Overdrafting

Last updated
Within a long period of groundwater depletion in California's Central Valley, short periods of recovery were mostly driven by extreme weather events that typically caused flooding and had negative social, environmental and economic consequences. 1960- Groundwater loss - depletion - Central Valley of California.svg
Within a long period of groundwater depletion in California's Central Valley, short periods of recovery were mostly driven by extreme weather events that typically caused flooding and had negative social, environmental and economic consequences.

Overdrafting is the process of extracting groundwater beyond the equilibrium yield of an aquifer. Groundwater is one of the largest sources of fresh water and is found underground. The primary cause of groundwater depletion is the excessive pumping of groundwater up from underground aquifers. Insufficient recharge can lead to depletion, reducing the usefulness of the aquifer for humans. Depletion can also have impacts on the environment around the aquifer, such as soil compression and land subsidence, local climatic change, soil chemistry changes, and other deterioration of the local environment.

Contents

There are two sets of yields: safe yield and sustainable yield. Safe yield is the amount of groundwater that can be withdrawn over a period of time without exceeding the long-term recharge rate or affecting the aquifer integrity. [2] [3] Sustainable yield is the amount of water extraction that can be sustained indefinitely without negative hydrological impacts, taking into account both recharge rate and surface water impacts. [4]

There are two types of aquifers: confined and unconfined. In confined aquifers, there is an overbearing layer called an aquitard, which contains impermeable materials through which groundwater cannot be extracted. In unconfined aquifers, there is no aquitard, and groundwater can be freely extracted from the surface. Extracting groundwater from unconfined aquifers is like borrowing the water: it has to be recharged at a proper rate. Recharge can happen through artificial recharge and natural recharge. [5]

Mechanism

When groundwater is extracted from an aquifer, a cone of depression is created around the well. As the drafting of water continues, the cone increases in radius. Extracting too much water (overdrafting) can lead to negative impacts such as a drop of the water table, land subsidence, and loss of surface water reaching the streams. In extreme cases, the supply of water that naturally recharges the aquifer is pulled directly from streams and rivers, lowering their water levels. This affects wildlife, as well as humans who might be using the water for other purposes. [5]

The natural process of aquifer recharge takes place through the percolation of surface water. An aquifer may be artificially recharged, such as by pumping reclaimed water from wastewater management projects directly into the aquifer. An example of is the Orange County Water District in California. [6] This organization takes wastewater, treats it to a proper level, and then systematically pumps it back into the aquifers for artificial recharge.

Since every groundwater basin recharges at a different rate depending on precipitation, vegetative cover, and soil conservation practices, the quantity of groundwater that can be safely pumped varies greatly among regions of the world and even within provinces. Some aquifers require a very long time to recharge, and thus overdrafting can effectively dry up certain sub-surface water supplies. Subsidence occurs when excessive groundwater is extracted from rocks that support more weight when saturated. This can lead to a capacity reduction in the aquifer. [7]

Changes in freshwater availability stem from natural and human activities (in conjunction with climate change) that interfere with groundwater recharge patterns. One of the leading anthropogenic activities causing groundwater depletion is irrigation. Roughly 40% of global irrigation is supported by groundwater, and irrigation is the primary activity causing groundwater storage loss across the U.S. [8]

Around the world

Ranking of countries that use groundwater for irrigation. [9]
CountryMillion hectares (1×10^6 ha (2.5×10^6 acres))
irrigated with groundwater
India 26.5
USA 10.8
China 8.8
Pakistan 4.9
Iran 3.6
Bangladesh 2.6
Mexico 1.7
Saudi Arabia 1.5
Italy 0.9
Turkey 0.7
Syria 0.6
Brazil 0.5

This ranking is based on the amount of groundwater each country uses for agriculture. This issue is becoming significant in the United States (most notably in California), but it has been an ongoing problem in other parts of the world, such as was documented in Punjab, India, in 1987. [10]

United States

In the U.S., an estimated 800 km3 of groundwater was depleted during the 20th century. [8] The development of cities and other areas of highly concentrated water usage has created a strain on groundwater resources. In post-development scenarios, interactions between surface water and groundwater are reduced; there is less intermixing between the surface and subsurface (interflow), leading to depleted water tables. [11]

Groundwater recharge rates are also affected by rising temperatures which increase surface evaporation and transpiration, resulting in decreased water content of the soil. [12] Anthropogenic changes to groundwater storage, such as over-pumping and the depletion of water tables combined with climate change, effectively reshape the hydrosphere and impact the ecosystems that depend on the groundwater. [13]

Accelerated decline in subterranean reservoirs

According to a 2013 report by research hydrologist Leonard F. Konikow [14] at the United States Geological Survey (USGS), the depletion of the Ogallala Aquifer between 2001–2008 is about 32% of the cumulative depletion during the entire 20th century. [14] In the United States, the biggest users of water from aquifers include agricultural irrigation, and oil and coal extraction. [15] According to Konikow, "Cumulative total groundwater depletion in the United States accelerated in the late 1940s and continued at an almost steady linear rate through the end of the century. In addition to widely recognized environmental consequences, groundwater depletion also adversely impacts the long-term sustainability of groundwater supplies to help meet the Nation's water needs." [14]

As reported by another USGS study of withdrawals from 66 major US aquifers, the three greatest uses of water extracted from aquifers were irrigation (68%), public water supply (19%), and "self-supplied industrial" (4%). The remaining 8% of groundwater withdrawals were for "self-supplied domestic, aquaculture, livestock, mining, and thermoelectric power uses." [16]

Environmental impacts

Groundwater extraction for use in water supplies lowers the overall water table, the level that groundwater sits at in an area. The lowering water table can diminish streamflow and reduce water level in other water bodies such as wetlands and lakes. [17] In Karst systems, large-scale groundwater withdrawal can lead to sinkholes or groundwater-related subsidence. The overdrafting leads to the pressure in limestone containments to become unstable and sediments to collapse, creating a sinkhole. [18] Overdrafting in coastal regions can lead to the reduction of water pressure in an aquifer, allowing saltwater intrusion. If saltwater contaminates a freshwater aquifer, that aquifer can no longer be used as a reliable source of freshwater for settlements and cities. Artificial recharge may return fresh water pressure to halt saltwater intrusion. However, this method can be economically inefficient and unavailable due to the high cost of the process. [18]

When aquifers or groundwater wells experience overdraft, chemical concentrations in the water may change. Chemicals such as calcium, magnesium, sodium, carbonate, bicarbonate, chloride, and sulfate can be found in groundwater sources. [19] Changes to water quality as a result of overdrafting may make it unsafe for human consumption; rendering the groundwater sources unusable as a source of drinking water. [19]

Overdrafting can also affect organisms living within groundwater aquifers known as stygobionts Loss of habitat for these creatures through overdrafting has reduced biodiversity in certain areas. [20]

Environmental impacts of overdrafting include:

This section is an excerpt from Groundwater-related subsidence.[ edit ]
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. [21]

Socio-economic effects

Overdrafting has socio-economic impacts due to cost inequities that increase as the water table drops. As the water table drops, deeper wells are required to reach water in the aquifer. This not only requires deepening of already existing wells, but also digging new wells. [22] Both processes are expensive. Research from Punjab found that the high cost of technology to continue water access hurts small landholders more than it does large landholders because large landholders have more resources "to invest in technology." [22] Therefore, small landholders, who traditionally have a lower income than large landholders, are unable to benefit from the technology that allows greater water access. [22] This creates a cycle of inequity as small landholders that are dependent on agriculture have less water to irrigate their land, producing a lower output of crops.

Additionally, overdrafting has socio-economic impacts due to prior appropriation laws. Prior appropriation rights declare that the first person to use water from a water source will maintain the right to water. These rights result in socio-economic inequities as businesses and/or larger landholders who have a higher income can maintain their water rights. Meanwhile, new businesses or smaller landholders have less access to water, resulting in less ability to profit. [22] Due to this inequity, small farmers in Punjab with less water rights tend to grow maize or less productive rice; meanwhile, larger landholders in Punjab can use more land for rice because they have access to water. [22]

Possible solutions

Artificial Recharge:

Since recharge is the natural replenishment of water, artificial recharge is the man-made replenishment of groundwater, though there is only a limited amount of suitable water available for replenishing. [23]

Water Conservation Techniques:

Other solutions include implementing water conservation techniques to decrease overdrafting. These include improving governance to ensure proper water management, incentivizing water conservation, improving agriculture techniques to ensure water use is efficient, changing diets to crops that require less water, and investing in infrastructure that uses water sustainably. [24] The state of California has implemented some water conservation techniques due to droughts in the state. Some of their techniques include prohibitions on: 1) outdoor watering that runs onto sidewalks or other on hard surfaces that don't absorb water, 2) washing vehicles with a hose that does not have a shutoff handle, 3) watering within 48 hours after a quarter inch of rain, and 4) watering commercial/industrial decorative grass. [25]

Water Conservation Incentivization:

Techniques used by California in emergency situations are useful; however, incentive to follow through on these is important. The city of Spokane has a program to incentivize sustainable landscapes called SpokaneScape. This program incentivizes water efficient landscapes by offering homeowners up to $500 in credit on their utility bill if they adapt their yards to water efficient plants. [26]

See also

Related Research Articles

<span class="mw-page-title-main">Irrigation</span> Agricultural artificial application of water to land

Irrigation is the practice of applying controlled amounts of water to land to help grow crops, landscape plants, and lawns. Irrigation has been a key aspect of agriculture for over 5,000 years and has been developed by many cultures around the world. Irrigation helps to grow crops, maintain landscapes, and revegetate disturbed soils in dry areas and during times of below-average rainfall. In addition to these uses, irrigation is also employed to protect crops from frost, suppress weed growth in grain fields, and prevent soil consolidation. It is also used to cool livestock, reduce dust, dispose of sewage, and support mining operations. Drainage, which involves the removal of surface and sub-surface water from a given location, is often studied in conjunction with irrigation.

<span class="mw-page-title-main">Aquifer</span> Underground layer of water-bearing permeable rock

An aquifer is an underground layer of water-bearing material, consisting of permeable or fractured rock, or of unconsolidated materials. Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related terms include aquitard, which is a bed of low permeability along an aquifer, and aquiclude, which is a solid, impermeable area underlying or overlying an aquifer, the pressure of which could lead to the formation of a confined aquifer. The classification of aquifers is as follows: Saturated versus unsaturated; aquifers versus aquitards; confined versus unconfined; isotropic versus anisotropic; porous, karst, or fractured; transboundary aquifer.

<span class="mw-page-title-main">Ogallala Aquifer</span> Water table aquifer beneath the Great Plains in the United States

The Ogallala Aquifer is a shallow water table aquifer surrounded by sand, silt, clay, and gravel located beneath the Great Plains in the United States. As one of the world's largest aquifers, it underlies an area of approximately 174,000 sq mi (450,000 km2) in portions of eight states. It was named in 1898 by geologist N. H. Darton from its type locality near the town of Ogallala, Nebraska. The aquifer is part of the High Plains Aquifer System, and resides in the Ogallala Formation, which is the principal geologic unit underlying 80% of the High Plains.

<span class="mw-page-title-main">Water extraction</span> Process of taking water from any source

Water extraction is the process of taking water from any source, either temporarily or permanently, for flood control or to obtain water for, for example, irrigation. The extracted water could also be used as drinking water after suitable treatment.

<span class="mw-page-title-main">Groundwater</span> Water located beneath the ground surface

Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.

<span class="mw-page-title-main">California Aqueduct</span> Water supply project in California, US

The Governor Edmund G. Brown California Aqueduct is a system of canals, tunnels, and pipelines that conveys water collected from the Sierra Nevada Mountains and valleys of Northern and Central California to Southern California. Named after California Governor Edmund Gerald "Pat" Brown Sr., the over 400-mile (640 km) aqueduct is the principal feature of the California State Water Project.

Sustainable yield is the amount of a resource that humans can harvest without over-harvesting or damaging a potentially renewable resource.

Fossil water, fossil groundwater, or paleowater is an ancient body of water that has been contained in some undisturbed space, typically groundwater in an aquifer, for millennia. Other types of fossil water can include subglacial lakes, such as Antarctica's Lake Vostok. UNESCO defines fossil groundwater as "water that infiltrated usually millennia ago and often under climatic conditions different from the present, and that has been stored underground since that time."

In hydrology, there are two similar but distinct definitions in use for the word drawdown:

<span class="mw-page-title-main">Groundwater recharge</span> Groundwater that recharges an aquifer

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 the vadose zone below plant roots and is often expressed as a flux to the water table surface. Groundwater recharge also encompasses water moving away from the water table farther into the saturated zone. Recharge occurs both naturally and through anthropogenic processes, where rainwater and/or reclaimed water is routed to the subsurface.

Groundwater-related subsidence is the subsidence 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.

Peak water is a concept that underlines the growing constraints on the availability, quality, and use of freshwater resources. Peak water was defined in 2010 by Peter Gleick and Meena Palaniappan. They distinguish between peak renewable, peak non-renewable, and peak ecological water to demonstrate the fact that although there is a vast amount of water on the planet, sustainably managed water is becoming scarce.

Water resources are natural resources of water that are potentially useful for humans, for example as a source of drinking water supply or irrigation water. These resources can be either freshwater from natural sources, or water produced artificially from other sources, such as from reclaimed water (wastewater) or desalinated water (seawater). 97% of the water on Earth is salt water and only three percent is fresh water; slightly over two-thirds of this is frozen in glaciers and polar ice caps. The remaining unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air. Natural sources of fresh water include surface water, under river flow, groundwater and frozen water. People use water resources for agricultural, industrial and household activities.

<span class="mw-page-title-main">Water management in Greater Mexico City</span>

Greater Mexico City, a metropolitan area with more than 19 million inhabitants including Mexico's capital with about 9 million inhabitants, faces tremendous water challenges. These include groundwater overexploitation, land subsidence, the risk of major flooding, the impacts of increasing urbanization, poor water quality, inefficient water use, a low share of wastewater treatment, health concerns about the reuse of wastewater in agriculture, and limited cost recovery. Overcoming these challenges is complicated by fragmented responsibilities for water management in Greater Mexico City:

<span class="mw-page-title-main">Environmental impact of irrigation</span> Land & irrigation

The environmental impact of irrigation relates to the changes in quantity and quality of soil and water as a result of irrigation and the subsequent effects on natural and social conditions in river basins and downstream of an irrigation scheme. The effects stem from the altered hydrological conditions caused by the installation and operation of the irrigation scheme.

<span class="mw-page-title-main">Santa Clara valley aquifer</span> Aquifer under the San Francisco Bay area

The Santa Clara valley aquifer is a groundwater aquifer located in the southern San Francisco Bay Area. The geology of the Santa Clara valley aquifer consists of a complex stratigraphy of permeable and impermeable units. Management of aquifer resources is associated with the Santa Clara Valley Water District.

Groundwater banking is a water management mechanism designed to increase water supply reliability. Groundwater can be created by using dewatered aquifer space to store water during the years when there is abundant rainfall. It can then be pumped and used during years that do not have a surplus of water. People can manage the use of groundwater to benefit society through the purchasing and selling of these groundwater rights. The surface water should be used first, and then the groundwater will be used when there is not enough surface water to meet demand. The groundwater will reduce the risk of relying on surface water and will maximize expected income. There are regulatory storage-type aquifer recovery and storage systems which when water is injected into it gives the right to withdraw the water later on. Groundwater banking has been implemented into semi-arid and arid southwestern United States because this is where there is the most need for extra water. The overall goal is to transfer water from low-value to high-value uses by bringing buyers and sellers together.

The Sustainable Groundwater Management Act (SGMA) is a three-bill package that passed the California state legislature and was signed into California state law by Governor Jerry Brown in September 2014. Its purpose is to ensure better local and regional management of groundwater use and it seeks to have a sustainable groundwater management in California by 2042. It emphasizes local management and formed groundwater sustainability agencies (GSAs) from local and regional authorities who submitted groundwater sustainability plans (GSPs) to the state between 2020 and 2022.

The Central Valley in California subsides when groundwater is pumped faster than underground aquifers can be recharged. The Central Valley has been sinking (subsiding) at differing rates since the 1920s and is estimated to have sunk up to 28 feet. During drought years, the valley is prone to accelerated subsidence due to groundwater extraction. California periodically experiences droughts of varying lengths and severity.

Groundwater recharge is the process of water being absorbed into the ground from precipitation, snowmelt, or artificial processes. Intentional groundwater recharge uses large, open basins that allow water to slowly seep into the ground. This water is filtered by sediment while traveling underground and is pumped back to the surface as a source of freshwater. In California, groundwater accounts for around 41% of the state's total water supply, although this number varies between wet and dry years. During years of greater than average rainfall, less groundwater is used to allow for reserves to be available during dry years. Up to 60% of all water can be sourced from groundwater during dry years. The amount of water in underground aquifers is carefully monitored by the State Water Resources Control Board and other regional water resource boards.

References

  1. ↑ Liu, Pang-Wei; Famiglietti, James S.; Purdy, Adam J.; Adams, Kyra H.; et al. (19 December 2022). "Groundwater depletion in California's Central Valley accelerates during megadrought". Nature Communications. 13 (7825): 7825. Bibcode:2022NatCo..13.7825L. doi: 10.1038/s41467-022-35582-x . PMC   9763392 . PMID   36535940. (Archive of chart itself)
  2. ↑ "Safe Yield". Water Education Foundation. 22 June 2020. Retrieved 2022-12-19.
  3. ↑ "Safe yield". solareis.anl.gov. Retrieved 2022-12-19.
  4. ↑ Rudestam, Kirsten; Langridge, Ruth (2014). "Sustainable Yield in Theory and Practice: Bridging Scientific and Mainstream Vernacular". Groundwater. 51 (S1): 90–99. Bibcode:2014GrWat..52S..90R. doi:10.1111/gwat.12160. PMID   24479641. S2CID   34864194 – via Wiley Online Library.
  5. 1 2 Lassiter, Allison (July 2015). Sustainable Water Challenges and Solutions from California. University of California. ISBN   9780520285354.
  6. ↑ "Orange County Water District".
  7. ↑ "Land subsidence". The USGS Water Science School. United States Geological Survey. 2015-08-20. Archived from the original on 2013-11-10. Retrieved 2013-04-06.
  8. 1 2 Condon, Laura E.; Maxwell, Reed M. (June 2019). "Simulating the sensitivity of evapotranspiration and streamflow to large-scale groundwater depletion". Science Advances. 5 (6): eaav4574. Bibcode:2019SciA....5.4574C. doi:10.1126/sciadv.aav4574. ISSN   2375-2548. PMC   6584623 . PMID   31223647.
  9. ↑ Black, Maggie (2009). The Atlas of Water. Berkeley and Los Angeles, California: University of California Press. p. 62. ISBN   9780520259348.
  10. ↑ Dhawan, B. D. (1993). "Ground Water Depletion in Punjab". Economic and Political Weekly. 28 (44): 2397–2401. JSTOR   4400350.
  11. ↑ Sophocleous, Marios (February 2002). "Interactions between groundwater and surface water: the state of the science". Hydrogeology Journal. 10 (1): 52–67. Bibcode:2002HydJ...10...52S. doi:10.1007/s10040-001-0170-8. ISSN   1431-2174. S2CID   2891081.
  12. ↑ Green, Timothy R.; Taniguchi, Makoto; Kooi, Henk; Gurdak, Jason J.; Allen, Diana M.; Hiscock, Kevin M.; Treidel, Holger; Aureli, Alice (August 2011). "Beneath the surface of global change: Impacts of climate change on groundwater". Journal of Hydrology. 405 (3–4): 532–560. Bibcode:2011JHyd..405..532G. doi:10.1016/j.jhydrol.2011.05.002. S2CID   18098122.
  13. ↑ Orellana, Felipe; Verma, Parikshit; Loheide, Steven P.; Daly, Edoardo (September 2012). "Monitoring and modeling water-vegetation interactions in groundwater-dependent ecosystems". Reviews of Geophysics. 50 (3). Bibcode:2012RvGeo..50.3003O. doi: 10.1029/2011RG000383 .
  14. 1 2 3 Konikow, Leonard F. Groundwater Depletion in the United States (1900–2008) (PDF) (Report). Scientific Investigations Report. Reston, Virginia: U.S. Department of the Interior, U.S. Geological Survey. p. 63.
  15. ↑ Zabarenko, Deborah (20 May 2013). "Drop in U.S. underground water levels has accelerated: USGS". Washington, DC: Reuters.
  16. ↑ Maupin, Molly A. & Barber, Nancy L. (July 2005). "Estimated Withdrawals from Principal Aquifers in the United States, 2000". United States Geological Survey. Circular 1279.
  17. ↑ Zektser, S.; Loáiciga, H. A.; Wolf, J. T. (1 February 2005). "Environmental impacts of groundwater overdraft: selected case studies in the southwestern United States". Environmental Geology. 47 (3): 396–404. doi:10.1007/s00254-004-1164-3. S2CID   129514582.
  18. 1 2 Brooks, Kenneth N.; Ffolliott, Peter F.; Magner, Joseph A. (2013). Hydrology and the management of watersheds (4. ed.). Ames, Iowa: Wiley-Blackwell. p. 184. ISBN   978-0-4709-6305-0.
  19. 1 2 Saber, Mohamed; Ahmed, Omar; Keheila, Esmat A.; Mohamed, Mohamed Abdel-Moneim; Kantoush, Sameh A.; Abdel-Fattah, Mohammed; Sumi, Tetsuya (2022). Assessment of the Impacts of Groundwater Overdrafting on Water Quality and Environmental Degradation in the Fares Area, Aswan, Egypt. Natural Disaster Science and Mitigation Engineering: DPRI reports. Springer. pp. 529–551. doi:10.1007/978-981-16-2904-4_22. ISBN   978-981-16-2903-7. S2CID   242196835.
  20. ↑ Devitt, Thomas (5 August 2019). "Creatures of the Deep Karst". American Scientist.
  21. ↑ USGS Fact Sheet-165-00 December 2000
  22. 1 2 3 4 5 Sarkar, Anindita (February 12–18, 2011). "Socio-economic Implications of Depleting Groundwater Resource in Punjab: A Comparative Analysis of Different Irrigation Systems". Economic and Political Weekly. pp. 61–63. JSTOR   27918148 . Retrieved November 25, 2023.
  23. ↑ Lassiter, Allison (2015). Sustainable Water. Oakland California: University of California Press. p. 186.
  24. ↑ Cousin, Ertharin; Kawamura, A.G.; Rosegrant, Mark W. (2019). "Strategies to Enhance Water, Food, and Nutrition Security". Chicago Council on Global Affairs: 28.
  25. ↑ "Water Conservation Portal - Emergency Conservation Regulation | California State Water Resources Control Board". www.waterboards.ca.gov. Retrieved 2023-11-25.
  26. ↑ "SpokaneScape". my.spokanecity.org. 2020-04-30. Retrieved 2023-11-25.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.