Water Quality

The Northwest region has an area of 35,637 km² and a population of 2.3 mill. people, of whom only 03.4 thousand live in urban areas. The main economic ctivities are agriculture, forestry and mining. The region is mountainous, and soils are acidic and of low fertility. Intense rainfall from late May to October, combined with steep topography and frequent seismic activity make the region highly susceptible to erosion.

Water Quality Issues
Social and economic development has not had a significant impact on water quality in this region. Water quality data are limited. However, available data for the Da River show, though not systematically, that organic content is low and the dissolved oxygen levels are acceptable. Generally the water quality is considered to be good although some localized deterioration occurs near the few urbanized locations in the region. Ground water quality is reportedly good and well within the national standards.

The Northeast region has a total area of 65,326 km² and a population of 9.0 mill. population, of which 1.7 mill. are in urban areas. The region is mountainous and hilly, with limestone. The coastal areas have port development and mining industries, but also have good fishing grounds and a high potential for mangrove plantations and aquaculture. The region is prone to typhoons mainly during June through August.

Water Quality Issues
Rivers of this region generally have good water quality. Upstream reaches of the Red River in the Lao Cai province fulfill Class A water quality criteria (Table 26a). To the north of Red River, the larger tributaries (the Lo, Gam, Cau, Thuong and Luc Nam) generally meet Class B standards (Table 26b). In dense urban and industrial areas, however, the water quality in these tributaries does not meet the standard. Hotspots include the section of the Red River around Viet Tri town, where COD and BOD5 exceed national standards by 2.3 and 3.8 times respectively. The Cau river that runs through the Thai Nguyen industrial zone is heavily polluted with concentrations of NO₂, NH₄ and BOD5 that exceed the standards by 10, 2 and 5 times respectively. TSS and H₂S exceed the standards by ten to hundred times.
Ground water quality is reported to be good and generally within the national standards, except in the coastal region where salinity causes a problem. The water quality is also affected in mining areas.

The Red River Delta covers an area of 14,788 km² with a population of 17.2 mill. people, of which 3.6 mill. live in urban areas. The capital city Hanoi and port city Hai Phong are located in this region. Major economic activities vary from industry and port transport to extensive services and intensive agriculture. The flat topography and alluvial soils are suitable for intensive agriculture.

Water Quality Issues
The water quality in the Red River–Thai Binh is generally acceptable and meets the standards of industrial and domestic use. However, near outlets from industries, Class A standards are exceeded (Table 27). The Nhue River, which receives effluence from Hanoi, is heavily polluted with oxygen levels down to 1-2 mg/l and NH₄ levels above 2.5 mg/l downstream from the confluence with the To Lich River. Cam and Tam Bac rivers (running through Hai Phong) are considerably polluted. Values of BOD5 and COD parameters have increased gradually from 1995-1997 for the two rivers, especially for the Tam Bac river.
Ground water quality in the region is generally within the standards. However, salinity intrusion is becoming an increasing problem (Map 1 in Annex 2).

Coastal Waters
The coastal ecosystems are threatened by oil spills. Since 1997, as many as seven oil spills have been reported in the region. Except for oil, phosphates, and nitrates, other parameters of coastal water quality are within the national standards (Table 28).

Table 14a. Red River Water Quality.

Class A Class B Out-of-range COD (mg/l)   X   BOD (mg/l)   X   NH4-N (mg/l)   X   DO (mg/l) X     Coli (MPN/100ml) X     Overall   X

Table 14b. Thai Binh River Water Quality.

Class A Class B Out-of-range COD (mg/l) X     BOD (mg/l)   X   NH4-N (mg/l)   X   DO (mg/l) X     Coli (MPN/100ml) X     Overall   X

Table 15. Quality of Coastal Water

Phosphate Nitrate COD BOD Oil Coliforms 1996 6.6 192 2.25 1.07 0.36 928 1997 17.75 30 4.3 1.3 0.34 804 1998 22.40 n.a. n.a. n.a. 0.56 866 1999 n.a. n.a. n.a. n.a. >0.05 >1000 2000 16.00 <50 n.a. 0.8 2.4 >1000 2001 >16.00 >50 n.a. n.a. 1.12 <1000 National Standards 10 µg/l 50 µg/l 30 – 40 mg/l 10 – 20 mg/l 0.05 mg/l 1000 (MNP)

Source: NEA (1997-2002) and HIO (1999).

The North Central Coastal region has an area of 51,501 km² and a population of 10.2 mill. people, of which 1.35 mill. live in urban areas. The major cities Thanh Hoa, Vinh, Dong Ha, and Hue are areas of moderate economic activity. Agriculture and tourism are the main income earners. The population is generally poor and the region is prone to typhoons, floods, and droughts. Yellow-red soils are found in the uplands, alluvial in the lowlands and sandy soils at the coast. The land is not fertile and more than one third of it has medium susceptibility to deterioration and erosion.

Water Quality Issues
Monitoring of water quality has not been carried out in any extensive way in the North Central Region. However, the upstream river water quality where measured has been found to be good within class A and B for various parameters (Table 29). In urban and industrialized areas near the coast the water quality deteriorates. Hieu river (through Dong Ha town) has BOD5 and COD concentrations exceeding class A standards by 2-3 times, NH₄ and PO₄ by 1.5-1.8 times. In the Huong river section running through Hue city the BOD5 and COD concentrations exceed the class A standards by 2.5 and 1.6 times respectively.
In the plains the groundwater has a complex chemical composition with alternating contents of compounds and total dissolved solids. However, the general quality standards for consumption are adhered to, except in low land areas influenced by tides where salinity intrusion takes place.
Increasing economic development in this region may cause further water quality problems in the coastal regions from urban and industrial wastewater discharges, unless adequate treatment is undertaken.

The South Central Coastal region has an area of 33,100 km² and a population of 6.7 mill. people, of which 1.9 mill. live in urban areas. The major economic activities include industries in Da Nang and Quy Nhon cities, and fishery, aquaculture, and intensive tourism in all provinces. Sandy aquaculture is expanding rapidly in the region, especially in the Ninh Thuan province.
The region is characterized by high temperatures, heavy rainfall during the wet season, and a prolonged dry season. Yellow-red soils are dominant in the uplands and white sandy beaches are all along the coastline.

Water Quality Issues
The water quality of rivers is generally good, especially in the upstream reaches (Table 30b.). Some sections of rivers have oil content of 0.1 mg/l. Pollution hotspots include coastal cities such as Da Nang, Quy Nhon, and Nha Trang. Dissolved oxygen levels in the Han River are good. How-ever, BOD5 and COD exceed Class A standards by 1-2 times and NH₄ by 1.4-2.6 times (Table 30a).
In mining areas, various heavy metals and other toxic substances constitute a problem. For example, cyanide in river waters exceeds the standard by 1.6-2 times in some mining areas. In the plains the quality of groundwater resources is good. In the estuaries saltwater intrusion is a problem.
Water quality in this region may deteriorate with increasing economic development and consequent urban and industrial waste water discharges, if not treated properly in future. Coastal water is contaminated mainly by oils, phosphates and nitrates (Table 31).

The Central Highlands Region coversan area 54,476 km² and a population of 4.3 mill. people, of which 1.2 mill. are living in urban areas. With a population density of 80 people per km² this constitutes the least densely populated region in Viet Nam. Economic activity is mainly related to forestry and agriculture with widespread cultivation of cash crops such as coffee, cashew nuts, and tea.
The region is characterized by a very prolonged dry season with severe droughts from January to May, followed by heavy rainfalls. More than two thirds of the land is susceptible to deterioration. The region has 1.8 million ha of basaltic soils with excellent potential for agriculture development.

Water Quality Issues
Under the National Monitoring Program, water quality data for the Central Highland Region are scarce. However, some data is available through the MRC monitoring program.
River water quality in this region is generally good (Table 32). The ammonia concentrations in the rivers are generally low, but occasionally higher than the standard of 0.050 mg NH₄-N. No available measurements were identified for BOD5, as this parameter is not part of the MRC program.
The ground water quality is generally within the national water quality standards.

Northeast of Mekong has a total area of 34,733 km² and a population of 12.4 mill. people, of which 6.5 mill. live in urban areas. The region is characterized by industrial development and high economic activity concentrated around HCMC, Binh Duong, Dong Nai, Vung Tau. Tourism is another main activity in Ninh Thuan, Binh Thuan and Vung Tau – Con Dao. Off-shore gas and oil industry is on the rise.

Water Quality Issues
Industrial and urban development characterize major parts of this region and significantly impact water quality. The downstream end of the Dong Nai river is relatively highly polluted (Table 33). Oil spills from shipwrecks and oil leakages from marine transportation are a major pollution problem. Hotspot areas include sections of Thi Vai and Sai Gon rivers. Thi Vai river is likened to a reservoir of industrial waste-water from Bien Hoa and Phu My industrial zones. Dissolved oxygen levels are under 2 mg/l over a 16 km stretch. In Go Dau BOD5 and COD exceed the standard by 10 to 15 times. Coliforms exceed standards by 50 to 100 times. Nitrogen and phosphorus also exceeds the standards. However, heavy metals including chromium, lead, mercury and arsenic are measured in concentrations within the standards.
The Holocene groundwater aquifers have the highest grade of pollution, mainly zones with high salinity in the seashore band and the zone between the Mekong and Dong Nai Rivers. The deep aquifers are less contaminated and can be used directly for water supply.

The Mekong River Delta region covers an area of 39,713 km² and has a population of 16.5 mill. people, of which 3 mill. live in urban areas. With a population density of 416 persons/km² this is one of the most densely populated coastal regions in the world. Agriculture and aquaculture dominate, along with the food processing industry.
Annual rainfall of 2000 mm arrives in late June and ends in November. The region is best known for its dense hydrological network and heavy waterway transport. Flooding is a permanent phenomena in the delta. Soils are mostly alluvial, but there are extensive areas of acid sulfate and saline soils.

Water Quality Issues
Based on measurements provided by the national monitoring program and MRC, it can be concluded that the water quality in the major rivers of the Mekong River Delta is within the standard classes A-B (Table 34). The only parameter that exceeds stan-dards is BOD5, and occasionally NH₄.
However, in the smaller tributaries, especially in the urban and in-dustrialized areas, the water quality will be found to be exceeding the standard. A notable feature is the low pH values in the rivers of the Mekong River Delta (3.8-5.0).
The ground water quality in the Mekong River Delta region is variable. Salinity intrusion is a major problem in the coastal parts of the delta (map 2 in Annex 2). In addition high concentrations of nitrogen com-pounds have been registered in bore holes in the Holocene aquifers.
Coastal water is deteriorating in most of the quality parameters, mainly due to the high intensity of economic activities in the region (Table 35).