Caohai

Caohai

Caohai, also known as Nanhaizi and baxianhai, is located in the southwest of Weining County in western Guizhou Province, with a water area of 46.5 square kilometers. As a complete and typical plateau wetland ecosystem, it is an important wintering place and transfer station for 228 species of birds, such as black necked Crane.

Caohai is the largest plateau natural freshwater lake in Guizhou, an important wetland of grade I in China, and a national AAAA tourist attraction. It is one of the top ten bird watching bases in the world, and has been selected as the most popular tourist attraction in the world by National Geographic magazine.

Formation and evolution

Caohai is developed on the Weining Shuicheng anticline, which is mainly composed of middle and lower Carboniferous limestone. The formation of the lake basin is controlled by two groups of faults in NE and NW. The lake area is a developed agricultural area in Weining Yi, Hui and Miao Autonomous County, with flat terrain and thick soil layer. There are Lake erosion terraces from the lake bank. There are 85 meters thick lacustrine deposits in and around the lake, and there are common fossils in the middle and late Pleistocene giant panda Stegodon fauna, which indicates that Caohai has a complex development history and may have experienced many times of ponding shrinking This process is obviously closely related to the tectonic uplift and karst development and evolution since the Quaternary. The general trend is from large to small. Caohai Lake was formed in the 27th year of Daoguang reign of the Qing Dynasty (1847). At that time, continuous rain, mountain torrents, sand laden with rocks, blocked Caohai water dissipation cave. Tombstones of the Qing Dynasty were seen when the lake water was drained. In 1970, the lake was once drained into the Yangjie River (Luoze River).

Geology and geomorphology

In terms of geological structure, Caohai Nature Reserve is located at the top of the mountain shaped West Wing Reflection Arc in Qianxi and the northward bend of Weining Shuicheng anticline. From the geomorphological point of view, Caohai Nature Reserve is a steep plateau mountain narrow valley, and a stepped plateau mountain original landform. The topographic trend of Caohai basin is higher in the west, South and East. It gradually decreases northward from the center of the basin and becomes the discharge direction of Caohai Lake Basin. Caohai Lake Basin is surrounded by plateau gentle hills (Karst Hills), the terrain is gentle and open, and the ground undulation is very small. From the lake basin to the outside, the landform is plateau and Hilly Basin, and the ground fluctuates greatly.

Climatic characteristics

Guizhou Weining Caohai National Nature Reserve has a temperate climate with an average annual rainfall of 950 mm, an average annual temperature of 10.5 ℃ and an average relative humidity of 79%. The climate of the reserve is characterized by no severe cold in winter, no severe heat in summer, humid in summer and autumn, and dry in winter and spring. The dry and wet seasons are obvious. The dry season is from November to April of the second year, and the wet season is from May to October. The average annual temperature is 10.6 ℃, the average annual precipitation is about 1000 mm, and the relative humidity is 80%.

hydrographic features

Caohai belongs to the Yangtze River system and is the upper source lake of GEZE River, a tributary of Jinsha River. The water supply of Caohai is mainly from atmospheric precipitation, followed by groundwater supply. Caohai Lake is the largest natural freshwater lake in Guizhou Plateau, with a rainfall collection area of 120 square kilometers and an annual catchment of about 8-9 million m3. The rivers flowing into Caohai include maojiahaizi River, Dongshan River, Baima River and Dazhong river. Most of them are short streams originated from springs, and their flow varies with the seasonal variation of precipitation.

Caohai Lake has a water area of 46.5 square kilometers, a normal water level of 2171.7m and a maximum water depth of 5m. Affected by rainfall, the water area of Caohai Lake changes with seasons.

The soil types can be divided into four types: yellow brown soil, swamp soil, calcareous soil and stony soil. Among them, there are 15 kinds of cultivated soil, including yellow lime soil, black lime soil, pyrolime soil, clayey lime soil, small yellow mud soil, rhubarb soil, rock lime soil and lime clay.

Regional scope

The core area of Caohai Nature Reserve mainly includes bojiwan, huyelin, Zhujiawan, Xihai, wujiayantou and yangguanshan. There are shallow swamp, sedge wetland, meadow, grassland and other rare and endangered waterfowl habitats and foraging areas. History has proved that the water level of Caohai determines the hydrology and wetland area of Caohai, and plays a very important role in affecting the wintering population of black necked Crane in Caohai. Therefore, in order to comprehensively and effectively protect Caohai wetland ecosystem and rare and endangered waterfowl, its core area is defined by shallow swamp, sedge wetland, meadow, grassland and other rare and endangered waterfowl habitats, foraging area, aquatic biota concentration distribution area and some water areas formed at the highest water level of 2172.0m in Caohai, covering a total area of 2162.05 square kilometers, accounting for the total area of the reserve 52%. The buffer zone is defined by the land and water area of 100-500m around the core area, with an area of 539.51 square kilometers, accounting for 5.62% of the reserve area. The remaining areas outside the buffer zone in the reserve cover an area of 6898.44 square kilometers, accounting for 71.86% of the total area of the reserve.

Biological resources

plant resources

There are 43 species and 142 genera of aquatic plants in Caohai. The coverage rate of water, grass, agriculture and algae in Caohai reached 60%. At present, there are more than 40 kinds of aquatic plants, such as seaweed, reed, cattail, scallion, Azolla, Ceratophyllum, etc., and there are also many kinds of plants, such as agroalgae, discomorpha, etc. As of 2013, the plants in wet grassland and swamp of Guizhou Weining Caohai National Nature Reserve are Trifolium repens, Allium fistulosum, Polygonum hydropiper, Acorus calamus, Oenanthe javanica, Polygonum amphibium, tetragonum, Ceratophyllum, CHAROPHYTA, Plantago, myriophyta and Azolla. There are some artificial pine forests and shrub rhododendrons composed of Pinus armandii and Pinus yunnanensis in the surrounding area.

Animal resources

Among the fish resources, Weining fine fish is a rare specialty. It is 1-2 cm long, tender and delicious. In winter, it is also a cold resort for black necked Crane, white stork, wild goose, wild duck and other migratory birds.

Caohai is one of the most important wintering places for black necked cranes in China. With the restoration of wetlands and the protection of cranes. The number increased from 35 in the mid-1970s to 305 in 1983 / 1984 and 307 in 1985 / 1986. The cranes arrive in mid and late October and leave in mid and late March. About 1500 cranes also wintered in this swamp (up to 2178 in 1983). There are also black stork and white headed crane and other rare birds. The wetland is also an important wintering site for geese, ducks, Snipes and bony crests. In the middle of January 1988, there were more than 20000 waterfowls, including 24 crested Greyhound, 55 heron, 19 white spoonbill, 440 grey geese, 1660 spotted geese, 1680 Red duck, 5400 other ducks (mainly including red necked duck, mallard, white browed duck and red headed diver), 580 grey crane, 235 black crowned crane and 10000 white bone crowned crane). According to the records of Guizhou ornithology, 47 species of non passerine wintering birds have been collected in this area since 1975, including (2 species), cormorant, Heron (5 species), wild goose (2 species), river duck (9 species), diving duck (4 species), Merganser (1 species), raptor (7 species), crane (2 species), bony top (2 species), snipe (11 species) and Red Headed Gull.

Among the birds, the most precious one is the black necked Crane. There are 15 kinds of cranes in the world today, and the black necked Crane is the latest one, which is one of the rare waterfowl in the world. It is the only crane that lives on the plateau. It is more than 1 meter tall and wears gray and white feathers. Its long neck is surrounded by a black ribbon like down, and its head is decorated with bright red beads. The tail and the end of the wings are black, which is easy to distinguish from other cranes.

In addition to the black necked Crane, there are grey crane, spotted goose and so on. Caohai has become a winter resort for cranes and other birds.

The whole body is gray or brown, the back neck is dark brown, the throat and neck side are white, and the mouth and legs are red yellow. It mainly eats grass. Its feather and down are ideal filling materials for high-grade cold proof quilt and mountaineering sportswear.

As of 2013, nine species of fish have been recorded in Guizhou Weining Caohai National Nature Reserve, including carp, grass carp and grass carp, nine species of reptiles (including bamboo leaf green and water red chain swimming snake), and 14 species of amphibians.

Ecological characteristics

Caohai is rich in biological resources because of its superior natural conditions. Caohai has shallow water, good water quality, high transparency, and mud bottom, so there are many kinds of aquatic higher plants. All kinds of aquatic plants are almost full of aquatic higher plants in Caohai, including 37 species, 26 genera, 20 families. All kinds of green grass grow under the water Due to its thick natural conditions, Caohai has become a paradise for all kinds of waterfowl, with 228 species. Among them, black necked Crane, white headed crane, black stork, white stork and white tailed Sea Eagle are the first class protected birds, while white spoonbill, kite, white tailed Harrier, peregrine falcon, kestrel, grey crane and short eared owl are the second class protected birds.

Development and utilization

Tourism information

Caohai, also known as Nanhaizi lake and baxianhai lake, is one of the three famous plateau lakes (Caohai Lake, Dianchi Lake and Qinghai Lake) in China. It is a limestone dissolution lake and the largest natural freshwater lake in Guizhou, with a water area of 46.5 square kilometers. As a plateau wetland ecosystem, Caohai is listed as a national nature reserve.

The average water depth of Caohai is only about 2 meters, and the water is clear and pollution-free

Chinese PinYin : Cao Hai