Chapter 23 Section 1 The low-lying and rainy Taihu Lake Basin

The Taihu Basin is centered on Taihu Lake, including the southern part of Jiangsu Province, the northern part of Zhejiang Province, and most of Shanghai.It starts from Maoshan Mountain and Tianmu Mountain in the west, the East China Sea in the east, the Yangtze River in the north, and Hangzhou Bay in the south.The area is 36500 square kilometers.The western part of the basin is mountainous and hilly, about 8,000 square kilometers, accounting for 22% of the entire basin area.Except for the main peak of Tianmu Mountain, the height of mountainous areas is generally 200-500 meters.The central and eastern parts are waters (lakes, rivers), depressions and plains.The water area covers an area of ​​more than 6,000 square kilometers, accounting for about 16% of the entire basin area.Lake Taihu is the largest, more than 2400 square kilometers.The area of ​​depressions and plains is about 22,000 square kilometers, accounting for 62% of the whole basin.The shape of the Taihu Lake basin is like a shallow dish. Except for the mountains and hills in the west, the height of the east, south, and north is also between 418 meters. There is a depression in the middle, and the height is mostly about 3 meters.

The Taihu Lake Basin has abundant rainfall, with an average annual precipitation of 1100 milliliters.It belongs to the subtropical monsoon climate zone. Every year at the turn of spring and summer, the northward warm air flow and the southward cold air flow meet here.The rainy season is good for rice growth, but if it lasts too long or the rainfall is too heavy, it will cause floods, especially harmful to rapeseed and wheat.And because the Taihu Lake Basin is located on the southeast coast, typhoons often make landfall here in July, September and September every year.The typhoon is fierce, and the daily rainfall is often as high as several hundred millimeters.If the drainage facilities are not good, especially in the central and eastern parts, it will lead to severe flooding.Throughout the year, the Taihu Lake Basin also has a season with less rainfall. At this time, if there is no irrigation equipment, droughts will also occur in places with higher terrain, especially the upper reaches of the Taihu Lake Basin.

In the early days of our country's history, the Taihu Lake Basin was considered the worst place in the country.It was written in the Warring States Period (475 BC-221 BC), one of the earliest geographical documents in my country - "Yu Gong", which divided the whole country into Kyushu and determined the level of each state. The best is "Shangshang" , the worst is "Xia Xia", a total of nine grades.At that time, the Taihu Lake Basin belonged to Yangzhou among Kyushu, and Yangzhou was listed as the worst "Xiaxia" and so on.During the Song, Yuan, Ming and Qing dynasties, the status of the Taihu Lake Basin represented by Suzhou (zhou) and Hangzhou (zhou) rose sharply, and it was considered the best place in the country and a "paradise" on earth.In the long river of history, why the status of the Taihu Lake Basin has changed so dramatically is related to the rapid development of agriculture here.Agriculture is the main body of my country's ancient economic structure, and the level of agricultural production is the main basis for demarcating land grades.In the early history of our country, the agricultural output in the Taihu Lake Basin was extremely low, and many places were still barren, so people naturally listed it as "Xiaxia" and so on.Since the Southern Song Dynasty, the agriculture here has been extremely developed, and it has become the granary of the whole country. There is a saying that "Su (zhou) lake (zhou) is cooked, the world (Southern Song Dynasty) is full", people take it for granted that it is a "paradise" on earth.

The land is the original land, and the climate is not much different from ancient to modern. Why the agricultural production in the Taihu Lake Basin has jumped from a very low level to the first in the country. Although the reasons are very complicated, it is very important. When it is related to water conservancy construction close relationship.In the early days, there were very few water conservancy projects here. If there was a few days of drought, the agriculture in the highlands would be in disaster; if there was a little more rain, the farmland in the lowlands would become a country, so the level of agricultural production was very low.Later, with the development of water conservancy, high townships with ponds like stars, lowland rivers and puddles formed a network, and the ability to resist floods and droughts was enhanced. Therefore, the level of agricultural production increased rapidly.

Generally speaking, the water conservancy construction in the Taihu Lake Basin was in the preliminary construction stage before the Qin and Han Dynasties. It had preliminary development during the Three Kingdoms, Jin and Southern and Northern Dynasties.