Final Report IGPVN Activities and Achievements Proposal of Recommendations and Measures for Water Resources Management in S6c Träng

Hoang Thi Hanh
Roland Bäumle

Final Report
IGPVN Activities and
Achievements
Proposal of Recommendations
and Measures for Water
Resources Management
in S6c Träng
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Ministry of Natural
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Federal Ministry
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and Development, BMZ


Final Report
IGPVN Activities and Achievements,
Proposal of Recommendations and Measures for Water
Resources Management in Sóc Trăng
Technical report Phase III -1

Authors: Hoang Thi Hanh, Roland Bäumle

Date: May 2017


German Technical Cooperation with Vietnam
Improvement of Groundwater Protection in Vietnam

Authors:

Hoang Thi Hanh (IGPVN Project Team Member), Roland Bäumle (BGR)

Commissioned by:

Federal Ministry for Economic Cooperation and Development
(Bundesministerium für wirtschaftliche Zusammenarbeit und
Entwicklung, BMZ)

Project:

Improvement of Groundwater Protection in Vietnam (IGPVN, 20122015)

BMZ-No.:

2013.221.2

BGR-No.:

05-2374

BGR-Archive No.:
Date:

May 2017

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Table of Contents
1

Project framework and objectives ..................................................................................... 1

2

Investigation Area .............................................................................................................. 3

3

2.1

Location ....................................................................................................................... 3

2.2

Topography .................................................................................................................. 3

2.3

Edaphology .................................................................................................................. 4

2.4

Climate ......................................................................................................................... 5

2.5

Population, socio-economic conditions ...................................................................... 6

Overview on water resources ............................................................................................ 7
3.1

3.1.1

Surface water ....................................................................................................... 7

3.1.2

Groundwater ........................................................................................................ 7

3.2

Current status of groundwater exploitation and use ................................................ 10

3.2.1

Groundwater abstraction for water supply in urban areas ............................... 11

3.2.2

Groundwater abstraction for water supply in rural areas ................................. 13

3.2.3

Groundwater abstraction at household scale.................................................... 13

3.2.4

Groundwater abstraction for industry, agriculture and aquaculture ................ 13

3.3

4

Main water resources of Sóc Trăng Province .............................................................. 7

Current state of water resources management and protection ............................... 14

3.3.1

Advisory to the PPC to issue secondary regulations and implementation of the
legal documents in the water resources sector................................................. 14

3.3.2

Water resources planning and basic investigation ............................................ 15

3.3.3

Water resources licensing .................................................................................. 16

3.3.4

Water resources financing ................................................................................. 16

3.3.5

Inspection, examination and handling of the legislation violations in the water
resources sector ................................................................................................. 17

3.3.6

Communication, dissemination, education on legislation in the water resources
sector.................................................................................................................. 17

Approach and Study Methods ......................................................................................... 18
4.1

Construction of the monitoring wells........................................................................ 18

4.1.1

Site selection, drilling and development............................................................ 18

4.1.2

Geodetic survey.................................................................................................. 19

4.1.3

Drill cuttings sampling and analysis ................................................................... 19
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4.2

4.2.1

Sampling for hydrochemical analysis ................................................................. 21

4.2.2

Sampling for groundwater dating and recharge ................................................ 24

4.3

Groundwater dating methodology............................................................................ 29

4.3.1

Groundwater dating using 3H............................................................................. 29

4.3.2

Groundwater dating using 14C............................................................................ 29

4.4

Groundwater level monitoring .................................................................................. 31

4.4.1

Monitoring equipment ....................................................................................... 31

4.4.2

Periodical check, extraction and processing of the monitoring data ................ 32

4.5

5

Water sampling and analysis ..................................................................................... 21

Capacity building for Sóc Trăng DONRE .................................................................... 32

4.5.1

Equipment .......................................................................................................... 32

4.5.2

Training ............................................................................................................... 32

4.5.3

Study tour on water resource management...................................................... 32

4.5.4

IWRM workshop ................................................................................................. 33

4.5.5

Guidebook .......................................................................................................... 33

Study results ..................................................................................................................... 33
5.1

Grain size analysis ...................................................................................................... 33

5.2

General hydrochemical characteristics of groundwater ........................................... 38

5.2.1

Data base ............................................................................................................ 38

5.2.2

Water type.......................................................................................................... 38

5.2.3

Major ion composition ....................................................................................... 41

5.2.4

Major ion ratios and geochemical processes ..................................................... 44

5.2.5

Regional distribution .......................................................................................... 49

5.3

Hydrochemical characteristics of water samples collected in 2013 by IGPVN ......... 51

5.3.1

Water type.......................................................................................................... 51

5.3.2

Major ion composition ....................................................................................... 53

5.3.3

Major ion ratios .................................................................................................. 63

5.3.4

Saturation indices ............................................................................................... 64

5.4

Water quality ............................................................................................................. 64

5.4.1

Surface water ..................................................................................................... 64

5.4.2

Groundwater ...................................................................................................... 65
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6

5.5

Stable isotopes analysis results ................................................................................. 66

5.6

Groundwater dating .................................................................................................. 69

5.6.1

3H

5.6.2

Groundwater dating in Sóc Trăng using 14C ....................................................... 70

activity of water samples in Sóc Trăng Province ........................................... 69

5.7

Groundwater flow direction and groundwater transit velocity ................................ 71

5.8

Groundwater level monitoring results ...................................................................... 72

Proposed Recommendations and Solutions for Groundwater Management in Sóc Trăng
Province ............................................................................................................................ 78
6.1

Review and assessment of the implementation of legal documents and secondary
regulations in water resource sector ........................................................................ 78

6.2

Water resources planning ......................................................................................... 78

6.3

Specific tasks regarding to water resources management ....................................... 79

6.3.1

Groundwater exploitation licensing................................................................... 79

6.3.2

Investigation for updates of the status of groundwater exploitation and use .. 79

6.3.3

Water resources allocation ................................................................................ 80

6.3.4

Protection of fresh/slightly saline aquifers ........................................................ 80

6.3.5

Management of saline aquifer ........................................................................... 81

6.3.6

Artificial recharge ............................................................................................... 82

6.3.7

Groundwater monitoring ................................................................................... 82

6.4

Development of guidebooks ..................................................................................... 83

6.5

Strengthening the integrated water resources management, networking and
information sharing .................................................................................................. 84

6.6

Awareness raising on water resources...................................................................... 84

7

Conclusions and suggestions for further investigations .................................................. 86

8

References ........................................................................................................................ 89

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List of Tables
Table 1

Groundwater production wells for domestic and service water supply in the
urban areas of Sóc Trăng Province (Source: Chân (2010)) ................................ 12

Table 2

Groundwater production wells for domestic water supply in rural area in Sóc
Trăng Province ................................................................................................... 13

Table 3

Number of private wells of each aquifer (Source: Chân (2010)) ....................... 14

Table 4

Number of groundwater production wells for industry, agriculture and
aquaculture use in Sóc Trăng (Source: Chân (2010)) ......................................... 14

Table 5

IGPVN monitoring wells in qp2-3 aquifer, Sóc Trăng Province ........................... 18

Table 6

Information recorded during the IGPVN monitoring well flushing in Sóc Trăng
Province.............................................................................................................. 19

Table 7

Coordinates and elevations of the monitoring wells determined by geodetic

measurement ..................................................................................................... 19

Table 8

List of the drilling core samples taken for grain size analysis ............................ 20

Table 9

Water samples collected in Sóc Trăng Province in April and November 2013 . 22

Table 10

Water samples collected in Sóc Trăng Province in June, 2013 for 14C and 3H
dating ................................................................................................................. 26

Table 11

Grain size analysis results .................................................................................. 34

Table 12

Hydraulic conductivities (m/day) calculated for each aquifer using various
methods by SizePerm......................................................................................... 37

Table 13

Summary of groundwater samples used for the interpretation of groundwater
chemistry in Sóc Trăng Province (IGPVN database)........................................... 38

Table 14

Field parameters of water samples collected in Sóc Trăng Province ................ 52

Table 15

Chemical analytical results of water samples collected in Sóc Trăng Province in
April 2013 ........................................................................................................... 54

Table 16

Chemical analytical results of water samples collected in Sóc Trăng Province in
November 2013 ................................................................................................. 55

Table 17

Stable isotope composition of water samples collected in Sóc Trăng in 2013 . 67

Table 18

3H

Table 19

13C

activity of water samples collected in Sóc Trăng Province in June, 2013 ..... 70

concentration, 14C activity and estimated groundwater age in Sóc Trăng
Province.............................................................................................................. 70

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List of Figures
Figure 1

Administrative
map
of
Sóc
Trăng
Province
(Source:
) ............................................................................. 3

Figure 2

Edaphological groups in Sóc Trăng Province ....................................................... 5

Figure 3

Schematic representation of sedimentary aquifer succession in Sóc Trăng
Province.............................................................................................................. 10

Figure 4

Groundwater abstraction in m³/d and % as by user groups in Sóc Trăng Province;
Total current abstraction amount are estimated at about 201,500 m³/d. ....... 11

Figure 5

Map of the sampling locations in Sóc Trăng Province in April and November,
2013.................................................................................................................... 23

Figure 6

Location map of water sampling for radioactive isotopes (14C and 3H) and stable
isotopes (2H, 18O) in Sóc Trăng Province in June, 2013 ...................................... 25

Figure 7

A device used to collect TDIC in groundwater samples ..................................... 27

Figure 8

Scheme of the device used to trap CO2 evolved from the reaction between
BaCO3 and H3PO4 1M (adapted from Feltz & Handshaw (1963)) ...................... 28

Figure 9

Piper diagram of groundwater of Holocene and Pleistocene aquifers in Sóc Trăng
Province.............................................................................................................. 39

Figure 10

Piper diagram of groundwater of Pliocene and Miocene aquifers in Sóc Trăng

Province; selected analysis numbers provided, please refer to text. ................ 40

Figure 11

Box charts showing major ion composition of aquifers in Sóc Trăng Province.
Units are mg/l except for pH.............................................................................. 42

Figure 12

Plot of Na/Cl ratio against fraction of seawater fSea of groundwater samples .. 45

Figure 13

Plot of Na/(Ca+Mg) ratio against fraction of seawater fSea of groundwater
samples .............................................................................................................. 46

Figure 14

Binary graphs of major ions that can be regarded a result of geochemical
processes other than conventional fresh/saltwater mixing for groundwater
samples of qp2-3 and n12: (a) Plot of alkalinity against sodium content; (b) sulfate
against alkaline earth metal content. ................................................................ 47

Figure 15

Binary graphs of major ions that can be regarded a result of geochemical
processes other than conventional fresh/saltwater mixing for brackish or saline
groundwater samples (fSEA >0.2): (a) Plot of alkaline earth metal against sodium
content; (b) alkaline earth metal against sulfate content. ................................ 49

Figure 16

Distribution of chloride content expressed as fraction of seawater fSea for
Holocene and Pleistocene aquifers in Sóc Trăng Province ................................ 50

Figure 17

Distribution of ratio between SO4React and (Ca+Mg)React for Holocene and
Pleistocene aquifers of Sóc Trăng Province ....................................................... 50
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Figure 18

Piper diagram visualizing hydrochemical facies of water samples in Sóc Trăng.
Samples in dry season indicated by orange symbols; samples in rainy season
indicated by blue symbols.................................................................................. 52

Figure 19

Schöller diagrams showing the change of major ion composition of surface water
in Sóc Trăng Province between dry and rainy season in 2013. ......................... 56

Figure 20.

Schöller diagrams showing the change of major ion composition of groundwater

in Sóc Trăng Province between dry and rainy season in 2013. ......................... 58

Figure 21

Spatial and temporal variation in the major ion compositions of surface water
and groundwater in Sóc Trăng Province ............................................................ 62

Figure 22

Molar ratio of Na/Cl vs. Cl concentrations of water samples in Sóc Trăng Province
in 2013................................................................................................................ 63

Figure 23

Concentrations of selected ions in water samples in Sóc Trăng Province during
dry and rainy season in 2013: a) phosphate, b) nitrate, c) sulfate .................... 66

Figure 24

Stable isotope compositions (2H, 18O) in water samples taken in the rainy (empty
symbols) and dry season (filled symbols) in Soc Trăng Province in 2013.
Rainwater samples were collected from July to November 2013. Groundwater
samples collected from the IGPVN monitoring wells are indicated by circles and
groundwater samples collected from private tube wells are indicated by
squares; surface water samples are indicated by upwards triangles. ............... 68

Figure 25

Groundwater contour line and flow direction in qp2-3 aquifer in Sóc Trăng
Province according to the monitoring data in 2005 provided by DWRPIS ........ 72

Figure 26

Fluctuation of groundwater level at ST1 (Phú Lộc Town, Thạnh Trị District, Sóc
Trăng Province) .................................................................................................. 73

Figure 27

Fluctuation of groundwater level at ST3 (An Thạnh I Commune, Cù Lao Dung
District, Sóc Trăng Province) .............................................................................. 74

Figure 28

Groundwater levels at ST3 at hourly intervals (orange line) and daily intervals
(blue line), change in water level per hour (dark brown line) and different moon
phases. ............................................................................................................... 75

Figure 29

Stage at Station Đại Ngải, Hậu River (Source: Center for Meteo-hydrology
Network and Environment) ............................................................................... 75

Figure 30

Fluctuation of groundwater level at ST4 (Trần Đề Town, Trần Đề District, Sóc
Trăng Province) .................................................................................................. 76

Figure 31

Fluctuation of groundwater level at ST7 (Thạnh Phú Commune, Mỹ Xuyên

District, Sóc Trăng Province) .............................................................................. 76

Figure 32

Fluctuation of groundwater level at ST11 (Vĩnh Tân Commune, Vĩnh Châu
District, Sóc Trăng Province) .............................................................................. 77

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List of Abbreviations
BGR
CTU
DONRE
DOST
DWRPIS
IGPVN
INST
LOD
MARD
MOH
MONRE
MWL, GMWL
NAWAPI
PPC
TDS

TU
WTP

Bundesanstalt für Geowissenschaften und Rohstoffe (Federal Institute for
Geosciences and Natural Resources)
Can Tho University
Department of Natural Resources and Environment
Department of Sciences and Technology
Division for Water Resources Planning and Investigation for the South of
Vietnam
Improvement of Groundwater Protection in Vietnam
Institute for Nuclear Sciences and Technology
Limit of Detection
Vietnam Ministry of Agriculture and Rural Development
Vietnam Ministry of Health
Vietnam Ministry of Natural Resources and the Environment
Meteoric water line, Global meteoric water line
National Center for Water Resources Planning and Investigation
Provincial People’s Committee
Total dissolved solids
Tritium Units
Water treatment plant

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Executive Summary
Authors:

Hoang Thi Hanh, Roland Bäumle

Title:

IGPVN activities and achievements, Proposal of recommendations and
measures for Water Resources Management in Sóc Trăng (Technical Report
Phase III-1)

Keywords:

Groundwater management, groundwater protection, groundwater monitoring,
grain size analysis, water quality, stable isotopes, groundwater dating

This study is carried out under Phase 3 (2015-2017) of the project “Improvement of
Groundwater Protection in Vietnam” (IGPVN) with the overall objective of strengthening the
groundwater resources management and protection in the Mekong Delta in order to prevent
groundwater degradation and depletion and salt water intrusion under the impact of climate
change. The current phase comprises policy consultancy at national and provincial levels
(policy and legal documents development), technical assistance to enhance understanding of
the current status of groundwater resources and improve the groundwater management in
the target provinces of the Mekong Delta, capacity building for partners and public awareness
raising on groundwater resources protection.
Population and social-economic growth have led to a strong increase in groundwater demand,
causing serious concern related to degradation and depletion of groundwater, increasing
saltwater intrusion, water pollution and land subsidence. In recent years, the coastal
provinces of the Mekong Delta are constantly facing problems with saltwater intruding far
inland during the dry season and tidal flooding during the rainy season. This was evidenced by

the severe drought during the dry season 2015/2016, which forced eight provinces/cities in
the Mekong Delta to announce the state of emergency on drought and salinization.
This report summarizes activities implemented in Sóc Trăng Province since 2010 that aim at
strengthening the capacity on groundwater monitoring, forecasting and management for the
Sóc Trăng DONRE. They include i) the construction of five new groundwater monitoring
stations that were handed over to the Sóc Trăng DONRE for management and operation, ii)
the collection of valuable hydrogeological data, iii) analysis and evaluation of data with respect
to the assessment of the current state of groundwater exploitation, use and management in
Sóc Trăng, iv) support to Sóc Trăng DONRE in establishing and disseminate and promote
practices of integrated water resources management (IWRM), and v) the development of
recommendations and measures for improved water resources management in Sóc Trăng.
The report includes detailed recommendations for the improvement of groundwater
management in Sóc Trăng Province, based on the existing legal framework. The
recommendations relate to aspects of water resources planning, groundwater exploitation
licensing, water resources allocation, protection of fresh water, management of saline water,
options for artificial recharge as well as groundwater monitoring. It furthermore provides
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recommendations towards the development of guidebooks, networking and information
sharing among stakeholders and awareness raising on water resources.
The evaluation of hydrological data showed that the aquifer system in Sóc Trăng is more
complex than presumed: Besides the differences in chemical water composition between the
individual aquifer layers of Holocene to Miocene age, the hydrochemical and isotope
compositions of groundwater samples in qp2-3 also differ significantly in lateral direction. It is
assumed that lateral variations in hydrochemistry are related to paleo-marine transgressions,

with areas experiencing only minor flushing by fresh water. The available data including
radiocarbon ages does provide no evidence of recent groundwater recharge of the deeper
aquifers in the Province. It is expected that recharge from surface water to aquifers in Sóc
Trăng only occurs outside the vicinity of Sóc Trăng Province. Most likely, the recharge
area/source is located beyond the borders of Vietnam (i.e. in Cambodia).
While determined groundwater quality in the main aquifer qp2-3 is overall good, and in
particular no critical contents of heavy metals or trace elements were observed, observed
changing redox reactions within the aquifer between dry/wet season make it probable that
some interaction with overlying aquifers exists, e.g. by way of hydraulic windows or leakages
at poorly designed boreholes.
The observed progressive regional decline of groundwater levels in all major aquifers proves
that current groundwater usage in the Province and beyond is unsustainable, i.e. that - despite
large volumes of stored groundwater - the amount of groundwater flux into the Delta cannot
keep up with current abstraction. Furthermore, groundwater levels in all major aquifers were
drawn 6 to over 10 m below mean sea level, a constellation which will inevitably lead to the
saltwater-freshwater interface moving further inland. It is also understood that overdrafting
of aquifers may further enhance land subsidence, especially due to the abundance of silt and
clay beds in the sedimentary succession of the Delta. The imminent threat of water scarcity,
saltwater intrusion and land subsidence requires the development of new water supply
strategies that incorporate a stepwise reduction of groundwater abstractions and the
provision of alternative water sources. It is recommended that the fresh deep aquifers are
conserved as a strategic water reserve for domestic use and for prolonged drought or extreme
water scarcity. A comprehensive monitoring network that records groundwater levels, water
quality and abstraction data needs to be established and maintained which can provide the
information required to clarify to which extent measures of reduced groundwater usage can
contribute to reverse the trend of declining groundwater levels. The observed drop in
groundwater levels is not restricted to Sóc Trăng Province but is observed all over the Mekong
Delta and across all aquifers. This makes quantitative predictions on the future decline of
groundwater levels in the Province difficult as the decline in water levels may also be due to
reduced recharge and flow from the headwaters rather than solely to increased groundwater

abstraction in the Province. Notwithstanding these uncertainties, it is regarded certain that
groundwater levels will continue to decline under current hydrological conditions.
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1

Project framework and objectives

The project “Improvement of Groundwater Protection in Vietnam” (IGPVN) is carried out
under the umbrella of the German Technical Cooperation with Vietnam, and is jointly
implemented by the National Center for Water Resources Planning and Investigation
(NAWAPI), which is part of the Vietnam Ministry of Natural Resources and the Environment
(MONRE), and the German Federal Institute for Geosciences and Natural Resources (BGR). The
first two phases of the project (2009-2014) focused on technical assistance and capacity
building for Vietnam partners, and were implemented in Nam Định, Hà Nam, Hanoi, Quảng
Ngãi and Sóc Trăng Provinces. One major output of the technical cooperation included the
design and construction of the groundwater monitoring networks in Nam Định, Quảng Ngãi
and Sóc Trăng Provinces and handing over to the respective Departments of Natural Resources
and Environment (DONRE).
Phase 3 of the project (2015-2017) was proposed with the overall objective of strengthening
the groundwater resources management and protection in the Mekong Delta in order to
prevent groundwater degradation and depletion and salt water intrusion under the impact of
climate change. The project is under the priority areas “Environmental policies and sustainable
use of natural resources" within the framework of bilateral development cooperation
between the two governments. In addition, the project is part of the programme "Integrated

coastal and mangrove forest management for climate change adaptation” by the Federal
Ministry of Economic Cooperation and Development (BMZ) to support the Green Growth
Strategy (2011 - 2020) of Vietnam.
The current phase consists of 4 components:
1. Policy consultancy at national and provincial levels (policy and legal documents
development)
2. Technical assistance to enhance understanding of the current status of groundwater
resources and improve the groundwater management in the target provinces
3. Capacity building for partners in the investigation, assessment, monitoring and
forecasting of groundwater resources
4. Public awareness raising on groundwater resources protection
There are about 4.5 million people in the Mekong Delta depending on groundwater sources.
Population and social-economic growth have led to a strong increase in groundwater demand,
causing serious concern related to degradation and depletion of groundwater, increasing
saltwater intrusion, water pollution and land subsidence.
In recent years, the coastal provinces of the Mekong Delta are constantly facing problems with
saltwater intruding far inland during the dry season and tidal flooding during the rainy season.
During the dry season 2015/2016, almost all of the Mekong Delta were suffering from a severe
historic drought and saltwater intrusion occurring once in a 100 years-time period. There were

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8 provinces/cities in the Mekong Delta announcing the state of emergency on drought and
salinization.

Being implemented in Sóc Trăng Province since 2010, the IGPVN project is reaching its aim of
strengthening the capacity on groundwater monitoring, forecasting and management for the
Sóc Trăng DONRE by conducting the following activities:
• Construction of 5 new groundwater monitoring stations and handing over to the Sóc Trăng
DONRE for management and operation;
• Collecting available documents in conjunction with field surveys and investigations to collect
additional data; evaluation of data in order to build a comprehensive and professional
hydrogeological database;
• Analysis and evaluation based on relevant documents and development of a consolidated
final report on the current state of groundwater exploitation, use and management in Sóc
Trăng, and proposal of recommendations and measures for water resources management in
Sóc Trăng;
• Supporting the Sóc Trăng DONRE in organizing integrated water resources management
(IWRM) Workshops to strengthen the networking and information sharing with other
provinces and stakeholders in the water resources sector; cooperating with the Sóc Trăng
administration to organize awareness raising and communication activities on water
resources protection.

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2
2.1

Investigation Area

Location

Sóc Trăng is one of the coastal provinces in the Ca Mau peninsula belonging to the Hậu estuary.
Sóc Trăng shares the border with Trà Vinh Province in the east (separated by the Hậu River),
the East Sea in the south (with the coastal line of about 72 km), Bạc Liêu Province in the west,
Hậu Giang Province and part of Vĩnh Long Province in the north (Figure 1). The total area of
the province is 3,332 km2. Sóc Trăng Province comprises Sóc Trăng City and 10 districts, namely
Cù Lao Dung, Kế Sách, Long Phú, Mỹ Tú, Mỹ Xuyên, Ngã Năm, Thạnh Trị, Châu Thành, Vĩnh
Châu and Trần Đề (with 10 wards, 12 townships and 87 communes).
The province extends from 09o14’ to 09o56’ Northern latitude and from 105o30’ to 106o20’
Eastern longitude.

Figure 1

2.2

Administrative map of Sóc Trăng Province (Source: )

Topography

Sóc Trăng is relatively low and flat, consisting of the flat land interspersed with low areas and
sand dunes. The entire province of Sóc Trăng is located to the west and south of the Hậu River
estuary, with the elevation varying from about 0.2 - 2 m relative to sea level.
In general, Sóc Trăng is situated in the lowland, including 3 types:
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Accumulative plain along the river: accounts for the major area of the province with
the prevalent elevation of about 0.5 – 1.5 m.
Accumulative plain along the sea: makes up a small territory of the province from Lịch
Hội Thượng to Vĩnh Châu with the average elevation from 0.5 – 2.0 m.
Ancient sand dunes: distributed in bow-shaped strips in parallel to the seashore with
elevations from 1.5 – 2.0 m.
Due to the low elevation, with the land being separated by a system of rivers and irrigation
canals and adjacent to the sea, the province is very vulnerable to saline intrusion (salinity),
especially in the dry season.
The bathymetry along the coastal line is clearly divided into 3 levels of depth:
At a depth from 0 – 10 m relative to sea level: in general, the topography is either
gently aslope or flat. The topography of the estuarine area is fairly complex and may change
over season. Due to the dynamic interactions between the river and the sea, there are many
sand dunes and sand bars interweaving with narrow passages.
At the depth of 10 – 20 m relative to sea level: Slopes are developed. The terrain of the
estuarine areas (in the northeast) is steeper than that of the southwest. It is the outer
boundary of modern sedimentary deposits and therefore, the terrain is usually changing over
time.
At the depth of 20 – 30 m relative to sea level: the topography is gently aslope and
abundant with sandy waves. Submarine sand dunes can be found in some areas.
2.3

Edaphology

Sóc Trăng Province has a total area of 331,176 hectares. The land is known to be of high
fertility, suitable for the development of wet rice, industrial crops such as sugar canes,
soybeans, corn, vegetables like onions, garlic, and fruit-trees such as grapefruit, mango and
durian.

The land of Sóc Trăng can be divided into six edaphologic groups (www.soctrang.gov.vn):
The group of sandy soils has an area of 8,491 ha; it includes the relatively elevated sand
dunes with heights from 1.2 to 2 mand consists mainly of fine sand to sandy loams;
The group of alluvial soil covers an area of 6,372 ha and is suitable for intensive rice
cultivation and special fruit-trees;
The group of lowland with 1,076 ha is suitable for 1-crop rice cultivation;
The group of of saline soil accounts for an area of 158,547 ha and can be divided into
several categories: high-level saline soil, medium-level saline soil, low-level saline soil and
saline wetland for Aegiceras shrubs and trees and mangroves forest (tidal flood), of which the
high-level saline soil covers a large area of 75,016 ha suitable for cultivation of rice, vegetables,
fruits, industrial crops, short-term and long-term plants;

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The group of alkaline soil covers an area of 75,823 ha and is divided into two types
including active and potential alkaline soil which can be used for multi-cultivation modes, i.e.
rice cultivation combined with aquaculture;
The group of reclaimed soil covers an area of 46,146 ha.
The relative proportions of the different edaphological groups are displayed in Figure 2.
Despite the limitations in the natural conditions such as the lack of fresh water and salt water
intrusion during the dry season and the fact that some areas are affected by acidity, the land
of Sóc Trăng brings many fundamental advantages for the diverse development in the sectors
of agriculture and fisheries. In particular, there are the strips of islets located in Kế Sách, Long
Phú and Cù Lao Dung districts stretching out to the sea, where a variety of tropical fruit-trees

are grown, and areas providing fresh air like Mỹ Phước islet, Song Phụng Resort and Cù Lao
Dung. This all forms ideal conditions for the development of eco-tourism.

Figure 2

2.4

Edaphological groups in Sóc Trăng Province

Climate

The climate of the Province is characterized by the equatorial tropical monsoon and divided
into two distinct seasons. The rainy season lasts from May to November and the dry season
from December to April.
According to the (Chân, 2010) the climatic characteristics of Sóc Trăng Province are as follows:
Temperature: The annual average temperature is 26.6⁰C, the highest temperature occurs in
April (28.2⁰C) and the lowest temperature in January (25.4⁰C).
Sunshine: The total annual average radiation is relatively high, reaching 140 – 150 kcal/cm2.
The total annual sunshine hours amount to 2,293 (about 6.3 hours/day); the peak is observed
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in March with an average of 282.3 hours and the lowest sunshine often occurs in September
with an average 141.5 hours.
Precipitation: the annual average precipitation varies between 1,600 – 2,230 mm; it is

characterized by a distinct seasonal pattern. The rainy season accounts for 90 % of the total
while very little rainfall occurs during the dry season; sometimes, there are months without
any precipitation.
Humidity: The average annual humidity is 84 % (highest 89 % in rainy season and lowest 75 %
in dry season).
Wind: located in the tropical monsoon area, prevailing wind directions in Sóc Trăng are: West,
Southwest, Northeast, and Southeast. The wind is divided into two distinct seasons, namely
the Northeast Monsoon and the Southwest Monsoon. The rainy season is primarily influenced
by the southwest monsoon, while the dry season is mainly influenced by the Northeast
monsoon. The average wind speed is about 1.8 m/s.
Other climatic factors: Sóc Trăng is located in the region which is less frequently hit by storms.
According to the meteorological data recorded in the past 100 years, only 2 hurricanes have
hit Sóc Trăng (in 1952 and 1997) causing significant damages. In recent years, whirlwinds have
frequently occured in Sóc Trăng. Even at weak intensity, they affected the people's livings and
production.
2.5

Population, socio-economic conditions

The population of the Province in 2009 amounted to 1,293,165 people, with an urban
population of 252,054 (accounting for 19.5 %). From 2006 to 2009, the Province’s total
population increased by 16,692 people, creating an annual average growth rate of 0.43 %. The
population in urban areas also increased but at a lower rate.
The average density is 3.9 people/ha, and hence, the Province is relatively under-populated
compared to the average rate of the country.
According to the social economic development plan of Sóc Trăng Province, the population was
expected to rise to about 1,433,000 people by 2015 and to exceed 1.5 million by 2020 (Data
Source: (Vietnam, 2017).
Obviously, the population growth will lead to increased demand for natural resources, for
instance, for clean water.

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3
3.1

Overview on water resources
Main water resources of Sóc Trăng Province

3.1.1 Surface water
Surface water of Sóc Trăng is relatively abundant with an intricate canal system (Figure 1),
including a number of rivers and channels:
The Hậu River flows along the eastern boundary of the Province, with a length of about 60 km.
The Hậu River flows to the sea through the two esturies of Trần Đề and Định An. It remains
the major source of fresh water for the Province, despite being intruded by saline water from
the East Sea.
The Mỹ Thạnh River has a fairly wide cross-section with an average width of about 200 m and
an average depth of 11.5 – 14 m.
The Quản Lộ – Phụng Hiệp Canal connects the Hậu River, which runs along the northern
boundary of the Province. The canal is a vital freshwater conveyor. The section passing
through the territory of Sóc Trăng Province has an average width of 60 – 90 m with a depth of
4 – 8 m.
Sóc Trăng's rivers and canals are located in the areas affected by uneven semi-diurnal tides.
The average tidal amplitude varies between 194 and 220 cm.

Water sources in the rivers and canals of Sóc Trăng Province are a mixture of in situ rainfall,
sea water and the discharge from the Hậu River.
The flow of the Hậu River is relatively powerful in the rainy season, which is also the flood
period of the Hậu River.
Being influenced by tidal flows, the river water is intruded by saline water in the dry season
and becomes fresher during the rainy season. The water in the rivers and canals close to the
sea is saline throughout the year, therefore, it can not be used for agricultural irrigation but in
return, it facilitates aquaculture.
3.1.2 Groundwater
Groundwater in Sóc Trăng Province is overall of relative good quality and includes plentiful
reserves. Groundwater in deep aquifers of about 100 to 180 m depth has high quality and is
suitable for domestic consumption. The quality of groundwater in the shallow aquifer of 5 –
30 m depth depends on rainfall and direct recharge amounts; aluminum concentrations are
often elevated and groundwater is overall salty in the dry season. As shown in Figure 3, there
are seven aquifers in the study region, which from top to bottom are as follows:
Holocene porous aquifer (qh) is formed of various sediments of Holocene age, including two
types:
- the marine sediments and marine-winds sediments (m, mvQ22-3 or mQ23) exposed to the
surface in forms of sand dunes. It is distributed at the elevation of 0.5 – 2.0 m in the coastal
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areas of Long Phú, Vĩnh Châu, Sóc Trăng and Mỹ Tú. The sand dunes are usually in prolonged
arch-form parallel to the seashore in northeast-southwest or northwest-southeast direction.
Their length ranges from 3 – 4 km, their width from 200 – 300 m and their thickness from 1 –

12 m. The components consist of fine to medium-sized sand mixed with yellowish gray silt.
- the fine sand and blackish gray silty sand located in the lower parts of the cross section of
oceanic sediments belonging to Hậu Giang Formation (mQ21-2hg). The upper parts are usually
covered by silty clay and clay layers belonging to the very poor water-bearing formation of
Holocene age and often lying above the very poor water-bearing Pleistocene formation Q13.
The thickness ranges from several meters to over 30 m.
Upper Pleistocene porous aquifer (qp3): includes coarser-grained sediments of the Late
Pleistocene Long Mỹ Formation (mQ13lm); the major components are fine sand, fine to
medium-size sand mixed with small amounts of greenish-grey and whitish-grey gravel and
shells. It is distributed in the entire area of Sóc Trăng with a thickness ranging from 3 – 51 m
(average 20.5 m). The depth of the aquifer’s top is from 24 to 95 m (average 50.4 m) and the
depth of the bottom is from 30 to 125 m (average 70.7 m). The recharge sources for the qp3
aquifer are mainly from the flows from surrounding areas and partly from leakage from
adjacent aquifers. In natural conditions, the water levels tend to fluctuate seasonally with an
average amplitude of about 1.2 m. In addition, the water level is daily-fluctuating in
accordance with the tidal regime of the East Sea.
Middle – upper Pleistocene porous aquifer (qp2-3): is formed by fine to medium sand and silt
in the lower part of the Middle-Late Pleistocene Long Toàn Formation (amQ12-3lt). The qp2-3 is
distributed in the entire area of Sóc Trăng. It is not exposed to the surface but covered by the
very poor water-bearing formation mQ12-3lt and unconformably lying upon the very poor
water-bearing Bình Minh Formation m,amQ11bm. The depth of the aquifer’s top is often seen
in the range 54 to 137 m (average 82.6 m) and the bottom is at the depth of 92.0 to 175 m
(average 131.5 m). The aquifer’s thickness fluctuates from 7 to 81 m (average 49.8 m). The
lithological components are sand of different grain sizes mixed with water-bearing gravel and
thin clayey silt lenses.
Lower Pleistocene porous aquifer (qp1): is formed of the lowest sequences of the Early
Pleistocene Bình Minh Formation (m,amQ11bm). The prominent lithological components
consist of fine to coarse sand mixed with little gravel. The cross sections often describe some
relatively thick aquiclude lenses. The aquifer is distributed in the entire area of Sóc Trăng. It is
not exposed to the surface. Its roof is often found at a depth from 110.5 to 192 m (average

145.3 m) and the bottom is at the depth from 146 to 250 m (average 187.4 m). The aquifer’s
thickness is from 6 to 79.5 m (average 40.3 m). It mainly consists of fine, medium and coarse
sand containing yellowish grey gravel that has good water-bearing capacity. It is also
intermingled with thin lenses of clay, silty clay and sandy silt.
Middle Pliocene porous aquifer (n22): is formed of sediments of the Năm Căn Formation
(a,amN22nc). The aquifer is covered with very poor water-bearing upper Pliocene (mN22nc)
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formation and lying above the very poor water-bearing lower Pliocene Cần Thơ Formation
(mN21ct). The aquifer is distributed throughout the region and not exposed on the surface.
The aquifer’s roof is at the depth from 156 to 273 m (average 201.4 m) and the bottom is at
the depth from 236 to 355 m (average 297.6 m). The prominent lithological components
consist of fine to coarse sand mixed with little gravel. The cross sections often describe some
relatively thick aquiclude lenses. The aquifer’s thickness is from 20 to 147 m (average 96.2 m).
Lower Pliocene porous aquifer (n21): is formed of lower sequences of the Cần Thơ Formation
(a,amN21ct). The lower Pliocene aquifer is distributed in the entire area of Sóc Trăng. It is
usually covered with very poor water-bearing mN21ct formation and lying directly above the
very poor water-bearing Late Miocene Phụng Hiệp Formation (mN13ph). The roof of the
aquifer is located at a depth from 262 to about 390 m (average 320.2 m) and its bottom is at
the depth from 298 to 451 m (average 388.4 m). The lithological components of the n21 aquifer
are mainly fine to medium sand mixed with silt in greenish-gray and reddish-brown in some
areas; sometimes intermingled with thin lenses of clay, silty sand containing carbonate. The
thickness of the aquifer is from 35 to 98 m (average 65.4 m).
Upper Miocene porous aquifer (n13): formed of the lowest sequences within the Phụng Hiệp

Formation (a,amN13ph). The aquifer’s roof is found at the depth from about 307 to 485 m
(average 403.7 m), its bottom is at the depth of over 500 m. The lithological components of
the n13 aquifer mainly consists of fine to coarse sand mixed with thin lenses of clay and/or silt.
The average thickness is about 96.3 m.

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Figure 3

3.2

Schematic representation of sedimentary aquifer succession in Sóc Trăng Province

Current status of groundwater exploitation and use

Currently, the local people in Sóc Trăng mainly use groundwater for domestic consumption
due to the fact that the surface water is contaminated and/or saline. Moreover, people exploit
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groundwater for industrial production, agriculture (e.g. onion irrigation in Vĩnh Châu District)
and aquaculture.
According to the report on “Planning for Groundwater exploitation, use and protection for Sóc
Trăng Province up to 2020” (Chân, 2010), the total water demand of the Province is about
225,000 m3/day in 2015 and 320,000 m3/day in 2020. Pressure on groundwater increases by
time especially because the quality of surface water is threatened by contamination and salt
water intrusion.
The groundwater abstraction rate in 2010 amounts to about 201,500 m³/d according to the
abstraction figures provided in the sections below. The groundwater usage by user groups is
shown in Figure 4.

Figure 4

Groundwater abstraction in m³/d and % as by user groups in Sóc Trăng Province; Total
current abstraction amount are estimated at about 201,500 m³/d.

3.2.1 Groundwater abstraction for water supply in urban areas
Currently there are 32 well groups with 56 production wells exploiting groundwater for
domestic and service water supply. The total production is about 32,890 m3/day, which mainly
occurs in Sóc Trăng City (Table 1).
Centralized water supply stations are available in most of the towns in all the districts of Sóc
Trăng Province. There are about 1 to 4 pumping wells operated at each station.
The centralized production wells exploit groundwater of the qp1 and n22 aquifers with a wide
depth range of 100 – 480 m. Other production wells of lower pumping rate exploit
groundwater of the qp2-3 and qp1 with the depth varying between tens of meters to over
100 m.
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Table 1

Groundwater production wells for domestic and service water supply in the urban areas of
Sóc Trăng Province (Source: Chân (2010))
Basic information

Name

Year of
constr
uction

Start of
operation

Depth
(m)

Screening depth
(m)
From

To

Operation

Target
aquifer

Pumping
rate
(m3/day)

Pumping
time
(hr/day)

TCN TT Châu Thành

1992

2004

136

70

71

qp1

320

n.a.

TCN Trà Quýt

1998

2002

128

120

132

qp1

144

18

TCN Trà Quýt A1

2008

2011

170

115

125

qp1

648

24

XNCN Kế Sách

1991

1998,
2006,
2009,

170

157

165

qp1

1,300

24

XNCN Long Phú

1996

2008

115

148

168

qp1

2,800

15

TCN TT Long Phú

2004

2004

150

100

112

qp1

70

24

XNCN Mỹ Tú

1997

1998

157

132

148

qp1

500

24

XNCN Mỹ Tú

2005

2005

170

141

154

qp1

250

n.a.

4,204

24

XNCN TT Mỹ Xuyên

2006

2006

463

437

460

n13

TCN ấp 2

2002

2002

100

90

98

qp2-3

168

24

TCN ấp 4

2003

2003

125

110

122

qp1

24

24

TCN ấp 7

2004

2004

130

n.a

n.a

qp1

0

0

XNCN Ngã Năm

2011

2011

100

90

98

qp2-3

900

24

TCN Hưng Lợi

2008

2008

120

103

115

qp1

1,440

24

XNCN Thạnh Trị

1991

1991

105

86

103

qp2-3

1,000

24

XNCN Phú Lợi

2005

2005

126

110

125

qp1

5,000

16

TCN khóm 6

2001

2001

112

100

110

qp1

30

24

TCN khóm 5

2003

2003

126

105

125

qp1

50

24

Công ty TNHH MTV
cấp nước Sóc Trăng

2003

2003

205

180

200

n22

10,000

24

n.a

n.a

155

138

152

qp1

24

10

1,600

17

NMN P7
TCN Cao Minh Chiếu

2005

2005

480

422

440

n13

TCN khu 6

2004

2004

120

110

118

qp1

24

24

TCN khu3

2003

2003

130

n.a

n.a

qp1

48

24

TCN phường 8

2006

2006

140

118

138

qp1

80

24

TCN khu 7

2006

2006

145

n.a

n.a

qp1

120

24

1,500

17

XNCN Sung Dinh

2007

2007

480

422

440

n13

XNCN Trần Đề

2008

2008

150

130

145

qp1

1,920

24

XNCN Vĩnh Châu

2005

2005

150

98

110

qp1

2,000

24

TCN Phường 2

2003

2003

128

106

126

qp1

250

24

TCN ấp Chợ

2008

2008

110

105

108

qp2-3

12

4.8

TCN Phước Hòa B

2008

2008

158

135

155

qp1

144

24

Total 1 (Combined pumping rate)

36,570

Total 2= Pumping Rate x Operation time in %

32,890

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*n.a: information not available

3.2.2 Groundwater abstraction for water supply in rural areas
There are 121 centralized production wells for water supply in rural areas in Sóc Trăng
Province, managed by the Center for Rural Water Supply and Sanitation in Sóc Trăng. The total
pumping rate is about 23,395 m3/day (Table 2). The pumping rate of each production well
varies between 10 - 1,900 m3/day (average of 193 m3/day). The well depth is from 100 –
560 m. There are 53 out of these 121 production wells possessing an exploitation license.
Table 2

Groundwater production wells for domestic water supply in rural area in Sóc Trăng
Province

No. District

No. of wells

Pumping rate (m3/day)

No. of licensed wells

1 Châu Thành

15

2,665

9

2 Kế sách

12

1,402

10

3 Long Phú

11

1,652

4

4 Mỹ Tú

16

1,777

8

5 Mỹ Xuyên

10

3,288

4

6 Ngã Năm

9

1,124

1

7 Thạnh Trị

9

1,836

4

8 Trần Đề

27

6,647

8

9 Vĩnh Châu

10

2,554

4

10 Cù Lao Dung

2

450

1

121

23,395

53

Total

3.2.3 Groundwater abstraction at household scale
There are totally 79,981 private wells exploiting groundwater from qh, qp2-3 and qp1 aquifers
in Sóc Trăng Province; of which 65,288 wells extract groundwater from qp2-3 and only 4 wells
extract groundwater from n22 and 76 wells from n13 (Table 3). Applying a conservative
estimate for the abstraction rate from each well of 1,500 liters per day, the total abstracted
volume from private wells amounts to almost 120,000 m³/d.

3.2.4 Groundwater abstraction for industry, agriculture and aquaculture
There are about 121 production wells for industry, agriculture and aquaculture water use of
25,249 m3/day (average of 208 m3/day), with the depth of 90 – 460 m, exploiting groundwater
from the qp2-3, qp1 and n22 aquifers (Table 4).

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