Aquifer

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An aquifer , formerly also the groundwater horizon or groundwater carrier , is a rock body with cavities that is suitable for the conduction of groundwater .

Definition of terms aquifer and groundwater aquifer (in Germany)

The term aquifer ( lat. Aquifer "water- carrying " or "water carrier" from aqua water and ferre carry), which was adopted from the English-speaking area, has meanwhile also experienced a wide spread , but it has not been included in the hydrogeological definition of the German DIN 4049- 3 taken over. Although in parts of the German professional world mostly used as a synonym for the aquifer, an aquifer originally referred to a sequence of layers or parts thereof suitable for the discharge of significant amounts of water. This includes water in the unsaturated zone , which is not the case in the definition of groundwater valid for Germany. In contrast to an aquifer, an aquifer therefore only extends over the saturated zone. It follows that both terms can only be used as synonyms in individual cases. However, it can be assumed that when the term aquifer is used in German-speaking countries, an aquifer is meant.

Types of aquifers and properties

There are three types of aquifers:

  1. Pore ​​aquifers consist of loose or solid rock, the pore space of which is traversed by groundwater
  2. Fissured aquifers consist of solid rock, they contain fissures and rock joints that affect the flow
  3. Karst aquifers consist of karstified carbonate rocks with flow-effective karstings

An aquifer is geologically bounded by impermeable layers (e.g. clays) called aquifuge .

Knowing them and exploring them is important for the production of drinking water (see also dewatering ) and the influence of mining on the groundwater (open pit drainage).

The most important property of an aquifer is its transmissivity .

Terms and types

Cross-section through a typical aquifer

A groundwater non- conductor is a body of rock that does not conduct groundwater . A low conductor, on the other hand, has a very low permeability coefficient , whereby the transition to a non-conductor is defined fluently. An area that delimits the aquifer with poor permeability is an aquifer. Common to all of these are mostly small grain sizes and low porosity . The English terms are Aquiclude for the non-conductor and Aquitarde for the low conductor.

A groundwater body is a groundwater resource that can be clearly defined spatially, whereas the groundwater space denotes the rock body filled with groundwater. The groundwater thickness is defined as the perpendicular distance between the groundwater surface and the groundwater bed, i.e. between the upper and lower limit of the groundwater body.

Furthermore, a distinction is made between constrained and unconstrained aquifers, which are defined by the relative position of the groundwater surface and the groundwater pressure surface. The groundwater pressure area is the area up to which the water would rise according to its hydrostatic pressure in a free well. In so far as this area corresponds to the groundwater surface, it is an unconstrained or free aquifer. However, if the rise in the groundwater is prevented by a non-conductive or poorly conductive layer before the pressure surface is reached, then there is a confined aquifer. This distinction has a significant effect on the behavior of an aquifer when installing groundwater measuring points as well as carrying out pumping tests and the ultimate groundwater extraction.

Artesian aquifers form a special case of the confined aquifer, where the pressure surface is above the ground and the groundwater would thus form a source under unconstrained conditions (e.g. through a borehole).

Use, risks

storage

Warmth, cold

Aquifers can be used to store thermal energy in the long term and thus make it available for heating or cooling buildings. For this purpose, warm water from an aquifer z. B. used in winter to heat buildings and cools down. This cooled water is fed back into the aquifer and can then be used to cool the building in summer. When cooling the building, the water can also be used afterwards, e.g. B. heated by solar panels and stored again in the aquifer. For this process, at least two wells, an intake and an extraction well, are required, which change their function depending on the season.

In non-volcanic areas, the underground temperatures can be very different. To obtain heat from an aquifer, deeper boreholes are usually necessary: ​​temperatures above 100 ° C are required for economical electricity generation. If these are present, water can be pumped, cooled and reinjected. One then speaks of hydrothermal geothermal energy .

CO 2

Storage in aquifers far below a usable groundwater depth (from a depth of 900 meters) is seen as an intermediate technology for avoiding CO 2 emissions during energy generation due to the limited storage potential.

In contrast to the sequestration period in oceans (up to 10,000 years), a storage period of over 1 million years can be expected. Storage in the oceans, however, harbors enormous ecological dangers if a storage bubble does penetrate the surface.

Extraction of raw materials

natural gas

The solubility of a gas in a liquid increases with increasing pressure and decreases with increasing temperature. The solubility decreases due to the increasing temperature in increasing depth. In the sum of both effects, the water held in rock pores (formation water ) can bind larger amounts of gas with increasing depth. When the pressure is relieved, part of the gas is released and either escapes into the atmosphere as free gas or, if the geological-structural conditions are suitable, is trapped in storage facilities. The part remaining in the formation water is called aquifer gas. The main problem with mining is land subsidence , as observed in Japan and Italy . However, this can be countered by reinjection of the degassed water.

Drinking water

(Drinking) water from a tap
An ultrafiltration system for drinking water treatment

Only around 1% of the world's fresh water is usable for humans - this corresponds to around 0.007% of the total ( salt , fresh, etc.) water that occurs on earth at all.

The share of 2.5% fresh water in global water resources is 68.7% as "bound water" in the ice layers of the polar ice caps , the remaining 31.3% is distributed in aquifers or is stored as soil moisture .

Across the world, aquifers are used to a large extent for the production of drinking water . If the extraction exceeds the inflow, or if non-renewable fossil water is used, sustainable and permanent use is not given.

Approx. 25% of the world's population get their drinking water from karst aquifers. The Institute for Applied Geosciences at the Karlsruhe Institute of Technology (KIT) published as a project of IAH Karst Commission ( International Association of Hydrogeologists ) in September 2017 at the 44th annual congress of the IAH in Dubrovnik in addition to the 2000 published groundwater - World Map (WHYMAP, World-wide Hydrogeological Mapping and Assessment Program ) together with the Federal Institute for Geosciences and Natural Resources (BGR) and UNESCO a " World Karst Aquifer Map ".

In drinking water treatment , methods for enriching the groundwater are used in some cases: surface water is often re-infiltrated into the aquifer in order to use the cleaning effect (demanganisation, iron removal, biological degradation) of the subsoil. However, pollutants can also enter the soil as a result. These pollutants then have to be used again in the further process of drinking water treatment. B. be eliminated by activated carbon filters . In order to keep the pollution as low as possible, the water infiltrated into the aquifer is often pretreated.

irrigation

An irrigation canal

The use of non-renewable water for agricultural irrigation is very controversial from an economic and ecological point of view.

Water level of the Ogallala Aquifer near Morton, Kansas, USA: has fallen by approx. 25 m in 15 years
Water level of the Ogallala aquifer near Seward / Kansas, USA: dropped by approx. 20 m over 15 years during the observation period

The Ogallala aquifer in Central North America was used for agricultural irrigation from 1911. As the amount of water withdrawn soon exceeded the amount of water flowing in, the water level began to drop rapidly. According to current estimates, the ratio of withdrawn to supplied water is around 25, which means that for every 25 liters of withdrawn water, only one liter of new water flows in through infiltration, and in some places the water level has dropped by up to 1.50 meters per year measured. Some parts of the aquifer are therefore already waterless today; if this drying up continues, agriculture in the area could become impossible in the medium term. Some rivers in the region are also sometimes deeper than the groundwater level, which also removes water from the aquifer. The magnitude of such a drop in the water level becomes even clearer if one takes into account the extent of this aquifer (see table below).

The use of fossil groundwater is extremely problematic. In western Egypt, after the artesian springs had dried up, the Nubian aquifer was tapped in some oases ( Bahariya , Farafra , Abu Minkar , Dahkla and Kharga ) . In this region, due to the prevailing hyperarid climate, there is almost no new groundwater formation rate. Due to the heavy use of groundwater resources, the groundwater level of the Nubian aquifer fell by around 60 m by 2009.

In the north-west Indian aquifers in the New Delhi area , in Punjab and in the Indian states of Haryana and Rajasthan , the water level has fallen by more than 30 centimeters per year over the past six years (2009); the loss is over 100 km³. Across the country, the area of ​​irrigated arable land tripled between 1970 and 1999. According to a study by the nature conservation organization WWF , Indian farmers use 400 km³ of water annually to irrigate their fields. Only 150 km³ of this comes from precipitation, the rest comes from aquifers.

In California's Central Valley (California Central Valley) approximately 20 cubic kilometers of groundwater have been lost due to intensive agricultural use.

pollution

Garbage dump in Bliesendorf , 1990

Many groundwater bodies worldwide are subject to enormous pollution from industry and agriculture. B. from direct discharges of sewage or cooling water or from indirect inputs such as the seepage of spray and fertilizers. Responsible use of the environment (for example, organic farming can significantly reduce nitrate pollution) is reflected in the reduction in pollution of the groundwater. The main problem is that contaminants can be stored for decades or longer and will therefore be effective for a long time to come.

arsenic

In many regions of the USA, South America and Asia, very high concentrations of arsenic occur in the groundwater. Excessive values ​​also occur in Europe, especially in Great Britain. In Germany, the groundwater in the Black Forest is contaminated with arsenic in places.

salt

De-icing salt

A study presented in the winter of 2014 by the American Cary Institute for Ecosystem Studies in Milbrook shows that the salt pollution from road salt in rivers and lakes in southeast New York state is almost the same and unexpectedly high in summer and winter. It assumes that de-icing salt loads that have entered the aquifers over decades are reflected in the increase in salt concentrations in surface waters and drinking water wells . In the cool and snowy Michigan , changes in the specific water densities were found in two of the lakes investigated, with a resulting hindrance to the circulation between the water layers . In one of the lakes there was no longer any mixing at all: there was an oxygen-free and very salty, constant layer of water close to the ground with corresponding changes in flora and fauna .

Potassium chloride (potash salt)

In the southern German-French Upper Rhine aquifer, there are in some cases considerable loads from salt input from spoil heaps and old storage basins from the mining of potash that has been abandoned here.

Salt water intrusion

In the course of the “ salt water intrusion ”, salt water naturally penetrates into the sea near fresh water sources due to the different density of fresh and salt water. Changes in the water level, e.g. B. as a result of constant overuse of freshwater resources by humans can seriously disturb the natural balance that has grown. An example of this is the Chicot Aquifer on the Gulf Coast of the United States of America, part of the Gulf Coast Aquifer .

nitrate

In people with atypical intestinal flora and in infants in the intestine, nitrate can be converted to nitrite , which is toxic. In addition, nitrate is viewed as an indicator of undesirable nitrogen-containing organic pollution.

Anthropogenic increased nitrate content in groundwater is a phenomenon known worldwide, which usually occurs in densely populated areas and is caused by intensive agriculture ( nitrogen or manure fertilization ). Certain soils allow more nitrate to seep through, and dry periods associated with climate change (in which plants absorb less nitrate) increase the entry through the connoted heavy rain with increased leaching. In order to determine nitrate inputs from the soil-plant system into the groundwater, a deterministic nitrate displacement model is sometimes used, which calculates the mean nitrogen input from the area. The limit value for drinking water in the European Union is currently (2010) 25 mg / l.

Even in unpopulated, semi-arid areas, increased nitrate levels in groundwater can occur that are not due to anthropogenic influences and are therefore caused by natural processes. In the countries of southern Africa ( Republic of South Africa , Namibia , Botswana ) local nitrate concentrations of up to 600 mg / l are found, which are considerably above the limit value of the World Health Organization (WHO) of 50 mg / l. It has not yet been clearly clarified where the causes of these increased nitrate levels lie.

Sustainable use strategies

Limitation of water consumption

Some public water suppliers have started to support water-saving technologies and installations also for end users in the form of advisory services and financial subsidies in order to reduce water consumption. This can make a lasting contribution to the stabilization of groundwater resources and water quality.

Keeping things clean through ecological forestry and agriculture

With its waterworks, the city ​​of Munich has been supporting farmers in the area on a large scale who are converting to organic farming . In this way, the nitrate pollution, which had risen sharply at the end of the 1960s, was stabilized at a medium level and the groundwater obtained could be sent to Munich without further treatment.

Transparency about material flows

As part of a “ farm gate balance ”, industrial fattening farms are supposed to provide a balance sheet for the nutrients they use. B. residues emitted via slurry application become possible.

Comparison of large aquifers worldwide

In April 2015, UNESCO and the German Federal Institute for Geosciences and Natural Resources (BGR) presented a world groundwater map at the seventh World Water Forum in Daegu, South Korea .

To the table, for comparison: Researchers last estimated (March 2017) the volume of all lakes worldwide at almost 200,000 cubic kilometers.

Name of the aquifer Expansion / km² Length / km Width / km Volume / km³ Max. Depth / m approximate thickness / m Age / years geology geography
Aquífero Alter do Chão 86,000 Brazil : states of Amazonas , Pará and Amapá
Acuífero Guaraní 1,200,000 1,500 1,500 South America : Argentina , Brazil , Paraguay , Uruguay
Great Artesian Basin (Great Artesian Basin) 1,711,000 64,900 3,000 50-250 million Australia
Upper Rhine aquifer 45 on average 70, up to 260 Debris / debris filling Germany: Upper Rhine Graben , South Baden , France ( Alsace )
Nubian Sandstone Aquifer (Nubian Sandstone Aquifer) 2,000,000 373,000 up to 4,500 90 4,500-5,000 Fossil water Middle East : Egypt , Libya , Sudan , Chad
Ogallala aquifer 450,000 122 160 approx. 5 million North America : Great Plains
for comparison: Lake Constance 536 63 14th 48 250 3 million fluvioglacial eroded tongue basin or glacier edge lake from the Würm Ice Age in the course of the Rhine river. Germany: South Baden
for comparison: Hornberg basin 0.17 0.7 0.3 0.44 65 1974 artificially created pumped storage power plant - upper basin Germany: South Baden
for comparison: Lake Baikal (20% of the free fresh water) 31,500 636 80 23,000 1,642 25-30 million River basin of the Angara between the Baikal Mountains Russia ( Asia ): Siberia
for comparison: Three Gorges Reservoir 1,085 660 39 about 110 Completion 2008 artificial reservoir for energy over the course of the Yangtze -Flusses China

Other large aquifers worldwide

Further cross-national examples

See also

literature

  • DIN 4049-3 - Hydrology, Part 3: Terms for quantitative hydrology.
  • Hanspeter Jordan, Hans-Jörg Weder: Hydrogeology. Basics and methods . 2., heavily revised. u. exp. Edition. Spectrum Academic Publishing House, 1995, ISBN 3-432-26882-3 .
  • Bernward Hölting, Wilhelm Georg Coldewey: Hydrogeology. Introduction to General and Applied Hydrogeology . 6th edition. Spectrum academic publishing house, Munich 2005, ISBN 3-8274-1526-8 .
  • Wolfgang Kinzelbach, Randolf Rausch: Groundwater modeling: an introduction with exercises . Borntraeger, 1995, ISBN 3-443-01032-6 .
  • R. Allan Freeze, John A. Cherry, Alan R. Freeze: Groundwater . 5th edition. Prentice Hall, 1979, ISBN 0-13-365312-9 .

Web links

Wiktionary: Aquifer  - explanations of meanings, word origins, synonyms, translations
General
For irrigation from aquifers
For CO 2 storage in aquifers
For generating energy from aquifers

Individual evidence

  1. ↑ Glossary - terms clearly explained: Aquifer ( Memento of the original from January 20, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , stoltenberg-energie.de  @1@ 2Template: Webachiv / IABot / www.stoltenberg-energie.de
  2. ↑ VDI-Nachrichten 42, October 19, 2007, Carla Regge: Store energy in aquifers - Neubrandenburg saves excess heat from the thermal power station at a depth of 1,250 m  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , eflocon.de, October 3, 2010@1@ 2Template: Dead Link / www.eflocon.de  
  3. ↑ MC Grimston, V. Karakoussis, R. Fouquet, R. van der Vorst, P. Pearson, M. Leach: The European and global potential of carbon dioxide sequestration in tackling climate change . In: Climate Policy . tape 1 , no. 2 , 2001, p. 155-171 , doi : 10.3763 ​​/ cpol.2001.0120 .
  4. ↑ Department of Hydrology and Water Management at Christian-Albrechts-Universität Kiel , Seminar Regional Water Management , SS / 2005, July 2005, Freya-Elisabeth Hensgens: Water supply and wastewater disposal of megacities ( Memento of the original from April 20, 2006 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , P. 1, .1, Introduction: Water Resources on Earth  @1@ 2Template: Webachiv / IABot / www.hydrology.uni-kiel.de
  5. ↑ Article 388 of 2028, July 18, 2010: from: www.pressetext.de, Johannes Pernsteiner, 2010: China is drying out - groundwater crisis threatens the population , sonnseite.com, October 3, 2010
  6. ↑ Merk, Markus (AGW): KIT - AGW: WOKAM. September 10, 2017, accessed December 8, 2017 (German).
  7. ^ Nico Goldscheider, Neven Kresic: Karst hydrogeology home. Retrieved December 8, 2017 .
  8. ↑ BGR - WHYMAP. Retrieved December 8, 2017 .
  9. ↑ BGR - WHYMAP - BGR, KIT, IAH, and UNESCO presented new World Karst Aquifer Map. Retrieved December 8, 2017 .
  10. ↑ German-Arab Society, Kristina Bergmann, Abu Minkar: Problematic new land reclamation in Egypt - Fossilized groundwater for agricultural projects  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , dag.de, September 18, 2010@1@ 2Template: Dead Link / www.dag.de  
  11. ↑ German-Arab Society, Kristina Bergmann: Problematic new land reclamation in Egypt - Fossilized groundwater for agricultural projects - Managed migration  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. , dag.de, October 6, 2010@1@ 2Template: Dead Link / www.dag.de  
  12. ↑ Horst Rademacher: Dowsers in space , faz.net, January 7, 2010
  13. ↑ WWF: Germany's water footprint. Where does the water in our food come from? (PDF), 2009.
  14. ↑ Matthew Rodell, Isabella Velicogna, James S. Famiglietti: Satellite-based estimates of groundwater depletion in India. In: Nature. 460, 2009, p. 999, doi: 10.1038 / nature08238 .
  15. ↑ WWF: Germany's water footprint. Where does the water in our food come from? (PDF), 2009.
  16. ↑ JS Famiglietti, M. Lo u. a .: Satellites measure recent rates of groundwater depletion in California's Central Valley. In: Geophysical Research Letters. 38, 2011, p. N / a, doi: 10.1029 / 2010GL046442 .
  17. ↑ Wolfhard Petzold: Lanxess filters arsenic out of water , wz-newsline.de, March 17, 2010, accessed on October 5, 2010
  18. ↑ Bernd Schröder: Bangladesh: Arsenic in drinking water, arsenic in rice - the greatest mass poisoning in human history affects the food chain , heise.de, December 16, 2004
  19. ↑ Late consequences of centuries of mining in the southern Black Forest: Increased heavy metal content in the soils of Möhlin, Neumagen, Sulzbach and Klemmbach , breisgau-hochschwarzwald.de, District Office Breisgau-Hochschwarzwald, October 5, 2010 (PDF; 484 kB)
  20. ^ Elisabeth Willers: High arsenic values ​​in the exploratory tunnel , badische-zeitung.de, May 26, 2010
  21. ↑ Monika Seynsche : Road salt and its consequences , deutschlandfunk.de, January 6, 2015
  22. ↑ Dagmar Röhrlich : Strategies against Shrinkage , deutschlandfunk.de , November 4, 2015
  23. ↑ Gulf Coast Aquifer, Texas , academic.emporia.edu, Nov. 4, 2015
  24. ↑ State Institute for the Environment, Measurements and Nature Conservation Baden-Württemberg , July 2016: Groundwater monitoring program - results of the 2015 sampling - short report (December 8, 2016)
  25. ↑ badische-zeitung.de , November 10, 2016, Sebastian Wolfrum: Where does the high nitrate pollution of the groundwater in the Rhine plain come from (November 11, 2016)
  26. ↑ State Institute for Environment, Measurements and Nature Conservation Baden-Wuerttemberg , October 9, 2010 lubw.baden-wuerttemberg.de: nitrate leaching model ,
  27. ↑ Investigation of the nitrate enrichment processes in the Ntane sandstone aquifer in Botswana. In: bgr.bund.de. Federal Institute for Geosciences and Natural Resources, accessed on November 10, 2015 .
  28. ↑ Drinking water production ( Memento of the original from May 15, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , swm.de, October 7, 2010 @1@ 2Template: Webachiv / IABot / www.swm.de
  29. ↑ badische-zeitung.de , November 8, 2016, Daniela Weingärtner: Nitrate: The EU is suing the Federal Republic (November 11, 2016)
  30. ↑ Federal Institute for Geosciences and Natural Resources (BGR), Global groundwater maps ( Memento of the original from June 22, 2015 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , bgr.bund.de @1@ 2Template: Webachiv / IABot / www.bgr.bund.de
  31. ↑ Experts present world groundwater map . Süddeutsche Zeitung , April 15, 2015, accessed on August 26, 2020 .
  32. ↑ Federal Institute for Geosciences and Natural Resources (BGR), Endangerment of the drinking water supply from droughts, floods and tsunamis: BGR and UNESCO present new world groundwater map , bgr.bund.de, May 13, 2015
  33. ↑ DLF24 , March 20, 2017: The world's lakes are generally shallower than expected (March 21, 2017)
  34. ↑ The Oberrheingraben: The groundwater in the Oberrheingraben ( Memento of the original from August 29, 2011 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. , lubw.baden-wuerttemberg.de, accessed on July 29, 2011 @1@ 2Template: Webachiv / IABot / www.lubw.baden-wuerttemberg.de
  35. ↑ Martin Luther University Halle-Wittenberg: Nubian Aquifer System - short version , 3d-geology.de, December 31, 2010
  36. ^ Martin Gehlen: Irrigation: Sahara water for Libya's coast. In: Zeit Online. December 27, 2010, accessed December 28, 2010 .
  37. ^ Henrike Berkefeld: The desert swims , badische-zeitung.de, April 23, 2011
  38. ↑ Gulf Coast Aquifer, Texas , academic.emporia.edu, Nov. 4, 2015
  39. ↑ Dagmar Röhrlich : Strategies against Shrinkage , deutschlandfunk.de , Research News , November 4, 2015
  40. ↑ www3.gaf.de (p. 18)
  41. ^ Pradeep Kumar Naik, AK Awasthi, AVSS Anand, PN Behera: Hydrogeochemistry of the Koyna River basin, India . In: Environmental Earth Sciences . tape 59 , no. 3 , February 11, 2009, ISSN  1866-6280 , p. 613-629 , doi : 10.1007 / s12665-009-0059-8 .
  42. ↑ Groundwater resources assessment of the Koyna River basin, India (April 26, 2017)
  43. ↑ itv.com, September 10, 2013: Exclusive: Huge water reserve discovered in Kenya (April 26, 2017)
  44. ↑ Observatoire du Sahara et du Sahel (“Observation of the Sahara and the Sahel ”), oss-online.org: Projet “Système Aquifère du Sahara Septentrional” - SASS  ( page no longer available , search in web archives )  Info: The link was created automatically marked as defective. Please check the link according to the instructions and then remove this notice. (April 26, 2017)@1@ 2Template: Dead Link / www.oss-online.org  
  45. ↑ Organization for the Development of the Senegal River , cda.portail-omvs.org: Système aquifère du Sahara Septentrional  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (April 26, 2017)@1@ 2Template: Dead Link / cda.portail-omvs.org  
  46. ↑ Global Water Partnership , gwp.org: Système Aquifère du Sahara Septentrional (April 26, 2017)