Aquifers are essential to our survival. They store ground water and enable life to flourish in regions that would be otherwise virtually uninhabitable. Humans have become very good at exploiting natural resources such as aquifers, but this very fact makes them vulnerable. Our ever-increasing water demands mean that some aquifers are being depleted more rapidly than they can be replenished, which means the water supply is coming under threat.
For exploitation of an aquifer to be sustainable it is necessary for its water content to be replenished at least as quickly as it is extracted. Water is normally drawn from aquifers using wells, although if an aquifer outcrops at the Earth’s surface then drilling a well may not be necessary as groundwater can seep from it naturally. Where this occurs in a desert it will normally result in the formation of an oasis.
Wells drilled into aquifers may either be ‘artesian’ (the water flows from the well under its own pressure) or pumped. If water is extracted from the aquifer more rapidly than it is replenished the water level (and therefore pressure) in the aquifer drops, and artesian wells may cease to flow.
Extraction of water from aquifers can be a large-scale operation. For example, the Ogallala Aquifer in the United States provides water for the crops fields of the mid-West. According to Jane Braxton Little in the March 2009 Scientific American article “The Ogallala Aquifer: Saving a Vital U.S. Water Source” (accessed August 15 2010), $20 billion a year depends on the aquifer. Unfortunately, this water resource is being over-exploited
Aquifers are also sensitive to pollution, such as is the case in Bangladesh where aquifers have been poisoned with arsenic. According to the article “Ground Water” by SOS-arsenic.net (accessed August 15 2010) it is estimated that the most significant health risk from drinking water from tubewells in Bangladesh is chronic arsenic poisoning.
Aquifers are a vital resource and good management is essential. Because rates of water replenishment and flow are so low within an aquifer, any issues such as over-exploitation or pollution may take thousands of years to remedy. Aquifers are also sensitive to changes in precipitation, so any changes in rainfall patterns have the potential to increase the vulnerability of these natural resources.
Aquifers are found across the world in the shallow regions of the Earth’s crust. At depths of around 10km rocks have been so compressed and altered that their void spaces have been closed and they can be assumed to be impermeable. These deep rocks effectively confine groundwater to the shallow crust.
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