Study the effects of natural, environment, and socio Economic condition to groundwater resources in Gio Linh, Quang Tri

1 INTRODUCTION 1. Problem statement Groundwater resources is affected by natural and socio-economic factors such as: extending of agriculture area, deforestation, socio- economic 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 2 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 3 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 4 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 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 5 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. 6 - 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 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. 7 - 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 8 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 Lower- Middle Holocence aquifer of alluvium-marine sediment (am Q21-2); Bazan fracture-unconsolidated Lower Holocence aquifer (Q12); 9 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. 11 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 expo