Dianchi Lake

Dianchi Lake

Dianchi Lake, also known as Kunming Lake, Kunming Lake, Nanze lake and dianhai lake. In the southwest of Kunming City, there are rivers such as Panlong River. The lake is 1886 meters above sea level and covers an area of 330 square kilometers. It is the largest freshwater lake in Yunnan Province, known as the Pearl of the plateau. The average water depth is 5 meters and the deepest is 8 meters. The lake, known as Tanglangchuan, is the upper source of Pudu River, a tributary of Jinsha River in the upper reaches of the Yangtze River.

With beautiful scenery, Dianchi Lake is a national tourist resort in China. Surrounded by Yunnan Ethnic Village, Yunnan Ethnic Museum, Xishan Huating temple, Taihua temple, sanqingge, Longmen, Qiongzhu temple, Daguanlou, Jinning Panlong temple, Zhenghe Park and other scenic spots. The resort covers an area of 18 square kilometers.

In 1262, Songhua Dam was built on the Panlong River. In 1268, Haikou river was dug to increase the discharge of Dianchi Lake and reduce the flood around the lake. Since 1955, more than ten large and medium-sized reservoirs have been built in the upper reaches of the lake, and dozens of electric irrigation and drainage stations have been built along the lake to relieve the flood disaster and ensure the water supply for farmland irrigation and urban industry and life. The lake produces carp, crucian carp, goldfish, etc.

Business card picture: landscape of the northwest Bank of Dianchi Lake

The origin of the name

Dianchi Lake is also called Kunming Lake. There are four opinions about the origin of the name of Dianchi Lake. According to the chronicles of Huayang · chronicles of nanzhong written by Chang Yu of Jin Dynasty, Dianchi Lake is called Dianchi Lake because it is "shallow and narrow, like a backward flow." This is geographically speaking. Another way of saying is to study the meaning of the sound, that "Dian, Dian also." Some people think it is the meaning of "dian" in Yi language, that is, dabazi. The third argument is based on the national appellation. According to the biography of Southwest Yi in historical records, "dian" is the largest tribe name in this area in ancient times (DI Qiang "suzu", "Bo Zu" or "Furong"). After Zhuang Qiao, the general of Chu, came to Yunnan and became the king of Dian according to the custom. Therefore, the name of Dian Chi came first from Dian Chi tribe. The fourth view is that "dian" is the "Pavilion" or "ancestral temple" in Zhuang language, which refers to the location of ancestral temple.

According to the historical geography of Dianchi Lake area, the cultural traditions of the ancient Qiang people are "limb bending burial" and cremation. In the excavation of hundreds of tombs in the pre Qin and Han Dynasties in Dianchi Lake area, there is only one "bent limb burial", and the rest are "buried on the back of the body". The remains of cremation have not been found and reported. This proves that the residents of Dianchi area in the pre Qin and Han dynasties had little to do with di and Qiang. Kunming people, the forefathers of Yi people, first came to Dianchi area after the Eastern Han Dynasty. The historical records of the Western Han Dynasty says: "during the reign of King Wei of Chu, general Zhuang Qiao When it comes to Dianchi Lake, the place name "Dianchi Lake" has been recorded in history. Li Daoyuan of the Northern Wei Dynasty said: "pool The upper source is deep and wide, and the lower one is shallow and narrow, but it is like a backward flow, so it is called Dianchi Lake. " Therefore, "the theory of water system inversion" is more reliable.

Formation and evolution

Dianchi Lake is a seismic fault subsided lake. At the end of Mesozoic and the beginning of Cenozoic (about 70 million years ago), the ancient Panlongjiang river has developed. Due to long-term water erosion, it has become a wide and shallow valley near Kunming. By the late Miocene of Cenozoic (about 12 million years ago), the land of Yunnan had experienced several intermittent unequal uplifts, followed by the appearance of large north-south faults. To the west of the fault line, the crust is uplifted, forming a steep western mountain, which seems to rise from the lakeside; to the east of the fault line, the fault line is relatively sinking, coupled with the uplift of the citongguan mountain at the junction of the southwest of Jinning County and Yuxi City, resulting in the blocking of the south flow path of the gupanlong River and the accumulation of water, thus forming the ancient Dianchi Lake.

Another theory is consistent with this theory, that the ancient Dianchi lake belongs to the red river system, flowing into the Red River from the Erythrina pass. Later, when the waters of Dianchi Lake dropped below 1940 meters, after a long time, the Erythrina pass rose and the Haikou River sank, the outflow of Dianchi Lake was blocked, and then it changed from the Haikou River to the Jinsha River system from the west to the north.

In ancient times, Dianchi Lake started from Songhuaba in the north, Baofeng in Jinning in the south, wangjiaying in Chenggong in the East and the foot of jinmajie mountain in the West. From the Warring States period to the Western Han Dynasty, the water level on the Northeast Bank of Dianchi Lake dropped to about 1915 meters. Today, a large area of hills near luosuopo, Longtou street and Huangtupo have been exposed. By the Tang and Song Dynasties, the water level of Dianchi Lake had dropped to 1890 meters, with 510 square kilometers; in the Yuan Dynasty, it had shrunk to 410 square kilometers, 350 square kilometers in the Ming Dynasty, 320 square kilometers in the Qing Dynasty, and today it is less than 300 square kilometers. The storage capacity of Dianchi Lake is also decreasing with the area. It was 1.85 billion cubic meters in the Tang and Song Dynasties and 1.6 billion cubic meters in the Qing Dynasty. It was estimated that the storage capacity of Dianchi Lake was about 1.57 billion cubic meters in 1947 and only about 1.3 billion cubic meters today.

Location context

Dianchi Lake, located in the center of Kunming Bazi, starts from Chenggong District in the East, reaches the foot of Xishan Mountain in the west, faces Daguan Park in the north and Jinning County in the south

. All of them are located in Kunming, the capital of Yunnan Province, and the half of Beijing University is under the jurisdiction of Kunming. Among them, the northwest part is Xishan District, accounting for about one-third of the total area, with Qianwei street, Fuhai street, Biji Town, Haikou town and other places along the coast; the upper part of the northeast part is Guandu District, accounting for about one sixth of the total area, with Liujia street, Guandu Street, Yiliu street and other places along the coast; the lower part of the northeast part is Chenggong District, with Dounan street, Longcheng street, Dayu Township, majinpu Township and other streets or towns along the coast Villages and towns. About one-third of the south is Jinning County. Along the coast are Xinjie Township, Jincheng Town, Shangsuan Township, Kunyang Town, Erjie Township, etc.

Dianchi Lake is the largest lake in Southwest China. The basin area (excluding the river basin area below Haikou) is 2920 square kilometers. The Dianchi Lake is 40 km long (including Caohai Lake) from north to South (about 32 km long), 7 km wide from east to west, and 12.5 km wide at the widest point. The lake is 1886 meters above sea level, and its shoreline is about 150 kilometers long.

In the north of the lake, there is a sea ridge across the East and West, which is a barrier bar with a length of 3.5 km and a width of 300 m. the east end of the lake is connected with the Panlong River Delta, and the west end extends into the Dianchi Lake. The lake is divided into two parts, the inside and the outside, which has the reputation of "one line equally divides the autumn". The south of the ridge is called the open sea, which is the main part of Dianchi Lake, covering an area of 289.065 square kilometers, accounting for 97.2% of the total area of Dianchi Lake; the north of the ridge is called the inland sea, also known as Caohai, covering an area of about 10 square kilometers. The average depth of Dianchi Lake is about 5 meters, and the deepest is about 8 meters. The northern Caohai Lake is shallow, only more than 1 meter deep.

hydrographic features

Water quantity

The upstream Panlongjiang river basin covers an area of 903 square kilometers, with an average annual runoff of 165 million cubic meters.

After the sluice was built in Haikou, the water level of Dianchi Lake was basically under human control. According to the regulations of Yunnan Province on the protection of Dianchi Lake, the controlled operating water level of Dianchi Lake is: normal high water level 1887.5m, minimum working water level 1885.5m, countermeasure water level 1885.2m in extremely low water year, limited water level 1887.2m in flood season and maximum flood level 1887.5m in 20 years. Years of data show that it is basically within the controllable range.

In 2013, the Niulanjiang Dianchi water supply project was put into operation. As of December 11, 2018, 2.8 billion cubic meters of ecological water has been supplied to Dianchi Lake and 115 million cubic meters of emergency water has been supplied to Kunming

.

Water Quality

In the 1960s, the water quality of both Caohai and open sea in Dianchi Lake was classified into two categories, in the 1970s it was classified into three categories, in the 1980s it was classified into five categories and in the open sea it was classified into four categories, and in the 1990s it was further deteriorated. They are super 5 and 5. In the past 30 years, water quality has declined by three grades. In the 1950s, the transparency of Caohai was up to 2 meters, and that of the open sea was about 1 meter. In some places, it was even clear to the bottom. In the 1980s, Caohai was only 0.40-0.60 meters, and the open sea was 0.65-0.75 meters. In the 1990s, the transparency of Caohai was only 0.25 meters, and that of the open sea was only 0.41 meters. In the 1950s, Dianchi Lake was rich in aquatic higher plants, which accounted for more than 90% of the lake surface. By the end of 1970s, the vegetation area was less than 20%. The community of cauliflower is one of the main characteristics of Dianchi Lake. Before the 1960s, Caohai was once known as "Flower Lake" for its flourishing cauliflower. In the 1970s, there were few cauliflower. Today, cauliflower has been replaced by water hyacinth, and water eutrophication is becoming more and more serious. In the past, Dianchi Lake was rich in aquatic resources with a variety of fish, among which carp was the most abundant and golden thread fish was the most valuable. However, due to the pollution of water quality in recent years, the structure of biota has undergone adverse evolution. In the mid-1950s, there were 44 species of aquatic plants in Dianchi Lake, but in the mid-1980s, there were 29 species; there were 23 original fish species in Dianchi Lake, including 15 indigenous fish species, and now there are only 4 indigenous fish species.

There are three main reasons for water pollution in Dianchi Lake. First of all, Dianchi Lake is located in the lower reaches of Kunming City, which is the lowest concave area of Kunming Basin, so it has objectively become the "sewage bucket" of Kunming. This "bucket" must constantly accept domestic sewage, industrial wastewater and agricultural sewage containing pesticides and fertilizers. In addition, the rapid development of urbanization in Dianchi Lake Basin has increased the amount of sewage. According to statistics, about 200 million cubic meters of sewage, or about 200 million tons, are discharged into Dianchi Lake every year. Secondly, Dianchi Lake is a semi closed lake, lack of sufficient clean water to replace the lake water. In addition, in the process of natural evolution, the lake surface of Dianchi Lake shrank, the lake basin became shallow, and the endogenous pollutants increased

Chinese PinYin : Dian Chi