and 2 15mm in Yishu Sishui System.

The annual distribution of runoff is also very uneven, mainly concentrated in the flood season. The measured inflow of control stations in the main stream of Huaihe River accounts for about 60% of the whole year in flood season, and the tributary of Yishu-Sishui River system accounts for a larger proportion in flood season, accounting for about 70% ~ 80% of the whole year.

Extended data

During the flood season from May to August in Huaihe River Basin, the rainfall in three months is usually 500-600 mm, especially in June-July, which is a unique rainy season in Jianghuai area, and the rainfall can last for one or two months. Wide range, covering the whole basin; Rainy years alternate with poor harvest years, and the average difference in precipitation is four or five times.

Typhoon, vortex shear, north-south shear and cold shear line are the weather systems that produce heavy rain in Huaihe River basin, and the first two are mostly. Vortex shear type is the main type in the early rainy season, and typhoon is involved in the later rainy season. The typhoon track covers the whole basin.

The trend of rainstorm is generally consistent with the movement of weather system, and the center movement of typhoon rainstorm is related to the typhoon path. Cold peak rainstorm usually moves from northwest to southeast, and vortex rainstorm usually moves from southwest to northeast. With the intersection of north-south airflow, the shear line or front swings north-south, southeast and northwest, and the rainstorm center moves with it.

References:

Baidu encyclopedia-Huaihe River