Summary of Doctoral thesis Geography of Environmental resources :Study the effects of natural, environment, and socio-economic condition to groundwater resources in Gio Linh, Quang Tri

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INTRODUCTION
1. Problem statement
Groundwater resources is affected by natural and socio-economic
factors such as: extending of agriculture area, deforestation, socioeconomic development, environmental pollution, natural disasters, and
climate change that prevent the percolation and infiltration process and
quality of groundwater [1]. Nowaday, these factors are rapidly changed
combined with the negative impacts of climate change have an direct
influence on groundwater resources and an indirect influence on
groundwater users [2]. Infact in coastal Center of Vietnam, freshwater
storage that can be extracted from shallow aquifer are declined, thus it
effect to living, agriculture production, industry, transportation, and
construction in urban areas and as well as coastal areas[4]. In both
science and practical terms, study on evaluation of declination and
adaptation of coastal aquifers to the needs of water supply under climate
change-sea level rise scenarios which will help decision makers in
planning of water resources allocation and looking for alternative water
resources (if needed)[5].
Gio Linh plain in Quang Tri province is in coastal Center areas with
a coastlines of 15.5km extends from Cua Viet town to Trung Giang ward.
It has two main aquifers are Pleistocene and Holocene aquifer that are
abstracted for living and production water usage. However, groudwater
resources are declined in recently years. The lacking of water supply and
increasing of saltwater intrusion in dry season of 2012-2013 due to the
changing of rainfall that affect to the storage of water at main water
reservoirs in the province. To identify the science basis for proposed
solutions for rational use and protection of groundwater resources is
important in progress of subtainable development in the region.
Consequently, the disertation of « Study the effects of natural,
environment, and socio-economic condition to groundwater resources in
Gio Linh, Quang Tri taking into account the impact of climate change

and sea level rise » was sellected to study and complete.
2. Objectives and scopes of the study
2.1 Objecttives of the study


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To construct scientific and practical basises in proposed solution for
rational use and protect groundwater resources based on analysis, evaluate
and estimate the impact of natural, environment, and socio-economic
factors, climate change and sea level rise in Gio Linh, Quang Tri.
2.2 Scopes of the study
- Overview and construct science basis on analysis, evaluate and
estimate the impact of natural, environment, and socio-economic factors,
climate change and sea level rise to groundwater resources in coastal plain.
- Study the groundwater resources characterization of Gio Linh, QT.
- Analyze the impact of natural, environment, and socio-economic
factors, climate change and sea level rise to groundwater resources.
- Modelling and prediction groundwater recharge with climate
change sea level rise scenarios using numerical hydrological model.
- Evaluate the recharge of rainwater and surface water to aquifers.
- Determine the hydraulic relation between Pleitocence and Holocence
aquifers and rainwater and surface water.
- Quality evaluation and modeling groundwater level and
groundwater quality change with climate change and sea level rise scenarios
- Propose the solutions in rational use and protect groundwater
resources of Gio Linh area under changing of natural, socio-economic,
and environment taking into account the present impact of climate
change and sea level rise.
3. Study subject and area
- Study subject: Groundwater in Pleistocene and Holocence

aquifers.
- Study area: Gio Linh coastal plain, Quang Tri province wih a
study area of 204 km2.
4. Scientific and practical contributions
4.1 Scientific contribution
The study result supplements the evidences on relationship
between aquifers, the components involved in formation of groundwater
reserve and intergrated impact of natural, socio-economic, environment


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to groundwater in Gio Linh coastal plain, Quang Tri province in context
of climate change and sea level rise
4.2 Practical contribution
The study results provides scientific basis for policy makers in
planning, management, exploitation and use water resources in Gio Linh
coastal plain, Quang Tri province.
5. Defended theses
Thesis 1: Groundwater resources in Quaternary aquifers is main
water supply for living, services, and industrial production in Gio Linh,
Quang Tri. The characteristics of geographical conditions and the
changing of natural, socio-economic, environment factors and potential
impacts of climate change and sea level rise have influence the
declination of this resources.
Thesis 2: Groundwater recharge plays an importation role in
formation of groundwater reserves in Quaternary aquifers in Gio Linh,
Quang Tri. In context of the aquifers are vulnerable due to impact of
external factors, the maintain and developing the recharge are main
solutions in oriented rational use and protect groundwater resources.
6. New findings

Using intergrated methods (Experiment, statistic, numerical
model,…) to evaluate natural water recharge to Quaternary aquifer in Gio
Linh coastal plain, Quang Tri province.
To prove the changing of salt-fresh water boundary of Holocence
aquifer are still going on due to climate change and sea level rise.
7. References and data of dissertation
- References were collected having related contents to the
dissertation
- Project researches and studies that I had involved in are related to
my dissertation.
- Documents and data were directly updated and calculated
8. Dissertation structure


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The dissertation is reported in 140 pages. Beside introduction,
conclusion, references, and appendices, the dissertation consists of 3 chapters:
Chapter 1. Scientific basis and methodology of the study on the
effect of natural and environment conditions and climate change-sea
level rise to groundwater resources.
Chapter 2. Groundwater resources characteristics and effect of
natural and environment conditions and climate change-sea level rise to
groundwater resources in Gio Linh, Quang Tri.
Chapter 3. Evaluate the effect of factors to groundwater and
propose rational solutions in use and protect groundwater resources in
Gio Linh, Quang Tri.
9. Acknowledgment .
The dissertation is completed at geographical department, Institute of
Science and Technology, Vietnam Academy of Science and Technology
in the effort of PhD candidate under the supervision of Associate

Professor Pham Quy Nhan (Hanoi University of Natural Resources and
Environment), and Associate Professor Dang Xuan Phong (Vietnam
Academy of Science and Technology ).
I would like to express my sincerely thanks to Geographical
department, Graduated training section, Nafosted fund of Vietnam, FWO
fund of Belgium, Water resources faculty- Hanoi university of HUNRE,
NAWAPI, and colleagues.
CHAPTER 1. SCIENTIFIC BASIS AND METHODOLOGY OF
THE STUDY ON THE EFFECT OF NATURAL AND
ENVIRONMENT CONDITIONS AND CLIMATE CHANGE-SEA
LEVEL RISE TO GROUNDWATER RESOURCES
1.1 Overview on related studies
1.2.1. In the world
There are numbers of research on groundwater resources flutuation
due to effect of natural and environment conditions and climate changesea level rise around the world and as well as in Vietnam [29]. The major
group studies and directions related to this topic as follows :
a. Group study on the effects of saltwater intrusion
b. Group study on the factors that effect to groundwater recharge


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c. Group study on the factors that effect to groundwater using
combination of climate model and groundwater model.
General comment:
- The studies on saltwater intrusion in aquifers due to impacts of
natural, socio-economic, environment conditions and climate change and
sea level rise show that the main reasons cause saltwater intrusion in
coastal aquifers are: geological structure, hydrogeology, over groundwater
extraction, changing of recharge, changing of discharge area. This study
direction was implemented in Netherlands, Australia, India,…

- The studies on groundwater recharge due to effect of
geographical, socio-economic, environment conditions and climate
change and sea level rise focus on research on soil classification,
vegetation cover, rainfall, temperature, water evapotranspiration,water
budget, GIS and DEM. Evaluate water recharge in aquifers based on the
result of model with climate change scenarios has been applied in
Belgium, Netherlands, England, and India.
- The studies on combination of groundwater model and climate
model have been studied in details by using “weather machine” models,
rainfall model, recharge combines with GIS, hydraulic model of HELP,
WetSpass, groundwater model of Modflow and GMS, weather model of
GCMs. The combination of models brings high efficiency on evaluate the
changing of groundwater through climate change and sea level rise scenarios.
General assessment: Three mentioned approaches on effects of
geographical, socio-economic, environment conditions and climate
change and sea level rise to groundwater are all the evaluation of factors
that effect to groundwater in order to find groundwater protection
solutions under negative impacts of climate change and sea level rise.
These approaches are distinguish on properties, impact source, and
impact level of each factors.
1.2.2 In Vietnam
- In general, there are few studies on evaluation of climate
change impact to groundwater in Vietnam, most of the studies focus on
environment, socio-economic, and surface water resources.


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- The studies on groundwater are just focus on determination of
fresh-saltwater boundary, saltwater intrusion, calcutate duration and rate
of fresh-saltwater boundary based on hydrogeological condition of the

study area, required groundwater extraction rate, as well as corelation
between sea water and groundwater in coastal area.
- Most of studies have not mentioned on the effect of natural
recharge to groundwater due to impact of climate change and sea level
rise. Especially, the use of combination tools in assesment of water
recharge, hydraulic relationship between rainwater, surface water and
groundwater under impacts of geographical, environment, and socioeconomic condition, and climate change-sea level rise is limited.
1.2 Theoretical basis
a. Scientific problems in evaluation of the effects of geographical,
socio-economic, environment conditions and climate change and sea
level need to solve need to be solved.
Study on the changing of groundwater recharge due to effects of
natural, environment conditions, socio-economic development,
urbanization and climate change.
Study on saltwater intrusion in groundwater, Nghiên cứu xâm nhập
mặn NDĐ, the trend of changing in groundwater quality in present
compares with these in the past in order to evaluate and predict the
changing of fresh-saltwater boundary in future under impact of climate
change-sea level rise;
Study the relationship between groundwater in aquifer with
rainwater, in which focus on evaluation of hydraulic correlation between
groundwater level and rainwater with time, determine the trend of
grounwater level changing with rainwater;
Study on the relationship between surface water and groundwater
based on constrution of the relationship between groundwater and
surface water to check the role of surface water in formation of
groundwater;
b. Combination tools and technical use in solving problems of
evaluate the effect of natural, socio-economic, environment conditions
and climate change - sea level rise to groundwater.

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- Downscaling of climate change scenarios for a small area.
- Modelling and evaluation of the recharge of groundwater using
hydraulic numerical model of Wetspass.
- Using numerical groundwater resources model to calculate and
predict groundwater level, movement of saltwater boundary with time
and climate change- sea level rise senarios.
- Water pouring tests
- Seepage tests.
- Using Cl balance method
- Construct 3D numerical model
1.3. Point of views, methods, and workflows of the study
a. Point of views
- Systematic point of view
- Synthetic point of view
- Subtainable development point of view
b. Methods of the study
- Dowscalling of climate change scenarios for a small area
- Modelling and evaluations of water recharge using hydraulic
numerical model
- Field survey
- Laboratory and field testing
- Numerical model and 3D block model.
- Groundwater numerical model
- Mapping and GIS
c. Workflows of the study.
Step1: Data collection, field survey and field tests. Analyze, evaluate
natural, socio-economic, environment conditions and climate change-sea

level rise scenarios in Gio Linh.
Step 2: Construction of research methodology and research contents
Step 3: Proposed solutions


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Figure 1.1. Workflows chart of the study
CHAPTER 2. GROUNDWATER RESOURCES
CHARACTERISTICS AND EFFECT OF GEOGRAPHICAL,
SOCIO-ECONOMIC, AND ENVIRONMENT CONDITIONS AND
CLIMATE CHANGE-SEA LEVEL RISE TO GROUNDWATER
RESOURCES IN GIO LINH, QUANG TRI.
2.1 Groundwater resources characteristics
The aquifer system of the study area consists of unconsolidated
aquifer of wind-marine sediment (wm Q32); unconsolidated LowerMiddle Holocence aquifer of alluvium-marine sediment (am Q21-2);
Bazan fracture-unconsolidated Lower Holocence aquifer (Q12);


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unconsolidated Middle- Upper Pleistocene aquifer of alluvium-marine
sediment. Unconsolidated Lower- Middle Pleistocene aquifer of
alluvium-diluvium sediments (ad Q11-2). Fracture aquifers of Neogene,
Devon, and Ocdovie – Silua.
The calculation result of potential reserve of qh aquifer is 26.000
m3/d; qp aquifer is 16.249 m3/d.
2.2 Effect of natural factors
a. Geology
Upper Ordovican, Lower Jurassic, Long Dai formation (O3 - S1 lđ)
Lower-Middle Devonian, Tan Lam formation (D1-2tl)

Middle-Upper Devonion, Co Bai formation Co bai (D2-3cb)
Neogene, Gio Viet formation (N gv)
Quaternary formation consists of: Basalt eruption formations
(Q); Unconsolidated sediments of Quaternary formations (a, m, am,
mlQ); undivided Quaternary sediments.
b. Topographic, geomorphological features: The study area are the
plain area of communes of Gio Linh, Cam Lo, and Dong Ha districts.
Topographic boundary: Ben Hai river in the North, Thach Han river in
the South, mountainous areas with basement rocks in the West, and the
sea in the East.
c. Weather: Gio Linh plain has annual rainfall is from 1900 to
3400mm, an average annual rainfall of 2,359.5 mm. The heavy rainfall is
a rich water recharge source for groundwater.
d. Hydrology: Gio Linh has two main river system are Ben Hai
river system and Thach Han river system. The Ben Hai river system:
flow in WSW-ENE direction, and reach the sea at Cua Tung. There are
three lakes in the study area that are Truc Kinh, Kinh Mon, and Ha
Thuong. They are artificial lakes formed on basalt. These lakes are
located in the Western part of the high elevation area of the plain, it plays
an important role in recharge to groundwater in the study area.
e. Vegestation cover: Vegestation cover in Gio Linh is quite
diverse, it can be divided into four main types: Mangrove vegetation;


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Freshwater aquatic vegetation; Vegetation in the sand; Vegetation
drained in mountainous areas.
f. Soil characterization: Along with the diversity of basement
rocks, topographic and weather, the soil in Gio Linh is also quite diverse
and complex which consists of groups as follows: sandy soil group; Soil

group; Salty soil; Alluvial soil; The gray soil on ancient alluvium; Valley
land due to condensation products; The eroded soil in stone.
2.3 Group of environment factors
a. Water level
Unconsolidated Holocene aquifer of wind-marine sediments was
studied and monitored its movement. Groundwater level is changed with
season. The depth of static groundwater level is 0.5 - 2m. Rainwater is
source of water supplying for the aquifer. The average annual monitoring
result of groundwater level in qh aquifer is from -0.17 to -0.49m.
Unconsolidated middle-upper Pleistocene of alluvial-marine
sediment (amQ1). Groundwater movement of qp aquifer in the study area
is meteorological movement. Seasonal fluctuations are very obvios. The
average delay is 3-4days indicating that groundwater source of this
aquifer is relatively close to the monitoring area of VBqp borehole.
b. Saltwater intrusion status
River saltwater intrusion
During studying, the author is performed field survey to measure,
collect samples, and quick analyze the water quality of Thach Han and
Ben Hai rivers based on the changing of TDS in August 2015. The result
shows that in the study area the saltwater intrusion occurs in dry season
with a great value. In some places, the saltwater intrusion can reach a
distance of 15-20km from the river mouth.
Saltwater intrusion in Holocene aquifer
Based on electrical imaging measurement data in East side that
validated by borehole log data at QT10, geophysical cross-section by
electrical method, and the monitoring date at VBqh from 2012 to 2015,
one has sufficient information to confirm the fresh-saltwater boundary
and saltwater area in the study area.

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2.4 Group of socio-economic factors: Population, economic
activities, Status of land use, Status of groundwater extraction and
groundwater usage
Comment:
In the study area, the groundwater resources in Quaternary
sedimentary is characterized by two main aquifers are Holocene and
Pleistocen and one aquitard. Holocene aquifer has a an average thickness of
15.45m, average flow rate of 0.1l/s, average permeability, K of 2.49 m/d.
Holocene aquifer is exposed to Southeast area of the plain and is considered
as medium, poor water reserve that only enough for the needs of domestic
consumption in form of dig well, well that drilled by hand. Pleistocene
aquifer has an average thickness of 42.85m, average flow rate of 2.29l/s,
average permeability, K of 19.94 m/d. Pleistocene aquifer is distributed over
the plain, exposed to west and evaluated as rich water reserve that meet the
needs of industrial consumption. The aquitard is formed of clay, sandy clay
sediment, in the Northeast of the study area this layer is formed of Basalt
with age of early Holocene. The potential extraction reserve of Quaternary
aquifers is determined as 42,248 m3/d. The groundwater resources
characteristic in the study area indicated that natural, socio-economic, and
environment factors and conditions interact with each other that obviously
affect to groundwater resources and is vulnerabe.
Group of geographical, environment factors shows that the study
area has a relative flat terrain, small terrain slope gradient with the slope
gradient reduces from west to east, groundwater levels of qh and qp
aquifers are good to fair relationship with the terrain surface (R2 from
0.86 to 0.65). Thus, terrain surface has the similar shape with
groundwater level surface and the direction of surface flow. There are
three big water reservoir in the western side of the study area that are
Truc Kinh, Kinh Mon, Ha Thuong with total store volume over 96

million m3. Average rainfall of the study area recorded at meteorological
stations at Cua Viet, Dong Ha is more than 2000 mm/year. Vegestation
cover was quite developed in the West with total covered area is around
44.5%. For geological characteristics, the qp sediment is mostly exposed
at the West of the plain in which the qh aquifer has major and direct
recharge water of rainwater, and the Pleistocene aquifer is recharged by


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rainwater and surface water from lakes. These are important input factors
of recharge model and numerical groundwater model of the study.
For environment factor, groundwater level monitoring is
conducted at qh and qp aquifers. The monitoring result shows that, water
levels in qh and qp aquifers are very much affected by meteorological
element, and fresh-saltwater boundary in qh aquifer at monitoring
location is not change very much, distributed in patchy form.
The group of socio-economic indicates that groundwater in Gio
Linh is extracted to use for various purposes such as agriculture, industry,
living… In Gio Linh, the water used for agriculture water agriculture
(irrigation) is 77%, living is 12%, and industry is 11%. It is forecasted that
by 2025 Gio Linh will use about 74% of agricultural water, 13% of its
industrial use and 13% of its daily life. In particular, water used for
agriculture is 100% surface water; water used for industry is 11% surface
water and 89% groundwater, water used for living is 100% of ground
water. Total current groundwater exploitation in the area is 21,138 m3/day
in which the rural daily-life consumption is 5,587 m3/day; groundwater
extraction by the large users such as offices, big department is 551 m3/day;
Gio Linh Water Plant is 15,000 m3/day. Thus, if the detailed breakdown
for each aquifer then qp aquifer is fully exploited in the dynamic reserves
and a small amount of static reserves leading to the lowering of water level

that recorded at Gio Linh water plant.
The exploitation projects are lack of planning, the exploitation of
groundwater without permission and incorrect technique are polular
occurrence, thus in some areas where the water level has decreased, local
despression, reduces water quality and affects the use of water, or
contamination. Consequently, socio-economic factors are strongly
affected to groundwater resources.
CHAPTER 3. EVALUATE THE EFFECT OF FACTORS TO
GROUNDWATER AND PROPOSE RATIONAL SOLUTIONS IN
USE AND PROTECT GROUNDWATER RESOURCES IN GIO
LINH, QUANG TRI
To evaluate the effects of geographical conditions, environment,
socio-economic, and climate change-sea level rise to groundwater
resources. The study is conducted in following steps:


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Dowscalling climate change scenarios for Gio Linh plain
Evaluate geographical, environment, socio-economi conditions to
construct input data for models
Evaluate groundwater characteristic (aquifer system, distribution,
water storage, and hydrogeological parameters…) to construct 3D model
and flow model, movement of saltwater boundary in aquifers.
Determine groundwater extraction rate to evaluate the effect of this
activities to groundwater resources;
Determine recharge rate using modeling methods
Construct model to simulate water level, groundwater quality in
present and in future (with climate change scenarios)
3.1 Simulate and evaluate the effect of climate change and sea
level rise

a. Create rainfall series for Gio Linh by downscaling method.
In the previous studies, evaluate the effect of climate change to
water resources, three are some information need to be care about that
are maximum rainfall, the average rainfall time and maximum rainfall
time under the scenarios. This result has led to the methodology and
workflows that helps in extracting this information from the
computational results of global GCM models.
Through application to the Gio Linh plain, one can see that
analyzing the interpretation of this information can help to assess the
impacts of climate change on water resources in general and groundwater
in particular.
b. Simulation of recharge determination by Wetspass under
climate change scenarios.
By Wetpass, the study calculated the daily recharge to the
groundwater system of the study area for the periods 1981 - 2010, 2011 2030, 2046 - 2065 and 2080-2099 according to climate change scenarios
From recharge calculation results, there are some comments as follows:
The recharge to aquifers is reduced 14.5% at the beginning of the
century (2011 – 2030) and tended to recover at the middle and late or 21st
century. At the beginning of the 21st century, the impact of climate


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change will be the lowest if climate change occurs under the RCP6.0
scenario. In contrast, in the middle and late centuries, the effect of
reducing natural recharge will be minimal if climate change occurs under
RCP4.5 and RCP8.5.
For qp aquifer, the current extraction rate is 15,551 m3/d, in which
the dry season has extraction rate of 8,553 m3/d, the rainy season has
extraction rate of 6,998 m3/d. Recharge rate of qp aquifer in dry seasion
is 4,407 m3/d, that rate in rainy season is 7,517 m3/d. These are the

surface recharge calculation results that not yet take into account of
recharge from qh aquifer and Neogene aquifers to qp aquifer. Extraction
rate in dry season is high as 1.94 times of recharge, that rate in rainy
season is equal to 0.93 times of recharge. Consequently, annual
extraction rate is high as 1.3 times of recharge showing that there is a
decline of groundwater level in Pleistocene aquifer, which is shown by
static water level monitoring data at G11 has reduced from +2,06 m in
16/9/2000 to -0.83 m in 2/12/2012 , and -7.06 m in 6/8/2017.
For qh aquifer, the recharge in both rainy and dry season are much
higher than extraction rate. Specifically: extraction rate in dry season is
3,072 m3/d equal to 0.20 times of recharge rate (14.729 m3/d); extraction
rate in rainy season is 2,514 m3/d equal to 0.11 times of recharge rate
(21,547 m3/d).
If the extraction rate increased by 1%/year (corresponding to the
increasing of population rate by 0,98%/year and rate of economic
development of 8.05%/year). Then, in middle of 21st century, total
groundwater extraction in Holocene aquifer is about 2,651,000 m3/year
(around 0.15x recharge rate to this aquifer) and that extraction rate in
Pleistocene is about 7,379,000 m3/year (more than 1.3 recharge rate).
Consequently, if there aren’t suitable plans of exploitation, protection,
and additional recharge source, groundwater resources in qp aquifer will
be declined. In this case, the impact of climate change to groundwater
resources under any scenarios is negligible compared to the demand for
water exploitation. (as shown in Fig 3.1).


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3.2 Evaluate recharge rate
a. Determine surface and ventilation zone permeability by pouring
water in drug test

The result of pouring water in drug test over the study area allows
dividing recharge area for Holocene aquifer, this also use to validate
Wetspass model. Average recharge for wind-marine sediment area is
around 204.76mm/year, that for clay and sandy clay deposits is
7.48mm/year, and that for basalt weathering soils is 12.59mm/year.
b. Determine the hydraulic correlation between surface and
groundwater by seepage test.
The results of 28 seepage tests at locations along Ben Hai, Thach
Han, Hieu, Canh Hom, Truc Kinh lake that conducted in August 2013
show that at most of locations the surface water supply to groundwater.
Especially, at 03 locations in Thach Han at section from Lam Xuan to
Cua Viet found that the groundwater supplies to surface water with an
average flow rate of 7,557 m3/day.
At the center of Gio Linh plain, the area that Canh Hom river
flows through plain, surfacewater always supply to groundwater with an
amount of 37.25 ml/m2.day to 85.24 ml/m2.day. Ben Hai river, daily
recharge of surfacewater to groundwater is 23,02 ml/m2day. Truc Kinh
lake, surface water supplies to groundwater with an average amount of
22.10 ml/m2.day.
Based on above analysis, one can see that the resistance of river
bed sediment in Gio Linh plain area is relatively high, average vertical
permeabiltiy at river bed, lake is from 0.0058 to 0.049 m/day. Movement
direction of groundwater is North, Northwest to South, Southeast.
c. Determine the relationship between rainwater and groundwater
by Clo balance method
The average recharge value of the rainy season was 131.33 mm,
equivalent to 7.1% of the total rainfall in the rainy season, accounting for
75% of the total yearly recharge, while the dry season supplementation
was 44.57 mm, corresponding to 9% of total dry season rainfall,
accounting for 25% of the total yearly recharge to Holocene in the study

area. With an area of Holocene aquifer is 195.5 km2, the estimated


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conversion recharge rate is 31,324 m3/day. Calculated recharge result
using the WetSpass model for the Gio Linh plain is 36,275 m3/day. Thus,
it can be confirmed that the water level in Holocene is not reduced, but it
depends on rainfall in seasons.
d. Determine recharge line and flow direction of groundwater
using 3D model (as shown in Fig 3.2)
Based on the 3D fence diagram in figure 3.2, one can interpolate
the distribution and recharge line to aquifer as follows:
- The Holocene aquifer exposes on the central and eastern sides
along the coast, varying in thickness from 0 ÷ 37 m and growing to the
seabed and to the southeast along the coast. In the study area, this aquifer
was cut by Ben Hai and Thach Han rivers, thus assuming a hydraulic
relationship with these two rivers. The main source of recharge to the qh
aquifer is the rainwater, the surface water is infiltrated to the aquifer.
Groundwater level in all dug wells and shallow wells are 3 ÷ 5 m higher
than river and sea water levels, so the water in this aquifer moves and
goes out to the sea and to the two sides of Ben Hai and Thach Han rivers.
- In the study area, the Pleistocene aquifer is only visible in the
west, southwest of Gio Linh, and the rest is covered by aquitard. This
aquifer lies at an average depth of -35.5 m, with a thickness of 19.5 ÷ 59
m and tends to thicken towards the sea and to the south. In covered areas,
the static water level in this aquifer fluctuates between +1 ÷ -4.56 m and
is usually lower than the ground level. Therefore, the main source of
recharge for this aquifer is rainwater, surface water absorbed from the
ground surface
The above results allow us to conclude that the recharge

distribution and recharge line to the Holocene and Pleistocene aquifers
are similar, the Pleistocene is mainly due to the direct recharge of
rainwater through the western, the Holocene aquifer is due to rainwater
and surface water in some of the major rivers and lakes in the area
(through experimental results). The monitoring results show that the
synchronous fluctuations of the two aquifers are dependent on the
meteorological factors, as shown in Figure 3.3


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3.3 Construct numerical model to predict groundwater
fluctuation, saltwater intrusion with climate change-sea level rise
scenarios
a. Construct model input data
b. The results of flow model and saltline transportation model of
groundwater
c. The forecast water level results and movement of saltline of
groundwater with climate change scenarios.
The current model is designed to simulate the alteration of water
resources in the past. This model was adjusted through two steps. The
steady state adjustment to adjust the boundary conditions and
hydrogeological parameters of the aquifers in the model. This unstable
adjustment step is run as follows: divide 12 computational time steps.
Each time step is equivalent to 1 month. Steady-state running time is
from 1/1/2013 to 31/12/2013.
The flow model for data taken in 2013 as shown in Fig 3.4, 3.5, 3.6
d. Water level forecast result and saltline movement of groundwater
with climate change scenarios
- Distribution of fresh-saltwater, fluctuations of groundwater
level in the Holocene aquifer are complex with each scenarios and the

specific area as follows:
- The calculated forecast result of water level fluctuation shows
that with all climate change-sea level rise scenarios, recharge in the study
area increase with scenarios and average increasing of extraction is 1%
per year, if the vegetation cover condition and land use are not change
the water level of qh and qp aquifer are still tended to decline. From now
to 2100, water level of qh aquifer reduces with the value varies from
0.72m to 0.86m, qp aquifer has higher water level reduction of from
1.94m to 2.24m.
- With survey data and collected data, confirm that climate
change and sea level rise are directly effect to groundwater of Holocene
aquifer;


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- In which, saltwater area of the aquifer is 19.994 km2, this is the
data that sellected based on the investigation and survey data in stages.
According to the published climate change scenarios by Ministry of
Natural Resources and Environment in 2012, the sea level rise up 0.74cm
in 2100 with corresponding submerge area of 3,85 km2, however due to
climate change the rainfall is also increased. According to the recharge
calculation with respectively scenarios the Holocene aquifer is recharged
an amount freshwater of 36.276 m3/day. This will speed up the salinity
washing process in the salty areas of the study area, reducing the salinity
area. Therefore, in general, in 2100, under the impact of climate change
and sea level rise with the scenarios: RCP4.5, the salinity area will be
reduced to 13.56% of the current area; RCP6.0, the salinity area will
decrease by 3% of the current area; RCP8.5, the salinity area will
increase by 7%.
- The forecast results show that the groundwater level changes in

the Holocene aquifer are very obvious: the salinity area varies in
complexity over time, the saltwater intrusion area in the continent tends
to decrease, however the coastal area and the area affected by the Ben
Hai and Thach Han rivers, the salinity area increased due to the impact of
flooding. In the last decades of the 21st century, the fresh-saltwater
boundary was much more affected, changing more rapidly as the aquifer
is affected by the sea level rise, and within the continent the rapid
salinization process took place; According to the high emission scenario
(RCP8.5), by 2100 the salinity area of the whole study area is 17,582
km2.
3.4 Propose the solutions in rational use ad protection of
groundwater resources.
a. Scientific and practical basis for the proposal.
b. Spatial orientation of rational use, protection of groundwater
resources.
- Orientation for protection of
Construction of groundwater protection maps

groundwater

resources.


19
- Orientation for rational use of natural resources: construct
sustainable exploitation of groundwater maps based on group of 4
criteria.
c. Orientation for rational use of natural resources, protection of
groundwater resources.
- Establish a reasonable water regulation regime for the salinity

prevention system
- Construction of underground dams.
- Renovation of water reservoirs and sea dykes.
- Planting coastal forests.
- Non-structural methods
- Educational and communication measures.
- Controlling the groundwater exploitation and limits saltwater intrusion.
- Plant restructuring to adapt to saline soil.
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
The results of the study lead us to the following conclusions:
1- The dissertation collected and synthesized professional data to
complete the simulation of groundwater system in an area of 204.1 km2.
Statistical data were compiled, calculated and edited to obtain detailed
information on groundwater resources in the whole study area. The
dissertation was the first to use a combination of field experiments, 3D
models, numerical hydrological models, numerical groundwater models,
downscalling of climate change scenarios and sea level rise in one area to
determine the amount of recharge, recharge line and saltwater intrusion.
2- On hydraulic relationship between surfacewater and
groundwater as follows: At most locations along the Ben Hai, Thach
Han, Hieu, Canh Hom river and Truc Kinh lake surface water supply for
groundwater with value of from 22.10 ml/m2.day to 85.24 ml/m2.day.
Especially, at 03 locations on the Thach Han River from Lam Xuan to
Cua Viet the groundwater supplies to river water with an average flow
rate of 7,557 m3/day. That indicated the sediment resistance of the river
bed in the Gio Linh plain is relatively large, the mean vertical


20

permeability at the river bed and the lake is from 0.0058 to 0.049 m/day.
The movement of groundwater is from the north, northwest to south and
southeast. The results also show that the relationship between qh and qp
aquifers is quite coherent, as shown by the results of two groundwater
levels monitoring in the study area.
3- The correlation between natural factors is recharge and socioeconomic factors are the exploitation of qp and qh aquifer, indicating that
the amount of exploitation aquifer is now 1.94 times more in dry season
and equal to 0.93 times in rainy season; that of qh aquifer is 0.20 times
dry season and 0.11 times in rainy season. Under the scenario of socioeconomic development, the exploitation volume increases about 1%/year
(corresponding to the population growth rate of 0.978%/year and the
economic development rate is about 8.05% / year). By the middle of the
21st century, the total volume of water extraction in the qh aquifer is
2,651,000 m3/year (equal to 0.15 times recharge to this aquifer) and in
the qp aquifer is about 7,379,000 m3/year (more than 1, 3 times the
amount of recharge). This represents the rate of decline in water level in
qp aquifer is 0.53cm/year. Consequently, with any climate change
scenario, there is no meaning when the rate of exploitation increases
without adjustment of additional resources for qp aquifer, in the coming
time, the water level continues to decline without any sign of stopping.
4- The fluctuations in water levels in the Holocene and Pleistocene
aquifer are forecasted for climate change scenarios up to 2100. In which,
the fluctuations in water level in Holocene aquifer are likely to increase
in the RCP8.5 scenario is from 3.28 to 5.52m, for RCP4.5 scenario is
from 3.55 to 5.49, for scenario RCP6.0 is from 3.55 to 5.52m; The
fluctuation in water level in the Holocene aquifer tended to increase
according to RCP8.5 scenarios from 1.35 to 2.22 m, scenario RCP4.5
ranged from 1.47 to 2.21 m, scenario RCP6.0 ranged from 1.47 to 2 m.
Forecast of salinity intrusion area of Holocene aquifer in 2100 under the
scenarios RCP4.5 is 13.42 km2, RCP6.0 is 15.57 km2, RCP8.5 is 17.58
km2 but then the sea level rise of 0.75cm will submerge the total area of

3.85 km2. Therefore, by 2100 salinity area compared to that in present ist
19,994 km2 under the scenarios: RCP4.5 down 13.56%; RCP6.0
decreased 2.86%; RCP6.5 increased by 7.2%. Thus, it can be seen that


21
climate change increases the amount of recharge to saline inland so the
sea level rise increases the salinity in the lowlands and estuaries.
5- To propose solutions to rational use and protection of
groundwater resources through the establishment of a groundwater
protection map and a map of sustainable exploitation of groundwater
resources in Gio Linh area. Indicate the areas to be strictly protected V, I,
IV-1 mainly on the qp aquifer at the the west side, basalt, sand dunes; the
area can be exploited sustainably respectively A1-1, A1-2 with an area of
141 km2;
6- In addition, according to the functions and tasks of the water
resources management, the applicability of the results of the dissertation
is appropriate.
- The dissertation results suggest that the management of
groundwater resources in Gio Linh area in the impact of climate change to
groundwater resources under any scenario is negligible with the demand
for groundwater exploitation. It is therefore necessary to strengthen the
management of groundwater resources in terms of quantity, quality and
sustainable exploitation.
- Providing management agencies for digital modeling tools on
water level and groundwater quality is forecasted to saltwater intrusion
under the climate change scenarios and sea level rise from which the need
information in licensing activities can be pursued, well allocation of water
plant construction.
RECOMMENDATIONS

1. Continuing to monitor the saltwater intrusion evolution of the
Holocene aquifer, determine the changing in the area and depth for
comprehensive studies to meet the requirements in the complicated
situation of climate change – sea level rise.
2. Develop a monitoring system for water level, water quality in
the Holocene and Pleistocene aquifers.
3. Establishment of prohibited areas, exploitation restriction and
protection galleries for groundwater resources in the study area.


22
4. Strengthen the management and planning of the exploitation and
rational use of water sources to ensure the security and safety of water
sources in the study area and Dong Ha city.

Figure 3.1. Correlation chart between recharge rate and extraction rate
of aquifers

Figure 3.2 3D hydrogeological fence diagram of the study area


23

Figure 3.3. Groundwater level in Pleistocen (qp) and Holocen
(qh)aquifers

Figure 3.4 Water level of qh aquifer in 2016


24

Figure 3.5 Water level of qp aquifer in 2016
- The saltwater intrusion model result of qh aquifer in 2016.

Figure 3.6 Saltwater intrusion of qh aquifer in 2016


25130
sustainable exploitation of groundwater maps in Gio Linh Quang Tri

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Quang Tri
Hình 3.37 Bản đồ phân vùng khai thác bền vững n-ớc d-ới đất vùng Gio Linh- Quảng Trị

15

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