Kwan Phayao
19°10'N, 99°52'E; the wetland extends up to four km north and west of the town of Phayao, Phayao Province.
2,300 ha.
Biogeographical Province:
Wetland type:
14 & 19.
Description of site:
A large, permanent, freshwater lake (1,980 ha), fringed by approximately 3,000 ha of rice paddy to the south and west and with a marshy area and some old oxbows (c.300 ha) at the northern end where the Nam Mae Ing empties into the lake. There is also some inflow from the Mae Tam which empties into the lake from the south. The eastern shore of the lake is largely built-up, and the town of Phayao lies near the southeast corner. The lake empties to the east, via the Nam Mae lag, into the Mekong. The water level is controlled by a sluice gate and a spillway; the mean depth is 1.7m, and the pH varies from 6.0-9.1. Kwan Phayao is one of the largest semi-natural wetlands in northern Thailand.
Climatic conditions:
Tropical monsoonal climate with an average annual rainfall of 1,064 mm. The mean monthly relative humidity ranges from 70 to 80%; the mean monthly temperature, from 19.5 to 27.5°C.
Principal vegetation:
Thirty-six species of aquatic plants have been recorded. Najas graminea and Ceratophyllum demersum are the predominant submerged plants. There is also much Salvinia cucullata, Eichhornia crassipes, Nelumbo nucifera, and some Scirpus grossus. Adjacent areas are almost entirely cultivated (mainly rice paddy with some maize, groundnuts and tobacco).
Land tenure:
The lake is in public ownership, but the adjacent shoreline is mainly privately owned. Surrounding areas are privately owned farmland, much of which is leased to tenant farmers.
Conservation measures taken:
Conservation measures proposed:
Land use:
Fishing with the aid of gill-nets, and cultivation of lotus; mainly rice paddy (one crop per year) with some cultivation of green vegetables, tobacco, maize and groundnuts in surrounding areas.
Possible changes in land use:
The wetland is one of three sites proposed for the Large-Scale Inland Fisheries Project (L.S.I.F.P.) of the Department of Fisheries. This has recommended increasing fish production by manipulation of water levels, dredging to improve spawning grounds, fish stocking and increased pen culture of fishes. The project also recommends the utilization of aquatic macrophytes for biogas production, animal feed and fish feed.
Disturbances and threats: Most emergent lakeshore vegetation has already been destroyed due to lotus cultivation. The use of boats on the lake by fishermen and the widespread hunting of waterfowl around the lake have greatly reduced usage of the area by waterfowl. The implementation of L.S.I.F.P. could have some damaging impact upon the ecosystem since reduced fluctuations in water level would reduce feeding opportunities for wading birds. There could also be changes in the lakeshore vegetational succession. Any additional impact on the diversity of wild fish populations would need to be evaluated. However, there has already been so much human disruption of the lake ecosystem (e.g. through the introduction of Tilapia nilotica) that any further impact may be minor. The collection of vegetation for biogas, if restricted to Eichhornia, would not be damaging.
Economic and social values: The average net income from fishing has been estimated at Bht.7,800 per household per year (approximately US$312). The lake is important as a source of municipal water supply (7,680 cu.m per day). Approximately 5,000 fishermen operate in the lake, but a total of 500,000 persons are dependent to some extent on the lake's resources (Anon, 1985).
Fauna: The standing crop of fish has been estimated at 159 kg/ha. Twenty-two species have been recorded, but just five species make up over 90% of the fish biomass. Chief among these are Tilapia nilolica (productivity 21.9 kg/ha/year) and Anabas testudineus (2.19 kg/ha/year).

Forty-seven species of resident and migratory birds were recorded during a one day survey in January 1982. The only wildfowl present were a few Anas acuta and unidentified Anas sp. Usage of the open water by waterfowl is low, but would probably increase if disturbance by fishermen could be reduced. The surrounding marshes and paddies support Circus (aeruginosus) spilonotus and C. melanoleucos in winter.
Special floral values: None known.
Research and facilities: A Government Fisheries Station is sited at the lake, the annual reports of which are available through the library of the National Inland Fisheries Institute at Kasetsart University, Bangkok. Staff and students of the Biology Department, Chiang Mai University, have conducted research on the aquatic fauna and flora.
References: Land Use Classification Division (1977-1979).
Criteria for inclusion: 1e.
Jira Jintanugool and Philip D. Round.