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

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.

1 INTRODUCTION 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 Objectives and scopes of the study 2.1 Objecttives of the study 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 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 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 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 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 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 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 Dissertation structure The dissertation is reported in 140 pages Beside introduction, conclusion, references, and appendices, the dissertation consists of chapters: Chapter 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 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 Evaluate the effect of factors to groundwater and propose rational solutions in use and protect groundwater resources in Gio Linh, Quang Tri 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 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 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 - 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 - 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 Figure 1.1 Workflows chart of the study CHAPTER 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); 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; 10 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 12 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 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: 13 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 14 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) 15 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 16 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 ÷ 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 ÷ 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 17 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 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; 18 - 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 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, 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 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 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 Develop a monitoring system for water level, water quality in the Holocene and Pleistocene aquifers Establishment of prohibited areas, exploitation restriction and protection galleries for groundwater resources in the study area 22 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 0,9 LK603 -6 10 K 0,7 11 ,8 0,8 o a suè i § 42 46 78 0,4 15 21®åi 27 ® å i L ß i Ch ï a 0,7 liƯt sÜ 0,4 ,4 t Cơ Trung Hải Trung Giang Đứ c Dụ c hồ 16 10 29 21 kh e 97 - i C Hã Gia Vßng hydrology sation qq 16 48 42 49 28 27 40 i LK402 24 b µ u L Ðc 25 122 íp M- 95 TT gio linh 50 43 114 h å H¶ i L a m Tróc Kinh Lake Tr a 74 Lß 28 64 46 44 47 20 28 LK403 36 QL9 µ e M i LK908 63 Õ u g H i s« n 18 36 H 10 iÕ u qp qp s« ng LK904 LK906 59 s« H 12 hồ Khe Mây LK907 19 87 đ Ë p Ph a n X¸ hå HiÕu Nam 08 27 o-s o-s 57 S o-s o-s S g h T h¹ c LK409 25 50 hå NghÜa Hy 13 69 18 Đ ịn h 27 18 LK420 28 23 58  53 Ün h 3 50 36 H · n 50 h å Ngh Üa Hy Ob g V LK410 qp qp hå Trung ChØ 22 15 LK416B 10 38 13 The 4 25 16 Wa 63 LK406 tp đông đông hµ hµ Bor 3 iÕ u LK414C LK903 20 2 -1 25 -1 30 ng Đông Thanh qhÔ qhÔ -6 13 20 16 69 46' 42'' N 106 49'16'' E -6 13 L é am Þn h kh -5 LK423 Đông Hà meteorology station LK905 33 A1-2 A1-2 Đông Giang B1 B1 Cam Thủy 16 qh£ qh£ 42 58 § 13 32 đ ậ p Tâ n Ki m 24 5 cam cam lé lé g >1000mg/l nh V Ü «n 7 Sg N.Tô i Mô n áB 63 III Notaion ot 2 4 K Đ Cam An qhÊ qhÊ b u Đá 5 Cam Thanh LK408 68 k he LK415 32 25 22 Sg T ró c o-s o-s 39 42 B B B B triƯu triƯu phong phong ¹c h å Qu i Hà 45 53 34 N Hồ Kh ê 64 N Đá Bạ c 117 n 82 107 n h h· th Sg 26 50 132 h· 20 48 63 Gio Quang h nn HH·· ® Ë p Du y Ph i ê n hh ạạ4cc TThh nngg ô ô SS ,1 o-s o-s 102 33 ¹c th sg ,1 16 42 55 k he L ßn i 106 k he 38 62 74 B B B B 68 B1 B1 Cưa ViƯt hydrology station Gio Mai A1-1 A1-1 n LK902 h e t ,3 VB_qh Limited zone cưa cưa viƯt viƯt 0,9 B2 B2 Gio ViƯt qhÔ qhÔ 20 k 74 VB_qp qp qpLK411 17 A A A A A A B2 B2 A2-1 A2-1 16 hå H¶i T©n A1 A A A1 A A B2 B2 10 47 91 Gio Ch©u 36 LK90145 HCM 69 Gio H¶i LK401 qq 88 Exploited zone Gio Thµnh 27 No A A A A A A C¸i 68 12 kh e 30 56 73 Hà Th-ợng Lake 156 đồi Cồn Tiên Zone A2-2 A2-2 LK405 II Limited zone hå 16 66 19 -6 30 34 47 78 0,4 LKG5 qh£ qh£ 20 31 e kh LKG1 38 26 63 66 3 29 qp qp A A A A A A qhÔ qhÔ LK432 33 qq 42 48 Gio Phong 32 36 m/o-s m/o-s 13 gio gio linh linh b µ u Lệ M ô n 18 qhÔ qhÔ A1-1 A1-1 Gio Mü qh£ qh£ 23 10 25 45 65 ng LK601 23 Rä B1 B1 A2-1 A2-1 24 32 Kinh M«n lake 42 e QL1A qp£ qp£ 13 h å Kin h M « n 44 29 22 A1-2 A1-2 ò 33 kh m m HHòò nnhh CCáá nngg SSôô 14 28 LK404 Trung Sơn 24 n H Bế bàu Sỏi / 17 07' 51'' N ng S g ¶i 23 B2 B2 i Hả Bế n Sg đô 0,9 24 43 12 11 14 3000 16 10 ®åi 17 47 0m Ĩn bi 16 ®åi 15 1500 24 0,5 17 25 ««nn0,7 0,9 gg BB ÕÕnn HH¶¶ 0,7 ii liƯt sÜ 0,7 VÜnh VÜnh Linh Linh cöa cöa tïng tïng 22 g B 24 20 0,9 S 27 18 0,4 LK602SS -1 18 0,7 Tỷ lệ: 1:150.000 (đ-ợc thu từ đồ tỷ lệ 1:50.000) 18 qq 0,6 mũi Thừa Long 0,6 ài c B Bạ qhÊ qh£ I- Distribution o 19 0,8 B¶n B¶nvÏ vÏ vÏsè sè sè06 06 06 B¶n vÏ sè 06 B¶n vÏ sè 06 33 B¶n 107 14'12'' E i 0,8 19 36 legend 28 Sg B Õ n H¶ hå L a N gµ 2,6 73 23 10 17 07' 51'' N 18 13 08 10649'16'' E 10 28 16 qh£ qh£ 46' 42'' N 33 107 14'12'' E Figure 3.7: sustainable exploitation of groundwater maps in Gio Linh Quang Tri Hình 3.37 Bản đồ phân vùng khai thác bền vững n-ớc d-ới đất vùng Gio Linh- Quảng Trị 15 QL1A Gro GL 15 11: 72: Co Hig Ri Stu 26 legend 107 14'12'' E B¶n B¶n B¶nvÏ vÏ vÏsè sè sè06 06 06 vÏ sè 06 B¶n B¶n B¶n vÏ sè 06 00) / qh£ qh£ 18 qhÔ qhÔ Fresh water aquifer qp qp Salt water aquifer m/o-s m/o-s None 78 II Limited zone and to be exploited 19 I- Distribution of fresh water aquifer 17 07' 51'' N Zone 73 Exploited zone Notation A1-1 A1-1 A1-1 A1-1 A1-1 A1-1 - More than fresh water aquifer and rechage A1-2 A1-2 A1-2 A1-2 A1-2 A1-2 - No ssalt water aquifer, more than aquifer, rechage A2-1 A2-1 A2-1 A2-1 A2-1 A2-1 - Have fresh water aquifer, rechage A2-2 A2-2 A2-2 A2-2 A2-2 A2-2 Limited zone cưa cưa viƯt viƯt t Characteristics - Water level of Pleistocen less 10m B1 B1 B1 B1 B1 B1 - Have a salt water aquifer B2 B2 B2 B2 B2 B2 - Have salt water aquifers, a fresh water auifer 68 station III Notaion others >1000mg/l ong ong ££ Border of fresh water and salt water Holocen aquifer qhÔ qhÔ Water level Pleistocen aquifer (hd=10m) 63 The last Borehole S Observation borehole (2012-2015) g V ĩn h Đ ịn h 58 18 16 46' 42'' N 107 14'12'' E Linh- Qu¶ng TrÞ  15 QL1A Groundwater extraction site GL: Name of water factory 15.000: Capacity (m3/ng®) 11: Total of borehole 72: Depth of borehloe (m) Contour line High way / rail way River Study of area ... 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... 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. .. 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