Place
Tonle Sap
ទន្លេសាប
Tonle Sap (ទន្លេសាប) is the great lake of Cambodia and the river that joins it to the Mekong at Phnom Penh. For part of each year the river runs backward, and the lake swells to become the largest in Southeast Asia.[1][2][3] Its fish feed much of the country, and people live on its water in floating and stilt villages.[4][5]
The river that reverses
The Tonle Sap River runs about 70 miles from the lake to the Mekong, which it meets a few hundred meters from the port of Phnom Penh.[2] In the wet season, from about June, the Mekong floods and pushes water up the river into the lake. In the dry season, from about November to May, the river turns and drains the lake back into the Mekong.[2] The Earth Observatory of NASA, the United States space agency, gives the lake's area as about 3,000 square kilometers in the dry season and about 10,000 in the flood.[6] News reports put the growth at four or five times its low-water size.[3][7] The fisheries scientist Nicolaas van Zalinge writes that the area under water at the peak of the flood differs widely between years, from about 10,000 to 15,000 square kilometers.[8] When the dry season returns, the water the lake releases helps hold back salt water in the farmland of the Mekong Delta.[6]
The Water Festival
The Water Festival, Bon Om Touk, marks the end of the monsoon and the time when the swollen Mekong turns the Tonle Sap River upstream.[9] Its boat races are rowed on the river in Phnom Penh. For the races of November 2024, the national organizing committee registered 348 boats and 22,042 rowers, as reported by Fresh News and CamboJA News.[10]
Fish and the people of the lake
Sources give the lake's yearly catch differently. A 2017 commentary for Radio Free Asia put it at more than 400,000 tons, and ranked the Tonle Sap first among the world's inland fisheries in both size and yield.[11] Al Jazeera's figure in 2019 was 500,000 metric tons, which it said made up some 70 percent of the protein Cambodians eat.[4]
Families live on the lake in floating villages, among them Chong Prolay in Siem Reap province.[2][7] In Kampong Phluk commune, in Siem Reap's Bakong district, houses stand high on stilts above the road, and in the rainy season the lake floods the villages and turns their roads into canals.[5] Many ethnic Vietnamese families live in floating homes around the lake and fish for a living, moving to the middle of the lake in the dry season and closer to shore in the wet season. The news site Voice of Democracy (VOD) reported in 2023 that the community at Chong Khneas had shrunk to around 300 families, down from some 1,000 at its height.[12]
Angkor and the lake
Van Zalinge writes that the rise of the Angkor empire may have owed much to the lake's rich fishery, together with its rice irrigation. He points to the many fish carved on the reliefs of the Bayon and Angkor Wat, and to the temples' nearness to the lake.[8]
Biosphere reserve and Prek Toal
The Cambodia Daily reported in June 1998 that UNESCO, the United Nations cultural and scientific agency, had designated the lake a biosphere reserve.[13] The Wildlife Conservation Society writes that the Tonle Sap Biosphere Reserve was set up by royal decree in December 2001, with three core zones at Prek Toal, Boeng Chhmar and Stung Sen.[14]
Prek Toal became a Ramsar site, a wetland of international importance, in 2015.[15] Surveys reported by the Wildlife Conservation Society in 2016 counted over 400 lesser adjutant stork pairs nesting there, and about 150 pairs of greater adjutants, the largest colony of that species in the world. Former bird hunters had become rangers guarding the nests.[15]
A shrinking flood
The Mekong River Commission called the lake's low water in 2019 unprecedented.[4] That year the river did not turn until August instead of June, and it flowed toward the lake for six weeks rather than the usual five or six months. Fish catches were reported at 10 to 20 percent of earlier years.[3] The three years from 2019 to 2021 were the driest on record, and a study by the commission found that the reverse flow started later on average from 2010 to 2020 than in the decade before.[7] A 2022 study in Hydrology and Earth System Sciences found that the wet-season flow into the lake fell by 56.5 percent between the years 1962 to 1972 and 2010 to 2018, and that the lake's wet-season area shrank by about a fifth.[16]
The causes are argued. Reports in Al Jazeera and CamboJA News point to dams on the Mekong and its tributaries, including those on the upper river in China.[4][5] The authors of the 2022 study found that dams alone could not explain the decline, and named irrigation and the deepening of river channels in Cambodia as important causes.[16] CamboJA News reported in 2022 that the Cambodian government attributed falling catches mainly to population growth and illegal fishing.[5]
References
- ↑ Radio Free Asia Khmer, Fishing communities on the Tonle Sap lake expect no fish this year because of the water shortage (July 23, 2020; in Khmer)
- ↑ 2.0 2.1 2.2 2.3 Radio Free Asia, Sovannarith Keo and Joshua Lipes, Drought, Dams on Mekong River Drop Cambodia's Tonle Sap Lake to Record Low Levels (July 27, 2020)
- ↑ 3.0 3.1 3.2 The Cambodia Daily, The fate of Tonle Sap Lake is decided upriver (April 24, 2020)
- ↑ 4.0 4.1 4.2 4.3 Al Jazeera, Cambodia's lifeline threatened as Mekong recedes to historic low (September 23, 2019)
- ↑ 5.0 5.1 5.2 5.3 CamboJA News, Fishers Struggle With Declining Fish Catch, Citing Irregular Water Levels (September 2022)
- ↑ 6.0 6.1 NASA Earth Observatory, Mekong Floods Fill Tonle Sap (2001)
- ↑ 7.0 7.1 7.2 VOA Khmer, Colin Meyn and Kann Vicheika, 'New Normal is Uncertainty' for Cambodia's Key Tonle Sap Lake, Researchers Say (March 29, 2024)
- ↑ 8.0 8.1 Nicolaas van Zalinge, Data Requirements for Fisheries Management in the Tonle Sap, FAO and Mekong River Commission (about 2003)
- ↑ The Cambodia Daily, How wild is Cambodia's Water Festival (November 21, 2018)
- ↑ CamboJA News, All Systems In Place For Annual Water Festival Boat Race in Phnom Penh (November 13, 2024)
- ↑ Radio Free Asia, Rapid Decline in Tonle Sap Raises Alarms For Key Southeast Asian Fishery (December 27, 2017)
- ↑ VOD, Fiona Kelliher and Keat Soriththeavy, Chong Khneas' Ethnic Vietnamese Fishers Are Leaving Amid Fishing Crackdown, Arbitrary Fees (February 10, 2023)
- ↑ The Cambodia Daily, Unesco Cautious About Tonle Sap Development (June 12, 1998)
- ↑ Wildlife Conservation Society Cambodia, The Tonle Sap Biosphere Reserve (undated)
- ↑ 15.0 15.1 Wildlife Conservation Society, Waterbirds Make Dramatic Comeback to Cambodia Wetlands (January 22, 2016)
- ↑ 16.0 16.1 S. D. X. Chua, X. X. Lu, C. Oeurng, T. Sok and C. Grundy-Warr, Drastic decline of flood pulse in the Cambodian floodplains (Mekong River and Tonle Sap system), Hydrology and Earth System Sciences 26 (2022)