Giáo trình tiếng anh chuyên ngành địa chất thủy văn địa chất công trình

TRƯỜNG ĐẠI HỌC MỎ - ĐỊA CHẤT NGUYỄN BÁCH THẢO (Chủ biên) TRẦN VŨ LONG Giáo trình TIẾNG ANH CHUYÊN NGÀNH ĐỊA CHẤT THỦY VĂN-ĐỊA CHẤT CƠNG TRÌNH HƯỚNG TỚI KỶ NIỆM 50 NĂM THÀNH LẬP TRƯỜNG ĐẠI HỌC MỎ - ĐỊA CHẤT TRƯỜNG ĐẠI HỌC MỎ - ĐỊA CHẤT NGUYỄN BÁCH THẢO (Chủ biên) TRẦN VŨ LONG Giáo trình TIẾNG ANH CHUYÊN NGÀNH ĐỊA CHẤT THỦY VĂN-ĐỊA CHẤT CÔNG TRÌNH HƯỚNG TỚI KỶ NIỆM 50 NĂM THÀNH LẬP TRƯỜNG ĐẠI HỌC MỎ - ĐỊA CHẤT LỜI NÓI ĐẦU Cuốn giáo trình Tiếng Anh chuyên ngành Địa chất thủy văn – Địa chất cơng trình bao gồm 30 đọc thuộc lĩnh vực chuyên ngành địa chất, ĐCTV-ĐCCT phân chia thành hai phần: Các chủ đề chung (General topic) gồm 13 đọc giới thiệu kiến thức 17 đọc chuyên sâu (Technical topic) sâu vào phương pháp nghiên cứu chuyên ngành ĐCTV-ĐCCT, đặc tính nước đất đá Ngồi ra, giáo trình cịn giới thiệu đọc thêm thông tin liên quan đến trạng sử dụng, công tác quản lý bảo vệ, văn pháp lý lĩnh vực tài nguyên nước Việt Nam để sinh viên có thêm thơng tin tài nguyên nước phạm vi lãnh thổ Việt Nam, nắm bắt cách thức viết báo, báo cáo chuyên ngành Các đọc chọn lọc, tổng hợp từ sách uy tín hay báo quốc tế công bố Mỗi đọc có phần giải nghĩa thuật ngữ chuyên ngành (Anh-Việt) để sinh viên hiểu rõ vấn đề trình bày nội dung đọc Phần giải thích thuật ngữ tham khảo từ Từ điển giải thích Anh – Việt Địa sinh thái, Địa môi trường, Địa kỹ thuật tập thể chuyên gia đầu ngành lĩnh vực biên soạn Mỗi từ giải thích cụ thể (ý nghĩa, phạm vi áp dụng, nguồn gốc ) đồng thời đưa từ đồng nghĩa, trái nghĩa Ngoài ra, câu hỏi dạng trắc nghiệm, trả lời ngắn gọn dạng True/False giúp sinh viên bổ sung thêm từ mới, nắm bắt nội dung đọc củng cố lại kiến thức chuyên ngành, so sánh với kiến thức học chương trình Ở chủ đề, giáo trình giới thiệu tới người đọc sách, công trình, báo đường dẫn trang web, đoạn phim liên quan đến nội dung học, giúp người đọc tìm đọc thêm thơng tin hữu ích, dễ hiểu thơng qua đoạn phim đồng thời giúp người đọc luyện thêm kỹ nghe-hiểu Phần cuối giáo trình, chúng tơi giới thiệu đến người đọc phần giải thích thuật ngữ phổ biến chuyên ngành địa chất, địa chất thủy văn địa chất cơng trình (khoảng 200 thuật ngữ) Các thuật ngữ giải thích Anh – Anh nhằm mục đích giúp sinh viên hiểu ý nghĩa từ chuyên ngành, dễ dàng tra cứu sử dụng Như vậy, đọc giáo trình đề cập đến lĩnh vực địa chất, địa chất thủy văn địa chất công trình từ ngữ thường gặp thuộc ngành liên quan (địa lý, địa chất, khí tượng, thuỷ văn, thổ nhưỡng học, sinh vật học, sinh thái học, y học, du lịch sinh thái, bảo tồn thiên nhiên ) Mục đích sách cung cấp cho sinh viên, học sinh trung học chuyên nghiệp cán khoa học - kỹ thuật làm công tác điều tra - nghiên cứu, giảng dạy, quản lý thuộc lĩnh vực kể kiến thức thuật ngữ tiếng Anh để đọc sách báo, văn liệu phần để giao tiếp với người nước ngồi cơng việc chun mơn Ngồi ra, cịn tham khảo số lượng lớn văn liệu nước gồm Từ điển, sách báo, internet, mà phần số chọn lọc, liệt kê danh mục tài liệu tham khảo cuối sách Chúng xin trân trọng cám ơn ý kiến đóng góp quý báu bạn đồng nghiệp thuộc Bộ môn Địa chất thủy văn – Trường Đại học Mỏ - Địa chất, đồng nghiệp Trường Đại học Tài nguyên Môi trường Hà Nội, Viện Hàn lâm Khoa học Công nghệ Việt Nam suốt thời gian biên soạn giáo trình Những người biên soạn CONTENTS LỜI NÓI ĐẦU CONTENTS PART I TECHNICAL TEXTS I.1 GENERAL TOPIC UNIT THE STRUCTURE OF THE EARTH UNIT SOIL FORMATION 10 UNIT SOIL PROPERTIES AND CLASSIFICATION SYSTEMS 14 UNIT ELEMENTS OF THE HYDROLOGIC CYCLE 18 UNIT HYDROLOGY AND HYDROGEOLO.GY 22 UNIT GROUNDWATER FORMATIONS 26 UNIT PROPERTIES OF AQUIFERS 31 UNIT PROPERTIES OF GROUNDWATER 35 UNIT GROUNDWATER DEVELOPMENT AND MANAGEMENT 38 UNIT 10 MINERAL WATER 41 UNIT 11 KARST HYDROGEOLOGY 44 UNIT 12 MINING HYDROGEOLOGY 47 UNIT 13 THE FUTURE FOR GROUNDWATER 49 I.2 ADDITIONAL TEXTS 52 TEXT GROUNDWATER RESOURCES IN VIETNAM 52 TEXT GROUNDWATER SUPPLY AND QUALITY 55 TEXT SUSTAINABLE USE OF GROUNDWATER RESOURCES 57 TEXT LAW ON WATER RESOURCES 59 TEXT GROUNDWATER MANAGEMENT IN VIETNAM 63 II.1 SPECIFIC TOPIC 65 UNIT 14 AQUIFER BOUNDARIES 65 UNIT 15 DARCY’S LAW AND HYDRAULIC CONDUCTIVITY 68 UNIT 16 AQUIFER TESTS 73 UNIT 17 FIELD METHODS 77 UNIT 18 DRILLING AND WELL CONSTRUCTION 83 UNIT 19 GROUNDWATER/SURFACE-WATER INTERACTIONS 86 UNIT 20 GROUNDWATER RESOURCES ASSESSMENT 90 UNIT 21 GROUNDWATER FLOW 93 UNIT 22 GROUNDWATER MODELLING 97 UNIT 23 WATER POLLUTION 101 UNIT 24 CHEMISTRY OF WATER 107 UNIT 25 IMPACTS OF CLIMATE CHANGE 110 UNIT 26 IMPACTS OF OVER-EXPLOITATION 114 UNIT 27 SALTWATER INTRUSION 118 UNIT 28 GROUNDWATER-RELATED SUBSIDENCE 122 UNIT 29 ARTIFICIAL RECHARGE 125 UNIT 30 WELLHEAD PROTECTION AREAS FOR GROUNDWATER CATCHMENTS 128 II.2 ADDITIONAL TEXTS 130 TEXT UNSATURATED FLOW 130 TEXT FLOW IN FRACTURE ROCK 131 TEXT RECHARGE AND DISCHARGE 132 TEXT GROUNDWATER FLOW MODEL 134 REFERENCES 142 PART I TECHNICAL TEXTS I.1 GENERAL TOPIC UNIT THE STRUCTURE OF THE EARTH The interior structure of the Earth is layered in spherical shells, like an onion These layers can be defined by their chemical and their rheological properties Earth has an outer silicate solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, and a solid inner core Scientific understanding of the internal structure of the Earth is based on observations of topography and bathymetry, observations of rock in outcrop, samples brought to the surface from greater depths by volcanoes or volcanic activity, analysis of the seismic waves that pass through the Earth, measurements of the gravitational and magnetic fields of the Earth, and experiments with crystalline solids at pressures and temperatures characteristic of the Earth's deep interior Mass The force exerted by Earth's gravity can be used to calculate its mass Astronomers can also calculate Earth's mass by observing the motion of orbiting satellites Earth’s average density can be determined through gravitometric experiments, which have historically involved pendulums The mass of Earth is about 6×1024 kg Structure Schematic view of the interior of Earth continental crust – oceanic crust – upper mantle – lower mantle – outer core – inner core – A: Mohorovičić discontinuity – B: Gutenberg Discontinuity – C: Lehmann–Bullen discontinuity The structure of Earth can be defined in two ways: by mechanical properties such as rheology, or chemically Mechanically, it can be divided into lithosphere, asthenosphere, mesospheric mantle, outer core, and the inner core The interior of Earth is divided into important layers Chemically, Earth can be divided into the crust, upper mantle, lower mantle, outer core, and inner core Figure Structure of the Earth The layering of Earth has been inferred indirectly using the time of travel of refracted and reflected seismic waves created by earthquakes The core does not allow shear waves to pass through it, while the speed of travel (seismic velocity) is different in other layers The changes in seismic velocity between different layers causes refraction owing to Snell's law, like light bending as it passes through a prism Likewise, reflections are caused by a large increase in seismic velocity and are similar to light reflecting from a mirror Crust Figure Cross section showing structure of the Earth The crust ranges from 5–70 km (~3–44 miles) in depth and is the outermost layer The thin parts are the oceanic crust, which underlie the ocean basins (5–10 km) and are composed of dense (mafic) iron magnesium silicate igneous rocks, like basalt The thicker crust is continental crust, which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks, like granite Many rocks now making up Earth's crust formed less than 100 million (1×108) years ago; however, the oldest known mineral grains are 4.4 billion (4.4×109) years old, indicating that Earth has had a solid crust for at least that long Mantle Earth's mantle extends to a depth of 2,890 km, making it the thickest layer of Earth The mantle is divided into upper and lower mantle The upper and lower mantle are separated by the transition zone The lowest part of the mantle next to the core-mantle boundary The mantle is composed of silicate rocks that are rich in iron and magnesium relative to the overlying crust Although solid, the high temperatures within the mantle cause the silicate material to be sufficiently ductile that it can flow on very long timescales Convection of the mantle is expressed at the surface through the motions of tectonic plates As there is intense and increasing pressure as one travels deeper into the mantle, the lower part of the mantle flows less easily than does the upper mantle (chemical changes within the mantle may also be important) Core The average density of Earth is 5,515 kg/m3 Because the average density of surface material is only around 3,000 kg/m3, we must conclude that denser materials exist within Earth's core Seismic measurements show that the core is divided into two parts, a "solid" inner core with a radius of ~1,220 km and a liquid outer core extending beyond it to a radius of ~3,400 km The densities are between 9,900 and 12,200 kg/m3 in the outer core and 12,600–13,000 kg/m3 in the inner core The inner core is not necessarily a solid, but, because it is able to deflect seismic waves, it must behave as a solid in some fashion Experimental evidence has at times been critical of crystal models of the core The liquid outer core surrounds the inner core and is believed to be composed of iron mixed with nickel and trace amounts of lighter elements WORD TO KNOW Earth: Trái Đất, Địa cầu Một hành tinh Hệ Mặt Trời (khoảng cách trung bình đến Mặt Trời 149,5.106 km), đứng thứ độ lớn hành tinh (sau Sao Mộc, Sao Thổ, Sao Thiên Vương Sao Hải Vương) thứ khoảng cách từ Mặt Trời (sau Sao Thuỷ, Sao Kim) Trái Đất tự quay quanh vịng 23 giờ, 56 phút 4,0905 giây quay quanh Mặt Trời theo quỹ đạo hình elíp vịng 365,2564 ngày, với tốc độ 29, 76 km/s Các thông số chủ yếu Trái Đất: thể tích 1083.1012 km3; diện tích bề mặt 510,2.106 km2 (trong gần 71% bị phủ đại dương: 361.106 km2, tạo thành phần chủ yếu thuỷ quyển); chu vi xích đạo 40.075km, bán kính xích đạo 6378,245km; bán kính cực 6356,863km (trung bình 6371,032km); khối lượng 5976.1021 kg; khối lượng riêng 5518 kg/m3 Bề mặt trái đất gồ ghề, có chỗ nhơ cao gần 10km (trên mực nước đại dương giới) đỉnh Everest: 8872m, có chỗ sụt sâu 11 km vực biển Mariana phía đơng Philippin: 11034m Cấu tạo bên Trái Đất theo quan điểm đại bao gồm lớp (địa quyển), khác thành phần hoá học, trạng thái kết cấu tính chất vật lý, tính từ ngồi vào tâm gồm: lớp vỏ, manti trên, manti dưới, nhân nhân Cũng theo hướng từ vào yếu tố áp suất, khối lượng riêng, nhiệt độ tăng dần Tại tâm trái đất, áp suất đạt tới 3,6.1011Pa; khối lượng riêng 12,5.103 kg/m3; nhiệt độ 4000 đến 5.000oC Thành phần chủ yếu Trái Đất gồm: sắt 34,6%; oxy 29,5%; silic 15,2%; magie 12,7% Phía bên ngồi phần cứng (thạch quyển) Trái Đất bao phủ bầu khí dầy khoảng 1300km (Xem thêm: atmosphere) Trái Đất có vệ tinh thiên tạo Mặt Trăng earth crust: vỏ trái đất Lớp vỏ cứng Trái Đất, kể từ mặt đất đến bề mặt gián đoạn Moho (Xem thêm: Mohorovičić discontinuity) phần lục địa ranh giới vỏ chìm sâu đến 30 - 50 km, phần đại dương - nông hơn, đến - 15 km So với toàn Trái Đất, vỏ lớp "màng" mỏng phủ mặt chiếm chưa đến 1% thể tích 1% khối lượng Các đá cấu thành vỏ giàu silic (55,2% trọng lượng) nhơm (15,3%) nên cịn gọi sial Vỏ chia làm phần: vỏ lục địa (Xem thêm: continental crust) vỏ đại dương (Xem thêm: oceanic crust) Lưu ý: Không nên nhẫm lẫn vỏ (crust) với thạch (lithosphere): vỏ phần thạch quyển, thạch bao gồm vỏ phần cứng nằm ngồi manti (phía mềm, Xem thêm: asthenosphere) lithosphere: thạch Phần vật chất cứng Trái Đất, nằm mềm (Xem thêm: asthenosphere), bao gồm toàn vỏ trái đất (Xem thêm: earth crust) phần manti (Xem thêm: mantle), chiều dày thay đổi từ 50 đến 100km Theo thuyết kiến tạo mảng (Xem thêm: plate tectonics) thạch bị rạn vỡ thành nhiều mảng trôi dạt mềm, tạo thành lục địa đại dương Trái Đất Thuật ngữ gọi chung phần cứng Trái Đất, phân biệt với phần lỏng (nước) - tức thuỷ (hydrosphere) phần khí - tức khí (atmosphere) mantle: manti Lớp "cùi" lót bên vỏ bên nhân Trái Đất với ranh giới bề mặt gián đoạn Moho (Xem thêm: Mohorovičić discontinuity) nằm chiều sâu từ 25 - 35 km (dưới lục địa) đến - 11km (dưới đáy đại dương) ranh giới bề mặt gián đoạn Gutenberg (Xem thêm: Gutenberg discontinuity) (ranh giới tiếp xúc với nhân) chiều sâu 2.900 km, chiếm 83% thể tích 67% khối lượng toàn hành tinh Manti chia thành manti (upper mantle) - từ bề mặt Moho đến chiều sâu 670km manti (lower mantle) - từ 670 km đến ranh giới Manti lại chia thành đới (upper zone) cứng, phân bố đến chiều sâu 100km, hợp với vỏ tạo thành thạch (Xem thêm: lithosphere) đới (lower zone) mềm dẻo, đơi chỗ nóng chảy gọi UNIT 30 WELLHEAD PROTECTION AREAS FOR GROUNDWATER CATCHMENTS The establishment of wellhead protection areas is intended to safeguard the quality and quantity of groundwater obtained from urban supply wells They are of crucial importance because of the risk posed by human activity in the vicinity of such extraction points The wellhead protection area delimits an area around the well in which graduated controls restrict or prohibit activities or installations that might contaminate groundwater or that could affect the flow of water intended for human supply Wellhead protection areas to protect groundwater and safeguard drinking water supplies must at the same time be compatible with the socio-economic activity in the area surrounding the well The protection system most commonly applied consists of dividing the area around the well into different zones, graduated from highest to lowest risk and importance, and on this basis determine the restrictions applicable to other activities To delimit these zones, detailed knowledge is required of the aquifer over which the well is sited, and of the latter’s design and characteristics To protect the quality of groundwater, three zones are normally considered: alluvial valley of the Bajo Guadalquivir Immediate or absolutely restricted zone: the definition criterion for this zone is a water transit time* of 24 hours or a small, arbitrarily determined area (100-400 m2) Within this zone, all activities not directly related to water extraction are usually prohibited A boundary fence preventing access to the area is recommended Proximal or maximum restriction zone: the limits of this zone are generally fixed according to a water transit time of 50-60 days, to provide a measure of protection against microbiological contamination Distant or moderate restriction zone: the most appropriate parameter to decide the limits of this zone is that the period of water tran sit should be several years; complementary hydrogeological criteria should also be considered, to protect the well from long-lived contaminating agents Moreover, Spanish legislation contains various protection procedures: zones have been established to protect water and the environment, to prevent contamination of what is termed the Public Water Domain, to protect areas of special ecologic, lands cape, cultural or economic interest, to reduce or eliminate over exploitation and to guarantee the conservation of wetlands When protection planning is considered for a particular region, it is a good way to to establish wellhead protection areas for each of the towns in that region Firstly, studies must provide the information needed to define, for each well point, the criteria (distance, water table fall, transit time, hydrogeologic criteria, self-cleaning capability of the terrain) and the methods (analytical, mathematical models, hydrogeological studies) considered optimum to define each of the zones making up the wellhead protection areas Legislation in Spain enables two ways for a wellhead protection area to be established: via a Water Plan (article 42 of the definitive text of the Water Act) or, if no Water Plan exists or if it needs to be complemented, by the River Basin authority (article 56.3 of the same Law) The procedure may be initiated ex officio by the relevant offices of the River Basin authority, at the request of the municipal authority or at the request of another authority with powers in the field 128 Wellhead protection area boundary delimitation is the responsibility of the Government Board of the River Basin Organism (which is called the Hydrographic Confederation), taking into consideration the previous report of the Water Council The activities that may be restricted or prohibited in the area defined by the wellhead protection area are detailed in article 173.6 of the Regulations on the Public Water Domain and affect public works, urban activities, agricultural and livestock activities, industrial activities and recreational activities The definition of wellhead protection areas is far from being a reality in Spain, despite the fact that article 7.3 of the Water Framework Directive states that member states of the European Union may establish wellhead protection areas for water sources intended for human consumption WORDS TO KNOW Transit time: the time a particle of water takes from when it reaches the saturated zone until it arrives at the well point by the fastest path, or until it emerges at the surface by natural means QUESTIONS What does a wellhead and a baby seal have in common? A: nothing B: they both need a sanitary seal C: they both have heads D: they both exist in water 129 II.2 ADDITIONAL TEXTS TEXT UNSATURATED FLOW The unsaturated zone is the part of the subsurface between the land surface and the groundwater table The definition of an unsaturated zone is that the water content is below saturation (for the specific soil) Hence, ‘unsaturated’ means that the pore spaces between the soil grain particles or the pore space in cracks and fissures are partially filled with water, partially with air The unsaturated zone can be from meters to hundred of meters deep If an unsaturated zone exists below the ground surface the water infiltrating through the top soil will flow vertically through the unsaturated zone before the water recharges the saturated zone From the unsaturated zone, the water is lost by i) plant uptake (transpiration), ii) direct soil evaporation and iii) recharge In the unsaturated zone, the driving force for the flow of water is the vertical gradient of the hydraulic head (consisting of gravity and capillary forces), and the soil characteristics (unsaturated hydraulic conductivity) The vertical flow through an unsaturated soil is solved numerically using the Richards Equation This equation is developed by combining the Darcy’s law with the law of conservation of mass and the result is a partial differential equation for one-dimensional vertical flow in unsaturated soil Figure 24 Unsaturated flow MORE INFORMATION Website https://www.youtube.com/watch?v=ego2FkuQwxc https://www.youtube.com/watch?v=vmo0FRAVgkM https://www.youtube.com/watch?v=ZUkhkgRHppQ 130 TEXT FLOW IN FRACTURE ROCK Fractures are mechanical breaks in rocks; they originate from strains that arise from stress concentrations around flaws, heterogeneities, and physical discontinuities They form in response to lithostatic, tectonic, and thermal stresses and high fluid pressures They occur at a variety of scales, from microscopic to continental Fractures are important in engineering, geotechnical, and hydrogeological practice because they provide pathways for fluid flow Many economically significant petroleum, geothermal, and water supply reservoirs form in fractured rocks Fracture systems control the dispersion of chemical contaminants into and through the subsurface They also affect the stability of engineered structures and excavations The application of fracture characterization and fluid flow analysis in engineering, geotechnical, and hydrogeological practice involves addressing three key questions: How can fractures that are significant hydraulic conductors or barriers be identified, located, and characterized? How flow and transport occur in fracture systems? How can changes in fracture systems be predicted and controlled? These questions are discussed in turn below How can fractures that are significant hydraulic conductors or barriers be identified, located, and characterized? A fundamental step in understanding and predicting the behavior of fractures involves the identification and location of hydraulically significant fractures Such fractures are conduits for fluid flow and are connected to other hydraulically conductive fractures to form systems or networks Conductive fracture networks may include a large number of inter connected hydraulically active features or may be limited to a very small proportion of the total fractures in the rock mass Sometimes it is necessary to locate the hydraulically active fractures explicitly In other cases, it may be sufficient to determine the types of patterns (i.e., regularly repeating geometrical arrangements of fractures) that the fractures form or their statistical properties (e.g., orientation and density) or to locate only the major fractures explicitly The requirements vary from site to site and from application to application How flow and transport occur in fracture systems? Numerical models are used to obtain quantitative estimates of flow and transport behavior in fracture systems The first step in the development of a numerical model is the construction of an appropriate conceptual model of the fracture system The conceptual model is a physical model of the system that describes the main features of the geology and hydrology that control the flow and transport behavior of interest A conceptual model incorporates an interpretation or schematization of reality that is the basis of mathematical calculations of behavior How can changes in fracture systems be predicted and controlled? The flow and transport behavior of fracture systems can be perturbed by natural processes or by the activities of people For example, extraction of fluids from a fracture system can lower the fluid pressure, which will increase the effective stress (the stress transmitted directly from particle to particle) in the rock, thereby causing the fractures to close Temperature-induced stresses can have similar effects Changes in fluid chemistry can lead to either mineral precipitation or mineral dissolution on the fracture walls In general, any change in the void geometry of a fracture system will alter the flow and transport behavior 131 TEXT RECHARGE AND DISCHARGE Groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process where water moves downward from surface water to groundwater Recharge is the primary method through which water enters an aquifer This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface Recharge occurs both naturally (through the water cycle) and through anthropogenic processes (i.e., "artificial groundwater recharge"), where rainwater and or reclaimed water is routed to the subsurface Groundwater discharge Groundwater discharge is the volumetric flow rate of groundwater through an aquifer Total groundwater discharge, as reported through a specified area, is similarly expressed as: Q = (dh/dl)*K*A (15) where Q is the total groundwater discharge ([L3·T−1]; m3/s), K is the hydraulic conductivity of the aquifer ([L·T−1]; m/s), dh/dl is the hydraulic gradient ([L·L−1]; unitless), and A is the area which the groundwater is flowing through ([L2]; m2) For example, this can be used to determine the flow rate of water flowing along a plane with known geometry Processes Groundwater is recharged naturally by rain and snow melt and to a smaller extent by surface water (rivers and lakes) Recharge may be impeded somewhat by human activities including paving, development, or logging These activities can result in loss of topsoil resulting in reduced water infiltration, enhanced surface runoff and reduction in recharge Use of groundwaters, especially for irrigation, may also lower the water tables Groundwater recharge is an important process for sustainable groundwater management, since the volume-rate abstracted from an aquifer in the long term should be less than or equal to the volume-rate that is recharged Recharge can help move excess salts that accumulate in the root zone to deeper soil layers, or into the groundwater system Tree roots increase water saturation into groundwater reducing water runoff Flooding temporarily increases river bed permeability by moving clay soils downstream, and this increases aquifer recharge Artificial groundwater recharge is becoming increasingly important in India, where over-pumping of groundwater by farmers has led to underground resources becoming depleted In 2007, on the recommendations of the International Water Management Institute, the Indian government allocated Rs 1800 crore (US$400million) to fund dug-well recharge projects (a dug-well is a wide, shallow well, often lined with concrete) in 100 districts within seven states where water stored in hard-rock aquifers had been over-exploited Another environmental issue is the disposal of waste through the water flux such as dairy farms, industrial, and urban runoff 132 Wetlands Wetlands help maintain the level of the water table and exert control on the hydraulic head (O'Brien 1988; Winter 1988) This provides force for groundwater recharge and discharge to other waters as well The extent of groundwater recharge by a wetland is dependent upon soil, vegetation, site, perimeter to volume ratio, and water table gradient (Carter and Novitzki 1988; Weller 1981) Groundwater recharge occurs through mineral soils found primarily around the edges of wetlands (Verry and Timmons 1982) The soil under most wetlands is relatively impermeable A high perimeter to volume ratio, such as in small wetlands, means that the surface area through which water can infiltrate into the groundwater is high (Weller 1981) Groundwater recharge is typical in small wetlands such as prairie potholes, which can contribute significantly to recharge of regional groundwater resources (Weller 1981) Researchers have discovered groundwater recharge of up to 20% of wetland volume per season (Weller 1981) Estimation methods Rates of groundwater recharge are difficult to quantify since other related processes, such as evaporation, transpiration (or evapotranspiration) and infiltration processes must first be measured or estimated to determine the balance Physical Physical methods use the principles of soil physics to estimate recharge The direct physical methods are those that attempt to actually measure the volume of water passing below the root zone Indirect physical methods rely on the measurement or estimation of soil physical parameters, which along with soil physical principles, can be used to estimate the potential or actual recharge After months without rain the level of the rivers under humid climate is low and represents solely drained groundwater Thus, the recharge can be calculated from this base flow if the catchment area is known Chemical Chemical methods use the presence of relatively inert water-soluble substances, such as an isotopic tracer or chloride,[3] moving through the soil, as deep drainage occurs Numerical models Recharge can be estimated using numerical methods, using such codes as Hydrologic Evaluation of Landfill Performance, UNSAT-H, SHAW, WEAP, and MIKE SHE The 1Dprogram HYDRUS1D is available online The codes generally use climate and soil data to arrive at a recharge estimate and use the Richards equation in some form to model groundwater flow in the vadose zone MORE INFORMATION Website https://www.youtube.com/watch?v=eEw_oL7PE9k 133 TEXT GROUNDWATER FLOW MODEL Groundwater models are computer models of groundwater flow systems, and are used by hydrogeologists Groundwater models are used to simulate and predict aquifer conditions Characteristics An unambiguous definition of "groundwater model" is difficult to give, but there are many common characteristics A groundwater model may be a scale model or an electric model of a groundwater situation or aquifer Groundwater models are used to represent the natural groundwater flow in the environment Some groundwater models include (chemical) quality aspects of the groundwater Such groundwater models try to predict the fate and movement of the chemical in natural, urban or hypothetical scenario Groundwater models may be used to predict the effects of hydrological changes (like groundwater abstraction or irrigation developments) on the behavior of the aquifer and are often named groundwater simulation models Also nowadays the groundwater models are used in various water management plans for urban areas As the computations in mathematical groundwater models are based on groundwater flow equations, which are differential equations that can often be solved only by approximate methods using a numerical analysis, these models are also called mathematical, numerical, or computational groundwater models The mathematical or the numerical models are usually based on the real physics the groundwater flow follows These mathematical equations are solved using numerical codes such as MODFLOW, FeFlow, HydroGeoSphere, OpenGeoSys etc Various types of numerical solutions like the finite difference method and the finite element method are discussed in the article on "Hydrogeology" Inputs For the calculations one needs inputs like: hydrological inputs, operational inputs, external conditions: initial and boundary conditions, (hydraulic) parameters The model may have chemical components like water salinity, soil salinity and other quality indicators of water and soil, for which inputs may also be needed Hydrological inputs The primary coupling between groundwater and hydrological inputs is the unsaturated zone or vadose zone The soil acts to partition hydrological inputs such as rainfall or snowmelt into surface runoff, soil moisture, evapotranspiration and groundwater recharge Flows through the unsaturated zone that couple surface water to soil moisture and groundwater can be upward or downward, depending upon the gradient of hydraulic head in the soil, can be modeled using the numerical solution of Richards' equation partial differential equation, or the ordinary differential equation Finite Water-Content method as validated for modeling groundwater and vadose zone interactions Hydrological factors at the soil surface determining the recharge Operational inputs 134 The operational inputs concern human interferences with the water management like irrigation, drainage, pumping from wells, watertable control, and the operation of retention or infiltration basins, which are often of an hydrological nature These inputs may also vary in time and space Many groundwater models are made for the purpose of assessing the effects hydraulic engineering measures Boundary and initial conditions Boundary conditions can be related to levels of the water table, artesian pressures, and hydraulic head along the boundaries of the model on the one hand (the head conditions), or to groundwater inflows and outflows along the boundaries of the model on the other hand (the flow conditions) This may also include quality aspects of the water like salinity The initial conditions refer to initial values of elements that may increase or decrease in the course of the time inside the model domain and they cover largely the same phenomena as the boundary conditions The initial and boundary conditions may vary from place to place The boundary conditions may be kept either constant or be made variable in time Parameters The parameters usually concern the geometry of and distances in the domain to be modelled and those physical properties of the aquifer that are more or less constant with time but that may be variable in space Important parameters are the topography, thicknesses of soil / rock layers and their horizontal/vertical hydraulic conductivity (permeability for water), aquifer transmissivity and resistance, aquifer porosity and storage coefficient, as well as the capillarity of the unsaturated zone For more details see the article on hydrogeology Some parameters may be influenced by changes in the groundwater situation, like the thickness of a soil layer that may reduce when the water table drops and/the hydraulic pressure is reduced This phenomenon is called subsidence The thickness, in this case, is variable in time and not a parameter proper Applicability The applicability of a groundwater model to a real situation depends on the accuracy of the input data and the parameters Determination of these requires considerable study, like collection of hydrological data (rainfall, evapotranspiration, irrigation, drainage) and determination of the parameters mentioned before including pumping tests As many parameters are quite variable in space, expert judgment is needed to arrive at representative values The models can also be used for the if-then analysis: if the value of a parameter is A, then what is the result, and if the value of the parameter is B instead, what is the influence? This analysis may be sufficient to obtain a rough impression of the groundwater behavior, but it can also serve to a sensitivity analysis to answer the question: which factors have a great influence and which have less influence With such information one may direct the efforts of investigation more to the influential factors When sufficient data have been assembled, it is possible to determine some of missing information by calibration This implies that one assumes a range of values for the unknown or 135 doubtful value of a certain parameter and one runs the model repeatedly while comparing results with known corresponding data For example, if salinity figures of the groundwater are available and the value of hydraulic conductivity is uncertain, one assumes a range of conductivities and the selects that value of conductivity as "true" that yields salinity results close to the observed values, meaning that the groundwater flow as governed by the hydraulic conductivity is in agreemnent with the salinity conditions This procedure is similar to the measurement of the flow in a river or canal by letting very saline water of a known salt concentration drip into the channel and measuring the resulting salt concentration downstream Dimensions Groundwater models can be onedimensional, two-dimensional, threedimensional and semi-three-dimensional Two and three-dimensional models can take into account the anisotropy of the aquifer with respect to the hydraulic conductivity, i.e this property may vary in different directions One-, two- and three-dimensional One-dimensional models can be used for the vertical flow in a system of parallel Figure 25 Three-dimentional grid in Modflow horizontal layers groundwater exploitation Two-dimensional models apply to a vertical plane while it is assumed that the groundwater conditions repeat themselves in other parallel vertical planes (Fig 4) Spacing equations of subsurface drains and the groundwater energy balance applied to drainage equation are examples of two-dimensional groundwater models Three-dimensional models like Modflow require discretization of the entire flow domain To that end the flow region must be subdivided into smaller elements (or cells), in both horizontal and vertical sense Within each cell the parameters are maintained constant, but they may vary between the cells Using numerical solutions of groundwater flow equations, the flow of groundwater may be found as horizontal, vertical and, more often, as intermediate Semi three-dimensional In semi 3-dimensional models the horizontal flow is described by 2-dimensional flow equations (i e in horizontal x and y direction) Vertical flows (in z-direction) are described (a) with a 1-dimensional flow equation, or (b) derived from a water balance of horizontal flows converting the excess of horizontally incoming over the horizontally outgoing groundwater into vertical flow under the assumption that water is incompressible There are two classes of semi 3-dimensional models: Continuous models or radial models consisting of dimensional submodels in vertical radial planes intersecting each other in one single axis The flow pattern is repeated in each vertical plane fanning out from the central axis Discretized models or prismatic models consisting of submodels formed by vertical blocks or prisms for the horizontal flow combined with one or more methods of superposition of the vertical flow 136 GLOSSARY adsorption Adhesion of solutes from a solution to aquifer solids advection Movement of solutes with groundwater air rotary A drilling method employing a high-speed rotating bit and air to circulate cuttings air sparging Pumping air into an aquifer to volatilize contaminants ambient monitoring Monitoring existing conditions in an aquifer anisotropic The magnitude of an aquifer property varies with direction about a point aquifer A formation producing useful quantities of water arbitrary boundary A flow net boundary not coinciding with a physical feature of an aquifer bucket auger A manual drilling device with a hollow head and cutting blades bulk density Dry mass divided by the total volume of a soil sample cable tool A drilling device employing a heavy drill string and chisel-like bit repeatedly raised and lowered into the ground capillary fringe A zone immediately above the water table in which water is drawn upward under negative fluid pressure capture zone The part of an aquifer that contributes water to a pumping well case-preparation monitoring Monitoring groundwater to obtain data for a lawsuit casing A pipe used to construct a well chain of custody A form that shows who collected and received groundwater samples concentration A measure of the amount of solute in water cone of depression The curved water table or potentiometric surface that develops around a pumping well confined aquifer An aquifer overlain by a confining layer confining layer A low-permeability layer that bounds an aquifer conservative solute A solute that does not adsorb onto aquifer solids or undergo chemical reactions constant-head boundary An aquifer boundary along which the hydraulic head is constant constant-head permeameter A device used to measure the hydraulic conductivity of an aquifer sample, under constant- head conditions consulting firms Private companies that employ hydrogeologists to solve groundwater problems corrective action plan A plan devised to clean a contaminated site Darcy’s law The volumetric discharge of groundwater is equal to the product of hydraulic conductivity, hydraulic gradient, and cross-sectional area of aquifer perpendicular to flow diffusion Movement of solutes in groundwater from areas of high concentration to low concentration 137 direct approach An approach to aquifer testing in which estimated aquifer properties are used to predict drawdown discharge area An area from which groundwater is leaving an aquifer dispersivity A measure of the ability of an aquifer to spread solutes by mechanical means distribution coefficient A measure of the tendency of a solute to attach to aquifer solids drawdown The amount the hydraulic head drops in an aquifer driven well A metal pipe with a conical tip driven into the ground with a hammering device dual-wall reverse-circulation A drilling method that circulates fluids down the annulus of a hole and up the drill stem effective porosity The volume of interconnected pore space in an aquifer sample divided by the total volume of the sample effluent river A river that receives groundwater electrical conductance The ability of rock, soil, or water to conduct an electrical current elevation head The elevation of a piezometer where it is open to an aquifer environmental law Laws pertaining to the environment environmental regulatory agencies Federal, state, or local agencies that enforce environmental laws equipotential line A line along which the hydraulic head is constant evaporation Transfer of water from the liquid phase to the vapor phase extraction wells Wells used to extract water from aquifers falling-head permeameter A device used to measure the hydraulic conductivity of an aquifer sample under falling-head conditions field blank A vial of purified water taken to the field and run through the sampling equipment filter pack Coarse sand packed around the screen of a well flow line A line depicting the path of flowing groundwater flow net A two-dimensional illustration consisting of equipotential lines and groundwater flow lines geographic information system A computer-based software package capable of storing, displaying, and querying location and attribute information for points, lines, or polygons Ghyben-Herzberg principle The distance from sea level to the freshwater/saltwater interface is approximately 40 times the distance from sea level to the water table groundwater Water present in the saturated zone beneath Earth's surface groundwater velocity The rate at which groundwater travels grout curtain A series of holes filled with bentonite used to create a groundwater flow barrier heterogeneous The magnitude of an aquifer property is spatially variable hollow-stem A drilling method employing hollow augers homogeneous The magnitude of an aquifer property is spatially uniform 138 hydraulic conductivity The product of intrinsic permeability, fluid density, and the acceleration of gravity, divided by fluid viscosity hydraulic gradient The difference in the hydraulic head between two points along a flow line, divided by the distance between the points hydraulic head The elevation of water in a piezometer, pertaining to the point at which the piezometer is open to an aquifer hydrodynamic dispersion Spreading of groundwater and its dissolved constituents by mechanical mixing and chemical diffusion hydrogeology The study of groundwater hydrologic budget Volumetric inputs minus outputs from a hydrologic system are equal to the change in storage in the system hydrologic cycle Continuous circulation of Earth's water infiltration Movement of water from Earth's surface into the vadose zone influent river A river that loses water to the subsurface in-situ remediation Cleaning contaminants in place intrinsic permeability A measure of the ability of an aquifer to transmit fluids inverse approach An approach to aquifer testing in which drawdown observations are used to estimate aquifer properties isotropic The magnitude of an aquifer property is uniform in all directions about a point jet percussion A drilling method employing a high-speed water stream leachate Chemicals dissolved from solid waste maximum contaminant level The concentration above which a contaminant poses a health concern monitoring well A cylindrical pipe open at the bottom used to measure water levels and collect groundwater samples multilevel sampling A sampling device open to an aquifer at different elevations nitrate A common groundwater contaminant, often derived from decaying vegetation, fertilizer, and animal waste no-flow boundary A boundary that cannot be traversed by flowing groundwater particle density The density of solid particles piezometer A pipe inserted into the saturated zone to measure the hydraulic head potentiometric surface The level to which water rises in piezometers tapping a confined aquifer potentiometric surface map An illustration in map view, consisting of equipotential lines and flow lines, depicting the movement of groundwater at some depth interval precipitation Falling products of condensation in Earth's atmosphere pressure head The height of the water column in a piezometer, pertaining to the point at which the piezometer is open to an aquifer 139 primary openings Pores between solid particles in a rock or unconsolidated deposit that were present when the rock or deposit formed pumping test A test in which a well tapping an aquifer is pumped, and drawdown is measured in observation wells tapping the same aquifer pumping well A well from which groundwater is pumped reactive solute A solute that tends to adsorb to aquifer solids or react chemically recharge area An area in which groundwater enters an aquifer refraction Bending of groundwater flow lines research monitoring Monitoring to learn about the basic behavior of groundwater and the chemicals it transports retardation factor A dimensionless number used to express the relative velocity of a chemical in groundwater risk-based analysis Evaluating the human and environmental risk of a contaminated site to determine an appropriate course of action runoff Water flowing over Earth's surface saltwater intrusion Underground saline water seeping into a freshwater well saturated zone The interval beneath the vadose zone, in which all of the openings are filled with water screen The slotted, open part of a well secondary openings Cracks or cavities in a rock or unconsolidated deposit that developed after the rock or deposit formed seepage meter A device used to estimate the rate at which water seeps into or out of the bottom or sides of a surface water body sheet flow Water flowing in a thin film over Earth's surface sheet piling Metal sheets driven into the ground to block groundwater flow Shelby tube A thin, cylindrical tube driven into the ground to extract a soil sample slug test A test in which the water column is displaced in a well, and then repeatedly measured at it migrates back to the original position slurry wall A trench filled with bentonite clay to block moving groundwater solid-stem A drilling method employing solid augers solute Anything dissolved in water source control Removing, enclosing, or controlling a source of contamination to prevent further subsurface pollution source monitoring Monitoring groundwater near a potential source of contamination specific capacity The discharge of a well divided by the stabilized drawdown in the well specific retention The volume of water a saturated sample retains against gravity, divided by the total volume of the sample specific yield The volume of water a saturated sample yields to gravity, divided by the total volume of the sample 140 spiked sample A sample containing a known concentration of a particular solute split sample A sample that is split into two smaller samples split-spoon A soil sampling device consisting of a cylinder that breaks lengthwise into two halves springs Places where groundwater seeps out at the land surface steady flow Groundwater flow in which hydraulic head does not change over time steam flushing Pumping steam into a contaminated aquifer to remove organic compounds storage coefficient The volume of water an aquifer sample releases, per unit surface area, per unit decline in hydraulic head stream discharge The volume of water flowing past a stream's cross-section, per unit time sublimation The transfer of water from the solid phase to the vapor phase TDS Total dissolved solids tensiometer A device used to measure fluid pressure in the vadose zone total porosity The volume of pores in an aquifer sample, divided by the total volume of the sample transient flow Groundwater flow in which the hydraulic head changes over time transmissivity The product of hydraulic conductivity and saturated thickness transpiration Release of water vapor from plants to the atmosphere tremie pipe A narrow pipe used to place annular material around a well casing trend test Measuring temporal changes in groundwater levels before conducting an aquifer test unconfined aquifer An aquifer not overlain by a confining layer vadose zone The zone immediately underlying Earth's surface, in which not all of the openings are filled with water vadose zone monitoring Deploying monitoring devices in the vadose zone variable-head boundary An aquifer boundary along which the hydraulic head attains different values viscosity A measure of the ability of a fluid to resist flow water and mud rotary Drilling methods that employ a high-speed rotating bit and water or mud to circulate cuttings water resources Water used by humans or other organisms water table An underground surface at which (gauge) fluid pressure is equal to zero water table map An illustration in map view, consisting of water table contours and flow lines, depicting the movement of groundwater in the upper interval of an unconfined aquifer 141 REFERENCES PHAM QUY NHAN, HOANG VAN HUNG, Special English, Tom Hanoi University of Mining and Geology, 1999 BUI HOC, VO CONG NGHIEP, PHAM XUAN, NGO VAN BUU, English-Vietnamese Glossary of Geoecology – Geoenvironment Geotechnics NXB Xây Dựng, 2008 ACWORTH, R I 2007 Measurement of vertical environmental-head profiles in unconfined sand aquifers using a multi-channel manometer board Hydrogeology Journal, 15, 1279-1289 ANDERSON, M P & WOESSNER, W W 2002 Applied Groundwater Modeling: Simulation of Flow and Advective Transport In: WOESSNER, M P A W (ed.) Applied Groundwater Modeling San Diego: Academic Press BEAR, J 1972 Dynamics of Fluids In Porous Media, American Elsevier Publishing Company CHẢLÉ FITTS, 2002 Groundwater science Academic Press FETTER, C W 2001 Applied Hydrogeology Fourth Edition, 598 JOHN M SHARP, A Glossary of Hydrogeological terms, 2007 KOLDITZ, O., RATKE, R., DIERSCH, H.-J G & ZIELKE, W 1998 Coupled groundwater flow and transport: Verification of variable density flow and transport models Advances in Water Resources, 21, 27-46 K LEE LERNER, BRENDA WILMOTH LERNER, 2004 Encyclopedia of water science, volume 1, and Thomson Gale LLOYD, J W 1992 J Bear & Y Bachmat 1990 Introduction to Modeling of Transport Phenomena in Porous Media xxiv+553 pp Dordrecht, Boston, London: Kluwer Price Dfl 340, US $198, £124 (hard covers) ISBN 7923 0557 Geological Magazine, 129, 373-374 LUSCZYNSKI, N J 1961 Head and flow of ground water of variable density Journal of Geophysical Research, 66, 4247-4256 POST, V., KOOI, H & SIMMONS, C 2007 Using hydraulic head measurements in variable-density ground water flow analyses Ground Water, 45, 664-671 TODD, D.K., 1980, Groundwater Hydrology (2nd ed.): John Wiley & Sons, New York, 535p TOLMAN, C.F., 1937, Ground Water: McGraw-Hill, New York, 793p 142 ... 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