Beung Boraphet
Location:
15°40'-15°44'N, l00°10'-100°20'E; 2.5-21.0 km east of the town of Nakhon Sawan, Muang District, Nakhon Sawan Province.
Area:
13,000 ha.
Altitude:
24m.
Biogeographical Province:
4.5.1.
Wetland type:
14.
Description of site:
A large freshwater lake, 18 km by 6 km. situated on the east bank of the Mae Nam Nan, close to its confluence with the Mae Nam Ping. The lake lies close to the western margin of the huge Central Plains area of Thailand and is surrounded by rice paddies. It was formed in 1930 by the damming of a freshwater swamp (which formerly covered an area of 64,000 ha) in order to develop the fishery. Embankments have been constructed in some areas around the north and west margins of the lake, together with spillways and lock gates to regulate water levels. The western shore is fringed by a railway line and lies close to the town of Nakhon Sawan. The lake was drained for one month in 1959 and again in 1972, each time being allowed to refill. There is much floating vegetation over the lake surface and some emergent vegetation around the margins. Tall emergent vegetation is very restricted in extent, occurring mainly as floating islands near the northwest corner of the lake. The lake is fed by many shallow streams which ramify throughout the basin, as well as overspill from the Mae Nam Nan during the flood season. Ouflow is via the Ban Pong canal at the southwest tip, into the Mae Nam Chao Phraya. There is a subsidiary outlet which empties into the Mae Nam Nan. According to one source (Anon, l985a), most of the lake is about l.6m deep and the maximum depth is 5m; according to Suraswadi (1976), the average depth is 3-4m. The lake reaches its maximum depth in the late wet season (October), and is usually at its shallowest in August. Fluctuations in water level and the amount of flooding around the lake margins are reduced by embankments and by the presence of spillways with water control regulators and flap gates. pH values range from 6.6 to 7.9, and Secchi disk values from 0.60 to l.80m. The oxygen content of the water is fairly high (3.0-8.0 ppm), due to the frequent mixing of waters in the rainy season.
Climatic conditions:
Tropical monsoonal climate with an average annual rainfall of 1,250 mm, most of which falls between July and October. The average monthly temperatures vary from 12.0°C in December to 34.0°C in May. Water temperatures are usually in the range 27-31°C, but rise to 33-34°C in April and May.
Principal vegetation:
Dense mats of floating vegetation, chiefly Coix aquatica, Isachne globosa, Leersia hexandra, Eichhornia crassipes, Salvinia cucullala, Nelumbo nucifera and Nymphaea lotus. Submerged aquatics include Hydrilla verticillata, Ceratophyllum demersum and Utricularia flexuosa. There are some floating islands of Phragmites karka, Saccharum sp and Cyperus spp, particularly near the northwest corner of the lake, and fairly extensive beds of low sedges Cyperus spp along the southern margin. Adjacent areas are almost entirely rice paddy, although there are scattered Borassus palms, particularly to the north and east, and some areas of scrub, particularly at the northwest end close to the town of Nakhon Sawan.
Land tenure:
The lake is state owned, although there are now many illegally established households around the shoreline. Surrounding areas are mainly in private ownership.
Conservation measures taken:
An area of 45,000 ha, covering the lake and surrounding areas of paddy, was declared as a Non-Hunting Area in 1975. Fishing is forbidden in certain parts of the lake.
Conservation measures proposed:
The Fisheries Department is proposing to take further measures to rationalize human use of the lake, and to relocate those households which have been illegally established around the lake shore. The remaining areas of reeds and waterside scrub should be protected more effectively from cutting and burning. The illegal trapping and shooting of birds in areas surrounding the lake should be suppressed, and the disturbance to roosting and nesting birds caused by tourists in boats should be carefully regulated. Some areas of the lake shore around the Non-Hunting Area headquarters could be managed to attract shorebirds. At the present time, foraging opportunities for these species are very restricted because of the absence of muddy shallows. Searches for the endemic and endangered White-eyed River-Martin Pseudochelidon sirintarae should be mounted.
Land use:
Fishing, using illegal methods such as gill nets which are set from small motor boats, throw nets and electrification, as well as by legitimate means such as hook and line and traps; also illegal propagation of lotus. Approximately 30,000 people live around the margins of the lake. The principal activities in surrounding areas are rice cultivation (one crop of wet-season rice per year), cattle grazing and pig farming. Small areas of corn, mung beans, cotton and groundnuts are grown in the upland areas around the basin.
Possible changes in land use:
The lake is one of three sites chosen for the implementation of the Large Swamp inland Fisheries Project (LSIFP) which seeks to increase fish yields through manipulation of water levels, dredging to improve spawning grounds and fish stocking. In addition, pen culture of fishes is recommended together with the utilization of aquatic macrophytes for biogas production.
Disturbances and threats: Local people continue to burn and cut Phragmites and other emergent vegetation in order to increase the areas under lotus cultivation. They also cut waterside scrub and trees for charcoal production. There is still much illegal hunting of waterfowl at the lake, and roosting flocks of small birds are netted for food. One of the principal trapping methods is to set a monofilament fishing line with hooks placed at 10-20 cm intervals across the flight lines of the birds. Baited hooks and lines are also used. Farmers occasionally put out large quantities of grain baited with acutely toxic chemicals in order to kill waterfowl which they claim are grazing on their rice paddies. The lake is littered with remnants of plastic fishing nets which may cause the deaths of many birds. There is some evidence to suggest that, in spite of stocking, present fish yields may be lower than in the past because of many successive years of over-exploitation.

There have been no checks to determine the levels of pesticide contamination in the lake basin. While persistent pesticides are little used in rice-growing areas, there is the possibility of contamination from persistent organochlorines used extensively on cotton crops in the nearby uplands. This may have contributed to the disappearance of larger predatory birds. There may now be reduced inflow of water into the lake due to increased diversion of streams for cultivation in the catchment area.
Economic and social values: Some 5,100 fishermen live around the lake, and as many as 1,000,000 persons may be dependent upon the resources of the swamp basin. The average net income per household from fishing is Bht.11,400 (about US$456) per year (Anon, 1985). Fish yields have ranged from 422,305 kg/year to 1,081,665 kg/year, the higher figure coinciding with the drainage of the lake, prior to refilling, in 1972. According to officials at the Fisheries Station, the "officially recognized" yield of fish per year is about 250 metric tonnes; in reality, the yield may be as high as 400-500 tonnes if fish from all areas in and around the lake are taken into consideration.

The lake is important as a source of water for irrigating rice and other crops and in ensuring fresh fodder for cattle. In addition, many people utilize the vegetation. The leaves of Nelumbo nucifera are utilized for wrapping material, and the seeds of Nelumbo and stems of Nymphaea lotus are utilized for food. Water Hyacinth (Eichhornia crassipes) and some other aquatic plants are fed to pigs. The lake is an important tourist attraction and many people visit it, either to stay at the Non-Hunting Area headquarters or to take boat rides on the lake. A proportion of these visitors hire local boatmen.
Fauna: The standing crop of fish has been estimated at 84 kg/ha (Anon, 1985) and at 79.4 kg/ha to 102.4 kg/ha (National Inland Fisheries Institute, 1980). A total of 148 species of fish has been recorded, chiefly of the families Notopteridae, Cyprinidae, Silurudae, Schilbeidae, Ophiocephalidae and Eleotridae. The predominant species in the catches are:

Osteochilus hasselti (16.2%) Ophicephalus striatus (10.6%)
Clupeioides hypsalosoma (7.05%) Labiobarbus liniatus (7.05%)
Pristolepis fasciatus (6.3%)  

Other edible fishes known from the lake include Pangasius fowleri, P. larnandii, Ophicephalus micropeltes, Tachysurus argyropleurum, Wallago sp, Albulichthys albuloides, Lutjanus annualris, Puntius sp, Notopterus notopterus, N. chitala, Monopterus albus, Macrones numerus, Callichrous bimaculatus, Probarbus jullieni, Labio dyochoilus, Kyphosus waigiensis, Clarias batrachus, Oxyeleossris marmorata, Mastacembelus armatus and Trichopodus trichopodus (Pramoj Waithayakul and David Ogle, pers. comm.).

Beung Boraphet is the most important known site for wintering ducks in Thailand, with yearly maxima of at least 16,000 Dendrocygna javanica and 30,000 Anas querquedula, smaller numbers of Anas acuta (2,500) and Aythya baeri (maximum 426), and a few Anas penelope, A. falcaza, A. crecca, A. clypeata, Ayshya nyroca and A. fuligula. One or two Sarkidiornis melanotos may occur from time to time. Nettapus coromandelianus is present throughout the year (100-1,000 birds), and up to 430 Fulica atra have been recorded in winter. Other wintering species include Ardeola bacchus, Bubulcus ibis, Egretta garzetta, E. intermedia, E. alba, Ardea cinerea, A. purpurea, Anastomus oscitans (400 in January 1988), Circus (aeruginosus) spilonotus, C. melanoleucos and, occasionally, Aquila clanga. There is one record of Haliaeetus albicilla in trade, said to have been taken from the vicinity of Nakhon Sawan. There are also large roosts of wagtails (Motacilla spp) and weavers (Ploceus spp) together with Yellow-breasted Buntings Emberiza aureola and Barn Swallows Hirundo rustica. The White-eyed River-Martin Pseudochelidon sirintarae is known only from this site; nine specimens were netted amongst H. rustica in January-February 1968, and there have been two subsequent sight records (King & Kanwanich, 1978; D. Ogle pers. comm.).

In the breeding season, both Ixobrychus sinensis and I. cinnamomeus are plentiful, and a few pairs of Ardea purpurea are said to breed near the east end of the lake. Otherwise, large Ciconiiform birds are absent, perhaps because of the lack of suitably extensive and undisturbed areas of swamp woodland or reed-beds. Other species which do breed include Dendrocygna javanica (10-100 pairs at the lake and undoubtedly many more nest scattered at low density throughout the surrounding paddy basin) and Tachybaptus ruticollis (over 100 pairs), Nettapus coromandelianus (10-100 pairs), Porzana cinerea (50-100 pairs), Porphyrio porphyrio (100-1,000 pairs), and Hydrophasianus chirurgus (100-1,000 pairs). This is almost certainly the most important breeding station for the latter species in the country. Pelecanus philippensis and Leptoptilos dubius have occasionally been reported on passage.

A scrub-covered outcrop at the eastern end of the lake still supports a population of Macaca fascicularis. A few Crocodylus siamensis are reported to occur in the lake, but some, if not all, of these may be individuals which have escaped from captivity.
Invertebrates include high densities of Planorbidae and Ampullaridae (Mollusca). The most abundant insect orders are Ephemeroptera, Trichoptera, Coleoptera, Diptera and Hemiptera. Crustaceans of the families Potamidae and Paleopteridae are widespread and abundant; these include the economically important giant freshwater prawns Macrobrochium rosenbergii and M. sintangense.
Special floral values: None known.
Research and facilities: The most detailed recent studies of the aquatic ecosystem are found in Suraswadi (1976) and Anon (1985a). The most accurate and detailed information on the bird species diversity and numbers are found in the reports of those bird-watchers who have filed their records at the Association for the Conservation of Wildlife in Bangkok. Thongaree (1982) completed a study of the breeding biology of Hydrophasianus chirurgus at the lake. Brother David Ogle of La Salle Chotiravi School, Nakhon Sawan, together with Pramoj Waithayakul and colleagues from the Nakhon Sawan Bird Club, make regular visits to the lake and carry out small-scale banding of passerine birds in lakeshore vegetation. Sophasan and Dobias (1984) gave an account of the bird-trapping methods formerly used by villagers at the lake and made recommendations for habitat surveys and the conservation of Pseudochelidon sirintarae. Annual reports of fish landing statistics are compiled by the Department of Inland Fisheries Station. The headquarters of the Non-Hunting Area is situated on the southern shore of the lake, while the Department of Inland Fisheries Station is located near the northwest corner.
References: Anon (1973 & 1985a); Association for the Conservation of Wildlife (1981); King & Kanwanich (1978); National Inland Fisheries Institute (1980); Ogle (1986); Sophasan & Dobias (1984); Suraswadi (1976); Thongaree (1982); Thonglongya (1968).
Criteria for inclusion: 123.
Source:
Jira Jintanugool and Philip D. Round.