Tài liệu Conditions of the surface water and ground water resources in the rural area of the Mekong Delta, Vietnam pptx

Conditions of the surface water and ground water resources in the
rural area of the Mekong Delta, Vietnam – exemplary investigations
at the study sites An Binh and Hoa An
Thomas Nuber1, Harro Stolpe1, Le Anh Tuan2, Vu Van Nam2
1

Environmental Engineering and Ecology, Ruhr-University Bochum, Germany, Universitätsstr. 150, 44780 Bochum, Germany

2

College of Technology, University of Can Tho, Can Tho City, Vietnam

1. Introduction
As a consequence of a fast-growing economy the Mekong Delta region is facing severe environmental problems related to industrial and agricultural activities. These environmental
problems include soil reclamation (LE QUANG MINH ET AL., 1997), deforestation (MILLER ET
AL., 1999) and water quality problems due to pollution of the water resources by pesticides,
herbicides and fertilizers (LE QUY AN, 2000). Besides those anthropogenic impacts on the
water resources also climatic and geogenic factors play an important role: severe floodings
occur during the end of the rainy season (NGUYEN VIET PHO, 2000), surface water bodies are
polluted by acid sulphate soils (LE QUANG MINH, 1996), saltwater intrudes into the surface
and ground water bodies from the sea (SIWRMP, 1995; NGUYEN HONG TOAN, 2000). Also
ground water is often polluted by high chloride or iron concentrations (DO TIEN HUNG ET AL.,
2000).
In this context a survey was carried out for the rural areas of the Mekong Delta. The goal of
the survey was the appraisal of the water resources in terms of quality and availability in order to develop a concept for the rural drinking water supply. In the focus of this survey were
two exemplary study sites in the rural area of the Mekong Delta.
The objective of this paper is the appraisal of the hydrological, hydrogeological, as well as
the chemical and microbiological conditions of the surface water and ground water resources
of the two study sites. In order to allocate the two study sites into a regional context an intense research on the conditions of the surrounding area was also matter of the survey.

2. Description of the study sites

2.1. General description
The investigations were done at the two study sites An Binh and Hoa An. The study site An
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Binh is located in the suburban area of Can Tho City, whereas the study site Hoa An is
approx. 40 km southeast of Can Tho City located in the Province Hau Giang (see figure 1).
Both study sites are characterized by an agricultural land use with farms, mainly cropping
rice and fruits. Some of the farms maintain small animal husbandries and fishponds. Surface
water, rain water and ground water are used for the drinking and the domestic water supply.
Many farms and households have small scale tube wells to withdraw ground water. In some
cases the waste water is treated with small biogas plants before discharged into the canals.
Usually the domestic waste water and waste water from the animal husbandries are discharged into the rivers, canals or ponds (see figure 2).
Besides the general similarities of the two study sites there are also major differences. In
addition to socio-economic differences (e.g. higher living standard in An Binh (see WIENEKE,
2005)) one of the most important differences are the soil-conditions. Here, the study site An
Binh is characterized by alluvial clay soils, whereas the study site Hoa An is burdened by
acid sulphate soils. This leads to different cropping systems and also to an acidification of the
surface water bodies in Hoa An.

2.2. Hydrological conditions
The entire Mekong Delta is characterized by a large network of rivers and canals of
10.000 km in length. Those canals are mainly used for irrigation and for transportation of
goods and people. The canal system is connected to the open sea.
In An Binh the canals are influenced by the tidal regime of the South Chinese Sea. Here, the
tidal amplitude is approx. 1.5 m. The study site Hoa An is located in an area where an interaction of the tidal regimes of the South Chinese Sea and of the Gulf of Thailand eliminate
each other. Here, the tidal amplitude is less than 10 cm. Because of its lower elevation severe flooding occurs in Hoa An by the end of the rainy season for approx. two or three
months.

2.3. Hydrogeological conditions

A detailed description of the hydrogeological conditions of the Mekong Delta can be found in
HUNG ET AL. (2000). According to HUNG ET AL. (2000) there are five major geological units in
the Mekong Delta: Holocene, upper-middle Pleistocene, lower Pleistocene, Pliocene and
upper Miocene (see table 1), whereas the ground water use from the upper-middle Pleistocene aquifer is prevailing.
According to geological profiles of the study site An Binh and Hoa An (see figure 3) the thickness of the covering Holocene layer in An Binh is approx. 65 m and in Hoa An about 60 m.
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At both study sites the Holocene layer is formed as an aquiclude, although with a water saturated layer in the first 5 to 10 m below surface. Underneath that Holocene layer is the upper
middle Pleistocene aquifer which consists of middle to coarse sand.

3. Methods
For the appraisal of the surface water and ground water resources water sampling and
analyses regarding the chemical and microbiological conditions were carried out. The investigations were carried out by the end of the rainy season 2003. The parameters and analytical methods are listed in table 2. The results of the analyses were tested on their plausibility
performing an ion-balance according to (DVWK, 1992).
Also, data on surface water and ground water quality, climatic data and data on ground water
levels was collected and evaluated for the surrounding area. Here, a GIS was set-up, various
evaluation-methods were used including the illustration with Piper-diagrams (PIPER, 1944)
and the ground water classification method according to (FURTAK & LANGGUTH, 1967).
The ground water resources of Can Tho City and Hau Giang province were also classified
regarding the concentration of the predominant water species. Here, the classification distinguishes three different ground water types following the Vietnamese standards for ground
water TCVN 5944 –1995 (see table 3). The results of the analyses of the surface water samples were compared to the Vietnamese standards for the use of surface water for drinking
water purposes TCVN 5942 –1995 (A).
Additionally slug & bail – tests for the determination of the hydraulic conductivity of the aquifers (Benstöm et al., 2005) and quality tests of the hand pumps were done (Nuber et al.,
2005).

4. Results and Discussion
4.1. Ground Water
For Can Tho City and Hau Giang province the spatial distribution of the different ground water types (see table 3) is illustrated in figure 4.
The study site An Binh is located in an area where the ground water quality is characterized

by a moderate hardness, a moderate chloride content (around the taste limit of 200 mg/l) and
a ferrous iron concentration around 2 mg/l. According to the classification method described
in chapter 3, it can be rated as ground water type II.
Unlike in An Binh, the ground water quality in the area of Hoa An is characterized by a high
chloride concentration, a high hardness and a high ferrous iron concentration. According to
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The classification method described in chapter 3 it can be rated as ground water type III.
Those observations can be confirmed by the water analyses taken at the study sites An Binh
and Hoa An during the survey (see table 4).
In figure 5 the ion-composition of the ground water samples taken at both study sites are
illustrated in a Piper-diagram. According to the classification method by FURTAK & LANGGUTH
(1967) the ground water in An Binh can be rated as a alkaline-earth water with higher alkaline content with a predominantly hydrogen carbonatic content whereas in Hoa An there is
alkaline ground water with a predominantly chloridic content.

4.2. Surface Water
As already described in chapter 2.2 the quality of the surface water is generally influenced by
the discharge of domestic and industrial waste water, agricultural entries and a high amount
of suspended solids as well as fuel residues. In comparison to the ground water situation
there are local differences regarding the water quality within Can Tho city and Hau Giang
province. But additionally and probably more important there are seasonal differences as
well.
The surface water at the study sites An Binh and Hoa An are influenced by leachate water
from the irrigation ditches of the rice fields. At both study sites the values for the pH, BOD,
NH4 and phosphate are conform to the requirements of the Vietnamese standards for the
use of surface water as drinking water TCVN 5942-1995 (see table 5). Only the values for
COD and the microbiological indicator values E.coli and total coliformes do not meet the requirements.
At the study site Hoa An the surface water quality is also influenced by the acid sulphate
soils (see chapter 2.1) which is the reason for the low pH-values. At both study sites the main

problems of the surface water bodies are the high amount of suspended solids and hygienically pollutants.

5. Conclusions and Outlook
Regarding the ground water and the surface water quality the two study sites Hoa An and An
Binh are typical for the conditions of the rural area of the Mekong Delta. At present, there are
substantial local differences within Can Tho city and Hau Giang province in terms of quality
and quantity of the available water resources. Thus, the improvement of the rural drinking
water supply requires investigations regarding the specific local conditions. For instance, two
totally different concepts are necessary for the improvement of the water supply situation at
the two exemplary study sites An Binh and Hoa An.
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In An Binh the usage of surface water should be minimized despite of its suitability for drinking water purposes. Here, it can be expected that the surface water quality is going to be
worsened because of its close location to Can Tho city. In the future the industrial and agricultural influence will grow. Thus, the use of ground water should be emphasized by the construction of small centralized ground water treatment plants in which the treatment is adapted
and optimized to the ground water quality.
In Hoa An the use of ground water for drinking water purposes should be minimized because
of the high chloride, high hardness and iron-concentrations. Here, the treatment of the
ground water requires a softening and desalinization which could be realized by reverse osmoses or ion-exchange. But those methods are technologically to complex and therefore to
expensive for an implementation on a regional scale. In spite of the moderate surface water
quality the use of surface water should be considered. Here, the combination of technologically simple but effective methods is possible. One possible treatment scheme could be a
flocculation with a rapid filter to eliminate the high amount of suspended solids in combination with a slow sand filter for the decay of organic matter and disinfection.
At both study sites and also for the entire Mekong Delta the use of alternative water resources (e.g. rain water) should be considered. In this context artificial ground water recharge or the pure storage of rain water in aquifers over the dry season could be a supplementary water resource. Especially in areas where the situation of the water resources is
very strained those methods could be applied.
But the water resources management and the water supply in the Mekong Delta will remain a
challenge in the future. Because of the high population- and economical growth rates it can
be expected that the water demand will increase rapidly. Additionally, the impact of waste
water on the surface waters will increase.

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6. Literature
Benstöm, F.; Nuber, T.; Stolpe, H.,2005: Determination of Hydraulic Conductivity with Slug
and Bail Tests in Small Diameter Wells in the South of Vietnam, in Department of Geology and Minerals of Vietnam (eds..): Journal of Geology, Series B, No. 25, Hanoi, pp.
58-63.
Do Tien Hung; Nguyen Hong Bang; Pham Van Giang, 2000: Availability and Quality of
Groundwater Resources, Ministry of Industry, Department of Geology and Minerals Division of Hydrogeology and Engineering Geology for the South of Vietnam (DHES), Ho
Chi Minh City
Furtak, H; Langguth, H.R., 1967: Zur hydrochemischen Kennzeichnung von Grundwässern
und Grundwassertypen mittels Kennzahlen, Mem. IAH-Congress, Hannover
DVWK, 1992: Entnahme und Untersuchungsumfang von Grundwasserproben – DVWKMerkblatt 128, Parey-Verlag, Hamburg
Lam Minh Triet and Nguyen Thanh Hung, 2001: Problems of Drinking Water Supply and Environment in Flood-prone Areas in the Mekong Delta, Journal of Environmental Protection. Ministry of Science, Technology and Environment. Hanoi, No. 4-2001
Le Anh Tuan, 2003: Research Proposal – SANSED Project, Work Group Hydrogeology and
Water Resources Management, SANSED Workshop, 24th – 29th March 2003, Can
Tho University, Can Tho City, Vietnam
Le Quy An, 2000 : Bio-diversification and Problemes in Biological Resources Protection,
Journal of Environmental Protection, Vol. 8, 6-10
Le Quang Minh, 1996 : Integrated Soil and Water Management in Acid Sulfate Soils – Balancing Agricultural Production and Environmental Requirements in the Mekong Delta,
Vietnam, PhD-Thesis at the University of Wageningen, Netherlands
Le Quang Minh, Tuong, T.P., Mensvoort M.E.F., Bouma, J., 1997: Contamination of surface
water as affected by land use in acid sulphate soils in the Mekong River Delta, Vietnam,
Journal Water Management and Ecosystems, Vol. 61, 19-27
Miller, F.,Nguyen Viet Thinh and Dio Thi Minh Duc, 1999: Resources Management in the
Vietnamese Mekong Basin. Asian Research Centre on Social, Political and Economic
Change, Murdoch University, Western Australia
Nguyen Hong Toan, 2000:Vietnam National Mekong Committee and Cooperation for Sustainable Development of the Lower Mekong Basin. In: Tran Cao Thanh (ed.) Vietnam
and Mekong Subregion Development Cooperation. The Gioi Publisher, Hanoi

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Nguyen Viet Pho, 2000: Management and Sustainable Development of the Mekong Delta,
Journal of Environmental Protection, Vol. 11, 8-11
Nuber, T. and Stolpe, H., 2004: Drinking water Resources in the Mekong Delta - Field Investigations and GIS Visualization, Proceedings of the International Symposium on Geoinformatics for Spatial Infrastructure Development in Earth and Allied Sciences, 16.09 18.09 2004, Hanoi, Vietnam
Nuber, T.; Stolpe, H.; Vu Van Nam; Tran Van Ty, 2005: Quality Tests of Hand Pump Wells in
the Mekong Delta, in Department of Geology and Minerals of Vietnam (eds.): Journal of
Geology, Series B, No. 25, Hanoi, pp. 63-69.
Piper, A.M., 1944:A graphic procedure in the geochemical interpretation of water analyses –
Trans. Am. Geophys. Union, 25; Washington D.C.,pp 914-928
SIWRMP, 1995: Major Issues in Water Resources Development in the Mekong Delta, Report
of the Sub-Institute of Water Resources Management and Planning, Ho Chi Minh City
Wieneke, F., 2005: Acceptance Anaylsis of New technologies for Sustainable Water Management and Sanitation – A Case Study of Operating Farm Households in the Mekong,
Delta, Vietnam, Disseration, Faculty of Agr., University of Bonn, Bonn Germany
World Bank, DANIDA and MONRE, 2003: Vietnam Environment Monitor 2003 – Water, Hanoi

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figure 1: provinces, provincial capitals and location of the study sites within the Mekong Delta

8


figure 2: setting of rural areas in the rural area of the Mekong Delta (modified after LE ANH
TUAN, 2003)

9

figure 3: geological logs in An Binh (left) and Hoa An (right)

10


figure 4: ground water types of Can Tho City and Hau Giang province

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80
60

80
60

40
Legend:

40

20

20

An Binh
Hoa An

Mg

SO4+NO3

80

80

60

60

40

40

20

Ca

20

80

60

40

20

Na+K

20

HCO3

40

60

80

Cl

figure 5: piper diagrams for the ground water samples in An Binh and Hoa An in mmol(eq%)/l

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table 1: geological units of the Mekong Delta (modified after HUNG ET AL., 2000)
description

symbol

lithology

thickness
(m)

stratigraphy

1st aquifer

/aquiclude

QIV

U,T,S

55 – 80

Holocene

2nd aquifer

QII-III

fS-mS, G

15 – 40

aquiclude

-

U,T

10 – 20

-

3rd aquifer

QI

gS, mS, fS

10 – 60

lower
Pleistocene

aquiclude

-

U, T

10 – 20

-

4th aquifer

NII

S, G

25 – 120

Pliocene

aquiclude

-

U, T

50 – 120

-

5th aquifer

NI

S, G

0 – 100

Miocene

upper-middle
Pleistocene

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table 2: Methods
Parameters

Method

ph, temperature, oxygen,
electric conductivity, redox

On-Site, DIN 38 404 C, WTW-Probes

chloride, alkalinity, arsenic

On-Site, Titration-method, Merckoquandt,

calcium, magnesium, ferrous Iron, mangaOn-Site, Reflectometric-method, Reflectoquandt,
nese, phosphate, nitrate
BOD

Off-Site, Dilution-method

COD

Off-Site, Dichromate-method

E.coli, total coliform

Off-Site, MPN-method (ISO 9308-2)

heavy metals

Off-Site, AAS

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table 3: ground water classification

ground water types

Type I

chloride
[mg/l]

hardness
[mg/l CaO]

ferrous
iron
[mg/l]

sulphate
[mg/l]

< 200

< 80

1–2

<200

Type IIa

200 – 600

80 – 180

>2

<200

Type IIb

200 – 600

80 – 180

>2

>200

Type III

> 600

> 180

>2

< 200 o. > 200

600

180

1

200

Limit according to
TCVN 5944 – 1995

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table 4: results of the ground water samples (selected parameters)
Parameter

Unit

An Binh

Hoa An

Limits according to
TCVN 5944-1995

pH

-

6,5 – 7

6,5 – 6,6

6,5 – 8,5

EC

µS/cm

1.000 – 1.300

3.800 – 4.100

no limit specified

chloride

mg/l

150 – 250

880 – 1.200

600

hardness

mg/l

80 – 130

560 – 630

180

ferrous iron

mg/l

1,6 – 2,5

6,2 – 7,1

1

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table 5: results of the surface water samples (selected parameters)
Parameter

Unit

An Binh

Hoa An

Limits according to
TCVN 5942-1995

pH

-

6,6 – 6,8

6,0 – 6,6

6 – 8,5

EC

[µS/cm]

148 – 220

179 – 250

no limit specified

BOD

mg/l

1,5 – 2

1,5 – 2

<4

COD

mg/l

8 –15

52 – 82

< 10

NH4-N

mg/l

0,01 -0,08

0,05 – 0,1

0,05

PO4

mg/l

< 0,5

< 0,5

no limit specified

E.coli

MPN/100ml

2 ⋅ 103 – 7 ⋅ 104

3,5 ⋅ 104

5 ⋅ 103

Total
Coliforme

MPN/100ml

2 ⋅ 104 – 7 ⋅ 106

1,6 ⋅ 10

6

5 ⋅ 103

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