The thesis aims to establish scientific and practical arguments in proposing measures to rationally use and protect underground water resources on the basis of analyzing, evaluating and estimating the impacts of geographic factors. natural, socio-economic, environmental, climate change and sea level rise in Gio Linh and Quang Tri regions.
Trang 1Gio 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
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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
Trang 44 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
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 change-sea 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
Trang 5- 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
Trang 6- 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 socio-economic 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 Q3); unconsolidated Lower-Middle Holocence aquifer of alluvium-marine sediment (am Q21-2); Bazan fracture-unconsolidated Lower Holocence aquifer (Q1 );
Trang 99 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
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
Trang 1212 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:
Trang 1313 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