Groundwater-related subsidence
Groundwater-related subsidence is the subsidence (or the sinking) of land resulting from unsustainable groundwater extraction. It is a growing problem in the developing world as cities increase in population and water use, without adequate pumping regulation and enforcement. One estimate has 80% of serious U.S. land subsidence problems associated with the excessive extraction of groundwater.[1]
Groundwater can be considered one of the last free resources, as anyone who can afford to drill can usually draw up merely according to their ability to pump (depending on local regulations). However, as seen in the figure, pumping-induced
Mechanism
The cause of the long-term surface changes associated with this phenomenon are fairly well known. As the groundwater is pumped out, the
Aquifer compaction is a significant concern along with pumping-induced land subsidence. A large portion of the groundwater storage potential of many aquifers can be significantly reduced when longterm groundwater extraction, and the resulting groundwater level decline, causes permanent compaction of fine sediment layers (silts and clays). A study in an arid agricultural region of Arizona[3] showed that, even with a water level recovery of 100 ft after groundwater pumping was stopped, the land surface continued to subside for decades. This is a result of the continued dewatering of aquitards (fine-grain layers that slow the movement of groundwater) from stresses mentioned in the previous paragraph.
The only known method to prevent this condition is by pumping less groundwater, which is extremely difficult to enforce when many people own water wells. Attempts are being made to directly recharge aquifers but this is still a preliminary effort.[citation needed]
Impacted geographies
The arid areas of the world are requiring more and more water for growing populations and
Groundwater-related subsidence often results in major damage to urban areas. In Mexico City, the buildings interact with the settlement, and cause cracking, tilting, and other major damage.[7] In many places, large sinkholes open up, as well as surface cavities. Damage from Hurricane Katrina was exacerbated due to coastal sinking, associated with groundwater withdrawal.
Major areas affected include the San Joaquin Valley in California,[8] Central Arizona,[2] Mexico City,[9] and Jakarta, Indonesia.[10]
See also
- Artesian aquifer– Confined aquifer containing groundwater under positive pressure
- Central Valley land subsidence
- UNESCO Working Group on Land Subsidence
- Sea level rise
- List of aquifers in the United States
References
- ^ USGS Fact Sheet-165-00 December 2000
- ^ a b USGS: Land Subsidence From Ground-Water Pumping, S. A. Leake, Aug. 2013
- ^ Evans and Pool (1999). "Aquifer Compaction and Ground-Water Levels in South-Central Arizona". USGS WRIR (99–4249): 1.
- ^ Lin II, Rong-Gong (May 14, 2014) "Depletion of Central Valley's groundwater may be causing earthquakes" Los Angeles Times
- ^ Timothy H. Dixon (2006) Space geodesy: Subsidence and flooding in New Orleans. Nature 441, 587-588 (1 June 2006)
- ^ Dhira Phantumvanit (1989) Coming to terms with Bangkok's environmental problems. Environment and Urbanization April 1989 vol. 1 no. 1 31–39
- ^ Sinking of a titanic city, Geotimes.org, July 2001
- ^ Serna, Joseph (February 9, 2017). "San Joaquin Valley continues to sink because of groundwater pumping, NASA says". Los Angeles Times. Retrieved 8 February 2018.
- ^ Katherine Kornei (December 20, 2017). "Sinking of Mexico City linked to metro accident, with more to come". Science. Retrieved December 22, 2017.
sinking by up to 30 centimeters per year, as groundwater is extracted
- ^ Michael Kimmelman (December 21, 2017). "Jakarta Is Sinking So Fast, It Could End Up Underwater". New York Times. Retrieved December 22, 2017.