Journal of Environmental Protection, 2011, 2, 882-887
doi:10.4236/jep.2011.27100 Published Online September2011 (http://www.SciRP.org/journal/jep)
Soil Aquifer Treatment as a Tool for Sustainable
Groundwater Use in Hanoi/Vietnam
Axel René Fischer1, Catalin Stefan1, Kay Silabetzschky1, Peter Werner1, Bui Hoc2
1Institute of Waste Management and Contaminated Site Treatment, Technische Universität Dresden, Pirna, Germany; 2Vietnam As-
sociation of Hydrogeology, Hanoi, Vietnam.
Received June 3rd, 2011; revised July 29th, 2011; accepted August 31th, 2011.
ABSTRACT
Due to the subtropical climate the average annual precipitation in Vietnam is high. Nevertheless it is observed that
groundwater levels in the capital Hanoi have decreased dramatically. As a consequence more and more settlemen ts of
buildings have been registered since the beginning of the new millennium. Reason for this tremendous impact is the
increasing demand of areas and the extensive surface sealing in the course of the industrial development. This paper
describes the “state of th e art” and the develo pmen t of sustainab le so lution s to maintain and even in crease th e declined
groundwater levels in Hanoi.
Keywords: Groundwat er Wi t hdrawal, Groundwater Recharge, Land Subsidence, Settlements
1. Introduction
Water resources in Vietnam are difficult to manage due
to the high levels of precipitations. During the last
decade groundwater was used intensively for different
purposes due to the growing demands of a fast devel-
oping nation. After the reunion of North and South
Vietnam in 1975, the country expanded more and more
to a leader under the crop and vegetable exporting na-
tions. In the course of this development groundwater
extraction became an important factor e.g. for the irri-
gation of coffee plants. For example Dak Lak province
is estimated to produce 405,000 t coffee per year for
the world market [1].
Due to the development of the infrastructure in fast
growing cities settlements of buildings by groundwater
drawdown are a worldwide and also well known phe-
nomenon [2,3]. At first view this should be excludable
in Vietnam because heavy rainfalls occur at least in the
summer time. However, an important degree for the
“water stress” of a country is not the overall rainfall but
rather the ratio of withdrawal to renewable water re-
sources. Although only weak water stress is generally
present in the South Eastern Asian region (ca. 4.8%),
the ratio in Vietnam (about 17% - 18%) is comparable
to Europe [4]. Additionally, the majority of rain fall is
supplied mainly during the rainy season. Therefore,
groundwater levels are fluctuating over the year to a
high extent. The enormous grow of industry in the
capital of Vietnam has influenced its water balance.
Hanoi’s population is estimated to reach five million
inhabitants by 2015 [5]. Groundwater levels in Hanoi
have decreased during the last years resulting in mani-
fold detriments e.g. settlements of buildings [6] and
elevated arsenic levels by vertical drawdown of water
from other groundwater stories [7].
In the course of this development efforts are made to
find sustainable solutions for the megacity Hanoi [8].
Hanoi will quickly develop in the next years which
offers also a chance to find a strategy with sustainable
solutions for a well balanced water economy which
could be also applied to similar cases.
2. State of the Art
2.1 Water Demand and Following Problems
The capital Hanoi is located in northern part of Vietnam.
There are five rivers and more than 100 lakes and ponds
within the city. Red river (northwest and south) and
Duong river (northeast) are the main streams of Hanoi
which serve also as receiving waters (Figure 1).
Beside some small “septic tanks” which have been in-
stalled for the wastewater of private houses Hanoi has no
sewerage system i.e. nearly all industrial and private
wastewaters are directly infiltrated into a recipient e.g.
the Red River. Groundwater levels are changing from

Soil Aquifer Treatment as a Tool for Sustainable Groundwater Use in Hanoi/Vietnam883
Figure 1. Map of Northern Vietnam.
month to month to a high extent due to the heavy rain-
falls.
Most of the rainwater occurs in hot season but more
than the half of this amount is lost by immediate evapo-
ration.
The wastewater is transported through a joint drainage
and sewage system to the water bodies throughout the
city [9]. Figure 2 shows the groundwater levels for wells
in some districts of Hanoi in 1993, 2005 and the sup-
posed levels in 2020, respectively [10,11]. A decrease of
the groundwater levels of up to 17 m in 15 years can be
observed. The intensity of the loss is not uniformly and
depends on the intensity of the groundwater usage in the
related areas.
Overall groundwater usage in Hanoi has increased
during the last years. In an approximately 5 km wide
zone along the Red River, the Holocene and Pleistocene
aquifers are mainly recharged from the river, with the
more distant Pleistocene aquifer predominantly re-
charged by vertical percolation from the Holocene aqui-
fer [12]. Near the beginning of Duong River the subsur-
face is composed of unconsolidated sediments of Pleis-
tocene and Holocene age as described in Table 1. It is
known that some soil layers consist of high permeable
sand fractions which can even connect the different aq-
uifers [13]. The analysis of vertical soil profiles in the
above region reveals a high un-homogeneity of subsur-
face layers caused by the long term development of the
area and by the steady actions of the two rivers (sedi-
ments deposition, changes of flow paths etc). A high
amount of arsenic is mobilized every year from the Hol-
ocene sand and discharged into the Red River [14].
The rapid urbanization caused an impervious pave-
ment of areas. It is known that soil and especially coarse
clay swells to a high extent if it imbibes high amounts of
Figure 2. Groundwater levels in some districts of Hanoi in
1993 (top), 2005 (middle), and 2020 (bottom) (prognosis
based on data from 1993 and 2005).
water [15]. Therefore, withdrawal of water in conjunc-
tion with coverage of possible influents led to a tremen-
dous impact of the geohydrology of Hanoi which has
influenced the static conditions of the soil. Figure 3
shows the surface settlements for 10 different districts in
Hanoi from 2003 to the end of 2006 [16].
Based on monthly monitoring data on groundwater

Soil Aquifer Treatment as a Tool for Sustainable Groundwater Use in Hanoi/Vietnam 884
Table 1. Hydrogeological stratigraphy of Hanoi between Red River and Duong River (near fork of both rivers, [11]).
Layer from top Layers Depth (m)
1 Unconfined Holocene aquifer 2-12 (mean: 6.8)
2 Pleistocen-Holocene 1-23 (mean: 10.2)
3 Semi-confined upper Pleistocene aquifer 2-28.3 (mean: 14.9)
4 Pleistocen impermeable layer 0-19 (mean: 6.4)
5 Confined mid-lower Pleistocene aquifer 21.5-47 (mean: 32)
6 Complex water stored Neogene system
Figure 3. Surface settlements in 10 districts of Hanoi (HCA,
2007).
level and land subsidence, the qualitative assessment of
land subsidence in Hanoi area has shown that:
- The land subsidence has been occurring at all moni-
toring stations
- Average land subsidence rate was nearly constant
over the whole year
- The biggest yearly subsidence rate has been observed
in Thanh Cong (46 mm/year)
Due to these facts a further intensive use of ground-
water is only advisable under the precondition that sus-
tainable methods for groundwater recharge would be
established.
2.2. Geological Conditions and Water Balance in
Hanoi
Hanoi metropolitan area relies mainly on groundwater
for its water supply. Due to the local geogenic conditions
some groundwater stories contain arsenic. The concen-
trations can differ even in a small region [17]. The people
are protected from the hazardous influence of this toxic
compound by the usage of groundwater levels which do
not contain remarkable amounts.
The detailed analysis of vertical soil profiles has
shown a high un-homogeneity of subsurface layers
caused by the long term development of the area and by
the steady actions of the two main rivers (sediments
deposition, changes of flow paths etc).
The existing intermediary impermeable layers situated
in between groundwater aquifers have a sporadic and
inconsistent character and appear in forms of lenses and
very thin layers. A calculation of groundwater replen-
ishment shows that only 5% of the annual precipitation
reaches the aquifer (Figure 4). Main loss is the evapora-
tion fraction (932 mm/a: 58.4%). The rapid urbanization
of Hanoi coupled with impervious pavements of devel-
oping areas and combined with extensive groundwater
withdrawal as sole source for drinking water led to
drawdown and land subsidence. Additionally, weak-
nesses within the internal administration and the lacking
awareness of the future problems prevented to date the
implementation of adequate methods and technologies.
3. Tools for Groundwater Recharge
Artificial groundwater recharge is worldwide a common
measure to secure an increase of groundwater levels. It is
often combined with natural attenuation measurements
i.e. a soil passage of wastewater effluents [18-20]. The
elected techniques depend from the origin of the used
water and comply mainly with the climatic conditions i.e.
the average precipitation. Cheap treatment of wastewater
Figure 4. Water balance in Hanoi (Hoc, 2009).

Soil Aquifer Treatment as a Tool for Sustainable Groundwater Use in Hanoi/Vietnam885
by infiltration into the vadose zone with groundwater
reclamation as a positive secondary effect is usually
made in arid regions like Israel [21]. Fresh water (rain)
for groundwater enrichment is preferred in wet regions
like India [22]. Rainwater harvesting can be managed by
many methods e.g. by using cisterns or settling tanks.
These measurements can be combined with cleaning
systems e.g. constructed wetlands. An important question
is in each case the kind of infiltration of the treated or
untreated water. Table 2 shows advantages and disad-
vantages of several infiltration scenarios. A sustainable
technique has to ensure that fecal coliforms are not de-
tectable or below certain limits. However, very small
values (< 1) of fecal coliform concentrations are only
possible after a lateral movement of about 100 m through
the aquifer [24] (Table 3).
The optimum solution would be a technique which
handles water from different sources e.g. from rain and
wastewater. At present all solutions are only theoreti-
cally feasible and a transformation into real changes
seems to be unlikely. The reason for that is not only the
expenditure. Due to the heavy rainfalls in Vietnam the
resource “water” is unappreciated and the strategy against
growing water demands is still the exploitation of the
groundwater. A rethinking of the people is necessary
and it must be achieved upon a political way. Only in the
long term it is feasible that the taxation system could be
renewed and taxation revenue could support the con-
struction and maintenance of sewage and drainage infra-
structure [9].
4. Conclusions
The capital Hanoi has falling groundwater levels and
subsequent damages like land subsidence. The lack of
water is enforced by the fact that surface sealings prevent
the heavy rainfalls during summer time from reaching
the groundwater. The frequent floods during the rainy
season are also amplified by that. First efforts have been
made to find sustainable solutions which take into ac-
count the fast growing need of areas. It is essential that
quality of reclaimed wastewater has to fulfill certain
health standards. Experiences from other wastewater
reclamation systems show that quality of the reclaimed
water is not the problem at all. However, all these efforts
are made without enough revenue for a complete renova-
tion of the wastewater systems. A solution of the prob-
lem could be a certain tax which should be allocated to
sewage, drainage and wastewater treatment in Hanoi.
However, this is a question where the answer lies in the
social and governmental levels.
Table 2. Comparison of selected recharge scenarios.
Criteria Recharge ponds Shaft wells Infiltrations wells
Hydrogeological condi-
tions
−
possible only in shallow
impermeable layers
+ +
suitable in some districts
+ +
recharge of confined and
unconfined aquifers
Land use
−
large parcels needed
mostly in green areas
+
less area than recharge
ponds
+ +
less land use
also inhabited zones
Costs + +
using existing ponds
+
can be dug manually
−
high drilling costs
Infiltration water quality
+ +
clogging prevention by sand
layers
+
aquifer clogging to be
avoided
−
higher quality of infiltration
water
Table 3. Cleaning efficiency of soil aquifer treatment (adapted from [24, 25]).
Parameter Typical input
values [mg/l]
Typical output
values [mg/l]
biological oxygen
demand (BOD) 250 ≤ 30
total suspended
solids (TSS)
total organic
carbon (TOC)
11
> 10
< 1
< 5
total nitrogen (TN) 60 < 10
total phosphorous (TP) 8 < 1
fecal coliforms (FC) > 10,000
[n/100 ml]
< 1 - 22
[n/100 ml]

Soil Aquifer Treatment as a Tool for Sustainable Groundwater Use in Hanoi/Vietnam 886
5. Acknowledgements
This paper was conducted as a part of the excellence ini-
tiative “International Water Alliance Saxony (IWAS)”,
Ref. No. 02WM1028. Additional support came from the
Bundesministerium für Bildung und Forschung (BMBF,
Germany; project no. 02WA1148 “Evaluation and en-
hancing ground water effluent recharge technology”).
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