An overview of the drinking water supply situation in the Mekong river delta, Vietnam

Chia sẻ: Haivan Haivan | Ngày: | Loại File: PDF | Số trang:0

lượt xem
  Download Vui lòng tải xuống để xem tài liệu đầy đủ

The Mekong delta (MD), the most downstream part of the Mekong river (See figure 1), is known as the biggest "rice bowl" of Vietnam. The Delta has a population of 17 million inhabitants living in 4 million hectares of land. All the people living in the Delta have to depend totally on the water resources, mainly the surface water, for domestic drinking, crop irrigating, fish-shrimp raising, goods transporating and industrial producing. As a general rule, any increase in industrial and agricultural activity from upstream may affect to water quality problems more or less in the downstream......

Chủ đề:

Nội dung Text: An overview of the drinking water supply situation in the Mekong river delta, Vietnam

  1. AN OVERVIEW OF THE DRINKING WATER SUPPLY SITUATION IN THE MEKONG RIVER DELTA, VIETNAM Le Anh Tuan, M.Eng. WRE. College of Technology, CanTho University, Vietnam E-mail: ------------------------------------------------------------------------------------------------------------ I. INTRODUCTION The Mekong delta (MD), the most downstream part of the Mekong river (See figure 1), is known as the biggest "rice bowl" of Vietnam. The Delta has a population of 17 million inhabitants living in 4 million hectares of land. All the people living in the Delta have to depend totally on the water resources, mainly the surface water, for domestic drinking, crop irrigating, fish-shrimp raising, goods transporating and industrial producing. As a general rule, any increase in industrial and agricultural activity from upstream may affect to water quality problems more or less in the downstream. As well as many other provinces in Vietnam, the MD are facing severe water problems. Especially since last decade, parallel with the fast-growing economy, situation of pollution, draught and flooding in the river are becoming worse more and more. To realize that the health of the people is one of factors to ensure sustainable development of the country, Vietnam government and international development agencies have implemented many water supply and environmental sanitation programs. Notice that, in the present time, about 75% of the inhabitants in the urban and 35% in the suburban and rural have access to clean water, this figure drops to 20% in far and deep areas. Since last 20 years to now, many drinking water plants and wells have been built. Most of them are located in the cities, small towns and suburban. In the deep and far rural areas, farmers still access water directly from rivers, canals, ponds or shadow wells. The Center of Rural Water Supply and Environmental Sanitation in each province is found since before 1990s and sponsored by UNICEF initially and Vietnam Central Government later. Their responsible are to serve clean water for rural people. For urban, there is Provincial Water Supply and Sewerage Company. II. WATER SUPPLY SITUATION II.1. Characteristics of water sources In the MD, water is almost present all over. Water movement not only defines the biophysical environment of the MD but largely determines the production options and livelihood strategies of its inhabitants. For drinking water, there are 3 sources, i.e. rain water, surface water and ground water. Depending on the location and the periods of the year as well as the difference living conditions, the people should choice their own-ways for collecting, storing and treating the water for domestic use. • Rain water: is used as one of favorite drinking water sources, special in the rural and suburban areas. In the urban places, rain water seems a minor source besides the tap water. The quantitative change of annual average rainfall in the MD is among 1,400 - 2,200 mm. About 90% of total rain water falls down the MD from May to October. In the delta, the dry season extends for 7 months resulting in serious shortage of rain water supply in many areas (See table 1). ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 1 in the Mekong river delta, Vietnam (Le Anh Tuan)
  2. • Surface water: is considered as a main source for water supply. Hydrological data records show that, each year, approximately 500 billion cubic meters (or nearly 15,000 m3/s) have flowed out to the sea via the delta. High rainfall combined with high flow of the river results in yearly flooding. Big flood occurs in the Mekong river for every 2, 3 or 4 years. There is a very big different in discharge between wet season and dry season. In the 5 months of the wet season, from May to October, the river discharges 2/3 the total annual flow. The rest amount of river flow is distributed in 7 months, from November to May, of the dry season (about 1,700 m3/s), from December to April. The low discharge of river water also leads to the salinity intrusion and it becomes the major water use problem in the coastal lands of the delta. Saline encroachment effects almost half of the MD. The salinity is caused by sea water intrusion in open mouths and estuaries. The phenomenon of salinity intrusion in the river branches is very complicated. The main factors that determine this process are river discharges, local rainfall and runoff, the tides and the depth of bars in the sea in front of the estuaries. Otherwise, in early rainy season, nearly 1,6 million hectares of the delta are infected by the acidity water due to the washing out aluminium and iron dissolve from the acid surphate soil. Preventation saline water intrusion to depression may cause a potential acid surphate soil become an activity acid surphate soil upon drainage and oxidation. Water quality of the Upper Mekong river is good with slightly alkaline, small dissolved salt content, and low potential toxic ions. The river carries 250 million ton of sediment per year. Sediments are rich in nutrients for agriculture cultivation but they are one of the drinking water treatment problems also. The sediment load of the river isnot so high if compared with Red river in the North of Vietnam. It is highest during the rise in discharge during the flood season. Few data is available, but in August - September the sediment content, considered as total dissolved and suspended solids, would be about 300 mg/l, thereafter less than 50 mg/l. An Giang, Dong Thap, Can Tho and Vinh Long, that are provinces located on the upper Mekong River, can get greater convenience for building surface water treatment plants. Data on small streams are scare, water quality however may vary consisderable. Rapid growths of industrialisation and urbanisation are leaded to increase water demand and also caused surface water pollution. Some streams flow through provinces/ cities and towns may be polluted by toxic chemicals at industrial production plants or domestic used waters, microbiological and biological aspects, insecticides,... There is no wastewater treatment plant in the city, except some wastewater treatment works in industrial zones. The project of fresh-watering the Ca Mau Peninsula to be invested in enlarging irrigation systems, widening channels and canals, building drains, dikes, tanks, controlling salted and acid surphate soil areas in the western and coastal part of the delta for increasing rice cultivation areas and improving the water supply to the people. So, implementating theses project objectives are to seem difficulty due to many limited factors, such as capital lacking, environmental impacts, conflicts between rice farmers and shrimp farmers, project manager's skill, ... Operation of water control system may have some disease incidence caused by altered hydrological regime. Water flow is one of important factors in transmission of diseases in ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 2 in the Mekong river delta, Vietnam (Le Anh Tuan)
  3. rural areas. Intestinal infections diseases including diarrhoea and dysestery occur more generally. Malaria and Dengue fever is seem common thoughout the delta, especially in backish and stagnant water areas, like Ca Mau, Bac Lieu, Tra Vinh, ... • Groundwater: is widely used in the many provinces along the coastal areas. Source of ground water is plentiful and present all over the delta. Ground water is exploited and pumped from 2 depth levels: at 80 - 120 meters for household wells and at 400 - 500 meters for groundwater plants (See Table 2). The upper level water is widely drilled and pumped out. UNICEF pump is commonly used but the water meet many problems with salinity and too high iron content. Salt water infiltration into ground water is very common in the coastal areas in the MD like Tien Giang, Ben Tre, Ca Mau, Kien Giang, etc. Although a lot of the wells have experienced quality problems of some kind - pH, high iron content, salinity and bad smell being most common - almost all plants for the future are based on increased groundwater withdrawal. The lower level water is better quality but it is costly in exploitation. Nevertheless, drilling the well very deep is necessary to be recommended. II.2. Drinking water collection, treatment and distribution Depending on the mean, place and time for water quality and quantity, the Mekong people have many ways for collection and treatment (See figure 2). Concerning the water supply, major problems in the delta, which effect people's living standards and health cares include: shortage of fresh water, salt water intrusion, acid surphate soil, industrial and agricultural pollutions and lacking capital for water treatment and system distribution. Moreover, sustained development of the MD is threatened by large scale destruction of mangroves for shrimp cultivation that leads to the pollution of the estuarine water bodies and in the future possible by overexploitation and un-calculation of groundwater aquifer. Even minor changes to local water management technologies may have unexpected and far-search impact on the hydrological environments of the neighboring locations. • Collecting rain water for domestic use is a traditional way in the MD. Storage of rain water in terra-cotta jars and cement-brick tanks or in large concrete containers is very common in rural, sub-urban areas and islands. The advantages of rain water in the MD are almost clean, purpose, easy to collect and very low cost. However, rain water is too short in the dry season and its storages are rather inoculated the mosquito pathogens or insect ovum. Otherwise, when falling from the air and flowing on the house roofs, arris-gutters rain water may be polluted by air-dust, bird-guano, ... A few of rain water analysis have recorded the acidity in the rain water in April, May yearly. No using of rain water in early rainy season is recommended as way to treat the air-dust and other pollutants deposited in the house-roofs after a long period of dry season. • Freshwater from river and canal is widely used in the upper parts of the delta, where the water quality isnot effected by high concentration of salinity and/or acidity and/or pollution. In An Giang and Kien Giang, building reservoirs in high lands for keeping stream water is one of the water collection ways. Commonly, surfate water taken from the rivers and streams is settled in settling tanks and then treated by aluminium sulphate (alum) and sand filter techniques. Finally, chlorination is used as a disinfectant. The purpose of sand filtration is to separate solid and liquid mixture. Alum treatment is used commonly in the delta for decreasing turbidity. This ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 3 in the Mekong river delta, Vietnam (Le Anh Tuan)
  4. chemical treatment will make surface water more clarify due to remove total suspended matter. Both sand filter and alum treatment are effective ways to remove total coliform bacteria as well. Depending on the special technical and financial conditions, gravity or pressure filtration, rapid or slow filtration will be chosen. Filter media are sand (size of 0.2 - 1 mm), gravel, activated coat, porous material or film are commonly used. Alum has been popular as a coagulant in treatment processes in the Mekong for quite a long time. In rural areas, villagers buy alum in solid form and stir it into river water in the storage jars. After a few minute stirring, the flocci are settled at the bottom of the jar. However, surface water treatment such as filtration and coagulation cannot ensure complete removal of the smallest bacteria and viruses as well as toxic matters from industrial and agricultural wastewater. • Ground water is the main source for the lower parts of the delta such as coastal areas and poor water-distribution places. In rural water supply, the opinion the groundwater is the preferable choice is widespread both among staff working with water supply and villagers. In the MD, ferrous iron (Fe2+) is found in groundwater commonly. It cause metallic taste and bad smell. Groundwater is pumped out and can be treated by aeration and filtration. Aeration is used to change iron content ferrous to ferric form (Fe3+) and to reduce tastes and odours. • Depending on the financial and management capacity, water suppliers can choice one of filtration processes, such as slow sand filter or pressure filters or upflow filters. Both surface and ground water are collected by electricity or hand pumps. Water Supply Plants are governed and placed in the cities and towns (see figure 3), all are the State- owned water suppliers. Treated water are stored in water tanks and distributed to households and other water users by pipe network mainly in cities, sub-urbans and small towns. Only 40 per cent to 50 per cent of the residents in the Mekong Delta have receive clean water from the State water plants. According to NEDECO data sources: The clean water production for 15 towns in the Delta was some 142,000 m3 in 1990, of which some 40% was unaccounted for; ground water took a share of 41,000 m3/day. The urban demand was estimated at 245,000 m3/day. Industrial water use is estimated at 34,000 m3/day, entirely from ground water. In the rural area, some 19,500 small wells have been drilled with an abstraction capacity of 90,000 m3/day for water supply of about 2.6 million people. • In accordance with a decision of Vietnam Government, from 3/2000 and depending on purpose of use, tap water prices were raised by 24.4% to 69.9%. New prices is listed as table 3. New charges seem no effect to the high income groups but it is really a problem for the poor communities. III. DISCUSSION Water in the MD is necessary to discuss in all its aspects. Although the amount of water on the delta is large if compared others regions on the world, but the capacity of clean water supply is finite in general and the demand is increasing due to a growing population, industrialisation, urbanisaltion and living standard. • Water supply is become a potential developing market in the MD. In last ten years, Vietnam Central Government invested US$ 1.3 billion into doubling the nation's water supply network. Besides the water supply projects built by the national budget, others are ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 4 in the Mekong river delta, Vietnam (Le Anh Tuan)
  5. generally funded through international organisations such as WB, ADB, UNICEF, UNDP and donor nations such as Finland, Denmark, France, Japan, the Netherlands, Australia, Sweden, South Korea and Germany. Looking at urban markets anywhere, we can count more than 20 trade-marks of bottled drinking water. This presents an increasing of number of drinking water suppliers if compared with a little number of them in the last decade. Water supply is as planned table 4 and table 5. • It is notice that water loss in water distribution systems is rather high, especial in the big cities. Up to 40%, even more, of water in Can Tho, Vinh Long, Long Xuyen and Ca Mau were lost through wastage or inefficiency. Average water loss stands at about 37% in the whole. In whole country, major causes of unaccounted for water as identified by provincial water companies, are: leaks in the distribution system; faulty meters and illegal taps (VN Water & Sewerage Ass. 2002), (See figure 4). • Pollution of water both surface and ground had led to a decreasing amount of water available for use. It really threat the sustainability of the country if we have no any way and mean to control and to improve. It is necessary to balance water supply and demand based on the economical/ social/ environmental objectives of maximizing net benefits of water use. • Being poor means limited capital resources to invest in living standard improvement related to clean water and environment. High prices of water supply will limit the number of water users in poor households. • Decentralised water supply for rural communities is recommended. Development many small drinking water treatment plants inside or nearby communes or districts may get a low cost on construction, a simple on distribution and an easy on management. • Environmental education programmes should be introduced to the schools, communities widely. Mass communication media should have a role on raising people’s awareness of water protection also. Others, a guidance how to save the tap water is also the way to decrease the water demand. • Socialisation and privatisation of the water supply systems should be encouraged and conducted. • The need for international collaboration and donor agencies to support the drinking water treatment technology, to train the water related staff and to facilitate cost-effective development is clear. • Other far and wide problems such as gender development, poverty alleviation, climatic change, globalisation and liberalisation of trade, etc. related water supply should be put forward for public discussions further and later. Le Anh Tuan March, 2003 ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 5 in the Mekong river delta, Vietnam (Le Anh Tuan)
  6. MAJOR REFERENCES 1. Josefin Abrahamsson, Veronica Svensson (2000). Rural Drinking Water - Quality and Supply in the Mekong River Delta (in English) 2. Le Anh Tuan (1995). Environment Impact Assessment on the Mekong Delta Irrigation projects. Cantho University (draft version, in English) 3. NEDECO, Government of Vietnam, World Bank, Mekong Secretariat, UNDP (1996). Master Plan for the Mekong Delta in Vietnam (in English) 4. SIDA (1999) Management and Use of Water Resources (in English) 5. SR Vietnam, VN Water & Sewerage Association, World Bank, (2002). Performance Benchmarking Urban Water Supply (in English, pdf. file) 6. State of the Environment Vietnam (2002). Specific characteristics of water resource and water supply in Vietnam. (Website: ... ) 7. Vietnam Government (1998). Decision No 237/1998-QD-TTg dated December 12, 1998 on approving the National Target Programmes of Clean Water and Rural Environmental Sanitation (in Vietnamese) 8. Vietnam Government, Ministry of Construction (1998). Strategic Orientation of Urban Water Supply up to 2020 (in Vietnamese) 9. Vietnam Government (2000). Decision No 104/2000-QD-TTg dated August 25, 2000 on approving the National Strategy for Clean Water Supply and Rural Environmental Sanitation up to 2020 (in Vietnamese) ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 6 in the Mekong river delta, Vietnam (Le Anh Tuan)
  7. TABLE APPENDIX Table 1: Roughly comparison the average monthly rainfall (mm) of some MD provinces Month 1 2 3 4 5 6 7 8 9 10 11 12 Σ Stations Can Tho 17 3 12 45 166 182 226 214 278 250 169 52 1604 Soc Trang 9 2 14 64 224 247 248 264 266 289 171 40 1840 Ca Mau 18 9 32 97 290 306 330 343 337 332 170 88 2360 Rach Gia 11 7 36 99 220 250 304 310 294 270 160 44 2015 Tan Chau 9 15 55 103 166 154 162 112 180 286 172 64 1478 Chau Doc 16 2 44 108 169 136 150 147 153 250 137 60 1385 Long Xuyen 12 2 13 97 211 162 194 197 235 287 144 57 1611 Phu Quoc 28 24 55 138 306 396 438 543 522 328 179 78 3038 Table 2: Calculated groundwater reserve of the Mekong River Delta Aquifers Area Flow rate Deep Reserve ( x 1,000 m3/day) 2 (km ) (l/s.m) (m) Dynamic Natural Static Elastic Upper Pleistoxen 19,500 0.1 - 1.1 32 80 972.5 17,160 478 Lower Pleistoxen 23,500 0.9 - 1.5 30 60 - 14,100 1,763 Plitoxen 21,500 0.1- 1.5 27 120 - 25,800 2,688 Mioxen 28,300 0.2 - 0.9 7 100 - 25,650 3,420 Sum = 97 972.5 82,710 8,349 • Sum of Ground water reserve = 92,128,000 m3/day • Ground water safe yield = 1,069,000 m3/day Source: Hydrogeological Division No.8 and NEDECO (1991) Table 3: Vietnam Tap water prices (effected on March, 1st, 2000) Water users Consumption rate Old charges New charges 3 (m used/month) (VN Dongs) (VN Dongs) Households Up to 4 1,300 1,700 From 4 to 6 1,300 2,500 From 6 to 10 1,500 3,200 Over 10 1,500 4,000 Administrative agencies & Up to 1 1,300 2,200 government organisations Over 1 1,300 3,000 Production units Over 1 3,100 4,000 Business and service units Over 1 5,200 6,500 Note : Sur-charges added include: Water use VAT (5%), Sewerage fee (180 VND/m3 water used), ... Table 4: Water supply planned Periods Percentage of water supplied Water supply rate Estimated cost population (%) (lit/day.person) (million USD) Urban Rural Urban Rural Urban Rural Up to 2010 95 85 120 60 2.165 unknown Up to 2020 100 100 120 60 3.570 unknown Data sources: + Vietnam National Strategy on Rural Water supply and Sanitation (1998) + Ministry of Construction (1998) ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 7 in the Mekong river delta, Vietnam (Le Anh Tuan)
  8. Table 5: Water Supply rates as planning stage in Vietnam Water supply rate (litters/day.person) Regions 50 - 60 Mountain, Half-mountain half-plain areas 60 - 70 Coastal areas 60 - 80 In field areas 70 - 90 Small and medium towns 80 - 100 Sururban, Out-of town areas 100 - 120 Cities, industrial zones 120 - 150 Big cities FIGURE APPENDIX Figure 1: The Mekong River Basin and the MD landforms 5 0 4 0 3 0 2 0 1 0 0 Tan Sa Cao My Vinh Tra Can Soc Bac Ca An Dec Lanh Tho Long Vinh Tho Trang Lieu Mau Water Loss (%) 30 47 13 47 35 38 30 35 47 35 Figure 4: Average water loss (%) in some water supply plants (Data sources: Ministry of Construction, 1998) ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 8 in the Mekong river delta, Vietnam (Le Anh Tuan)
  9. Cao Lanh 1 (S.1000) My Tho 1 (S.20000) Hung Dao Vuong (S.3650) Cao Lanh 2 (G.2500) My Tho 2 (G.20000) Cau Vong (S.1000) Sa Dec 1 (S.2000) Go Cong Dong (S.1400) Tra On (S.300) Sa Dec 2 (G.1000) Go Cong Tay (S.1000) Hong Ngu (S.600) Cho Gao (S.200) Thanh Binh (S.180) Cai Lay (S.1500) Tan An 1 (S.8000) Cai Be (S.1000) Tan An 2 (S.2000) Tan Hiep (S.500) Moc Hoa (S.1000) Duc Hoa (G.300) Long Xuyen (S.15000) Binh Phong Thanh (G.300) Chau Doc (S.5500) Ben Thu (G.300) Tan Chau (S.2400) Go Den (G.300) Cai Dau (S.500) Tan Chau (G.300) Cho Moi (G.1000) Tam Vu (G.300) Rach Kien (G.300) Rach Gia 1 (S.14000) Rach Gia 2 (G.2000) Son Dong (S.3000) Rach Soi (G.500) Bac Lieu (G.5500) Can Tho (S.40000) Thot Not (G.2400) O Mon (G.2400) Ca Mau (G.6800) P hungHiep (G.1000) Vi Thanh (S.1680) Long My (G.1000) Soc Trang (G.9000) My Xuyen (G.1000) Tra Vinh (G.4200) Vinh Chau (G.300) Binh Minh (G.250) Thanh Tri (G.300) Vung Liem (G.100) Name of Water Supply Plant Producing Capacity (m3/day) G: groundwater; S: surface water Figure 2: Water Supply Plants situation in the MD ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 9 in the Mekong river delta, Vietnam (Le Anh Tuan)
  10. New Water supply demand Yes Yes Is there existing To extend tap water system ? Is it enough ? tap water system No To distribute & No Alum-coagulation/ Sand filtration and Chlorrua-disinfection boil water when using Yes Yes Can collect To use filtered & Is is enough ? rain water ? boiled rain water Partly High Suspended solid No Yes Yes Can take How is High Salinity/ pH/ Chemical toxic concentration surface water ? Is is enough ? surface water quality ? Partly Good enough (level A) No Yes To apply advanced water treatments Yes Can drill a How is High Iron content groundwater well ? Is it enough ? groundwater Partly quality ? Aeration/ Sand filtration No Yes To transport and distribute Yes treated water by pipelines Are there water Can access from High Salinity/ pH/ or or water trucks treatment hi-tech other sources ? Chemical toxic concentration and enough money? No No To ask for the support to water experts/ government/ organisation Figure 3: Commonly water abstraction & treatment alternatives in the MD (Tuan, 2003) ----------------------------------------------------------------------------------------------------------------------------------- An overview of the drinking water supply situation 10 in the Mekong river delta, Vietnam (Le Anh Tuan)



Đồng bộ tài khoản