The upper boundary of the saturated zone, open to atmospheric pressure, is generally known as the water table. What is an aquifer? Aquifers are the saturated ...Oct 19, 2023 · 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 ... The saturated zone below the water table has water that fills the tiny spaces (pores) between rock particles and the cracks (fractures) of the rocks. ... Water in the saturated groundwater system moves slowly and may eventually discharge into streams, lakes, and oceans. Sources/Usage: Public Domain.Groundwater can be divide into two major zones: unsaturated and saturated. Unsaturated Zone. The unsaturated zone is the section between the surface of the Earth and the top of the water table. This zone is also known as the vadose zone after the Latin word for ‘shallow’. The capillary fringe is a section of the unsaturated zone where water ...In the saturated zone all spaces and fractures are completely filled with water. Water table. Unsaturated zone. Bedrock. Pores filled with air and water. Pores ...Aquifer. An aquifer is a term for a type of soil or rock that can hold and transfer water that is completely saturated with water. That means that all it is simply a layer of soil or rock that has a reasonably high porosity and permeability that allows it to contain water and transfer it from pore to pore relatively quickly and all of the pore spaces are filled with water.Continuing its downward route through the unsaturated zone, it moves through the interconnected openings of sand, gravel, silt, and clay or openings in rock until it reaches the "saturated zone" where it becomes groundwater. For more groundwater basics, visit Aquifers and Groundwater (leaves DEC website) from the USGS. Misconceptions about ...Continuing its downward route through the unsaturated zone, it moves through the interconnected openings of sand, gravel, silt, and clay or openings in rock until it reaches the "saturated zone" where it becomes groundwater. For more groundwater basics, visit Aquifers and Groundwater (leaves DEC website) from the USGS. Misconceptions about ...Saturated zone (groundwater) Water seepage Aquifers in Australia Sedimentary Basin Aquifers Fractured Rock Aquifers. Introduction to Groundwater Centre for Groundwater Studies 7 The unsaturated zone The unsaturated zone is the area between the surface and the watertable (top of an unconfinedThe water of unsaturated zone is called soil water, and can be subdivided as hygroscopic water, capillary water and gravitational water. The upper most surface or top level of the zone of saturation is called the water-table. It can also be defined as the level at and below which soil particles are completely saturated.Continuing its downward route through the unsaturated zone, it moves through the interconnected openings of sand, gravel, silt, and clay or openings in rock until it reaches the "saturated zone" where it becomes groundwater. For more groundwater basics, visit Aquifers and Groundwater (leaves DEC website) from the USGS. Misconceptions about ...The term groundwater usually refers to all subsurface water beneath the water table (the interface between the vadose and saturated zones, or the top of the saturated zone) in …For groundwater the first research step was to develop the Saturated Unsaturated Flow and Transport in 3D (SUFT3D) groundwater model and to check its effectiveness and accuracy to reproduce typical situations of seawater intrusion and then groundwater-river interactions influenced by seawater intru- sion.When precipitation falls, water travels on the surface and some can infiltrate into the ground. Groundwater is replenished when water moves from the surface, through unsaturated rocks or sediment (unsaturated), all the way down the saturated parts (saturated zone) in a process called infiltration and becomes groundwater (Figure \(\PageIndex{10}\)).The water of unsaturated zone is called soil water, and can be subdivided as hygroscopic water, capillary water and gravitational water. The upper most surface or top level of the zone of saturation is called the water-table. It can also be defined as the level at and below which soil particles are completely saturated. An Aquifer is a large body of permeable material where groundwater is present in the saturated zone. Hence, it is a water-bearing rock. Good aquifers have high permeability. Examples include poorly cemented sands, gravels, and sandstones or highly fractured rocks. Aquifers are of two types—Unconfined and Confined (Fig. 9.8a).To make a saturated solution of sodium chloride, find the solubility of sodium chloride in water, mix a solution of sodium chloride and water, and watch for saturation. The solubility of sodium chloride is 357 grams per 1 liter of cold wate...The unsaturated zone in the groundwater system is: a portion of the subsurface above the saturated zone where the pore space is not completely filled with groundwater. Why does subsidence sometimes take place when water is withdrawn from the groundwater supply?The unsaturated zone above the saturated zone extends to the surface. . Here the capillary force between pore water and the surfaces of the solid grains acts to pull groundwater upward from the water table against gravity, forming a zone of negative pressure and variable saturation, which is also referred as the “capillary zone”.Groundwater is one component of Earth's hydrologic cycle. Water is continuously transferred back and forth between Earth's different spheres. ... The saturated zone is where rocks are entirely saturated with water. If there is a significant and useable amount of water present in the saturated zone, it is called an aquifer.the saturated groundwater zone. Th us, overcoming the diffi culties and expanding the simula-tion capabilities of MODFLOW–MT3D solutions provided the basis for a comprehensive simulator that can be used for scop-ing studies as well as for detailed investigations. MODFLOW SURFACT achieves this by using the vadose zone fl ow andGroundwater is found in two zones. The unsaturated zone, immediately below the land surface, contains water and air in the open spaces, or pores. The saturated zone, a zone in which all the pores and rock fractures are filled with water, underlies the unsaturated zone. The top of the saturated zone is called the water table (Diagram 1).The saturated zone is a key player in the Earth's hydrologic cycle, the great cycle in which rainwater penetrates the earth to become groundwater that flows to the ocean, where it evaporates and becomes rainwater once more. Its depth below the surface, its overall depth, and its shape can place restrictions on both design and drilling operations.Mar 2, 2019 · Groundwater is simply the subsurface water that fully saturates pores or cracks in soils and rocks. Groundwater is replenished by precipitation and, depending on the local climate and geology, is unevenly distributed in both quantity and quality to nearby lakes, rivers, and wetlands. INFORMATION ON GROUNDWATER QUALITY AND QUANTITY The unsaturated zone above the saturated zone extends to the surface. . Here the capillary force between pore water and the surfaces of the solid grains acts to pull groundwater upward from the water table against gravity, forming a zone of negative pressure and variable saturation, which is also referred as the “capillary zone”.Imagine how much work it would be to lift water 8 meters high in the air. That is the energy that was lost to friction as the groundwater flowed from the top of the hill to the stream. Figure 11.6 A depiction of the water table in cross-section, with the saturated zone below and the unsaturated zone above. The water table is denoted with a ...Groundwater is merely freshwater present underneath the Earth’s surface between rock spaces or in saturated zones (Margat and Gun, 2013). Groundwater is found in two …2 days ago · Groundwater forms when precipitation, rain, snow, sleet, hail, or freezing rain soaks into the ground It settles into three main layers- the saturated zone, the water table, and the unsaturated zone. is recharged by precipitation Groundwater or ground water is water located within the ground's zone of saturation, where the soil pore spaces and fractures in the rock are completely ...Subsurface water is found in saturated and non-saturated zones in the ground. Groundwater is water that occurs in the zone of continuous saturation. Depending on its origin, groundwater can be meteoric water derived from the atmosphere through precipitation, juvenile water produced from within the Earth and brought to the surface by …Groundwater is simply the subsurface water that fully saturates pores or cracks in soils and rocks. Groundwater is replenished by precipitation and, depending on the local climate and geology, is unevenly distributed in both quantity and quality to nearby lakes, rivers, and wetlands. INFORMATION ON GROUNDWATER QUALITY AND QUANTITYThis graphic illustrates groundwater flow, two types of aquifers (confined and unconfined) and three types of wells (artesian; flowing artesian and a water ...The mean thickness of the saturated zone (=37.4 m) and the mean SWC in this zone were used to calculate the water stored in the saturated zone (referring to shallow groundwater resources). The mean saturated water content was determined from the 323 sites across the CLP as 0.34 m 3 m −3. The water stored in the saturated zone is, therefore ...The water-table fluctuation method uses fluctuations in groundwater levels over time to estimate recharge for unconfined aquifers; it is the focus of most of this chapter. Included in the discussion of the method are an analysis of mechanisms that can cause water-table fluctuations and a review of methods for estimating specific yield.This work extends the overlay and index methods for intrinsic groundwater vulnerability, that typically involve the soil surface and the vadose zone, to groundwater (saturated) transport. The method is “hybrid” as it combines the standard overlay and index methods with a simplified process-based approach for the groundwater component. For …in the saturated zone, the degree of saturation is equal to the porosity . primary porosity is the original proportion of void space ; secondary porosity includes the void space that develops with fracturing or solution or that is filled by precipitation and mineralization ; Groundwater flow in southeastern SaskatchewanPart 4: Groundwater terms and definitions . Groundwater refers to subsurface water, as distinct from surface water, specifically water in the saturated zone of an aquifer — the water stored underground in rock crevices and in the pores of geologic materials that make up the earth’s crust. Groundwater lies in the ground’s zone of ...For each zone, the geochemical features were characterized by low pH and high soil nutrients (e.g., TOC, TN, AP, humus) in the unsaturated zone (Fig. S2), whereas high pH and low nutrients were observed in the fluctuated zone and saturated zone, and some fluctuations were possibly caused by clay layer or groundwater table.For example, at the site characterized by Quinnan et al. , the saturated zone mass discharge is over 50 times higher than the unsaturated zone mass discharge (Table 1), indicating that the initial remediation priority might focus on controlling the groundwater plume rather than removing or controlling the unsaturated zone sources.Gravity pulls the water down through the spaces between particles of soil or through cracks in rocks. Eventually the water reaches a depth where all openings in soil or rock are filled with water; this is called the saturated zone. The water in the saturate zone is called groundwater. The top of the saturated zone is called the water table. The ...For groundwater the first research step was to develop the Saturated Unsaturated Flow and Transport in 3D (SUFT3D) groundwater model and to check its effectiveness and accuracy to reproduce typical situations of seawater intrusion and then groundwater-river interactions influenced by seawater intru- sion.The top of the saturated zone is called the _____. The water table rises and falls according to the season of the year and the amount of rain and snowmelt that occurs. It is typically higher in early Spring and lower in late Summer. Heavy rainfall or drought conditions may cause changes in the typical pattern, however.Area below the water table in which the soil is completely saturated with groundwater. Header link June 22, 2020. LinkedIn. Read more; Header link September 15, 2014. Cart. Read more; Header link November 3, 2015. Donate Now. ... Saturated Zone. Area below the water table in which the soil is completely saturated with groundwater. Print ...The upper part of the saturated zone remains either up to the point of saturation or is bounded by impervious levels. The lower part of saturated zone extends to the underlying impermeable rocks like bed rock or clay. In the absence of overlying impermeable rocks, upper level of saturated zone is called water table or groundwater level.Continuing its downward route through the unsaturated zone, it moves through the interconnected openings of sand, gravel, silt, and clay or openings in rock until it reaches the "saturated zone" where it becomes groundwater. For more groundwater basics, visit Aquifers and Groundwater (leaves DEC website) from the USGS. Misconceptions about ...Here, we reveal the long-term increase of temperatures in the groundwater beneath Cologne, Germany from 1973 to 2020. The rise in groundwater temperature trails atmospheric temperature rise in the rural areas and exceeds the rise in atmospheric temperature in the urban center. ... especially if these reach into the water-saturated zone [57 ...The water table is the boundary between the unsaturated zone and the saturated zone underground. Below the water table, groundwater fills any spaces between sediments and within rock. What is the saturated zone quizlet? Saturated zone. the part of the Earth where all the spaces and fractures of rocks are filled with water. Nothing.The water table is the boundary between the unsaturated zone and the saturated zone underground. Below the water table, groundwater fills any spaces between sediments and within rock. What is the saturated zone quizlet? Saturated zone. the part of the Earth where all the spaces and fractures of rocks are filled with water. Nothing.The groundwater is usually trapped above an impermeable soil layer, such as clay, and actually forms a lens of saturated material in the unsaturated zone. A perched water table is generally insufficient to supply domestic …The unsaturated zone above the saturated zone extends to the surface. . Here the capillary force between pore water and the surfaces of the solid grains acts to pull groundwater upward from the water table against gravity, forming a zone of negative pressure and variable saturation, which is also referred as the “capillary zone”.Groundwater is found in two zones. The unsaturated zone, immediately below the land surface, contains water and air in the open spaces, or pores. The saturated zone, a zone in which all the pores and rock fractures are filled with water, underlies the unsaturated zone. The top of the saturated zone is called the water table (Diagram 1).The quasi-saturated zone above the groundwater table reforms after the wetting front reaches the groundwater table. The formation of quasi-saturated zones is therefore induced by airflow pushing or water recharging, causing the pore-air pressure to exceed the matric suction; i.e., the pore-water pressure becomes positive. ...saturated zone is referred to as the water table. Water in the saturated zone below the water table is referred to as ground water. Below the water table, the water pressure is …In addition, Fig. 8 reveals that approximately great area of the porous media can be regarded as a saturated zone since the groundwater table is nearly close to surface and the vadose zone is not considerable; furthermore, in this configuration of soil layers, the top layer which has more hydraulic conductivity in comparison with the other ...Oct 19, 2023 · Underneath the water tableis the saturated zone, where water fills all spaces between sediments. The saturated zone is bounded at the bottom by impenetrable rock. The shape and height of the water tableis influenced by the land surface that lies above it; it curves up under hills and drops under valleys. groundwater. test your knowledge. Saturated Zone: section below the earth’s surface that is saturated with water. Water Table: boundary between unsaturated zone and saturated zone where most of the water is located. Water Quality: the level of cleanliness of water. Well: a hole dug or drilled into the earth’s surface to reach groundwater storedThe unsaturated zone is where (ideally) the concentration of all hazardous substances in any discharge is attenuated to below detectable levels before it enters groundwater (the saturated zone).When the soil zone becomes saturated, water percolates downward. A zone of saturation occurs where all the interstices are filled with water. There is also a zone of aeration where the interstices are occupied partially by water and partially by air. Groundwater continues to descend until, at some depth, it merges into a zone of dense rock.Introduction. Among the most widely used techniques for estimating recharge are those based on measurement of groundwater levels over time and space. The …The term groundwater usually refers to all subsurface water beneath the water table (the interface between the vadose and saturated zones, or the top of the saturated zone) in soils and geologic formations that are fully saturated. This definition excludes soil pore water in the vadose or unsaturated zone.In addition to anthropogenic factors, climate variability is a concurrent threat to the groundwater availability because it can alter the long-term aquifer and vadose zone water budget and can ...Overview Science Publications The ground stores huge amounts of water and it exists to some degree no matter where on Earth you are. Lucky for people, in many …Water in the saturated zone below the water table is called groundwater. ... Groundwater from aquifers can be brought to the surface by constructing bores or ...The water table marks the boundary between the unsaturated zone above and the saturated zone below, and corresponds to the height to which water will rise in a well in an unconfined aquifer. The position of the water table is not fixed, but instead migrates upward and downward in response to the dynamic balance between recharge (accumulation of ... Jun 6, 2018 · The tan area is the unsaturated zone, which is the top layer of the ground which gets saturated during a heavy rainfall, stays wet but not saturated, after a rainfall, and can become quite dry during times when no precipitation falls. This zone is the area that plants put down roots in, and thus draw water from. In some areas, it is difficult to locate the saturated zone because of rock formations or the extreme depths at which groundwater is located. Typically, there is a region above the saturated zone that contains some water in smaller pores, but larger pore spaces are not filled with water.Unsaturated Zone. The unsaturated zone is the portion of the subsurface above the groundwater table. The soil and rock in this zone contains air as well as water in its pores. In some places the unsaturated zone is absent, as is common where there are lakes and marshes, and in some places it is hundreds of meters thick, as is common in arid ...Aquifer. An aquifer is a term for a type of soil or rock that can hold and transfer water that is completely saturated with water. That means that all it is simply a layer of soil or rock that has a reasonably high porosity and permeability that allows it to contain water and transfer it from pore to pore relatively quickly and all of the pore spaces are filled with water.The water present in vadose zone is at or below atmospheric pressure. The unsaturated, vedose or aeration zone is further classified into three sub zones:-. a. Soil – water Zone: This begins at the ground surface and extends downward through the major root zone. Its total depth is variable and dependent upon soil type and vegetation.This is known as the zone of aeration. 3. The saturated zone lies below the zone of aeration and is the layer where the pores of the soil or rock are completely filled with water. 4. The groundwater table is the upper surface of the saturated zone. 5. Figure 12.9: The groundwater table: (a) intersects the land surface at lakes, marshes and streamsWater 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 ...This work extends the overlay and index methods for intrinsic groundwater vulnerability, that typically involve the soil surface and the vadose zone, to groundwater (saturated) transport. The method is “hybrid” as it combines the standard overlay and index methods with a simplified process-based approach for the groundwater component. For …Water table is the term for the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, [1] which may be fresh, saline, or brackish, depending on the locality. It can also be simply explained as the depth below which the ground is saturated.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 water/groundwater and sediments sampled at different depths during the experiment were analyzed to investigate the hydrochemical processes and correlations between As, Fe, and OM concentrations. Irrigation activities led to the accumulation of aqueous As in the saturated zone and increasing As content in the topsoil. Analyses of …Oct 10, 2018 · Groundwater is the area underground where openings are full of water. Groundwater is the saturated zone of soil/rock below the land surface. Groundwater might seem like magic to a youngster. Hot springs (Alaska) caused by geothermal activity underground. In 1942, groundwater levels were high enough to allow vegetation. Aquifers and Confining Layers. An aquifer is a geologic material capable of delivering water in usable quantities. Geologic material includes any rock or sediment. In order for a geologic material to be considered an aquifer, it must be at least partially saturated, where its open spaces are filled with water, and be permeable, i.e. able to transmit water. Oct 19, 2023 · 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 ... Uranium was mobilized in the saturated zone containing gypsum (gypsum-rich zone), the vadose zone (vadose-rich zone), ... Furthermore, groundwater co-contaminated by uranium and vanadium as a result of natural process and anthropogenic activities has also been reported frequently (Cinti et al., 2015). In an abandoned refinery at Grand Junction ...Initial Saturated Thickness of Aquifer: Thickness of the aquifer, or permeable layer that can contain or transmit groundwater, within the saturated zone measured from the seasonal high water table to the bottom of the aquifer. Note this saturated zone may be a localized or perched groundwater system rather than the regional groundwater system.Aquifers and Confining Layers. An aquifer is a geologic material capable of delivering water in usable quantities. Geologic material includes any rock or sediment. In order for a geologic material to be considered an aquifer, it must be at least partially saturated, where its open spaces are filled with water, and be permeable, i.e. able to transmit water.The vadose zone is the undersaturated portion of the subsurface that lies above the groundwater table. The soil and rock in the vadose zone are not fully saturated with water; that is, the pores within them contain air as well as water. The portion of the vadose zone that is inhabited by soil microorganism, fungi and plant roots may sometimes ... Gravity pulls the water down through the spaces between particles of soil or through cracks in rocks. Eventually the water reaches a depth where all openings in soil or rock are filled with water; this is called the saturated zone. The water in the saturate zone is called groundwater. The top of the saturated zone is called the water table. The ...What is a zoning map, how does it work, and why does it matter? This article explains what zoning maps are and how they are used. A zoning map shows the acceptable uses for property in a city or other area. Zoning information on these maps ...Groundwater refers to all subsurface water, specifically that part of groundwater which is in the saturated zone. Groundwater sources are called aquifers: geologic formations that contain sufficient saturated permeable material to yield significant quantities of water to wells and springs. For the purposes of the USGS water-use reports, groundwater with less than 1,000 milligrams per liter (mg ...Time of Travel (TOT): The time required for a particle of water to move in the saturated zone from a specific point to a well. A line can be drawn around the area for which groundwater is expected to reach the well within a chosen period. Transmissivity: A measure of the ability of an aquifer to transmit water. The rate at which water is ...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 ...
This graphic illustrates groundwater flow, two types of aquifers (confined and unconfined) and three types of wells (artesian; flowing artesian and a water .... Charlie basketball player
This work extends the overlay and index methods for intrinsic groundwater vulnerability, that typically involve the soil surface and the vadose zone, to groundwater (saturated) transport. The method is “hybrid” as it combines the standard overlay and index methods with a simplified process-based approach for the groundwater component. For …Groundwater in the unsaturated zone is the main carrier of solute transport, and solute is transported with the flow. Understanding and describing solute transport process in unsaturated zone is a key scientific problem in groundwater pollution control and river ecosystem restoration. ... (0≤k r ≤1); C=dθ/dh is the moisture content, which ...When the soil zone becomes saturated, water percolates downward. A zone of saturation occurs where all the interstices are filled with water. There is also a zone of aeration where the interstices are occupied partially by water and partially by air. Groundwater continues to descend until, at some depth, it merges into a zone of dense rock.The water-table fluctuation method uses fluctuations in groundwater levels over time to estimate recharge for unconfined aquifers; it is the focus of most of this chapter. Included in the discussion of the method are an analysis of mechanisms that can cause water-table fluctuations and a review of methods for estimating specific yield.The top of the saturated zone is called the water table, and sitting above the . water table is the unsaturated zone, where the spaces in between rocks and sediments are filled with both water and air. Water found in this zone is called soil moisture, and is distinct from groundwater.In this zone, the soil and rock are completely saturated with water, and groundwater is stored and moves through interconnected pores and fractures. In summary, the water table is the specific level at which the ground is saturated with water, while the zone of saturation refers to the entire area beneath the water table where all pores and ...As the summer season progresses, the saturated zone within the active layer tends to thicken as the thaw depth increases, which would increase groundwater flows ...The rate at which groundwater moves through the saturated zone depends on the permeability of the rock and the hydraulic head. The hydraulic head is defined as the difference in elevation between two points on the water table. The hydraulic gradient is the hydraulic head divided by the distance between two points on the water table.This is the zone from which plant roots draw water.The water table is the boundary between the unsaturated zone above and the saturated zone below. The saturated zone is where rocks are entirely saturated with water. If there is a significant and useable amount of water present in the saturated zone, it is called an aquifer.A perched water table (Figure 1) is an accumulation of groundwater that is above the water table in the unsaturated zone. The groundwater is usually trapped above an impermeable soil layer, such as clay, and actually forms a lens of saturated material in the unsaturated zone. A perched water table is generally insufficient to supply domestic ...Continuing its downward route through the unsaturated zone, it moves through the interconnected openings of sand, gravel, silt, and clay or openings in rock until it reaches the "saturated zone" where it becomes groundwater. For more groundwater basics, visit Aquifers and Groundwater (leaves DEC website) from the USGS. Misconceptions about ...The notion that groundwater pollution initiates as transport in the unsaturated zone, and the fact that common vadose zone methodologies have only limited ability to provide real-time alerts for pollution processes should push the research community to issue a clarion call to develop monitoring technologies for the unsaturated …The multiple redox conditions in partially-saturated VFCW have been reported to be favorable for the enrichment of microorganism associated with nitrification and denitrification, due to the existence of upper unsaturated layer (aerobic environment) and lower saturated zone (anaerobic/anoxic condition) (Pelissari et al., 2017a).Groundwater, which is in aquifers below the surface of the Earth, is one of the Nation's most important natural resources. Groundwater is the source of about 37 percent of the water that county and city water departments supply to households and businesses (public supply). ... The upper surface of the saturated zone is called the water table ...The mean thickness of the saturated zone (=37.4 m) and the mean SWC in this zone were used to calculate the water stored in the saturated zone (referring to shallow groundwater resources). The mean saturated water content was determined from the 323 sites across the CLP as 0.34 m 3 m −3. The water stored in the saturated zone is, …The underlying saturated (or phreatic) zone has spaces that are completely filled with water. The interface between the two zones is the groundwater table. Precipitation or melt water enters the ground and percolates downwards under the influence of gravity until it reaches either an impermeable layer or a preexisting saturated layer ….