UTILIZATION OF WATER RESOURCES OF MEKONG RIVER IN LAO PDR UNDER ADVERSE TOPOGRAPHICAL AND SOCIO-ECONOMIC CONDITIONS

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1 UTILIZATION OF WATER RESOURCES OF MEKONG RIVER IN LAO PDR UNDER ADVERSE TOPOGRAPHICAL AND SOCIO-ECONOMIC CONDITIONS R.K. Gupta 1 and R.K. Agrawal 2 ABSTRACT Lao People s Democratic Republic (Lao PDR) is largely mountainous, with mean elevation 500 m amsl. About 85% of the country s territory is part of the Mekong river basin, whose water resources are key to the development of the country s agriculture. Some of the target areas of the Government of Lao PDR for accelerated development of irrigated agriculture are the fertile lands in the Champassack province. Development of irrigation has been severely constrained due to adverse topography where only lift irrigation is possible from Mekong river. But this requires large scale installation of pumpsets and allied irrigation infrastructure. Major constraint was the lack of financial resources of the Government for capital works and general lack of equipment and trained man power for operation and maintenance of the existing irrigation infrastructure. For the rehabilitation of the Champassack Irrigation Project comprising six irrigation schemes in the Province, WAPCOS Ltd., of India was appointed Project Developer by the Government of Lao PDR. The Project had the following four components: (i) Completion of six irrigation schemes (5462 ha) (ii) Installation of ten existing large pump sets (iii) Conversion of existing diesel driven pump sets to electric driven pump sets (iv) Improving 3 pump service centres at Vientiane, Savannakhet and Pakse. These schemes have enabled the farmers to grow two rice crops and some cash crops in a year which has improved their socio-economic condition through sustainable food production. Keywords: Lift irrigation, Rice cultivation, Livestock raising, Irrigation infrastructure, Command area. 1. BACKGROUND Lao People s Democratic Republic (Lao PDR) is a land locked country. It is largely mountainous, with mean elevation above 500 m above mean sea level. It is characterized by steep terrain and deep narrow river valleys. Only about 4 per cent of the land area is arable. The total annual availability of fresh water is of the order of 330 km 3, including 38 km 3 of ground water. Thus the per capita water availability is 54,000 m 3 /annum which is the highest in Asia. However, the southern part of the country is drought prone. Due to adverse topography, most of the water requirement for various uses has to be met by pumping from the Mekong river. At present ground water is used for water supply in rural areas, small towns and small scale industries in 1 Chairman cum Managing Director 2 Sr. General Manager, WAPCOS Ltd., 5 th Floor, Kailash Building, 26, Kasturba Gandhi Marg, New Delhi , India: Tel. No.: , Fax No.: ; ho@wapcos.co.in and commercial@wapcos.co.in 1

2 low land areas where the depth of wells varies from 30 to 45 m with yields varying from 1 to 5 litres/sec. In plains and high land areas the yields are not adequate for irrigation of rice, which is the preferred crop in the counbtry. Rice cultivation, therefore, is dependent on highly variable and uncertain rainfall. In order to enhance agricultural productivity, following six irrigation schemes were planned in the Champasack province between 1992 and 1998, to create an irrigation potential of 5120 ha. (a) Thaphosy Irrigation Scheme (b) MuangSen Irrigation Scheme (c) Som Hong Irrigation Scheme (d) Ban He Irrigation Scheme (e) Savang Irrigation Scheme (f) SakMuang Irrigation Scheme These schemes were based on pumping water from the river Mekong together with a network of canals, distributaries and field channels. The construction work started in 1998 and pumps were imported from India. However, due to paucity of funds, these schemes could not be completed and were discontinued in after only partial commissioning of the planned works. Thus, the farmers had to revert back to the traditional rain fed cultivation, to grow only one rice crop in a year. During the period , the work of rehabilitation of the partially completed parts of the schemes, construction of the remaining parts and provision of additional facilities, was taken up and completed with Line of Credit from Government of India. WAPCOS Ltd. was the Project Developer. In the following paras, hydrology, crop water requirement and salient features of the six schemes are briefly discussed. 2. METEOROLOGICAL CONDITIONS The climate of the country is hot and tropical, with a six month long rainy season is usually between the months (May October), when the temperatures are at their highest. A cool and dry season is experienced from November through February, while a hot dry season is experienced in March and April. Normally, rainfall occurs at the same time in the entire country, with significant variations from year to year. Rainfall also varies regionally, with the highest precipitation of 3700 mm recorded annually on the Boloven Plateau in Champassack Province. City rainfall stations have recorded that Savannakhet averages 1,440 mm of rain annually; Vientiane around 1,700 mm, and Louangphrabang (LuangPrabang) around 1360 mm. However, on the whole rainfall is not always adequate for rice cultivation. When the rainfall is one-half or less of the norm, there is significant decline in rice yields. Such droughts are often regional, leaving production in other parts of the country unaffected. Temperatures range from highs around 40 0 C along the Mekong in March and April to lows of 5 0 C or less in the uplands of Xiangkhoang and Phongsali in January. The average relative humidity is around 80% or more during the period from June to October. Lowest humidity is observed during the period from December to March. Pakse is the headquarters of Champassack province whose main meteorological characteristics are highlighted in the following Table. 2

3 Table 1. Meteorological characteristics of Lao PDR Climate Details Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Mean Temperatu re (Mean 0 C) Temperatu re (Mean Max 0 C) Temperatu re (Mean Min 0 C) Rain (monthly Mean, mm) RH (Mean, %) RH (Mean of daily max. %) RH (Mean of daily min. %) Hydrological parameters Mekong river and its tributaries are the main source of surface water. An estimated 35% of all water in the Mekong river is contributed by watersheds within Laos PDR. These watersheds comprise about 26% of the total watershed area of the Mekong Basin. About 80% of the water flows during the rainy season and the remaining 20% during the dry season. A significant part of the water resources of Lao PDR comes from neighboring countries, viz km 3 per year from China and about 17.6 km 3 per year from Myanmar. However, the outflow from Lao PDR to other countries is mainly through Mekong River to Cambodia ( km 3 /year at Pakse) and small rivers, such as the Ca and Ma rivers (9.1 km 3 /year) to Vietnam. Taking into consideration all inflows and outflows, the internal surface water resources are of the order of km 3 per year. Groundwater resources are about 38 km 3 per year, which significantly contribute to the base flow of rivers. Mean monthly discharge in the Mekong river at Pakse are as follows: Table 2. Mean monthly discharge Month Discharge (m 3 /s) January 2800 February 2170 March 1840 April 1800 May

4 June 8810 July August September October November 7780 December 4190 It would be seen from the above Table that even the minimum discharge is more than adequate to meet the irrigation water requirements of the six schemes. However, the difference in minimum and maximum water levels is of the order of 15 m and therefore heavy duty pumps of 187 kw to 400 kw capacity have to be installed on pontoons. The river has a siltation rate of tonnes/km 2 /year, which during the rainy season, may be considered as high. The highest silting occurs in Nam Ou, Xebanghieng and Xedone. 2.2 Groundwater Resources Several hundreds of wells have been drilled throughout the country mainly for meeting rural water supply but also for a few cottage and small-scale industries. In most cases, the depth of the rural water supply wells in lowland areas varies between m and the yield vary from about 1 lps to 5 lps. The groundwater is the main source of rural and small town water supply, especially in lowland areas located far from surface water resources such as the Southern and Western part of Champassack Provinces, and the hinterland of the Xebangfay, Xebanghieng and Xedone valleys. 2.3 Water Quality The inhabitants in the beneficiary villages meet their domestic water need by direct pumping of water from the river Mekong and through handpumps. Open defecation is not uncommon, although a considerable proportion of the families has and makes use of WC lavatories, which are connected to soak pits. The sewage so generated, infiltrates or flows into the river Mekong. The domestic waste water from kitchens and bathrooms is let out into the open and not into designated or proper drains. Thus, this effluent generated from domestic sources ultimately reaches river Mekong through various streams, channels and natural drains. Since the population density is very low even under minimum flow conditions, the water available in the river is sufficient to dilute untreated sewage from domestic sources. There are no industries in the project area and agricultural fields are away from the river. Dissolved oxygen concentrations frequently exceed saturation levels and the nutrient level is low. River temperatures fluctuate between C and C, and the ph varies from 6.2 to 6.5. The average fertilizer application to the agricultural land is 9 kg/ha. Apart from compost, application of urea and DAP is also practiced. The area under agriculture near the project site is quite small and the use of agro-chemicals is negligible. As a result pollution loading is virtually negligible. Thus, water quality is good in the project area. 4

5 3. IRRIGATION WATER REQUIREMENT A review of the irrigation water requirement for each scheme was carried out taking into consideration various crops that are grown in the project area such as: (i) (ii) (iii) (iv) (v) Paddy Sugar cane Corn Vegetables viz carrot, chillies, cucumber, beans, peanuts etc. Horticulture crops like coconut, tamarind, mango, orange Irrigation water requirement at the main canal head and at various distribution points and outlets were worked out based on standard international practices taking into consideration factors such as ETo (Based on climatological parameters), crop factor, effective rainfall, conveyance efficiency etc. Based on this analysis, water allowance (m 3 /100 ha) was worked out. However, taking into consideration future irrigation needs this was increased by % for different schemes. 4. SALIENT FEATURES OF THE PROJECT Table 3. Salient features S.No. Name of irrigation scheme CCA (ha) Length of main canal (km) Length of secondary/tertiary canals (km) 1. Thaphosy MuangSen Som Hong Ban He Savang Muang PROJECT ACTIVITIES 5.1 Installation of 10 electrically operated pumps (187 kw to 400 kw) on pontoons after major repairs and servicing. 5.2 Conversion of 34 diesel driven pumps into electrically operated pumps including repairs and servicing. 5.3 Improvement of 3 nos. pump service stations located at Vientian, Savanakhet and Pakse involving: Provision of repairing equipment, tools and spare parts. Instruments for checking electrical systems Training of technicians and support staff Provision of transport vehicles to attend to service calls. 5

6 6. BENEFITS OF THE PROJECT Since the Commissioning of the project in September 2015, assured availability of irrigation water will enable the farmers to grow more than one crop in a year. Increased agricultural activity will also provide employment opportunities in crop husbandry and post-harvest operations for the local landless population who earlier had to look for employment in neighbouring countries. 7. CONCLUSION (i) (ii) (iii) (iv) (v) (vi) Lift irrigation schemes are techno-economically feasible even in conditions of adverse topography and socio-economic settings. For efficient O&M of irrigation schemes, strong institutional set up at grassroot level is required. Institutional linkages at various levels are required to ensure accountability in asset management. Indigenous capacity needs to be developed for manufacture of electrical /mechanical equipment required for sustainable irrigation development Capacity for manufacture of spare parts, equipment, tools etc needs to be developed in the vicinity of irrigation commands. Rural development programmes should include setting up of Training centers for developing local man power of Electro- Mechanical technicians Command area development programme should include all-weather rural roads to facilitate quick response to service calls from the field. 6