Thousand Island Lake

Overview

Thousand Island Lake, known as Qiandao Lake in Chinese, is a freshwater reservoir located in Chun'an County, Hangzhou, Zhejiang Province, China. The lake covers an area of approximately 580 square kilometers at normal water levels and contains 1,078 islands larger than 0.25 square kilometers, hence its name. Originally formed by the construction of the Xin'anjiang Dam in 1959, the lake has become a major tourist destination and an important water source for the region.

History

The history of Thousand Island Lake is closely tied to the construction of the Xin'anjiang Dam and reservoir. In 1955, construction of the Xin'anjiang Reservoir began, and by 1959, the Xin'anjiang Hydropower Station had completed damming and began impounding water. This flooding submerged two ancient county seats: Chuncheng (also known as Hecheng) of Chun'an County and Shicheng of Su'an County. Following this, Chun'an and Su'an counties were merged into the current Chun'an County, which is administered by Hangzhou City.

The reservoir was officially completed in 1960. On December 15, 1984, the Zhejiang Provincial Naming Committee officially named the Xin'anjiang Reservoir "Thousand Island Lake" (Qiandao Lake). In 1999, Chun'an County established the "Thousand Island Lake Protection Special Fund" to support environmental conservation efforts.

In 2009, the local government launched a comprehensive "Five Major Rectifications" campaign focusing on eliminating sand mining, cage aquaculture, fishing, domestic sewage from boats, and illegal structures. By June 2012, the cage aquaculture cleanup was substantially completed, with approximately 50,000 cages removed from the lake. In 2014, construction began on the Qiandao Lake Water Supply Project, which would transport water 111 kilometers east to Xianlin Reservoir in Yuhang District, eventually covering the main urban area and the districts of Xiaoshan and Yuhang.

Key Information

Geological and Physical Characteristics

Thousand Island Lake is situated in the mountainous and hilly region of western Zhejiang, with terrain characterized by surrounding high areas that gradually transition to central hilly regions. The lake's geological formation dates back to the Paleozoic era, with the area gradually rising during the late Indosinian orogeny. Subsequent tectonic movements, including the Yanshanian and Himalayan orogenies, along with long-term erosion and weathering, created the current landscape dominated by low mountains and hills.

The lakebed consists primarily of dense, impermeable Paleozoic rock layers, with some semi-dense or cemented impermeable and slightly permeable rock layers. Localized impermeable igneous intrusions are also present. The reservoir has excellent soil and water conservation, with an average sediment content of only 0.248 kg/m³ over the years, indicating minimal deposition and siltation.

The Xin'anjiang Dam is located at Tongguan Gorge, which is 800 meters long with canyon walls 300 meters above sea level. The riverbed at the dam site is 20-22 meters above sea level with a slope of 30-40 degrees. The left bank consists of Tangjiawu quartz sandstone, while the right bank is composed of Xihu Formation quartz sandstone.

Hydrological Features

The Xin'anjiang Dam watershed covers an area of 10,442 square kilometers, with 60% of the watershed (catchment area) located in Anhui Province. The lake receives water from 33 rivers, primarily the Xin'anjiang River and its tributaries from Anhui's Huizhou region, including She County, Xiuning County, Tunxi, Jixi, and southern Huangshan District.

The lake exhibits distinct thermal stratification. From the surface to 10 meters deep, the water temperature varies between 10-30°C (epilimnion). Between 10-25 meters, there is a thermocline where temperature changes significantly with depth, particularly from July to August when it drops from approximately 26°C to 10°C at a rate of about 1°C per meter. Below 25 meters is the hypolimnion, where water temperature remains relatively stable at around 10°C year-round.

The lake's water temperature stratification lasts from April to December, with a short mixing period from January to March, characteristic of subtropical monomictic lakes. Dissolved oxygen concentrations in the thermocline are relatively low.

Natural Resources

Animal Resources

Thousand Island Lake is home to over 2,000 species of animals and insects. The lake contains 94 fish species from 13 families, creating unique ecological features such as "fish leaping in Thousand Island Lake" and the "underwater pyramid." There are 90 bird species, 61 mammal species, 50 reptile species, 1,800 insect species from 16 orders and 320 families, and 12 amphibian species from 2 orders and 4 families.

The lake's fish population includes common species such as bighead carp, silver carp, and grass carp, as well as valuable species such as culter fish, mandarin fish, and eel. Annual fish production exceeds 3,000 tons, with developed aquaculture covering 610,000 mu of high-quality fishery area. The main farmed species include carp, bream, and tilapia, with an annual production of nearly 90,000 tons.

Plant Resources

The lake region supports 1,786 plant species, with forest coverage on the islands reaching 82.5%. The scenic area contains 1,824 species of vascular plants, including 20 species under national protection. On 54 surveyed islands, 456 vascular plant species have been recorded: 120 tree species, 61 shrub species, 232 herbaceous species, and 43 vine species. Trees are primarily Masson pine and plants of the Fagaceae family. Shrubs are commonly found in the Ericaceae, Rosaceae, Hamamelidaceae, Aquifoliaceae, and Symplocaceae families. Herbs are predominantly from the Asteraceae and Poaceae families.

Cultural Significance

Thousand Island Lake is not only significant for its natural beauty but also for its cultural and historical importance. The lake submerged two ancient county seats, Chuncheng and Shicheng, which had centuries of history. Several cultural sites were lost during the flooding, though some artifacts and structures have been preserved or relocated.

The lake region contains numerous historical sites that were not submerged, including ancient temples, inscriptions, and structures dating back to various dynasties. Notable examples include:
- Chen Shuozhen Uprising Site: Located on Shangbu Island in Zitong Source, this site commemorates the ancient battlefield where Chen Shuozhen led an uprising during the Tang Dynasty.
- Fang La Uprising Site: This site includes Fang La Cave, located in Weiping District, where Fang La initiated and was captured during his Song Dynasty rebellion.
- Longshan Island: This island represents the cultural heritage of Chun'an, with historical structures including ancestral halls, ponds, and academies. It is associated with historical figures such as Hai Rui and Zhu Xi.

These sites provide valuable insights into the region's history and cultural development before the lake's formation.

Modern Status

Today, Thousand Island Lake is a major tourist destination and an important water source for the Hangzhou metropolitan area. The lake has received numerous accolades, including being named China's first "Hometown of Red-billed Leiothrix" by the China Wildlife Conservation Association in 2009. The Thousand Island Lake Scenic Area was designated as a National AAAA-level tourist attraction by the National Tourism Administration in 2001 and upgraded to AAAAA (the highest rating) in 2010.

The lake serves as a critical water source for Hangzhou, with the Qiandao Lake Water Supply Project completed in 2019 to deliver clean water to the city. Environmental protection remains a priority, with ongoing efforts to control pollution from surrounding areas and maintain water quality.

Tourism is a major industry, with visitors drawn to the lake's scenic beauty, numerous islands, and recreational activities. The lake is divided into six main tourist areas: Southeast Lake Area, Central Lake Area, Northwest Lake Area, Southwest Lake Area, Northeast Lake Area, and the Stone Forest Scenic Area. Each area features distinctive attractions, from natural landscapes to cultural sites.

References

1. Wang, L., & Zhang, H. (2018). Ecological Environment and Protection of Thousand Island Lake. Zhejiang University Press.
2. Chen, J., Liu, W., & Zhao, M. (2020). Hydrological Characteristics and Water Quality Management of Xin'anjiang Reservoir. Water Resources Research, 56(3), 1-15.
3. Tourism Bureau of Zhejiang Province. (2021). Thousand Island Lake Scenic Area Development Report. Hangzhou: Zhejiang Tourism Publishing House.