Collect information about the Yangtze River and talk about your understanding of the Yangtze River.

I. Physical geography

The Yangtze River originates from the northern foot of Tanggula Mountain on the Qinghai-Tibet Plateau and the southern side of Gladding Winter Snow Mountain. The source of the river is Tuotuo River, and its main stream flows through Qinghai, Tibet, Yunnan, Sichuan, Chongqing, Hubei, Hunan, Jiangxi, Anhui, Jiangsu, Shanghai, etc. 1 1 province (city, district), passes through the three economic zones of Southwest China, Central China and East China, and flows into the East China Sea in Shanghai. The Yangtze River, with a total length of more than 6,300 kilometers, is the largest river in China and one of the largest rivers in the world, with a drainage area of about 6,543.8+0.8 million square kilometers, accounting for 654.38+0.87% of the country's total area. The shape of the Yangtze River basin is long from east to west, short from north to south, high in the northwest and low in the southeast.

Rivers in the main stream of the Yangtze River are divided into upper, middle and lower reaches according to the characteristics of rivers and the topography of river basins. From Jiangyuan to Yichang, Hubei, it is called upstream, with a length of about 4500km and a drainage area of 1 10,000 km2. Yichang to Hukou, Jiangxi Province is called the middle reaches, with a total length of more than 950 kilometers and a drainage area of 680,000 square kilometers. The reach from Zhicheng to Chenglingji, commonly known as Jingjiang River, is about 340 kilometers long. On the south bank, there are four ports, Songzi, Taiping, ouchi and Tiao County (Tiao County was blocked in 1959), which discharge water into Dongting Lake and connect with Hunan, Zi, Yuan and East Lake. After passing Chenglingji, the Yangtze River turns to the northeast. When it reaches Wuhan, the Han River flows into Hukou, where it receives the rivers of Jiangxi, Fuzhou, Guangxi, Rao and Xiu in Poyang Lake. Hukou to the Yangtze estuary is called the downstream, with a length of 938km and a drainage area of about 654.38+200,000 km2. The plain area in the middle and lower reaches of the Yangtze River is the key area for flood control.

See Figure 2- 1 for the distribution map of major rivers and hydrological stations in the Yangtze River Basin.

About 109 large reservoirs have been built in the Yangtze River basin, with a total storage capacity of 86.7 billion m3, including more than 12 in Three Gorges, with a total storage capacity of 818 billion m3. There are 929 medium-sized reservoirs with a total storage capacity of 23.8 billion m3, of which there are over three Gorges 163 reservoirs with a total storage capacity of 3.94 billion m3.

Second, the meteorological and hydrological characteristics

The Yangtze river basin is located in the subtropical region in the eastern part of Eurasia and has a typical monsoon climate. South winds prevail in summer, north winds prevail in winter, and Leng Xia is hot in winter, with four distinct seasons. The average annual precipitation in the basin is 1067mm, and the regional distribution and annual distribution of annual precipitation are very uneven.

The Yangtze River flood is formed by rainstorm, so the flood occurrence time and regional distribution are consistent with rainstorm. From the time of flood occurrence, the downstream is earlier than the upstream, and Jiangnan is earlier than Jiangbei. Dongting Lake and Poyang Lake have the earliest flood season, generally from April to July, and Lishui is from April to August. Wujiang River on the south bank of the upper reaches of the Yangtze River is from May to September; The tributaries of Jiangbei, including Jinsha River and Hanjiang River in the middle reaches, from June to10; The main stream of the middle and lower reaches is affected by the floods in Dongting Lake and Poyang Lake, and the flood season is from May to 10. The main flood season of Xiangjiang River, Zishui River and Poyang Lake is from April to June. May-July in Yuan, Lishui, Qingjiang and Wujiang; The tributaries in Jiangbei and the main stream above Hankou are from July to September; The main flood season of Datong Station is from June to August. In the main flood season of the main tributaries in Jiangbei and the main stream above Hankou, the water volume is the largest in July and August, and the flood peak opportunities are the most. The flood in the Yangtze River is mainly characterized by peak height, and the flood process of each tributary is generally about 10 day. Because the main stream collects tributary floods, especially the middle and lower reaches are regulated by lakes and river troughs, a flood lasts for a long time, with Pingshan and Yichang in the upper reaches about 10 ~ 30 days, and Hankou and Datong in the middle and lower reaches over 50 days.