Aquifer
An aquifer, formerly also aquifer or aquifer is a body of rock with cavities suitable for the management of groundwater. Wide dissemination has now also originated from the English -speaking term aquifer ( from Latin, aqua, dt water; ferre, dt wear ) learn, however, been without taken into valid for Germany hydrogeological definition according to DIN 4049-3 to be. Although mostly used in parts of the German art as a synonym for the aquifer, an aquifer referred originally to submit a significant amount of water suitable layer sequence or parts thereof. This includes water from the unsaturated zone explicitly includes what is in the valid for Germany definition of groundwater but this is not the case. An aquifer thus extends as opposed to an aquifer just above the saturated zone, which has the consequence that both terms can be used at most in each individual case as synonyms. However, one can assume that in the use of the term aquifer in German-speaking aquifer is meant.
There are three types of aquifers:
An aquifer is geologically (eg clays ) bounded by impermeable layers, which are then called Aquifugen.
Their knowledge and exploration is important for the production of drinking water and the mining groundwater influence (see: open pit drainage, water control ).
The most important property of an aquifer is the transmissivity.
- 2.2.1 natural Gas
- 2.2.2 drinking Water
- 2.2.3 irrigation
- 2.3.1 arsenic
- 2.3.2 potassium chloride ( potash )
- 2.3.3 nitrate
- 2.4.1 Pollution by ecological forestry and agriculture
- 2.4.2 Restriction of water consumption
Terms and types
A groundwater non-conductor is a rock body that conducts no groundwater. A low- head, however, has a very low hydraulic conductivity, the transition to a non-conductor is defined fluently. An aquifer limiting area with poor permeability is a groundwater inhibitors. All these together are often small grain sizes and low porosity. The English terms are aquiclude for the non-conductor and Aquitarde for the Low Head.
A body is a spatially clearly distinguishable groundwater resources, whereas the groundwater space called the rock filled with groundwater body. The groundwater thickness is defined as the vertical distance between the water table and groundwater sole, between the upper and lower limits of the groundwater body. Furthermore, a distinction between confined and unconfined aquifers, which are defined by the relative position of the water table and piezometric surface. The ground water pressure area is the area to which the water will rise in a free fountain according to its hydrostatic pressure. In this respect, this range corresponds to the groundwater surface, it is an unconfined aquifer or free. If the rise in the groundwater but stopped before reaching the printing surface by a non- or low-conductivity layer, then there is a taut aquifer. This distinction has a significant influence on the behavior of an aquifer during the placement of groundwater monitoring wells and conducting pumping tests and the final ground water extraction. A special case of the stressed aquifer form artesian aquifer, in which the printing surface is above the ground and thus the groundwater under unconfined conditions ( eg, by drilling a hole) would provide a source.
Use, risks
Storage
Heat, cold
Aquifers can be used to store thermal energy in the long term and make them as for heating or cooling buildings available. These warm water is used from an aquifer, for example, in the winter for heating buildings and cools down. This cooled water is returned to the aquifer and then in the summer turn serve to cool the building. Upon cooling of the building, the water in the wake can additionally be heated, for example by solar panels and stored back in the aquifer. At least two wells, one sip and one extraction wells are required for this procedure, which change depending on the season in their function.
In nichtvulkanischen areas, the temperatures in the substrate can be very different. For heat extraction from an aquifer deeper holes are then usually necessary: for an economic generation temperatures above 100 ° C are required. These are present, it can promote water can be cooled and reinjected. One then speaks of hydrothermal geothermal energy.
Compressed air
Compressed air can be stored among others in aquifers. These so-called ( CAES power plants ) can be used. Such systems are operated with the power plant and the power plant Huntorf McIntosh for many years. In these systems, the storage is, however, in salt dome caverns; for the future but is also storage in aquifers conceivable, as it is practiced successfully for natural gas.
CO2
The storage in aquifers far below a usable ground water depth (from a depth of 900 meters ) is seen due to the limited storage potential as an intermediate technology for the avoidance of CO2 emissions in energy production.
In contrast to Sequestrierungsdauer in oceans (up to 10,000 years ) can in this case be expected with a storage time of more than 1 million years. However, storage in oceans holds this enormous environmental hazards, if it does penetrate a memory bubble to 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. Due to the rising temperature in the depth increases, the solubility decreases. This effect is offset by the higher pressure. Decorated in rock pore water ( formation water ) can bind large amounts of gas with increasing depth. When pressure is released then solves a portion of gas and occurs either as free gas in the atmosphere or is caught in suitable geological- structural conditions in deposits. The remaining part in the formation water is called aquifer. Main problem with the promotion is the land subsidence, as observed in Japan and Italy. However, this can be countered by re-injection of degassed water.
Drinking water
For the people only about 1 % of the world's fresh water occurring is available - corresponding to a content of about 0.007 % of the total (salt, sweeteners, etc. ) water, which is present on the earth at all. The percentage of 2.5 % is fresh water on the world's water is in this case to 70% as bound water in the ice of the polar caps, the remaining 30% are distributed in aquifers or stored as soil moisture.
Worldwide aquifers are used to the fullest extent of drinking water. Exceeds the removal of the inflow, or is not used renewable fossil water, a sustainable and long-term use is not guaranteed.
Time and again in the supply of the naturally existing, but vital material private profit global corporations and service providers with the prospect of high profits in conflict with the formulated by the UN human right to water and the supply of public companies. Here, the classification of the element as a tradable commodity like any other ( European Commission) is in contrast to his understanding as a public good for ensuring primary health care and public services. In addition, the water supply company usually has in addition to the treatment plants and the distribution network and can protect themselves from competition.
In the process of drinking water treatment processes are used for groundwater recharge in some cases. This often surface water is in the aquifer reinfiltriert to the cleaning effect ( manganese, iron removal, biodegradation ) of the subsoil use. However, this can also be entered pollutants into the ground. These pollutants must be then eliminated in the further process of drinking water treatment, for example by activated carbon filters. To keep the pollutants as small as possible, the infiltrated into the aquifer water is often pre-treated.
Irrigation
The use of non-renewable water for agricultural irrigation is very controversial from an economic and environmental point of view.
The Ogallala Aquifer in central North America, has been used since 1911 for agricultural irrigation. Since the amount of water withdrawn soon exceed the amount of incoming water, the water level began to decline rapidly. Today's estimates, the ratio of retrieved to feed water is about 25, which means that only one liter of fresh water continues to flow for 25 liters of water withdrawn by seepage, in some places was a drop in the water level of up to 1.50 meters per year measured. Some parts of the aquifer are therefore already waterless; adhere to these dehydration, medium agriculture in the area might be impossible. Some rivers in the region are also partially deeper than the water table, which additionally removes the aquifer water. Even more clearly, the magnitude of such a lowering of the water level, considering the extent of this aquifer ( see table below ) into account.
Very problematic is the use of fossil groundwater. To the west of Egypt, the Nubian aquifer has been tapped by the drying up of artesian springs in some oases ( Bahariya, Farafra, Abu Minkar, Dakhla and Kharga ). Is in this region due to the prevailing hyperarid climate, almost no groundwater recharge rates available. Because of the heavy use of groundwater resources, the groundwater level of the Nubian aquifer dropped to 2009 by about 60 m.
In the north-western Indian aquifers in the greater New Delhi, Punjab and in the Indian states of Haryana and Rajasthan, the water level has dropped in the last six years (2009 ) per year to more than 30 centimeters; the loss is about 100 km ³. Throughout the country, the area of irrigated lands 1970-1999 has tripled. According to a study of the nature conservation organization WWF Indian farmers use to irrigate their fields 400 km ³ of water annually. Just 150 km ³ of which originate from precipitation, the rest comes from aquifers.
In the Central Valley, California ( California Central Valley) have gone km ³ of groundwater lost due to intensive agricultural use about 20 million.
Pollution with chemical substances
Worldwide subject to many groundwater bodies under intense pressure from industry and agriculture. These pressures come from direct discharges of waste or cooling water or from indirect entries about the infiltration of spraying and fertilizers. This is a responsible approach to the environment is reflected (organic farming, for example, can significantly reduce nitrate pollution ) in the pollution of ground water again. The problem is mainly that contamination of groundwater over decades and longer can be saved and thus long are detectable.
Arsenic
In many regions of the USA, South America and Asia occur in the groundwater very high concentrations of arsenic. Even in Europe, especially in Great Britain, occur excessively high values . In Germany, the ground water in the Black Forest in places is contaminated with arsenic.
Potassium chloride ( potash )
In the South German - French Upper Rhine Aquifer lie partly with considerable loads of salt additions of slag heaps and old storage pool of the abandoned mining here potash extraction.
Nitrate
Nitrate to nitrite can be converted in people with atypical intestinal flora in infants and in the intestine, which is toxic. In addition, nitrate is considered as an indicator of unwanted nitrogen-containing organic contaminants.
Anthropogenic elevated nitrate levels in groundwater are a world -known phenomenon that usually occur in densely populated areas and are caused by intensive agriculture ( nitrogen or liquid manure ). For the determination of losses of nitrates from the soil - plant system in a deterministic groundwater nitrate leaching model is partially used, which calculates the average of Nitrogen from the surface. The limit for drinking water of the European Union is present ( 2010) at 25 mg / l
Also in unpopulated, semi-arid areas may have elevated nitrate levels found in groundwater that are not due to anthropogenic influences and thus are caused by natural processes. In the countries of southern Africa (South Africa, Namibia, Botswana ) locally nitrate concentrations up to 600 mg / l are encountered that are significantly above the limit of the World Health Organization (WHO ) of 50 mg / l. It is not yet clear where the causes of these elevated nitrate levels are.
Strategies for the sustainable use
Pollution control by ecological forestry and agriculture
The city of Munich and supports with its water works for years in large-scale farmers in the area, which convert to organic farming. Thus, the end of the 1960s is steeply ascended nitrate pollution was stabilized at an average level and groundwater obtained are passed without further processing to Munich.
Restriction of water consumption
Some public water utilities are similar to the by now well-established form of energy transferred by saving to support water-saving techniques and installations also among consumers in the form of advisory services and financial subsidies to reduce water consumption. This can make a lasting contribution to the stabilization of groundwater resources and water quality.