Many million years ago it was an inland sea. Now a master plan for the Mun river watershed in northeastern Thailand has identified increasing salinity as a real danger to the region. Richard Mogg reports

The dusty dry Isaan plateau of northeastern Thailand rests on strata of rocksalt. As a result of the salinity and aridity, plus lack of modern communications, major industrial investment in the Isaan northeast is generally deterred, leaving it the poorest and least developed of Thailand’s regions.

Over the next 25 years, the Royal Thai Government plans dramatically to increase the water supply in the lower northeast’s Mun river basin. Agricultural, urban and industrial development, focused on the region’s two main provincial centres — Nakhon Ratchasima and Ubol Ratchathani, will radically increase the demand for water from the Mun catchment. But researchers at Khon Kaen University’s Groundwater Research Group agree that the northeast’s soil is packed with salt; informed opinion says that large diversion and irrigation schemes proposed for the region could disturb widespread heavy rocksalt deposits, to result in an agriculturally counterproductive increase in surface soil salinity.

Critical to further water resources development is that insufficient hydrological data exists on the inter-relationship between surface water, groundwater movement, and salinity. This lack is despite a continuing series of studies, dating from 1963. Money could be better spent, consultants believe, on rehabilitation or upgrading of existing small and medium irrigation schemes, and on increasing operation and maintenance (O&M) budgets for those already in place.

Using river basin simulation modelling, Binnie & Partners led a team of consultants in formulating the ‘Mun river basin water resources development master plan’. Associate consultants in the study were W S Atkins International (UK), ITC (the Netherlands), and two Thai specialist firms, ATT Consultants Co and TA&E Consultants Co. The study, including consultancy, equipment and training, was funded by an ECU1.5M grant from the European Community.

The Binnie Mun basin study has three general components:

•An analysis of existing and potential water usage.

•A hydrological model of the water resources.

•An integrated agricultural plan.

Main, but somewhat problematic assumptions are that adequate water will continue to be available, that participatory approaches will be adopted, that a fair level of economic growth will be maintained, and that the current national policy for agricultural development will continue. A new, possibly contentious, element could be the introduction of demand-side management, as well as the imposition of charges for irrigation water services.

The consultants’ study, however, greatly emphasises the urgent need for a unified regulatory authority to be established, for control and operation of the water, watershed and riparian resources of the Kingdom of Thailand’s 25 river basins, including the Mun. In the opinion of the consultants, both co-ordination at national level by a Ministry of Water Resources, and administration at basin level by a Water Resources Authority, endowed with unique statutory and plenary powers, are urgent priorities. Another critical recommendation is for incremental upgrading of existing irrigation schemes, rather than the imposition of large, and expensive, projects.

The study estimates a total development cost of 100,000 rai (1,600,000m2) of viable schemes, to be (1995) Baht 2,339M (US$93M). Annual operational and maintenance budget at the proposed level of improvement, for the same area, would total (1995) Baht 23.6M (US$0.9M). Over two decades between 1996 and 2005, the budget for rehabilitation and upgrading existing large and medium irrigation schemes, at an annual rate of 50,000 rai (800,000m2) is estimated by the Binnie study to be (1995) Baht 560M (US$22M).

But industrial and urban development proposed by Royal Thai Government, for the Mun basin area, will increase competition for the region’s already limited water resources. Deep-seated, seemingly insoluble problems of communication and co-ordination exist between the independently-minded organisations and agencies involved in water resources management and development in Thailand. The overall development picture tends to be one of a series of larger individual projects, in accordance with the sole vested interests of each implementing organisation or agency.

Planned integration, in the common public interest, tends to be ignored. The Royal Irrigation Department (RID) and the Electricity Generating Authority of Thailand (EGAT), with entirely different primary aims, are the two main implementing agencies for water resources projects throughout Thailand.

The Department of Energy Development and Promotion (DEDP), of the Ministry of Science, Technology and Environment, is a third, completely separate agency, engaged in water resources projects of its own. Moreover, DEDP projects are often in territory that overlaps and duplicates that of RID and EGAT schemes.

The Mun river system extends around 400km from its headwater at the Lam Ta Khong reservoir, to eventual confluence with the Mekong. Much of the southern boundaries of the Mun’s watershed are the lightly forested low mountains along the northern border of Cambodia. The Mun’s watershed covers approximately 70,000km — parts of ten northeastern provinces of Thailand. The Binnie study makes the unequivocal statement, ‘An integrated planning approach to the management of the limited water resources in the basin should be studied.’

The Chi river, with a further catchment area of about 50,000km2, flows into the Mun at its left bank just above the provincial capital of Ubol Ratchathani, and some 200km above the Mun’s confluence with the Mekong. The Mun river system is the largest tributary of the Mekong, contributing some 17% to its lower reaches.

Two main bones of contention arise from the Binnie study. One resides in whether large stand-alone water storage and diversion schemes, such as the proposed Kong-Chi-Mun basin transfer project, are suitable in preference to integrated enhancement of the traditional irrigation matrix. The other equally critical contention is that irrigation schemes may disturb large naturally occurring rocksalt deposits, to increase surface soil salinity.

Establishing a Mun River Basin Authority, according to the Binnie group, should have top priority. The need is for an authority to oversee integrated water resources management and enhance existing irrigation systems. Promotion of agricultural diversification away from traditional subsistence-level rice monoculture should also be addressed. Current water use tends to be inefficient, because farmers are not consulted on irrigation scheduling. Agricultural development also suffers from infertile soils, localised flash-flooding and lack of water for dry season crops.

Limited opportunities

A shortage of suitable sites, plus low average run-off, means the Mun basin offers only limited opportunities for an increase in total water storage in large- and medium-scale schemes. Situated in mainly lowland terrain, the Mun basin’s hydro power potential is limited to the existing 36MW Sirindhorn and 37MW Pak Mun generating stations of the Electricity Generating Authority of Thailand (EGAT). A pumped storage project is currently under construction for EGAT at Lam Ta Khong.

According to the Binnie study, about half the Mun basin’s water resources have been developed so far. The rest is consumed by rain-fed agriculture or lost by run-off during the heavy rains of the southwestern monsoon. Due to lack of storage capacity, intermittent shortages occur in meeting all demand categories. Indeed, water quality is declining downstream of urban areas, particularly around Nakhon Ratchasima — Thailand’s fifth largest producer of toxic and hazardous waste.

Data currently available indicate that the Mun basin’s groundwater resources are poor in both quality and quantity. Freshwater aquifers occur in about 60% of the basin, but have low storage and transmissivity values. Thus aquifers tend to yield in the range of 2-3m3/hour. The remainder of the basin has saline groundwater, or none at all. The total amount of usable groundwater in the basin is less than 1% of the annual surface run-off. ‘Insufficient data exists on the inter-relationship between surface and groundwater,’ according to the Binnie study, ‘and there is a potential salinity hazard if the present balance is disturbed by large-scale water resources development.’

As for all Isaan Thailand, the Mun basin climate is governed by the April-October northwest monsoon from the Indian Ocean, and the November-April monsoon from China. More than 90% of Isaan’s annual rainfall occurs during the southwest monsoon. The Mun’s highest average rainfall, 1400-1700mm, occurs in the vicinity of Sisaket, to the east; the lowest, some 900mm, occurs to the south of Nakhon Ratchisama, and makes it one of the driest areas in Thailand.

Average annual (1995) income for a five-person household amounted to only 15,000 baht (US$600), although the high incidence of barter transactions in village Isaan distorts this figure. Freshwater fish is important as family sustenance and as a barter commodity. Thus seasonal flooding of the Mun and other rivers in Thailand is part of the rural way of life, although rice yields may sometimes be reduced as a result. The Binnie study points out, ‘Floods are essential for maintaining the environment for flood plain forests, wetlands and fisheries.’

Under separate development by the DEDP are sub-stream storage dams on the Mun, the first stage in the three-part Kong-Chi-Mun basin transfer scheme to divert water from the Mekong river, via the Chi river, into the headwater of the Mun. The Binnie study treads warily on departmental toes, saying that, ‘In the light of the Agricultural Development Plan, the [Kong-Chi-Mun] scheme design criteria should be reviewed to verify that diversified farming (with a need to maximise dry season cropping potential) will be feasible in terms of irrigation supply and, more importantly, in terms of drainage.’

At the heart of the matter, is the ongoing tussle in Thailand between rural tradition and the political search for big-ticket construction projects. Isaan’s seasonal farming and freshwater fisheries have been developed over the centuries to cope with cyclical flood and drought, to balance with the needs of its widely dispersed population.

Until dialogue replaces diktat as the governmental modus operandi, attractively expensive large irrigation schemes will continue to be politically imposed on uncomprehending farmers and villagers.

Co-operation, co-ordination and communication are not terms in common use by Thai officialdom. Intra- as well as inter-departmental feuds, unhappily, tend to be the rule rather than the exception in Thailand’s governmental and admin-istrative circles. The Binnie study, generated in 1995, outlined both the parameters and the options — technical, social and economic — for integrated basin management of the Mun and other rivers in Thailand. But without overall project co-ordination, as well as truly verifiable project feasibility analysis, reports such as this can do little to halt irreversible water resource damage in Thailand’s poorest region.