Cheng Hai

Chenghai Lake, also known as Chenghai Lake and heiwuhai lake, is located in the middle of Yongsheng County, Yunnan Province. It is long from north to South and narrow from east to west. The lake covers an area of 77.2 square kilometers, with an altitude of 1503 meters. The average water depth is 25.9 meters, the deepest is 36.7 meters, and the water storage capacity is 1.987 billion cubic meters. It is 20 kilometers long from north to south, 4 kilometers wide from east to west, and 45.1 kilometers long. Chenghai Lake is now a closed lake. Chenghai originally entered Jinsha River from Haikou river. After 1609, the water level of Chenghai Lake decreased year by year and no longer connected to the river. It gradually evolved into an inland lake. Although Chenghai Lake had no outlet, it discharged part of the lake water by way of groundwater, so its salinity was not high and it was a freshwater lake. There are many kinds of fish in the lake, such as Cyprinus carpio, white streaked fish, red winged fish and so on. Chenghai is one of the three major Spirulina natural producing areas in the world.

Cheng Hai

Chenghai, a lake in Jinsha River Basin in Yongsheng County, Yunnan Province. It is located in the middle of Yongsheng County, Yunnan Province, with a general area of 78.8 square kilometers and a general volume of 2.7 billion cubic meters. Chenghai is located at the bottom of the basin formed by Chenghai fault zone. It was a tributary of Jinshajiang River in ancient times and then subsided into a lake. The lake water mainly comes from the mountain springs around the basin. The lake water flows into Jinsha River through the South Lake mouth and the lower reaches of Chenghe River (Haihe River and Qina River). In modern times, due to the change of hydrology and climate, the lake water no longer leaked out and became an inland lake.

As early as the Ming and Qing Dynasties, lake water was used for irrigation, and tobacco, agriculture, forestry and fruit industry flourished. Chenghai is also one of the three lakes where blue-green algae (Spirulina) grow naturally in the world, and is the largest Spirulina culture and production base in the world.

Origin of formation

Chenghai, formerly known as Chenghe, came from the Tang and Song dynasties. In ancient times, Chenghai was 60 kilometers from hushou to Jinsha River. According to Wanli's Yunnan general annals, Volume 4, beishengzhou historic sites, "Chenghai stone tablet: it is said that fishermen net fish and occasionally catch stone tablet. It is inscribed with the title of" great sage Cheng River, wonderful feeling of King ", and gaimeng's imitation fiefdom. Its stone drain has been dry for decades, and it is still moist." According to the newly compiled Yunnan general annals, Jinshi Kao: "according to the same record in volume 3 of Liu Wenzheng's Yunnan annals, only the Mengshi Fangfeng was changed to Duan's Fangfeng."

According to the historical records and maps of the Ming Dynasty, Cheng Hai is already in use. According to the records of the old annals, it is said that in the past, the land was inhabited by a person surnamed Chen, who became the sea overnight. Later, Chen was Cheng. "In terms of causes, this is the theory of affiliation, but in terms of name, there is a certain truth. At least in the Ming and Qing Dynasties, the surnames of Cheng, Chen and Hai lived together around Chenghai, which is a branch of Yi language. It shows that the name of Cheng Hai has a certain relationship with the surname of the residents.

Location context

The Chenghai Lake is a long and narrow river valley in the South and adjacent to the Sanchuan basin in the north. According to the records of Yongsheng County annals (1990 edition): in the 1980s, the average elevation (water level) of the lake was 1503 meters, the length of Chenghai Lake was 22 kilometers, the average width of the lake was 4.0 kilometers, the length of the lake bank was 45.1 kilometers, and the lake area was 78.8 square kilometers (equivalent to 115800 mu). It is one of the eight lakes in Yunnan Province.

The average annual precipitation of Chenghai Lake Basin is 732.4 mm, and the evaporation is three times of the rainfall. Due to the lack of large river supply and the 37 pumping stations along the Lake pumping water for agricultural production, the water level of Chenghai Lake continues to drop. According to the government website in 2018, by the beginning of the 21st century. The general water level is 1496.7 meters, the lake is 18 kilometers long and 4.5 kilometers wide, with a total water area of 77.21 square kilometers. It is one of the nine plateau lakes in Yunnan Province.

In the 1980s, the administrative region of Chenghai was Liangguan District of Yongsheng County in the north and Xinghu District in the south. According to relevant information in 2018, Chenghai water area is under the jurisdiction of Chenghai Town, 20 km south of Yongbei Town, Yongsheng County, 8 km straight away, and 18.5 km away from Yongsheng County.

hydrographic features

According to Yongsheng County annals (1990 edition): in the 1980s, the average water depth of Chenghai was 25.736 meters, the maximum water depth was 36.9 meters, the total water capacity was 2.7 billion cubic meters, and the water storage capacity was 1.987 billion cubic meters.

According to the information on the government website in 2018, by the beginning of the 21st century, the water level was 1496.7m, which was lower than the 1501m control line. The average water depth was 25.7m, the maximum water depth was 35m, the theoretical water storage was 1.98 billion cubic meters, and the actual water storage was 1.56 billion cubic meters.

According to the topographic survey of Hengduan Mountain Lake Group of Nanjing Institute of geography, Chinese Academy of Sciences in 1981, Cheng Hai has accumulated 1.987 billion cubic meters of water for many years, with an average water depth of 25.74 meters and the deepest of 35.1 meters. The pH value of the lake water is 9.1, showing a heavy alkali reaction. According to the observation of Hekou horizontal station, the annual rainfall is only 751.1 mm, and the evaporation is 2217.5 mm, which is 3.07 times of the precipitation. The accumulated water area is 318.3 square kilometers, and the annual water volume is 112 million cubic meters. Due to the lack of water supply, the lake level is declining year by year. From 1961 to 1981, the water level of Chenghai Lake decreased by 3.04 meters, with an average annual decrease of 0.152 meters. Chenghai Hekou Street station measured in 1981: the accumulated water area is 318.3 square kilometers, and the annual average runoff is 1.182 billion cubic meters.

According to the data from Yongsheng County Government, at the beginning of the 21st century, the lake water temperature was between 17.6 ℃ and 20.5 ℃, and the water quality was alkaline (pH 9.4).

Chenghai Lake is a natural inland closed lake, and its water purification function is relatively weak. With the increasing population along the lake, the poor vegetation along the lake and the extensive development of agricultural production, a large number of agricultural pollution sources, domestic pollution sources, enterprise sewage, soil erosion caused by natural disasters, etc., have caused serious pollution to Chenghai Lake The water quality of the lake belongs to four types, and the negative nutrition is becoming more and more serious.

Lake system

There are three sources of Chenghai water: first, there are underground springs in the northeast of Chenghai, which come from the lake and are the main sources; second, according to the old records, the Baqing river flows into Chenghai through Jiming mountain in Qingquan township; third, on the surface, Liujia River, Pumi River, Tuanshan River and Jiguan River in the east of the lake; erlangqing River and jinzaolangqing River in the west of the lake; Shanqing river around Heiwu in Hubei Province all seeps through them. Before the middle of Ming Dynasty, the water of Chenghai flowed into Jinsha River.

Chenghe River, also known as Haihe River and Qina River, is the lower reaches of ancient Chenghe river. It was originally connected with Chenghai River and mainly originated from Chenghai river. The outlet of Chenghai river flows to a section of Jinsha River, with a total length of 38 km. In the late Qianlong period of Qing Dynasty, due to the change of hydrology and climate, it became a seasonal river. In modern times, Chenghe River, on the surface water, has been separated from Chenghai and become an independent river. But the map of the Republic of China still shows that rivers and lakes are connected. The modern Chenghe river originates from Jiaoding mountain and flows into Jinsha River through Chenghai Town, Xinghu Town, Qina Town, Taoyuan Town, etc. The whole basin covers an area of 424 square kilometers.

It is speculated that Chenghai groundwater is still connected with Chenghe river. There is manguanlongtan in manguan Township in the lower reaches of Chenghai, where Chenghai sea water flows. The flow rate is 0.4 cubic meters per second. Besides irrigating the land of manguan and dagoutian, the remaining water flows into Chenghe river.

geographical environment

landforms

Chenghai Lake was formed in ancient times, which is called tertiary (quaternary) in the history of geology. The fault graben formed by Himalayan movement, formed in the middle depression, accumulated water to form lake, which is similar to the formation of Ninglang Lugu Lake in Erhai, Dali.

There are also historical records that Chenghai Lake was formed more than 1000 years ago by a subsidence earthquake. The earthquake reduced and dried up the water source, and the lake rose underwater, gradually becoming a closed inland lake.

At the northern end of the Chenghai fault zone, the fault is in a North, northeast north-south trend. At the southern end, it intersects with the Honghe fault zone at Midu Juli, extends to beixiangyun and Binchuan, enters from Pianjiao, passes through Jinsha River to Qina, Chenghai and other fault basins, passes through Chengxi Guanshan to dachangping, and then turns right in a north-east direction to extend to connect with the xiaojinhe fault in Sichuan. Tectonically, it is mainly located at the junction of the Sichuan Yunnan axis and the Yanyuan and Lijiang platform marginal depressions. Chenghai is connected with qinaba, which is in the north-south direction, and the west side of qinaba is controlled by the North-South fault.

Chenghai is located in the Chenghai fault zone, and the valley topography is significant. In the north is sanchuanba, covering an area of 85 square kilometers, with cultivated land of 63418 mu, belonging to fault subsidence paddy alluvial soil. In Qing Dynasty, mengchuan, Huichuan and Jichuan flowed through the dam. The terrain is north-south, slightly west inclined, long strip wide valley basin, with an altitude of 1550 meters, average annual precipitation of 821 mm and frost period of 269 days. It produces grain, sugarcane, tobacco and silkworm, which is the granary of Northwest Yunnan. Chengnan is located in Nanba, covering an area of 96 square kilometers and 96000 mu of cultivated land. In ancient times, it was a fault subsided valley basin, which was rectangular in shape, with Qina as the central market town, so it was named. The terrain is north-south, and the Chenghe river passes through the basin. The average altitude is 1430 meters, the average annual precipitation is 693 mm, and the frost free period is 260 days. It is rich in sugarcane, peanut, longan, watermelon and grain.

climate

Chenghai basin belongs to the monsoon climate of the middle subtropical plateau, with the prevailing south wind. The annual average temperature is 17.8 ℃, and the average temperature of the coldest month is 8-11 ℃

Chinese PinYin : Cheng Hai