2024 Groundwater porosity

The rate of groundwater movement depends upon the slope of the hydraulic head (hydraulic gradient), and intrinsic aquifer and fluid properties. 2-10. Porosity .... O u football schedule 2020

10 Exercises. 1) A 100 cubic centimeter (cm 3) sample of soil has an initial weight of 227.1 grams. It is oven dried at 105°C to a constant weight of 222.0 grams. The sample is then saturated with water and has a weight of 236.6 grams. Next, the sample is then allowed to drain by gravity in an environment of 100% humidity and is reweighted at ...Ground penetrating radar is a noninvasive geophysical technique that can be used to infer subsurface geological, geotechnical, and petrophysical attributes. For water contamination studies, ultimate target, i.e., contaminant flow, is demarcated with the help of dielectric permittivity, water content, and porosity. The dielectric permittivity facilitates to …In an area of 100 ha, the water table dropped by 4.5 m. If the porosity is 30% and the specific retention is 10% determine- (i) the specific yield of the aquifer, (ii) change in ground water storage. Solution: Porosity = S y + S r. 30% = S y + 10% S y = 30 – 10 = 20% or 0.2 . Change in ground water storage = Area of aquifer × drop in g.w.t ...Table 1 Porosity and Specific Yield of Selected Formations Formation Porosity, % Specific yield, % Clay 45-55 1-10 Sand 35-40 10-30 Gravel 30-40 15-30 Sand stone 10-20 5-15 Shale 1-10 0.5-5 Lime stone 1-10 0.5-5 It is seen from Table 1, that although both clay and sand have high porosity, the specific yield of clay is very small …A combination of a place to put water (porosity) and the ability to move water (permeability) makes a good aquifer—a rock unit or sediment that contains extractable groundwater. Well-sorted sediments have higher porosity because there are not smaller sediment particles filling in the spaces between the larger particles.Groundwater exists everywhere there is porosity. However, whether that groundwater is able to flow in significant quantities depends on the permeability. An aquifer is defined as a body of rock or unconsolidated sediment that has sufficient permeability to allow water to flow through it. The mission of The Groundwater Project is to provide accessible, engaging, high-quality, educational materials, free-of-charge online in many languages, to all who want to learn about groundwater and understand how groundwater relates to and sustains ecological systems and humanity. Our current effort is focused on producing online books that ...Some municipal, agricultural, and industrial groundwater users get their water from greater depth, but deeper groundwater tends to be of lower quality than shallow groundwater, so there is a limit as to how deep we can go. Porosity is the percentage of open space within an unconsolidated sediment or a rock. Primary porosity is represented by ...Water that has travelled down from the soil surface and collected in the spaces between sediments and the cracks within rock is called groundwater. Groundwater fills in all the empty spaces underground, in what is called the saturated zone, until it reaches an impenetrable layer of rock. Groundwater is contained and flows through bodies of rock ...Soil organic carbon dynamics: Impact of land use changes and management practices: A review. Thangavel Ramesh, ... Oliver W. Freeman II, in Advances in Agronomy, 2019 3.2.6 Porosity. Soil porosity refers to the fraction of the total soil volume that is taken up by the pore space (Nimmo, 2004).Mainly, pore spaces facilitate the availability and movement …Groundwater Storage and Flow R. W. Buddemeier, J. A. Schloss Boldface items are linked to other sections; italic items are linked to glossary definitions. Groundwater Storage, Porosity, and Specific Yield: Groundwater occupies the cracks and pore spaces between rocks and mineral grains below the land surface. In the saturated zone, essentially ...Groundwater Properties. Nov. 30, 2017 • 44 likes • 16,979 views. Download Now. Download to read offline. Environment. It includes the definition, properties, classification of groundwater with appropriate examples and figures in details. It also deals about the formation of groundwater. The properties of aquifers (all of 7) are described ...Development of Groundwater Model … Randa Hatamleh and Moayyad Shawaqfah - 372 - cooling and tectonic stress. Porosity can be high in vesicular lava flows, but the effective porosity is generally less than 1% in the solid lava flows. Young basalt generally has permeability higher than that of older flows. It is decreased by alteration related toGroundwater is water found below the water table in the zone of saturation within the pores and cracks of a wide variety of earth materials. Groundwater occurrence in porous material is described in terms of total porosity, effective porosity, void ratio, volumetric moisture content, specific yield, and specific retention.Box 4 Methods for Estimating Hydraulic Conductivity Hydraulic conductivity, K, is used to describe the capacity of a porous material to transmit water.Estimating representative values of hydraulic conductivity for a wide variety of porous media is required to quantitatively describe groundwater flow rates (Q), fluxes (q) and velocities (v), and determine the spatial and temporal distribution ...groundwater, streams, coasts, mass wasting, climate change, planetary geology and much more. It has a strong emphasis on examples from western Canada, especially British Columbia, and also includes a chapter devoted to the geological history of western Canada. The book is a collaboration of faculty from Earth Science departments at Universities ...Groundwater Groundwater is the water contained in interconnected pores below the water table. The depth of the water table or groundwater depends on the make-up of the aquifer. In some areas of Florida, it is as shallow as three feet below ground surface. In dry areas such as Arizona, the groundwater may be 200 feet below ground level.Groundwater is water found below the water table in the zone of saturation within the pores and cracks of a wide variety of earth materials. Groundwater occurrence in porous material is described in terms of total porosity, effective porosity, void ratio, volumetric moisture content, specific yield, and specific retention.The porosity of the aggregate is treated extensively elsewhere in this volume. Other void spaces such as honeycombing, which is the result of gross failure properly to consolidate the concrete, ... immersed in both de-ionized water and a synthetic chloride and sulfate bearing groundwater at 70°C. Pore Structure of Cement-Based Materials CRC PressGroundwater exists everywhere there is porosity. However, whether that groundwater is able to flow in significant quantities depends on the permeability. An aquifer is defined as …the vesicular basalts exhibit porosity. The movement of groundwater is therefore controlled by the secondary porosity developed by the presence of fractures and joints. The paleoweathering which is invariably observed at depth near the top of every flow, has given rise to good aquifers at depth.Groundwater is stored in a variety of rock types. A groundwater reservoir from which water can be extracted is called an aquifer. We can effectively think of an aquifer as a deposit of water. Extraction of water depends on two properties of …How does porosity affect groundwater storage? Porosity ultimately affects the amount of water a particular rock type can hold and depends on a couple of different factors. The ability of the ground water to pass through the pore spaces in the rock is described as the rock’s permeability.a. Porosity is the primary governing factor influencing the ability of rock or sediment to store fluids (e.g. groundwater or hydrocarbons) b. Types of Porous Openings (a) Intergranular Porosity = primary pore spaces present between particles of a sediment or rock deposit i) Intergranular Porosity influenced by: a) sorting b) grain packing c ...3.7 Interrelationship of Effective Porosity, Specific Yield and Specific Retention. 4 Darcy’s Law, Head, Gradient and Hydraulic Conductivity. 4.1 ... if pure benzene was spilled during a train accident and entered the top of the 10 °C groundwater system as liquid benzene, the saturated K value of the sand for benzene could be computed. In ...Central groundwater authority extends NOC deadline for them. India has granted relief to a bunch of big companies, including legacy businesses like Tata Sons and the Adani group, in cases related to overextraction of groundwater. This has c...Types of Materials Porosity and permeability of the underground materials have an impact on the storage and movement of groundwater. The variability in porosity exists as the underground materials are heterogeneous in nature. Porosity refers to the percentage of the total volume of rock with voids.Permeability is the property of rocks that is an indication of the ability for fluids (gas or liquid) to flow through rocks. High permeability will allow fluids to move rapidly through rocks. A rock with 25% porosity and a permeability of 1 md will not yield a significant flow of water. …. Porosity and Permeability.Figure 13 – Procedure for determining effective porosity, n e, specific yield, S y, and specific retention, S r: a) by measuring the total volume, V T, based on sample geometry, measuring the interconnected pore volume (V I) by measuring the volume of water needed to saturate an initially completely dry sample from below, then calculating the effective porosity, n e; b) by draining the ... Figure 7. Subdivision of the ERT image in eight distinct regions based on their average resistivity values and arbitrary thresholds. Table 1 presents characteristics of the temporal evolution associated with each region. - "Imaging groundwater infiltration dynamics in the karst vadose zone with long-term ERT monitoring"The majority of freshwater on earth is found in frozen glaciers and ice caps. This frozen water accounts for 68.7 percent of earth’s freshwater, with 30.1 percent found in groundwater. Only 1.2 percent of fresh water is exposed to the surfa...Calculated average porosity of the Edwards aquifer is 18 percent. Estimated total waterfilled pore volume of the Edwards aquifer within the study area is 173 million acre-feet. Only 3 percent of this total water lies in the traditionally used part of the aquifer between the highest and lowest recorded water levels.Two important properties of groundwater that influence its availability and movement are porosity and permeability. Porosity refers to the open or void space within the rock. It is …Two important properties of groundwater that influence its availability and movement are porosity and permeability. Porosity refers to the open or void space within the rock. It is …Porosity is a measure of the open space in rocks –expressed as the percentage of open space that makes up the total volume of the rock or sediment material. Porosity can occur as primary porosity, which represents the original pore spaces in the rock (e.g. space between sand grains, vesicles in volcanic rocks), or secondary porosity which ...-Porosity - Percentage of total volume of sediment or rock that is void/pore space. Thus, Porosity of Earth materials relates to the Storage of Groundwater and is expressedAs a Percentage or Decimal Value (e.g., 20% or 0.20).-Primary Porosity - Intergranular Porosity that develops when a rock formsThe total volume of open space in which the groundwater can reside is porosity. Porosity determines the amount of water that a rock or sediment can contain. Porosity In sediments or sedimentary rocks the porosity depends on grain size, the shapes of the grains, and the degree of sorting, and the degree of cementation. Groundwater …The residence time of water in a groundwater aquifer can be from minutes to thousands of years. Groundwater is often called “fossil water” because it has remained in the ground for so long, often since the end of the ice ages. Features of an Aquifer. To be a good aquifer, it must have good: porosity: small spaces between grainsAn accurate and reliable description of the porosity–permeability relationship in geological materials is valuable in understanding subsurface fluid movement.n e = Effective porosity - fraction of cross section available for groundwater flow (unitless) Effective porosity is smaller than total porosity. The difference is that total porosity includes some dead-end pores that do not support groundwater. Typical values for total and effective porosity are shown in Table 1.101: Groundwater ﬂow around wells - Excel model Reservoir Rock Properties and Basic Log Interpretation, Dr. Moustafa Oraby Lecture (1) Reservoir Data Analysis |Part.1 How To Prepare an Oral Research Presentation Applied Petroleum Reservoir Engineering - Chapter 1 Reservoir Simulation with ECLIPSE - GRID SECTION Geologi Dasar | Cross Section... porosity, permeability, aquifer gradient and outflow of the aquifer system. Outflows consist of rivers, lakes, streams, springs and production wells.rises and falls with precipitation. Groundwater _____. is recharged by precipitation. stays in one place and never moves. is only found in areas with wet climates. exists mostly as underground rivers and lakes. Groundwater forms when precipitation, rain, snow, sleet, hail, or freezing rain soaks into the ground It settles into three main layers ...Groundwater Properties. Nov. 30, 2017 • 44 likes • 16,979 views. Download Now. Download to read offline. Environment. It includes the definition, properties, classification of groundwater with appropriate examples and figures in details. It also deals about the formation of groundwater. The properties of aquifers (all of 7) are described ...Unsaturated zone Vadose zone Saturated zone Phreatic zone Groundwater Water from MEA 481 at North Carolina State University. Upload to Study. Expert Help. Study Resources. Log in Join. Unsaturated zone vadose zone saturated zone phreatic. Doc Preview. Pages 100+ Identified Q&As 35.Review groundwater flow, aquifers, porosity and permeability with students (see Introduction section). To complete activity as an inquiry-based project: Write porosity and permeability on the board as vocabulary terms and define each. The porosity of a material is a measurement of how much of its volume is open space (also called pore space ...Groundwater is a primary agent of chemical weathering and is responsible for the formation of caves and sinkholes. The Groundwater System. Groundwater resides in the void spaces of rock, sediment, or soil, completely filling the voids. The total volume of open space in which the groundwater can reside is porosity. Porosity determines the amount ... Rock formations can have both primary porosity (also called "matrix porosity") and secondary porosity. ... For karst to develop, the introduction of groundwater ...discharge area . What makes water flow from the recharge areas to the discharge areas? Recall that water is flowing in pores where there is friction, which means it takes work to move the water. There is also …a saturated layer of permeable soil or rock capable of storing and transmitting significant quantities of water to wells or springs. The UD arena is built upon this glacial material left from the Ice Age. outwash. Study with Quizlet and memorize flashcards containing terms like Groundwater is the largest reservoir of ________., Impermeable ...However, the secondary porosity seen in most ancient sandstones is the product of burial diagenesis. Permeability measures the ease with which a fluid flows through sediment or rock. The flow of fluid from one part of a rock to another, or from an aquifer to a bore hole, depends on the connections among pores and fractures.With a porosity of 15% for the shallow aquifer (Shen, 1992), the 4 He accumulation rate in groundwater from the in-situ matrix and external flux from the deep crust is 6.34 × 10 −11 cm 3 STP g −1 year −1 in the convergent margin and 7.63 × 10 −11 cm 3 STP g −1 year −1 in the extensional zone.This study presents the analytical expressions of drainable and fillable porosity for layered soils under shallow groundwater environments. The expressions of drainable porosity λ d and fillable porosity λ f for two-layered soils are first derived with water table depth change ∆d→0 under dynamic soil moisture conditions. The expressions of λ d and …Kiptum, C. K. et al. Application of Groundwater Vistas in Modelling Groundwater … AER Journal Volume 2, Issue 2, pp. 33-45, 2017 42 Table 5. Calculation of Porosity at Different Depths for a Site in the Study Area Depth Volume of sample cm3 Mass of dry sample g 3 Bulk density g/cm Initial Volume of water cm3 Volume of water5.1 Conditions Effecting Hydraulic Conductivity Values Hydraulic conductivity, K, represents the relative ease of groundwater movement though an earth material as stated in Section 4.It represents of the combination of the intrinsic permeability, k, and fluid properties (Equation 31).If the fluid properties are constant, then hydraulic conductivity …The porosity based on these openings is therefore less than n, and is called the effective porosity, n e. The revised equation for seepage velocity becomes: v = Ki/n e = q/n e . The direction of the water movement is obtained from the hydraulic gradient term in Darcy’s Law; as a first approximation, water flows in the direction given by the ...Groundwater is stored in a variety of rock types. A groundwater reservoir from which water can be extracted is called an aquifer. We can effectively think of an aquifer as a deposit of water. Extraction of water depends on two properties of …Madison asks, “Why are many fertilizer bags labeled 'phosphorus free'? I thought phosphorus was important for plants?"You're right that phosphorus is important, but it can also be a major source of groundwater contamination. Read to know wh...Groundwater Quality. Launch map. Watershed Watch Data Portal . Launch map. Lidar and Derived Layers. Launch map. Kentucky From Above. Launch map. Convert A Single Coordinate Value ...In recent years, drought and demand growth in most parts of the county have caused a dramatic increase in using groundwater for water supply purposes. Besides, unplanned excessive discharges from aquifers have led to aquifer degradation. In most integrated water resources management models, groundwater simulation is used for taking into account …Groundwater is often called “fossil water” because it has remained in the ground for so long, often since the end of the ice ages. Aquifers Features of an Aquifer. To be a good aquifer, the rock in the aquifer must have good: porosity: small spaces between grains; permeability: connections between pores; This animation shows porosity and ...Groundwater Resources. Groundwater is the water found beneath the Earth’s surface and occupies the very small cracks and spaces between rocks, gravel and sand. It is a common misconception that groundwater is in the form of underground lakes, streams and rivers, when in reality, groundwater is found inside rocks: in the small pore spaces ... Groundwater - 14% Rivers, Lakes, Resevoirs - 1% 50% of all drinking water comes from groundwater. 40% of all agricultural water comes from groundwater. Groundwater comes for INFILTRATION of rainwater. FEATURES ASSOCIATED WITH GROUNDWATER. POROSITY and PERMEABLILITY POROSITY: percentage of "empty" space (pores) in a …Groundwater Temperature's Measurement and Significance. Oscar E. Meinzer's discussion of the occurrence of groundwater in the United States (1923, The Occurrence of Ground Water in the U.S. with a Discussion of Principles, USGS Water-Supply Paper 489) is a classic in the science of groundwater and geology. It is an excellent reference for the ...Porosity. The percentage of a rock or sedimentary deposit that consists of voids and open space is its porosity —the greater its porosity, the greater its ability to hold water. Sediments are usually more porous than rocks. Sedimentary rocks tend to be more porous than igneous rocks because there is more open space between the individual ... The residence time of water in a groundwater aquifer can be from minutes to thousands of years. Groundwater is often called “fossil water” because it has remained in the ground for so long, often since the end of the ice ages. Features of an Aquifer. To be a good aquifer, it must have good: porosity: small spaces between grainsThe rate of groundwater movement depends upon the slope of the hydraulic head (hydraulic gradient), and intrinsic aquifer and fluid properties. 2-10. Porosity ...Groundwater (Aquifer, Porosity, Permeability) Sort & Match STATIONS Activity. by. KeepItSimpleStudents. 5. $4.00. $3.00. PDF. FOLLOW ME TO CHECK OUT MY OTHER FREE PRODUCTS AS THEY ARE RELEASED!!! This no-prep activity involves matching Groundwater vocabulary (Aquifer, Springs, Porosity, Permeability, Water Table) to …Other rock types, such as granite, usually have low porosity and low permeability so make poor aquifers. An aquifer is described as confined if it has an ...The availability of groundwater as a water source depends largely upon surface and subsurface geology as well as climate. The porosity and permeability of a geologic formation control its ability to hold and transmit water. Porosity is measured as a ratio of voids to the total volume of rock material and is usually described as a percentage.Groundwater exists everywhere there is porosity. However, whether that groundwater is able to flow in significant quantities depends on the permeability. An aquifer is defined as a body of rock or unconsolidated sediment that has sufficient permeability to allow water to flow through it.Porosity is the amount of empty space in sediments or rocks. I n a soil or rock the porosity (empty space) exists between the grains of particles or minerals. In a material like gravel the grains are large and there is lots of empty space between them since they have angularity or spherical shape. However, in a material like a gravel, sand and ...Apr 28, 2022 · n e = Effective porosity - fraction of cross section available for groundwater flow (unitless) Effective porosity is smaller than total porosity. The difference is that total porosity includes some dead-end pores that do not support groundwater. Typical values for total and effective porosity are shown in Table 1. Most of the materials beneath the Earth's surface are porous. That means that they contain tiny open spaces as well as solids, just like a sponge. The porosity of a material is the percentage of open pore space it contains. Loosely packed sand and gravel can have porosities as high as 25 percent. Solid rock is much less porous. Many rocks have a porosity of only a small fraction of a percent ...where V is the velocity of the groundwater, and n is the porosity (expressed as a proportion, so if the porosity is 10%, n = 0.1). We can apply this equation to the scenario in Figure 14.2.1. If we assume that the hydraulic conductivity is 0.00001 metres per second (m/s), we get q = 0.00001 × 0.08 = 0.0000008 m 3 per second per m 2. If the ... This video briefly introduces the concept of groundwater before explaining how two properties - porosity and permeability - combine to determine the availabi...porosity. Permeability is _____ . the ability of a solid to allow fluids to pass through the process by which plants release water vapor to the atmosphere the amount of water vapor in the air relative to the maximum amount of water vapor the air can hold. the percentage of pore space in the rock. The best groundwater reservoirs have _____ .? Groundwater exists everywhere there is porosity. However, whether that groundwater is able to flow in significant quantities depends on the permeability. An aquifer is defined as …When a water-bearing rock readily transmits water to wells and springs, it is called an aquifer. Wells can be drilled into the aquifers and water can be pumped out. Precipitation eventually adds water ( recharge) into the porous rock of the aquifer. The rate of recharge is not the same for all aquifers, though, and that must be considered when ...The availability of groundwater as a water source depends largely upon surface and subsurface geology as well as climate. The porosity and permeability of a geologic formation control its ability to hold and transmit water. Porosity is measured as a ratio of voids to the total volume of rock material and is usually described as a percentage.$,p are the fractional porosity and density of the rock, respectively, 222 X is the decay constant for Rn. 222 The equilibrium Rn content is reached after 20 days', residence in the ... Groundwater samples were collected for radioelement and inert gas analysis in September/October, 1980 and for inert gas analysis in December, ...The groundwater velocity is the product of hydraulic conductivity and hydraulic gradient, with adjustments for the porosity of the soil material (usually from 5 to 20 percent): groundwater velocity = hydraulic conductivity hydraulic gradient porosity This is called Darcy’s Law,named after the French engineer Henry Darcy who first dis-

In recent years, drought and demand growth in most parts of the county have caused a dramatic increase in using groundwater for water supply purposes. Besides, unplanned excessive discharges from aquifers have led to aquifer degradation. In most integrated water resources management models, groundwater simulation is used for taking into account …. Metal storage racks lowes

When a water-bearing rock readily transmits water to wells and springs, it is called an aquifer. Wells can be drilled into the aquifers and water can be pumped out. Precipitation eventually adds water ( recharge) into the porous rock of the aquifer. The rate of recharge is not the same for all aquifers, though, and that must be considered when ...Groundwater is stored in a variety of rock types. A groundwater reservoir from which water can be extracted is called an aquifer. We can effectively think of an aquifer as a deposit of water. Extraction of water depends on two properties of …- The origin of porosity and permeability; Groundwater movement; Main equations of flow and solute transport; Sources of groundwater contamination; Contaminants in groundwater; Risk assessment; Solute plumes as a manifestation of processes; Design and quality assurance issues in solute sampling: SamplingIn this zone, all the pore spaces and voids in the soil and rock are filled with water. The upper boundary of the saturated zone is called groundwater table or ...Groundwater is the water found beneath the Earth’s surface and occupies the very small cracks and spaces between rocks, gravel and sand. It is a common misconception that groundwater is in the form of underground lakes, streams and rivers, when in reality, groundwater is found inside rocks: in the small pore spaces between rock grains in sedimentary rocks, between sand and gravel particles ...-Porosity - Percentage of total volume of sediment or rock that is void/pore space. Thus, Porosity of Earth materials relates to the Storage of Groundwater and is expressedAs a Percentage or Decimal Value (e.g., 20% or 0.20).-Primary Porosity - Intergranular Porosity that develops when a rock formsKiptum, C. K. et al. Application of Groundwater Vistas in Modelling Groundwater … AER Journal Volume 2, Issue 2, pp. 33-45, 2017 42 Table 5. Calculation of Porosity at Different Depths for a Site in the Study Area Depth Volume of sample cm3 Mass of dry sample g 3 Bulk density g/cm Initial Volume of water cm3 Volume of waterPorosity The percentage of a rock or sedimentary deposit that consists of voids and open space is its porosity —the greater its porosity, the greater its ability to hold water. …· most sandstones are good sources of quality groundwater because they usually have a relatively high degree of porosity and permeability · rocks such as pumice, scoria, shale, clay stone, and siltstone may have good porosity but have poor permeability and would not be sources of quality groundwater. 3. Specific yielda) Water occupies all pore spaces (light blue spaces, VV) and the total porosity is n = VV / VT ; b) Some pore spaces are disconnected from other pores (red hatched spaces) and groundwater can only access the connected pore spaces (blue area, VI ), thus effective porosity is ne = VI / VT . The total volume of open space in which the groundwater can reside is porosity. Porosity determines the amount of water that a rock or sediment can contain. Porosity In sediments or sedimentary rocks the porosity depends on grain size, the shapes of the grains, and the degree of sorting, and the degree of cementation. Groundwater Page 1 of 11Groundwater is water that exists underground in saturated zones beneath the land surface. The upper surface of the saturated zone is called the water table. Contrary to popular belief, groundwater does not form underground rivers. It fills the pores and fractures in underground materials such as sand, gravel, and other rock, much the same …Figure 5. Image of the inverted resistivities for DD (a) and GD (b) data sets in average weather conditions (March 2017). Letters (A–D) indicate anomalies described in the main text. - "Imaging groundwater infiltration dynamics in the karst vadose zone with long-term ERT monitoring"Here Vp is potential of ground water, Va is volume of aquifer. As a result, porosity is one of the most important parameters in order to determine hydraulic.Jan 17, 2021 · Noah-MP, this time with the simple groundwater module (SIMGM, Niu et al., 2007), employs an empirical value fixed at 0.2 in deep water table situations (where the water level is below the soil column), and uses the effective porosity, which is the volume of air pore space within the soil (Niu et al., 2007), to represent the specific yield in ... E) sulfides. (No) C. Groundwater in an aquifer is sometimes called fossil water because. a. the water has been in the aquifer for thousands of years. b the water is not being replenished at anywhere near the same rate as when it formed. c. tiny microorganisms living in the aquifer are living fossils..

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