Coastal hydrogeology

Last updated
Sketch of an ocean basin indicating the study areas for terrestrial hydrogeology, coastal hydrogeology and marine hydrogeology. Modified from Wilson (2005). Coastal Hydrogeology modified.png
Sketch of an ocean basin indicating the study areas for terrestrial hydrogeology, coastal hydrogeology and marine hydrogeology. Modified from Wilson (2005).

Coastal Hydrogeology is a branch of Hydrogeology that focuses on the movement and the chemical properties of groundwater in coastal areas. Coastal Hydrogeology studies the interaction between fresh groundwater and seawater, including seawater intrusion, sea level induced groundwater level fluctuation, submarine groundwater discharge, human activities and groundwater management in coastal areas. [2] [3]

Contents

The freshwater-seawater interface is a dynamic boundary where freshwater mixes with seawater. [2] An interface in Coastal Hydrogeology refers to the location that freshwater from aquifer meets seawater. Steady freshwater-seawater interface is an equilibrium stage where the boundary locates in a relatively fixed location, while seawater intrusion or a strong recharge rate breaks the equilibrium, leading to an unsteady freshwater-seawater interface. [4] Mixing of groundwater and seawater creates a special chemical system that is a good indicator to show the interaction and the interface. [2]

Human activities such as pumping of groundwater and land reclamation break the equilibrium, leading to seawater intrusion, development of a seepage zone or pollution of the ocean. [5] [6] The interaction between groundwater system and the ocean is complex. Preventive actions and engineering measurements are adopted to mitigate the impacts.

Freshwater-Seawater Interface

Freshwater – Seawater interface or saltwater interface is an essential aspect in Coastal Hydrogeology that tries to figure out the location of the transition zone or mixing zone between freshwater and seawater. A sharp interface is formed when the transition zone is thin or narrow. [2] Coastal aquifers can be classified in the same three categories as all aquifer systems: Sedimentary Aquifers, Hard Rock Aquifers and Limestone Aquifers.

Types of aquifersDescription
Sedimentary AquifersSedimentary aquifers consist of different kinds of sediments including coarse-grained, fine-grained sediments and clay minerals. Permeability varies in these aquifers. [7] [8] Low-energy depositional environments and flat relief are common in coastal areas. Fine-grained sediments are common in the sea. Those sediments are less porous with low permeability. The permeability of this system drops towards the seaside. Water movement slows down with the change of permeability and the seawater-freshwater density. Igneous, sedimentary or metamorphic rocks can be the bedrock below the sedimentary aquifer system. [9] [10]
Hard Rock AquifersHard rock aquifers are composed of igneous rock or metamorphic rock or both. Low porosity hard rock with different orientation of joints and fractures provides space for the flow of groundwater, forming a hard rock aquifer. Groundwater flow direction is controlled by the orientation of fractures and geological structures like dykes. [11] [12]
Limestone AquifersA Limestone aquifer is an aquifer that is made of carbonate minerals namely marine limestone or bioclastic limestone. Fine-grained limestone has low porosity and permeability while bioclastic limestone is the antithesis. As groundwater may dissolve carbonates aquifer forming an extensive dissolution network which is a karst aquifer. [2] Water flows quickly and water can be stored in a karst aquifer. Groundwater would be rich in carbonic acid under a limestone or karst aquifer. [2] [13]

Ghijben – Herzberg Principle

The Ghijben – Herzberg Principle formulated the water table and the boundary of groundwater in an island or unconfined aquifer should form a lens-shape. This principle can estimate the bottom boundary of the interface which provides a general idea of the capacity of an aquifer. [14] By estimating the capacity of an aquifer, we can find out the available groundwater resource in some regions.

Freshwater-Seawater Interface in Coastal Aquifers

It is assumed that the aquifers below are homogeneous in the different models so that the hydraulic conductivity of each aquifer is uniform.

Types of AquifersIllustrationsDescription
Unconfined Continental Coastal Aquifer
Modified from Jiao and Post (2019) Unconfined coastal aquifer.png
Modified from Jiao and Post (2019)
 Groundwater replenishment of this type of aquifer can be either from rainfall or from terrestrial groundwater. The transition zone is inside the landmass. Due to the density difference between freshwater and seawater, the freshwater tends to flow upwards to the land surface.
Unconfined Continental Aquifer with Seepage zone
Modified Van der veer (1977) Unconfined aquifer with seepage coloured.png
Modified Van der veer (1977)
This aquifer system is similar to an unconfined continental coastal aquifer. There is a seepage zone in this case. Seepage would shift the interface towards the sea. The seawater within the seepage zone may have a slightly different chemical composition compared with seawater away from seepage zone.
Unconfined Circular Island Aquifer
Modified from Jiao and Post (2019). Unconfined island aquifer coloured.png
Modified from Jiao and Post (2019).
 Island is a case of an unconfined aquifer. As an island is surrounded by the sea, it is a coastal aquifer. Precipitation and infiltration recharge the groundwater with an island. If rainfall recharge of an island aquifer is significant, the seepage zone might form and shift the interface towards the sea. Ghijben – Herzberg Principle can be used to estimate the depth of groundwater. [16]
Confined Continental Coastal Aquifer
Modified from Oude Essink (1996) Confined aquifer coloured.png
Modified from Oude Essink (1996)
Regional groundwater flows can end up with confined aquifers in the coastal region and have an interface between seawater.
Confined Continental Coastal Aquifer with Seepage zone
Modified from Glover (1959) Confined aquifer with seepage coloured.png
Modified from Glover (1959)
Freshwater always flows into the sea. Forming seepage. If the hydraulic conductivity of the aquifer is low or the discharge of the aquifer is large, the seepage zone can push further to the sea.

The above figures simulate possible coastal aquifers. In reality, it is complex. Due to complex geology - non-uniform rock layers and weathering, both confined and unconfined aquifers can be found within a coast. It is possible to have multiple confined aquifers at the bottom and an unconfined aquifers at the top of a coast.

Seawater Intrusion

A: Horizontal seawater intrusion by pumping of water; B: Up-coning below a pumping well; C: Tide-driven and wave-driven seawater circulation in the inter tidal zone; D: Downward seawater intrusion due to flooding Seawater intrusion modified.png
A: Horizontal seawater intrusion by pumping of water; B: Up-coning below a pumping well; C: Tide-driven and wave-driven seawater circulation in the inter tidal zone; D: Downward seawater intrusion due to flooding

Seawater intrusion is a process where seawater intrudes into a freshwater aquifer. Natural or anthropogenic factors can cause seawater intrusion. [4] Salinization of a freshwater aquifer can be caused by the inflow of seawater due to a change in groundwater pressure, reduction in water recharge, reduction in groundwater discharge, or other sources of salt entering the aquifer. [19] The transition zone or the interface would shift either to the land or shift vertically. [2] Sea level rise, flooding or tsunami also leads to saltwater intrusion into the freshwater aquifer.

Pumping-Induced Saltwater Up-coning

Modified from Schmorak and Mercado(1969) Upward coning modified.png
Modified from Schmorak and Mercado(1969)

Pumping of groundwater from a well near the interface could cause seawater up-coning where seawater intrudes vertically to the aquifer. [21] [22] When the pumping rate exceeds the maximum pumping rate or critical pumping rate, seawater would be pumped out.

Effects of Heterogeneity and Anisotropy

Aquifers should be anisotropic and heterogeneous. A high permeability layer is associated with the freshwater flow. If the hydraulic conductivity of an aquifer in a vertical direction is lower than the horizontal direction, the transition zone would shift more in a horizontal direction. [23] [24]

Tides

Tides can push the transition zone towards the land and widen the transition zone. [25] [26] Tides can strengthen the freshwater seawater mixing due to dampening of the tidal pressure forming the non-uniform flow of groundwater. The greater the tidal amplitude, the greater the mixing effect. Less dampening in an aquifer would lead to a more uniform flow.

Other factors

Geological structures that cross-cut different layers such as faults or dykes can affect the direction and velocity of seawater intrusion. [27] Dykes, an igneous unit that is impermeable or low in hydraulic conductivity might stop the intrusion of seawater. [28] Faults also affect the direction of water flow which is studied by Fault Zone Hydrogeology. Both regular and catastrophic flooding can cause downward intrusion of seawater recreating the transition zone of the fresh-salt water. [29] Diffusion would also be responsible for seawater intrusion, as there is a net flow of solutes from high concentration to low concentration. [2] For example, a complete salinization of a 10 m thick layer of freshwater takes thousands of years through diffusion. Other factors can be pumping-induced seawater intrusion.

Submarine Groundwater Discharge

A sketch for the submarine groundwater discharge. Submarine groundwater discharge= meteoric water + freshwater from aquifers + recirculated seawater. Modified from Pacific Coastal and Marine Science Center (2021). SGD.png
A sketch for the submarine groundwater discharge. Submarine groundwater discharge= meteoric water + freshwater from aquifers + recirculated seawater. Modified from Pacific Coastal and Marine Science Center (2021).

Submarine groundwater discharge (SGD) is the groundwater flows across the interface of the aquifer and the sea. It refers to the flow of water shifting towards the sea. [31] Nearshore submarine groundwater discharge is defined as a range of 0 to 10 m, embayment SGD is defined as 10 m to 10 km and offshore SGD is defined as more than 10 km. [2] Topography, salinity and temperature convention and tidal pumping are responsible for the driving force for the submarine groundwater discharge. [26] [32]

Topography-Driven Flow

The topography and geology of an area affect the permeability and flow network of groundwater. [33] For an unconfined aquifer, groundwater discharges would be near shore and discharge decreases with the propagation towards the sea. [34] For confined aquifers, groundwater can flow further towards the sea to the embayment zone or even develop submarine springs. [35]

Groundwater Tidal Dynamics

A graph shows the groundwater level and sea level changes with respect to the tide on a small island in Portugal. The solid line represents the sea level change in the estuary and the dotted line is date from a piezometer that installed 50 m apart from the coastal line. It shows a time lag between the sea tide and the tide of groundwater. It indicates there is tide in the groundwater system. Modified from Erskine (1991) Tide of groundwater.png
A graph shows the groundwater level and sea level changes with respect to the tide on a small island in Portugal. The solid line represents the sea level change in the estuary and the dotted line is date from a piezometer that installed 50 m apart from the coastal line. It shows a time lag between the sea tide and the tide of groundwater. It indicates there is tide in the groundwater system. Modified from Erskine (1991)

Periodic sea level changes by tides would cause a fluctuation in the groundwater level of a coastal aquifer system. [37] The tidal signal of sea tides becomes more attenuated and delayed with increasing distance to the land. [2] Water level fluctuations in the wells can be caused by the degree of connection between the ocean and the aquifer; groundwater flows well connected to the sea; alternating loading and unloading of the sea tide leads to plastic deformation. [38] Tidal efficiency of the magnitude of the oscillation of water level in a well to the oscillation of sea level is about 42% to 44%. [39]  For example, if the magnitude of the oscillation of the sea level is 1 meter, the magnitude of the oscillation of water level will be 0.42 to 0.44 meter. However, the further away from the coast, the groundwater fluctuation would be lower.

Chemistry of Coastal Groundwater Systems

The coastal groundwater system consists of terrestrial (freshwater) groundwater, seawater and a mixture of two. Rainfall is the main source of the recharge of terrestrial groundwater. In the mixing zone, dilution occurs that results in the different chemical compositions of water there. [40] [41] [42] [43]

Salinity

Marine, natural terrestrial and anthropogenic terrestrial is the source of salinity. [2] The total dissolved solids (TDS) of the ocean are between 33 and 36.5 gl−1. The TDS of standard seawater at 25oC is 36gl−1. TDS of seawater would be lower near the coast as there is fresh water supply through a river. The charge in TDS of seawater can indicate the existence of groundwater supply, submarine spring and the transition zone. [44]

Table of Salinity Classes Based on Total Dissolved Solids (TDS) Concentrations [45] [46]
Classification of total dissolved solids (TDS)TDS (mg l−1)Description
Fresh0 – 1000Chemical is highly diluted. Drinking water.
Brackish1000-10000Evaporation of groundwater increases the chemical concentration of water. Or intrusion of seawater increases the chemical concentration of water. Water is too saline to be drinkable. [47]
Saline10000-36000Similar to seawater. Strong evaporation of groundwater or fully mixing with seawater.
Hyper-Saline36000-100000Strong evaporation on seawater or groundwater under a closed system.
Brine>100000Dissolution of rock salts or seawater being highly evaporated.

Electrical Conductivity

Electrical conductivity (EC) is another way to explain salinity. Electrical conductivity shows the ability of water to carry electrical current. Higher electrical conductivity reflects a higher concentration of dissolved ions. Electrical conductivity increases by 2% when the temperature increases by 1oC. [2]

Chemical Composition of Terrestrial Groundwater

Terrestrial groundwater is dominated by cations: potassium (K+), sodium (Na+), calcium (Ca+) and magnesium (Mg+) and anions: chlorine (Cl-), bicarbonate (HCO3-) and sulfate (SO42-). Each ion has a concentration of >1mgl−1. The chemical composition highly depends on the geology which is the composition of local rocks and the chemical composition of recharge sources like rainfall and rivers. Fresh groundwater is likely alkaline as there is calcium and magnesium. [2]

Chemical Composition of Seawater

Seawater is dominated by sodium (Na+) and chlorine (Cl-). The chemical composition of seawater has small variability between different oceans due to the long residence time which facilitates mixing. [48]

Chemical Processes in Coastal Aquifer

Chemical reactions in the coastal aquifer in a humid region. Modified Back et al. (1993) Chemical reaction at coast modified.png
Chemical reactions in the coastal aquifer in a humid region. Modified Back et al. (1993)

Physical and chemical reactions occur in coastal aquifers, including oxidation-reduction reactions, mineral dissolution and precipitation, acid-base reactions, ion exchange, and gases dissolution and exsolution. [50] [51] Those chemical processes also happen in terrestrial aquifer system. The rate of different chemical processes depend on temperature and pressure of different part of the aquifers. Rain is the major recharge for different aquifers. Thus, groundwater would be acidic. Groundwater becomes less acidic with increases flow path or flow distance. [49] [2]

Ion Exchange

Seawater mainly contains sodium and chlorine while fresh groundwater is dominated by calcium and bicarbonate. Cation exchange occurs in the transition zone given by the chemical equation:

Na++1/2Ca-X2 → 1/2Ca2++Na-X,

where X is the exchange site on the soil particles. [51] Compared to seawater, the water in the transition zone would have excess calcium and be depleted in sodium. Compare with fresh water, it is the opposite case. Other cations like magnesium and potassium exchange as well. Magnesium and calcium would be exchanged for sodium. [11]

A sketch explains the chemical evolution of groundwater in a coastal area. Modified from Back et al. (1993) Chemical evolution.png
A sketch explains the chemical evolution of groundwater in a coastal area. Modified from Back et al. (1993)

In a limestone aquifer, calcite dissolves due to the acidity of groundwater. With the presence of magnesium, dolomite may form in the transition zone. [52]

Mineral Dissolution and Precipitation

As rain is acidic, it dissolves different minerals. For example, rain dissolves calcite or dolomite inside the aquifer. [49] [52] In the transition zone where fresh groundwater meets seawater, dolomitization occurs due to abundant magnesium of seawater. Lead to precipitation of dolomite. [49] [52]

Reduction-Oxidation Reactions

Reduction-Oxidation reactions (Redox) takes place in the recharge areas where organic matter is available. [49] Oxygen dissolves into freshwater when rainfall or river penetrates soil with organic matter. [53] Oxygen may lost under redox reactions and microbiological processes. Oxidation of pyrite or sulphide minerals also consume the dissolved oxygen inside water. [53] Dissolved oxygen concentration level in groundwater decreases during long travel distance. Anaerobic conditions occur in deep confined aquifer. Under anaerobic conditions, sulphate reduction, methanogenesis and ferric iron reduction might occur. Leading to dissolve of iron, manganese, nitrogen dioxide, nitrogen, methane and hydrogen sulfide into groundwater. [54]

Chemical and Isotopic Indicators

The change in the chemical composition of groundwater is an indicator of seawater intrusion. It prevents the multi-sources of chloride, leading to a change in salinity of groundwater. Chemical concentration ratios including Na/Cl, Ca/Cl, Mg/Ca, Cl/Br, Ca/Mg and Cl/HCO3 can be used to distinguish the seawater intrusion. [2]

Standard seawaterFreshwater
RatioMolar ratioDescription
Na+/Cl-0.86 [55] In granitic and alkaline volcanic areas, the molar ratio of freshwater can reach 1.5-3. [51]
Mg2+/Ca2+4.5 -5 [48] In terrestrial fresh groundwater, the molar ratio <1. Limestone aquifer molar ratio =0.5-0.7. [56]
Br-/Cl-0.0015 [48] Br- concentration of seawater is greater than freshwater. [57]
Cl-/HCO-3318 [48] The Cl-/HCO-3 ratio of freshwater <2

Anthropogenic Impacts

Reclamation

This diagram tries to explain how an unconfined aquifer change after reclamation. Water divide and flow pattern to the aquifer change due to reclamation. Reclamation on a circular island coloured.png
This diagram tries to explain how an unconfined aquifer change after reclamation. Water divide and flow pattern to the aquifer change due to reclamation.

Land reclamation is a way to create flat land in coastal areas for coastal urban development. Reclamations affect regional groundwater flow systems, the location of groundwater discharge zones, seepage zones, groundwater divide, the interface between seawater and fresh groundwater and the water chemistry. [5] [2] It takes years to decades to reach a new equilibrium after reclamation. [5]

Reclamation – Chemical and Groundwater Change

Annotated diagrams show how the physical and chemical of groundwater change before, just after and after a long period of time reclamation. Pollutants may release out and pollute the groundwater. Modified from Jiao and Post (2019) Reclamation coloured.png
Annotated diagrams show how the physical and chemical of groundwater change before, just after and after a long period of time reclamation. Pollutants may release out and pollute the groundwater. Modified from Jiao and Post (2019)

Land-fill materials would change the equilibrium of the coastal areas. Land-fill materials interact with groundwater, seawater and marine sediments chemically and physically. Fill materials can be sand, completely weathered igneous rock or even waste. The placement of fill materials and diversity of fill materials can make the aquifer heterogeneous. [6] It is difficult to determine the chemical change in groundwater in a general way. It depends on the fill materials.

The groundwater discharge after reclamation decreases as the fill increases subsurface flow path length. As a result, the water level elevation in the upstream or attitude would rise. Rainfall recharges the new land and increases the storage capacity of the land. Increasing the water level and seaward groundwater discharge and shifting the water divide in the future. [5] Lengthening of the groundwater flow paths can dissolve the pollutants inside the marine mud and bring the pollutants to the ocean. [6]

Sea Level Changes to Coastal Hydrogeology

Water level and interface in an unconfined continental aquifer with a sloping shoreface after sea level rise with inundation. (Modified from Jiao and Post (2019)) Sea level rise in a unconfined system coloured.png
Water level and interface in an unconfined continental aquifer with a sloping shoreface after sea level rise with inundation. (Modified from Jiao and Post (2019))

Sea level rise and flooding would push the interface towards the land. Thus, seawater intrudes the land vertically and horizontally. [17] [58] A reduction in the recharge area leads to a reduction in the discharge of groundwater and groundwater level. [58] For islands, sea level rise would reduce the freshwater volume resulting in a smaller freshwater lens. Sea level rise also increases the coastal erosion rate leading to shoreline retreat. [59]

Seawater Intrusion Management

Seawater intrusion leads to social and economic loss. It is important to promote seawater intrusion management to prevent seawater intrusion including increases in freshwater recharge, pumping control, well design improvement, building barriers and land and water management. [60]

Increase of Freshwater Recharge

For areas that have sufficient fresh water supply, fresh water can be injected into the aquifers named aquifer storage and recovery (ASR). Apart from injection to pumping wells, infiltration basins or canals are used for infiltration and the replenishment of groundwater.

Well Design Improvements

A: horizontal pumping well; B: multiple pumping wells in well distributed; C: Radial wells, water is stored in the central tank; D: Seavenger well. Those well designs are expected to reduce the rate of up-coning. Modified from Sufi et al.(1988). Well designs coloured.png
A: horizontal pumping well; B: multiple pumping wells in well distributed; C: Radial wells, water is stored in the central tank; D: Seavenger well. Those well designs are expected to reduce the rate of up-coning. Modified from Sufi et al.(1988).

Improvements on the location and design of a well can minimize the effect of seawater intrusion. For example, building a well that is close to the water table, having a well that far away from the transition zone. Multiple wells with low pumping rate, horizontal pumping wells and radial wells can be built to reduce the chance of seawater intrusion. [61] As well as calculating the maximum pumping rate and critical pumping rate of a well. [61] Prevent the pumping rate from exceeding the limit which is over-pumping. [61]

Engineered Barriers

Types of barriers to control seawater intrusion. (A) Cut-off wall; (B) Injection well only; (C) Saltwater pumping only; (D) Pumping and injection wells (Pool and Carrera, 2010). Types of barriers to control seawater intrusion modified.png
Types of barriers to control seawater intrusion. (A) Cut-off wall; (B) Injection well only; (C) Saltwater pumping only; (D) Pumping and injection wells (Pool and Carrera, 2010).

Engineered barriers can be built to reduce freshwater flow to the sea and seawater intrusion into the aquifer. Engineered barriers can be hydraulic barriers or physical barriers. Hydraulic barriers operate by injecting fresh water into the well or pumping saltwater from the well. Water from rivers, precipitation, and treated wastewater can be injected into the well. The location of the injection well should be far away from the pumping well to prevent the neutralization of pumping and injection of water. Physical barriers are impermeable walls, that cut off the interaction between fresh groundwater and seawater. Cut-off walls have been built since the 1970s. [63] Slurry walls and grout walls are a type of cut-off walls. Slurry walls are made of water, soil and bentonite or concrete, forming an impermeable wall. [64] Grout walls are made of cement, bentonite or silicate reagents.

See also

Related Research Articles

<span class="mw-page-title-main">Aquifer</span> Underground layer of water-bearing permeable rock

An aquifer is an underground layer of water-bearing, permeable rock, rock fractures, or unconsolidated materials. Groundwater from aquifers can be extracted using a water well. Water from aquifers can be sustainably harvested through the use of qanats. Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude, which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could create a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer.

<span class="mw-page-title-main">Water table</span> Top of a saturated aquifer, or where the water pressure head is equal to the atmospheric pressure

The water table is the upper surface of the zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with water. It can also be simply explained as the depth below which the ground is saturated.

<span class="mw-page-title-main">Water extraction</span> Process of taking water from any source

Water extraction is the process of taking water from any source, either temporarily or permanently, for flood control or to obtain water for, for example, irrigation. The extracted water could also be used as drinking water after suitable treatment.

<span class="mw-page-title-main">Groundwater</span> Water located beneath the ground surface

Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.

<span class="mw-page-title-main">Hydrogeology</span> Study of the distribution and movement of groundwater

Hydrogeology is the area of geology that deals with the distribution and movement of groundwater in the soil and rocks of the Earth's crust. The terms groundwater hydrology, geohydrology, and hydrogeology are often used interchangeably.

Saltwater intrusion is the movement of saline water into freshwater aquifers, which can lead to groundwater quality degradation, including drinking water sources, and other consequences. Saltwater intrusion can naturally occur in coastal aquifers, owing to the hydraulic connection between groundwater and seawater. Because saline water has a higher mineral content than freshwater, it is denser and has a higher water pressure. As a result, saltwater can push inland beneath the freshwater. In other topologies, submarine groundwater discharge can push fresh water into saltwater.

Fossil water or paleowater is an ancient body of water that has been contained in some undisturbed space, typically groundwater in an aquifer, for millennia. Other types of fossil water can include subglacial lakes, such as Antarctica's Lake Vostok, and even ancient water on other planets.

The Floridan aquifer system, composed of the Upper and Lower Floridan aquifers, is a sequence of Paleogene carbonate rock which spans an area of about 100,000 square miles (260,000 km2) in the southeastern United States. It underlies the entire state of Florida and parts of Alabama, Georgia, Mississippi, and South Carolina.

<span class="mw-page-title-main">Edwards Aquifer</span> Source of drinking water in Texas

The Edwards Aquifer is one of the most prolific artesian aquifers in the world. Located on the eastern edge of the Edwards Plateau in the U.S. state of Texas, it is the source of drinking water for two million people, and is the primary water supply for agriculture and industry in the aquifer's region. Additionally, the Edwards Aquifer feeds the Comal and San Marcos Springs, provides springflow for recreational and downstream uses in the Nueces, San Antonio, Guadalupe, and San Marcos river basins, and is home to several unique and endangered species.

A dispersion is a system in which distributed particles of one material are dispersed in a continuous phase of another material. The two phases may be in the same or different states of matter.

<span class="mw-page-title-main">Groundwater recharge</span> Groundwater that recharges an aquifer

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. Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally and through anthropogenic processes, where rainwater and or reclaimed water is routed to the subsurface.

Submarine groundwater discharge (SGD) is a hydrological process which commonly occurs in coastal areas. It is described as submarine inflow of fresh-, and brackish groundwater from land into the sea. Submarine Groundwater Discharge is controlled by several forcing mechanisms, which cause a hydraulic gradient between land and sea. Considering the different regional settings the discharge occurs either as (1) a focused flow along fractures in karst and rocky areas, (2) a dispersed flow in soft sediments, or (3) a recirculation of seawater within marine sediments. Submarine Groundwater Discharge plays an important role in coastal biogeochemical processes and hydrological cycles such as the formation of offshore plankton blooms, hydrological cycles, and the release of nutrients, trace elements and gases. It affects coastal ecosystems and has been used as a freshwater resource by some local communities for millennia.

Overdrafting is the process of extracting groundwater beyond the equilibrium yield of an aquifer. Groundwater is one of the largest sources of fresh water and is found underground. The primary cause of groundwater depletion is the excessive pumping of groundwater up from underground aquifers.

Groundwater models are computer models of groundwater flow systems, and are used by hydrologists and hydrogeologists. Groundwater models are used to simulate and predict aquifer conditions.

Estuarine water circulation is controlled by the inflow of rivers, the tides, rainfall and evaporation, the wind, and other oceanic events such as an upwelling, an eddy, and storms. Estuarine water circulation patterns are influenced by vertical mixing and stratification, and can affect residence time and exposure time.

<span class="mw-page-title-main">Lens (hydrology)</span>

In hydrology, a lens, also called freshwater lens or Ghyben-Herzberg lens, is a convex-shaped layer of fresh groundwater that floats above the denser saltwater and is usually found on small coral or limestone islands and atolls. This aquifer of fresh water is recharged through precipitation that infiltrates the top layer of soil and percolates downward until it reaches the saturated zone. The recharge rate of the lens can be summarized by the following equation:

The State of California enforces several methodologies through technical innovation and scientific approach to combat saltwater intrusion in areas vulnerable to saltwater intrusion. Seawater intrusion is either caused by groundwater extraction or increased in sea level. For every 1-foot of freshwater depression (0.30 m), sea-salty waters rises 40 feet (12 m) as the cone of depression forms. Salinization of groundwater is one of the main water pollution ever produced by mankind or from natural processes. It degrades water quality to the point it passes acceptable drink water and irrigation standards.

Shirley Jean Dreiss (1949–1993) was an American scientist working in the fields of hydrology and hydrogeology. After gaining her PhD from Stanford University, she joined the faculty of the University of California at Santa Cruz, where she became Professor and Chair of the Department of Earth Sciences. She made important contributions to the understanding of water flow through karst aquifers and fluid flow in subduction zones. At the time of her early death in a car accident, she was studying the groundwater system of Mono Lake in California. She was awarded the Birdsall Distinguished Lectureship from the Geological Society of America, which was renamed the Birdsall-Dreiss Distinguished Lectureship after her death.

<span class="mw-page-title-main">Offshore freshened groundwater</span> Water located in the sub-seafloor

Offshore freshened groundwater(OFG) is water that contains a Total Dissolved Solid (TDS) concentration lower than sea water, and which is hosted in porous sediments and rocks located in the sub-seafloor. OFG systems have been documented all over around the world and have an estimated global volume of around 1 × 106 km3. Their study is important because they may represent an unconventional source of potable water for human populations living near the coast, especially in areas where groundwater resources are scarce or facing stress

An anchialine system is a landlocked body of water with a subterranean connection to the ocean. Depending on its formation, these systems can exist in one of two primary forms: pools or caves. The primary differentiating characteristics between pools and caves is the availability of light; cave systems are generally aphotic while pools are euphotic. The difference in light availability has a large influence on the biology of a given system. Anchialine systems are a feature of coastal aquifers which are density stratified, with water near the surface being fresh or brackish, and saline water intruding from the coast at depth. Depending on the site, it is sometimes possible to access the deeper saline water directly in the anchialine pool, or sometimes it may be accessible by cave diving.

References

  1. ↑ Wilson, Alicia M. (2005). "Fresh and saline groundwater discharge to the ocean: A regional perspective". Water Resources Research. 41 (2): 02016. Bibcode:2005WRR....41.2016W. doi:10.1029/2004WR003399. S2CID   129264765.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Jiao, J., & Post, V. (2019). Coastal hydrogeology. Cambridge University Press.
  3. ↑ Fisher, A. T. (2005). "Marine hydrogeology: recent accomplishments and future opportunities". Hydrogeology Journal. 13 (1): 69–97. Bibcode:2005HydJ...13...69F. doi:10.1007/s10040-004-0400-y. ISSN   1435-0157. S2CID   14334070.
  4. 1 2 Klassen, J., & Allen, D. M. (2017). Assessing the risk of saltwater intrusion in coastal aquifers. Journal of Hydrology (Amsterdam), 551, 730–745. doi : 10.1016/j.jhydrol.2017.02.044
  5. 1 2 3 4 Hu, L., & Jiao, J. J. (2010). Modeling the influences of land reclamation on groundwater systems: A case study in Shekou peninsula, Shenzhen, China. Engineering Geology, 114(3), 144–153. doi : 10.1016/j.enggeo.2010.04.011
  6. 1 2 3 Jiao, J.J. (2002). Preliminary conceptual study on impact of land reclamation on groundwater flow and contaminant migration in Penny’s Bay. Hong Kong Geology 8: 14–20.
  7. ↑ Jiao, JJ., Wang, Y., Cherry, J.A., Wang, X.S., Zhi, B.F., Du, H.Y. & Wen, D.G. (2010). Abnormally high ammonium of natural origin in a coastal aquifer-aquitard system in the Pearl River Delta, China. Environ Sci Technol 44: 7470–7475.
  8. ↑ Saha, Dipankar; Dwivedi, S. N.; Singh, Raj K. (2014). "Aquifer system response to intensive pumping in urban areas of the Gangetic plains, India: the case study of Patna". Environmental Earth Sciences. 71 (4): 1721–1735. doi:10.1007/s12665-013-2577-7. ISSN   1866-6299. S2CID   128744655.
  9. ↑ Anderson, H.R. (1978). Hydrogeologic Reconnaissance of the Mekong Delta in South Vietnam and Cambodia. US Government Printing Office, Washington, DC.
  10. ↑ Wang, Ya; Jiao, Jiu Jimmy (2012). "Origin of groundwater salinity and hydrogeochemical processes in the confined Quaternary aquifer of the Pearl River Delta, China". Journal of Hydrology. 438–439: 112–124. Bibcode:2012JHyd..438..112W. doi:10.1016/j.jhydrol.2012.03.008. ISSN   0022-1694.
  11. 1 2 Custodio, E., & Bruggeman, G. A. (1987). Groundwater problems in coastal areas : a contribution to the International Hydrological Programme. Unesco.
  12. ↑ Park, Hak-Yun; Jang, Kiyoung; Ju, Jeong Woong; Yeo, In Wook (2012). "Hydrogeological characterization of seawater intrusion in tidally-forced coastal fractured bedrock aquifer". Journal of Hydrology. 446–447: 77–89. Bibcode:2012JHyd..446...77P. doi:10.1016/j.jhydrol.2012.04.033. ISSN   0022-1694.
  13. ↑ Dreybrodt, Wolfgang (1988). Processes in Karst systems : physics, chemistry, and geology. Berlin: Springer-Verlag. ISBN   978-3-642-83352-6. OCLC   631758578.
  14. ↑ Verruijt, Arnold (1968). "A note on the Ghyben-Herzberg formula". International Association of Scientific Hydrology. Bulletin. 13 (4): 43–46. doi: 10.1080/02626666809493624 . ISSN   0020-6024.
  15. ↑ Van Der Veer, P. (1977). Analytical solution for steady interface flow in a coastal aquifer involving a phreatic surface with precipitation. Journal of Hydrology 34: 1-11
  16. ↑ Fetter, C.W. (1972). Position of saline water interface beneath Oceanic Islands. Water Resources Research. 8(5): 1307
  17. 1 2 Oude Essink, G.H.P. (1996). Impact of sea level rise on groundwater flow regimes: A sensitivity analysis for the Netherlands. Thesis, TU Delft, Delft University of Technology.
  18. ↑ Glover, R. E. (1959). "The pattern of fresh-water flow in a coastal aquifer". Journal of Geophysical Research. 64 (4): 457–459. Bibcode:1959JGR....64..457G. doi:10.1029/JZ064i004p00457.
  19. ↑ Comte, Jean-Christophe; Join, Jean-Lambert; Banton, Olivier; Nicolini, Eric (2014). "Modelling the response of fresh groundwater to climate and vegetation changes in coral islands". Hydrogeology Journal. 22 (8): 1905–1920. Bibcode:2014HydJ...22.1905C. doi:10.1007/s10040-014-1160-y. ISSN   1435-0157. S2CID   127484840.
  20. ↑ Schmorak, S., & Mercado, A. (1969). Upconing of fresh water – sea water interface below pumping wells, field study. Water Resource Research, 5: 1290–1311.
  21. ↑ Muskat, M. (1937). The flow of homogeneous fluids through porous media, by M. Muskat with an introductory chapter by R. D. Wyckoff. McGraw-Hill, 1937.
  22. ↑ Dagan, G., & Bear, J., (1968). Solving the problem of local interface upconing in a coastal aquifer by the method of small perturbations. Journal of Hydraulic Research6: 15–44.
  23. ↑ Kerrou, J., & Renard, P. (2010). numerical analysis of dimensionality and heterogeneity effects on advective dispersive seawater intrusion processes. Hydrogeology Journal, 18(1), 55–72. doi : 10.1007/s10040-009-0533-0
  24. ↑ Pool, M., Post, V. E. A., & Simmons, C. T. (2014). Effects of tidal fluctuations on mixing and spreading in coastal aquifers: Homogeneous case. Water Resources Research, 50(8), 6910–6926. doi : 10.1002/2014WR015534
  25. ↑ Underwood, M.R., Peterson, F.L., & Voss, C.I. (1992) Groundwater lens dynamics of Atoll Islands. Water Resources Research 28: 2889–2902.
  26. 1 2 Ataie-Ashtiani, B.; Volker, R. E.; Lockington, D. A. (1999). "Tidal effects on sea water intrusion in unconfined aquifers". Journal of Hydrology. 216 (1): 17–31. Bibcode:1999JHyd..216...17A. doi:10.1016/S0022-1694(98)00275-3. ISSN   0022-1694.
  27. ↑ Barker, Andrew P.; Newton, Robert J.; Bottrell, Simon H.; Tellam, J. H. (1998). "Processes affecting groundwater chemistry in a zone of saline intrusion into an urban sandstone aquifer". Applied Geochemistry. 13 (6): 735–749. Bibcode:1998ApGC...13..735B. doi:10.1016/S0883-2927(98)00006-7. ISSN   0883-2927.
  28. ↑ Comte, J.-C.; Wilson, C.; Ofterdinger, U.; González-Quirós, A. (2017). "Effect of volcanic dykes on coastal groundwater flow and saltwater intrusion: A field-scale multiphysics approach and parameter evaluation". Water Resources Research. 53 (3): 2171–2198. Bibcode:2017WRR....53.2171C. doi: 10.1002/2016WR019480 . hdl: 2164/9312 . S2CID   54654524.
  29. ↑ Villholth, K.G., & Neupane, B. (2011). Tsunamis as long-term hazards to coastal groundwater resources and associated water supplies. Tsunami – A Growing Disaster (Mokhtari M, ed.). InTechOpen, 87–104.
  30. ↑ Pacific Coastal and Marine Science Center. (2021) Submarine Groundwater Discharge. Retrieved from https://www.usgs.gov/centers/pcmsc/science/submarine-groundwater-discharge
  31. ↑ Burnett, W. C., Aggarwal, P. K., Aureli, A., Bokuniewicz, H., Cable, J. E., Charette, M. A., Kontar, E., Krupa, S., Kulkarni, K. M., Loveless, A., Moore, W. S., Oberdorfer, J. A., Oliveira, J., Ozyurt, N., Povinec, P., Privitera, A. M. G., Rajar, R., Ramessur, R. T., Scholten, J., … Turner, J. V. (2006). Quantifying submarine groundwater discharge in the coastal zone via multiple methods. The Science of the Total Environment, 367(2), 498–543. doi : 10.1016/j.scitotenv.2006.05.009
  32. ↑ Robinson, C.; Li, L.; Barry, D. A. (2007). "Effect of tidal forcing on a subterranean estuary". Advances in Water Resources. 30 (4): 851–865. Bibcode:2007AdWR...30..851R. doi:10.1016/j.advwatres.2006.07.006. ISSN   0309-1708.
  33. ↑ Fetter, C. W. (2001). Applied hydrogeology (4th ed.). Upper Saddle River, N.J.: Prentice Hall. ISBN   0-13-088239-9. OCLC   45058829.
  34. ↑ Fukuo, Yoshiaki; Kaihotsu, Ichirow (1988). "A theoretical analysis of seepage flow of the confined groundwater into the lake bottom with a gentle slope". Water Resources Research. 24 (11): 1949–1953. Bibcode:1988WRR....24.1949F. doi:10.1029/WR024i011p01949.
  35. ↑ Bakker, Mark (2006). "Analytic solutions for interface flow in combined confined and semi-confined, coastal aquifers". Advances in Water Resources. 29 (3): 417–425. Bibcode:2006AdWR...29..417B. doi:10.1016/j.advwatres.2005.05.009. ISSN   0309-1708.
  36. ↑ Erskine, A.D. (1991). The effect of tidal fluctuation on a coastal aquifer in the UK. Ground Water 29: 556–562.
  37. ↑ Jiao, Jimmy; Post, Vincent, eds. (2019), "Groundwater Tidal Dynamics", Coastal Hydrogeology, Cambridge: Cambridge University Press, pp. 73–103, doi:10.1017/9781139344142.004, ISBN   978-1-107-03059-6, S2CID   216621685 , retrieved 2022-11-16
  38. ↑ Veatch, A. C.-. (1906). Fluctuations of the water level in wells, with special reference to Long Island, New York, by A.C. Veatch. Govt. Print. Off., 1906.
  39. ↑ Steggewentz, J.H. (1933). De invloed van de getijbeweging van zeeën en getijrivieren op de stijghoogte van grondwater. Thesis, Technische Hoogeschool, Delft.
  40. ↑ Deusdará, K. R. L.; Forti, M. C.; Borma, L. S.; Menezes, R. S. C.; Lima, J. R. S.; Ometto, J. P. H. B. (2017). "Rainwater chemistry and bulk atmospheric deposition in a tropical semiarid ecosystem: the Brazilian Caatinga". Journal of Atmospheric Chemistry. 74 (1): 71–85. Bibcode:2017JAtC...74...71D. doi:10.1007/s10874-016-9341-9. ISSN   1573-0662. S2CID   99075204.
  41. ↑ Vengosh, A.; Rosenthal, E. (1994). "Saline groundwater in Israel: its bearing on the water crisis in the country". Journal of Hydrology. 156 (1): 389–430. Bibcode:1994JHyd..156..389V. doi:10.1016/0022-1694(94)90087-6. ISSN   0022-1694.
  42. ↑ Aswathanarayana, U. (2001). Water resources management and the environment. Balkema.
  43. ↑ Silva, B.; Rivas, T.; García-Rodeja, E.; Prieto, B. (2007). "Distribution of ions of marine origin in Galicia (NW Spain) as a function of distance from the sea". Atmospheric Environment. 41 (21): 4396–4407. Bibcode:2007AtmEn..41.4396S. doi:10.1016/j.atmosenv.2007.01.045. ISSN   1352-2310.
  44. ↑ McClatchie, Sam; Middleton, John F.; Ward, Tim M. (2006). "Water mass analysis and alongshore variation in upwelling intensity in the eastern Great Australian Bight". Journal of Geophysical Research. 111 (C8): C08007. Bibcode:2006JGRC..111.8007M. doi: 10.1029/2004JC002699 . ISSN   0148-0227.
  45. ↑ Post, V.E.A., Eichholz, M., & Brentführer, R. (2018). Groundwater Management in Coastal Zones. Federal Institute for Geosciences and Natural Resources, Hannover, Germany.
  46. ↑ "Saline Water and Salinity | U.S. Geological Survey". www.usgs.gov. Retrieved 2022-10-06.
  47. ↑ "Salinity and drinking water". Government of South Australia: SA Health. SA Health. Retrieved 2022-11-26.
  48. 1 2 3 4 Millero, F. J., Feistel, R., Wright, D. G., & McDougall, T. J. (2008). The composition of Standard Seawater and the definition of the Reference-Composition Salinity Scale. Deep-Sea Research. Part I, Oceanographic Research Papers, 55(1), 50–72. doi : 10.1016/j.dsr.2007.10.001
  49. 1 2 3 4 5 6 Back, W., Baedecker, M. J., & Wood, W. W. (1993). Hydrogeology: A Historical Perspective. Regional ground-water quality, 111.
  50. ↑ Stumm, W., & Morgan, J. J. (1996). Aquatic chemistry chemical equilibria and rates in natural waters (3rd ed.). Wiley.
  51. 1 2 3 Appelo, C.A.J., & Postma, D. (2005). Geochemistry, Groundwater and Pollution. A. A. Balkema, London.
  52. 1 2 3 Hanshaw, B. B., Back, W., & Deike, R. G. (1971). A geochemical hypothesis for dolomitization by ground water. Economic Geology, 66(5), 710-724.
  53. 1 2 Abesser, C., Shand, P., & Ingram, J. (2005). Millstone Grit of Northern England. Baseline Report Series 18. Environment Agency, Bristol, UK.
  54. ↑ Chapelle, Frank (2001). Ground-water microbiology and geochemistry (2nd ed.). New York, N.Y.: Wiley. ISBN   0-471-34852-X. OCLC   44267732.
  55. ↑ Jones, B. F.; Vengosh, A.; Rosenthal, E.; Yechieli, Y. (1999), Bear, Jacob; Cheng, Alexander H.-D.; Sorek, Shaul; Ouazar, Driss (eds.), "Geochemical Investigations", Seawater Intrusion in Coastal Aquifers — Concepts, Methods and Practices, Dordrecht: Springer Netherlands, pp. 51–71, doi:10.1007/978-94-017-2969-7_3, ISBN   978-94-017-2969-7 , retrieved 2022-11-26
  56. ↑ Rosenthal, E. (1987). Chemical composition of rainfall and groundwater in recharge areas of the Bet Shean-Harod multiple aquifer system, Israel. Journal of Hydrology (Amsterdam), 89(3), 329–352. doi : 10.1016/0022-1694(87)90185-5
  57. ↑ Alcalá, Francisco J.; Custodio, Emilio (2008). "Using the Cl/Br ratio as a tracer to identify the origin of salinity in aquifers in Spain and Portugal". Journal of Hydrology. 359 (1): 189–207. Bibcode:2008JHyd..359..189A. doi:10.1016/j.jhydrol.2008.06.028. ISSN   0022-1694.
  58. 1 2 Barlow, P. M. (2003). Ground water in freshwater-saltwater environments of the Atlantic Coast / by Paul M. Barlow. U.S. Dept. of the Interior, U.S. Geological Survey, 2003.
  59. ↑ Intergovernmental Panel on Climate Change, ed. (2014), "Coastal Systems and Low-Lying Areas", Climate Change 2014 – Impacts, Adaptation and Vulnerability: Part A: Global and Sectoral Aspects: Working Group II Contribution to the IPCC Fifth Assessment Report: Volume 1: Global and Sectoral Aspects, Cambridge: Cambridge University Press, vol. 1, pp. 361–410, doi:10.1017/cbo9781107415379.010, ISBN   978-1-107-05807-1 , retrieved 2022-11-26
  60. ↑ Abarca, Elena; Vázquez-Suñé, Enric; Carrera, Jesús; Capino, Bernardo; Gámez, Desiré; Batlle, Francisco (2006). "Optimal design of measures to correct seawater intrusion". Water Resources Research. 42 (9). Bibcode:2006WRR....42.9415A. doi:10.1029/2005WR004524. S2CID   108654361.
  61. 1 2 3 4 Sufi, A.B.; Latif, M.; Skogerboe, G.V. (1998). "Simulating skimming well techniques for sustainable exploitation of groundwater". Irrigation and Drainage Systems. 12 (3): 203–226. doi:10.1023/A:1006085700543. ISSN   1573-0654. S2CID   107912544.
  62. ↑ Pool, María; Carrera, Jesús (2010). "Dynamics of negative hydraulic barriers to prevent seawater intrusion". Hydrogeology Journal. 18 (1): 95–105. Bibcode:2010HydJ...18...95P. doi:10.1007/s10040-009-0516-1. ISSN   1435-0157. S2CID   129409675.
  63. ↑ Japan Green Resources Agency (2004) Technical Reference for Effective Groundwater Development. Kanagawa, Japan.
  64. ↑ Paul, D. B., & Davidson, R. R. (1992). Slurry walls: Design, construction, and quality control (Vol. 4). ASTM International.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.