Khwae Yai River System
Location:	14°40'-16°04'N, 98°37'-99°10'E; in the Dawna Hills region of western Thailand, shared between the Provinces of Tak, Uthai Thani and Kanchanaburi.
Area:	Length of river approximately 280 km along the main Khwae Yai (also known as the Mae Kiong) and Nam Mae Chan, and approximately 123 km along its major tributary, the Huai Kha Khaeng; also a great many smaller tributaries. The system drains a watershed of approximately 15,000 sq.km.
Altitude:	150-650m.
Biogeographical Province:	4.5.1.
Wetland type:	12.
Description of site:	Fast-flowing rivers running through hilly, wooded country, ranging from less than I 50m above sea level up to 650m in the upper reaches. Parts of the river beds are rocky; other parts are shallow with sand bars and gravel banks. Still backwaters and oxbow lakes occur, particularly along the upper part of the Huai Kha Khaeng. The lower reaches of the Khwae Yai flow through a gorge upstream of Ban Nam Choan. Below this, the area has been inundated by the Srinakarin Reservoir which was completed in 1980. The rivers are permanent but subject to wide seasonal fluctuations in level. Water levels begin to rise rapidly in July, and the flow reaches its maximum shortly after the cessation of the southwest monsoon in November. Depths range from no more than a few cm in places to several metres in parts of the Khwae Yai. The pH is 7.0, dissolved oxygen 8.4 mg/l, alkalinity 48 mg/l and Secchi Disk transparency 55 cm. (Measurements made at Nam Choan on the Khwae Yai; Chantsavang et al., 1986).
Climatic conditions:	Tropical monsoonal climate with an average annual rainfall of 984 mm, 80% of which falls during the southwest monsoon (May to October). The mean annual temperature is 27.8°C (range 5.5-43.5°C). (Data from Kanchanaburi, to the south of the site).
Principal vegetation:	No information is available on the aquatic vegetation. Adjacent areas support a mosaic of different forest types, ranging from dry dipterocarp forest savannas and mixed deciduous forest to dry evergreen forest (Neal, 1967). The area has been subject to a low level of human disturbance for many centuries and there is a local preponderance of large-cuim bamboos Bambusa spp. An evergreen gallery type formation occurs patchily along the banks of the rivers. Nearby mountains support a hill evergreen formation above 1 ,000m elevation.
Land tenure:	The rivers and surrounding areas are state owned. There are, however, several Karen villages along the River Khwae.
Conservation measures taken:	The entire lengths of the rivers under consideration are enclosed within the boundaries of the contiguous Thung Yai and Huai Kha Khaeng Wildlife Sanctuaries and are therefore totally protected in law.
Conservation measures proposed:	The site has been proposed as a World Heritage Site. A proposal has been made for the establishment of a research and training centre for forestry staff and students in the Huai Kha Khaeng Sanctuary, and there is also a proposal to produce a management plan for the site. The site should receive a comprehensive biological survey, in order to determine the populations of key riverine species, to map the crossing routes of large mammals and to locate mineral licks etc. There should be more frequent patrolling of remote riverine areas in both sanctuaries. This might be combined with an organized, recreational trekking programme.
Land use:	Wildlife conservation and recreational trekking. Inhabitants of the Karen villages along the Khwae Yai engage in subsistence hunting, rice cultivation and fishing. There is a considerable amount of illegal hunting and collection of forest products throughout the area.
Possible changes in land use:	The upper Khwae Yai has been proposed as the site of a major hydro-electric dam project, the Nam Choan Dam. This project was shelved, for the second time in six years, in April 1988. Hmong hilltribes, currently practising shifting cultivation on the hill range dividing the upper Khwae Yai from the Huai Kha Khaeng, are to be resettled elsewhere.
Disturbances and threats:	The Nam Choan Dam, if constructed, would have flooded all of the lowland riverine habitat remaining along the Khwae Yai (c.13,700 ha). This would have divided an existing contiguous protected area of approximately 500,000 ha into three smaller sub-units and would have effectively prevented gene flow between the populations of large mammals within them. Key habitats for such lowland bird species as Cairina scutulata, Ichthyophaga humilis, Torgos calvus, Paw muticus and Heliopais personata; as well as for many large mammals, would have been submerged. The recent proposal to revive the Nam Choan Dam project provoked heavy protest not only from conservation bodies, but also from local villagers and townspeople in Kanchanaburi Province, who opposed the project principally on the grounds that it would damage watersheds and because the dam would have been sited on a seismically active fault. Following a prolonged debate, the proposal was shelved by Thailand's Council of Economic Ministers in early April 1988. The project's suspension was due in large part to the substantial campaign of opposition mounted by a well-informed committee appointed to study the dam's impact. The considerable concern shown by international conservation bodies around the world may also have contributed. Although the Nam Choan Dam project has not been cancelled outright, it seems highly unlikely that it could be disinterred, given the present socio-economic climate in Thailand. The area is subject to a high level of disturbance by poachers. These include recreational hunters from Bangkok and other major centres of population. There are a number of mining operations around the western margins of Thung Yai and these undoubtedly cause some disturbance, the more so because access roads cross Thung Yai Wildlife Sanctuary. There are several Karen villages along the course of the Khwae Yai in Thung Yai Wildlife Sanctuary, while the uplands support a population of about 5,000 Hmong tribesmen. Both these ethnic groups practise subsistence hunting and shifting cultivation. Semi-evergreen forest habitats along the rivers and elsewhere are annually damaged by fires, deliberately set by rural people and other trespassers. This seems certain to affect the ecology of the forests and perhaps lead to a reduction in species diversity of plants and animals.
Economic and social values:	The area is of international conservation value and has been recognized as a site of World Heritage Quality (Commission on National Parks and Protected Areas, 1982). It is the only relatively little-disturbed riverine ecosystem remaining in the entire country. Together with its associated watershed, it is undoubtedly the single most important area for wildlife conservation in Thailand. It is a major water source for millions of people living downstream, in the major agricultural areas extending from the town of Kanchanaburi to the Gulf of Thailand at Samut Songkhram. The output of freshwater at the mouth of the Mae Klong is probably essential in maintaining the important coastal fishery and aquaculture industry. The impoundment of freshwater during the construction of the Srinakarin Dam on the lower River Khwae resulted in widespread encroachment of saline water into formerly rich agricultural areas in the Mae Kiong delta, and many coconut plantations and fruit orchards died. The impact of such impoundment upon the fishery and upon agriculture has never been assessed. The area has considerable recreational and amenity potential. Huai Kha Khaeng receives several hundred visitors per year, most of whom are Thai nationals.
Fauna:	The Khwae River system is an important fishery. At Ban Nam Choan, the standing crop was estimated at 123.75 kg/ha. A total of 33 species of freshwater fish was recorded by Chantsavang et al. (1986). Phumpakapun et al. (1986) list 52 species of freshwater fish for Huai Kha Khaeng. The area supports the following aquatic or predominantly riverine species of birds which are scarce or endangered in Thailand: Anhinga melanogaster, Cairina scutulata. Ichthyophaga humilis, Torgos calvus, Pavo muticus, Heliopais personata, Megaceryle lugubris and Rhyticeros subruficollis. It may be the only area which is large enough to support viable populations of these species. The continued presence of the endangered White-winged Wood-Duck C. scutulata was confirmed as recently as early 1988, when a pair and single bird were observed in the area (B. Stewart Cox, pers. comm.). The area is very rich in large mammals. These include five species of macaque monkeys Macaca spp (more than any other site in Asia), two or three species of leaf monkeys Presbytis spp, otters, probably both Lutra perspicillata and Aonyx cinerea, Asian Wild Dog, Asiatic Black Bear, Hog Badger, Leopard, Tiger, Asian Elephant, Tapir, Sambar, Banteng and Gaur (Cuon alpinus, Selenarctos thibetanus, Arctonyx collaris, Panthera pardus. P. tigris, Elephas maximus, Tapirus indicus, Cervus unicolor, Bos javanicus and Bos gaurus). A herd of about 50 Gaur sighted in Thung Yai Wildlife Sanctuary in March 1985 is the largest such ever seen in Thailand. The lower Huai Kha Khaeng also supports a small population of the Water Buffalo Bubalus bubalis, said to be wild, although their origins may be slightly suspect owing to the former presence of domestic stock at the site. Both the Sumatran Rhinoceros Dicerorhinus sumatrensis and the Brow-antlered Deer Cervus eldi are said to be present. Chunarch and Nabhitabhata (1986) list 61 species of reptiles for Huai Kha Khaeng Wildlife Sanctuary, and Phumpakapun et al. (1986) list 17 species of amphibians.
Special floral values:	The site comprises the only intact lowland riverine system within any park or sanctuary in Thailand.
Research and facilities:	Accommodation is available at the headquarters of both the Huai Kha Khaeng and the Thung Yai Wildlife Sanctuaries. Research facilities are available at the Wildlife Research Station at Khao Nang Rum in Huai Kha Khaeng, and a number of research projects, principally concerning terrestrial vertebrates, are in progress. A road suitable for access by four-wheel drive vehicles extends to the Huai Kha Khaeng in the vicinity of its confluence with the Huai Mae Dee, near the southern limit of the site. Dirt roads, used for access by mining trucks, cross Thung Yai Sanctuary in various places.
References:	Chantsavang et al. (1986); Chunarch & Nabhitabhata (1986); Commission on National Parks and Protected Areas (1982); Phumpakapun & Kutintara (1983); Phumpakapun et al. (1986); Round (1983).
Criteria for inclusion:	1b. 2a, 2b, 2c.
Source:	Jira Jintanugool and Philip D. Round.