Groundwater-Dependent Ecosystems (or GDEs) are

ecosystem An ecosystem (or ecological system) is a system formed by Organism, organisms in interaction with their Biophysical environment, environment. The Biotic material, biotic and abiotic components are linked together through nutrient cycles and en ...

s that rely upon

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

for their continued existence.

Groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

is water that has seeped down beneath Earth's surface and has come to reside within the pore spaces in soil and fractures in rock, this process can create

water table The water table is the upper surface of the phreatic zone or zone of saturation. The zone of saturation is where the pores and fractures of the ground are saturated with groundwater, which may be fresh, saline, or brackish, depending on the loc ...

s and

aquifer An aquifer is an underground layer of water-bearing material, consisting of permeability (Earth sciences), permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The s ...

s, which are large storehouses for

. An

is a community of living organisms interacting with the nonliving aspects of their environment (such as air, soil, water, and even

). With a few exceptions, the interaction between various

s and their respective

is a vital yet poorly understood relationship, and their management is not nearly as advanced as in-stream

Methods of identification

Isotopes

Examining the composition of stable

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

s in the water found in soil, rivers,

, and

xylem Xylem is one of the two types of transport tissue (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...

(or vein systems) of vegetation, using

mass spectroscopy Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used ...

, which measures and sort the masses in a sample, along with data on the changes in

depth coupled with the time and vegetative rooting patterns, shows spatial changes over time in the use of

by the vegetation in its respective

Plants

A groundwater-dependent ecosystem can also be inferred through plant water use and growth. In areas with high rainfall

reliance can be seen by monitoring the water use made by the plants of the

in relation to the water storage in the soil of the area. If the use of water in the vegetation exceeds that of the water being stored in the soil it is a strong indication of

utilization. In areas of prolonged drought the continuation of water flow and plant growth are highly indicative of a

reliant area.

Remote sensing/Geographical Information Systems (GIS)

Remote Sensing Remote sensing is the acquisition of information about an physical object, object or phenomenon without making physical contact with the object, in contrast to in situ or on-site observation. The term is applied especially to acquiring inform ...

is the scanning of Earth by

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

to obtain information.

GIS A geographic information system (GIS) consists of integrated computer hardware and software that store, manage, analyze, edit, output, and visualize geographic data. Much of this often happens within a spatial database; however, this is not ...

is a system designed to capture, store, analyze and manage

geographic Geography (from Ancient Greek ; combining 'Earth' and 'write', literally 'Earth writing') is the study of the lands, features, inhabitants, and phenomena of Earth. Geography is an all-encompassing discipline that seeks an understanding o ...

data. Together the data collected (such as

elevation The elevation of a geographic location (geography), ''location'' is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational equipotenti ...

and bore holes measuring groundwater levels) can very accurately predict where groundwater-dependent ecosystems are, how extensive they are, and can guide field expeditions to the right areas for further confirmation and data collection on the GDEs.

Classification

Due to the high variety of

s and their individual fluctuation in dependency on

there is some uncertainty when it comes to defining an

strictly as groundwater-dependent or merely groundwater-using. Each

expresses a varying degree of dependency. An

can be directly or indirectly dependent, as well as have a variation in

use throughout the seasons. There are a variety of methods for classifying types of groundwater-dependent ecosystems either by their

geomorphological Geomorphology () is the scientific study of the origin and evolution of topography, topographic and bathymetry, bathymetric features generated by physical, chemical or biological processes operating at or near Earth#Surface, Earth's surface. Ge ...

setting and/or by their respective

groundwater flow In hydrogeology, groundwater flow is defined as the "part of streamflow that has infiltrated the ground, entered the phreatic zone, and has been (or is at a particular time) discharged into a stream channel or springs; and seepage water."Cho ...

mechanism (deep or shallow).

Terrestrial

Arid to humid environments

Arid Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...

humid Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depe ...

terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...

environments with no standing water but deeply rooted vegetation relies upon

to support the producers of their

. The deeply rooted vegetation requires the

to maintain a consistent or semi-consistent level to allow for their continued health and survival.

Aquatic

Springs

Springs, arguably, rely the most heavily on the continued contribution of

because they are a natural discharge from relatively deep

flows rising to the surface. Springs are often in association with uniquely adapted plants and animals. Wetlands in Donana

Wetlands

Wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

s require a shallow discharge of

, it flows as a seepage into depressions in the land surface, in some instances

wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

s feed off of perched groundwater which is

separated from the regular

by an impermeable layer.

Marsh In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in genera ...

es are a type of

and though not directly reliant on

they use it as an area of recharge.

Bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and musk ...

s, are also a type of

that is not directly reliant on

but uses the presence of

to provide the area with recharge as well as

buoyancy Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...

Rivers

River A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...

s collect

groundwater discharge Groundwater discharge is the volumetric flow rate of groundwater through an aquifer. Total groundwater discharge, as reported through a specified area, is similarly expressed as: :Q = \fracKA where :''Q'' is the total groundwater discharge ( 3·T� ...

from

s. This can happen seasonally, intermittently or constantly, and can keep an area's water needs stable during a dry season.

Coastal

Lagoons/estuaries

Lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...

s and

estuaries An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

use

to help dilute the

salinity Salinity () is the saltiness or amount of salt (chemistry), salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensio ...

in the water and helps support their distinctly unique coastal

Threats

Extraction

The extraction of groundwater in both large and smaller amounts lowers the areas water table, and in too large of quantities can even collapse parts of the

and permanently damage the quantity of water the

can store.

Urbanization

Pollution

Due to the increase in populated areas

and other

aquatic ecosystem An aquatic ecosystem is an ecosystem found in and around a body of water, in contrast to land-based terrestrial ecosystems. Aquatic ecosystems contain communities of organisms—aquatic life—that are dependent on each other and on their environ ...

s face a greater threat of

pollution Pollution is the introduction of contaminants into the natural environment that cause harm. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the component ...

. In many cases groundwater can become polluted through

toxin A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...

s, or even just excessive amounts of certain

nutrient A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

s seeping down to the

. This polluting of the groundwater can have many different effects on the related

s in the case of an

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime enviro ...

Cape Cod Cape Cod is a peninsula extending into the Atlantic Ocean from the southeastern corner of Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer months. The ...

it was noted that an influx of new

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

had come from septic tank fields in the groundwater's flow path. Increased levels of

s can cause

eutrophication Eutrophication is a general term describing a process in which nutrients accumulate in a body of water, resulting in an increased growth of organisms that may deplete the oxygen in the water; ie. the process of too many plants growing on the s ...

which is the process of excessive introduction of

s causing an abundance of plant growth which can result in the death of a variety of aquatic life.

Recharge

Urbanization Urbanization (or urbanisation in British English) is the population shift from Rural area, rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. ...

of land has significant effects on

groundwater recharge Groundwater recharge or deep drainage or deep percolation is a hydrologic process, where water moves downward from surface water to groundwater. Recharge is the primary method through which water enters an aquifer. This process usually occurs in ...

deforestation Deforestation or forest clearance is the removal and destruction of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. Ab ...

and urbanizing limits the amount of surface area viable for water to actually

infiltrate Infiltration may refer to: Science, medicine, and engineering *Infiltration (hydrology), downward movement of water into soil *Infiltration (HVAC), a heating, ventilation, and air conditioning term for air leakage into buildings *Infiltration (me ...

and contribute to the

References

{{Reflist Hydrology Ecosystems Habitat