World’s largest distributed store of freshwater


  • Total groundwater volume in the upper 2 km of continental crust is approximately 22.6 million km3 of which 0.1-5.0 million km3 is less than 50 years old1
  • The volume of modern groundwater is equivalent to a body of water with a depth of about 3 meters spread over the continents2
  • Groundwater replenished over a human lifetime of 25-100 years is a finite, limited resource with a spatially heterogeneous distribution dependent on geographic, geologic and hydrologic conditions3
  • Accounts for as much as 33% of total global water withdrawals4
  • Over 2 billion people rely on groundwater as their primary water source5
  • 50% or more of the irrigation water used to grow the world’s food is supplied by groundwater6

            Source:  1,2,3–Gleeson, T., Befus, K. M., Jasechko, S., Luijendijk, E., & Cardenas, M. B.   (2015). The global volume and distribution of modern groundwater. Nature           Geoscience, 9(2), 161–167.doi:10.1038/ngeo2590 

            4,5,6–Famiglietti, J. S. (2014). The global groundwater crisis. Nature Climate Change,   4(11), 945–948.doi:10.1038/nclimate2425 

Groundwater Use by Country, in cubic kilometers per year

Source:  Fienen M.N., Arshad M. (2016) The International Scale of the Groundwater Issue. In: Jakeman A.J., Barreteau O., Hunt R.J., Rinaudo JD., Ross A. (eds) Integrated Groundwater Management. Springer, Cham, DOI The International Scale of the Groundwater Issue

37 Largest Aquifer Systems

Source: Map and table):  Richey, A. S., B. F. Thomas, M.-H. Lo, J. T. Reager, J. S. Famiglietti, K. Voss, S. Swenson, and M. Rodell (2015), Quantifying renewable groundwater stress with GRACE, Water Resour. Res.,51, 5217–5238, doi:10.1002/2015WR017349
Aquifer Map # Aquifer Name
1 Nubian Aquifer System (NAS)
2 Northwestern Sahara Aquifer System (NWSAS)
3 Murzuk-Djado Basin
4 Taoudeni-Tanezrouft Basin
5 Senegalo-Mauritanian Basin
6 Iullemeden-Irhazer Aquifer System
7 Lake Chad Basin
8 Sudd Basin (Umm Ruwaba Aquifer)
9 Ogaden-Juba Basin
10 Congo Basin
11 Upper Kalahari-Cuvelai-Upper Zambezi Basin
12 Lower Kalahari-Stampriet Basin
13 Karoo Basin
14 Northern Great Plains Aquifer
15 Cambro-Ordovician Aquifer System
16 Californian Central Valley Aquifer System
17 Ogallala Aquifer (High Plains)
18 Atlantic and Gulf Coastal Plains Aquifer
19 Amazon Basin
20 Maranhao Basin
21 Guarani Aquifer System
22 Arabian Aquifer System
23 Indus Basin
24 Ganges-Brahmaputra Basin
25 West Siberian Basin
26 Tunguss Basin
27 Angara-Lena Basin
28 Yakut Basin
29 North China Aquifer System
30 Song-Liao Basin
31 Tarim Basin
32 Paris Basin
33 Russian Platform Basins
34 North Caucasus Basin
35 Pechora Basin
36 Great Artesian Basin
37 Canning Basin

Global Aquifer Depletion Hotspots in Arid and Semi-arid Zones

Aquifer Country
Northwest Sahara      #2 Algeria, Libya, Tunisia

California Central Valley 
High Plains (Ogallala) #17 USA
Guarani                    #21 Argentina, Brazil, Paraguay, Uruguay
Northern Middle East Iran, Iraq, Syria, Turkey
Arabian                      #22 Iraq, Jordan,Oman,Qatar,Saudi Arabia,
UAE, Yemen
Northwestern India #23 India, Pakistan
North China Plain      #29 China
Canning Basin         #37 Australia

Adapted from:  Famiglietti, J. S. (2014). The global groundwater crisis. Nature Climate Change, 4(11), 945–948.doi:10.1038/nclimate2425 

Highlights from Global Aquifer Hotspots: Central Valley, California (#16)

  • Most productive agricultural area in the United States
  • 40%+ of Central Valley’s water supply comes from gw, primarily to meet agricultural demand
  • Groundwater use increased from 0.75 to 2.5 km3 per year between 1962-2003
  • 2007-2010 severe drought caused a permanent aquifer system storage loss of ~2%, due to irreversible compaction of the aquifer system
    • Source: Ojha, et al., Sustained Groundwater Loss in California’s Central Valley Exacerbated by Intense Drought Periods, Water Resources Research, June 2018, 54(5575). Doi:  10.1029/2017WR022250)Most productive agricultural area in the United States

May 7, 2015 – September 10, 2016
Several trouble spots that were identified in 2015 have continued to subside at rates as high as 0.6 meters (2 feet) per year. Significant subsidence was measured in subsidence bowls near the towns of Chowchilla, south of Merced; and Corcoran, north of Bakersfield. These bowls cover hundreds of square kilometers and continued to grow wider and deeper between May 2015 and September 2016. Subsidence also intensified near Tranquility in Fresno County, where the land surface has settled up to 51 centimeters (20 inches) in an area that extends 11 kilometers (7 miles).  NASA Earth Observatory map by Joshua Stevens, using modified Copernicus Sentinel SAR data (2016) courtesy of Tom Farr and Cathleen Jones, NASA Jet Propulsion Laboratory. Caption by Alan Buis (Jet Propulsion Laboratory) and Ted Thomas, California Department of Water Resources; edited by Mike Carlowicz.

Declining groundwater storage appears to be part of the Central Valley’s future

Central Valley groundwater storage trends and simulations
The GWD Model simulations for both the past and future years. The simulated groundwater storage changes for the years 1980–2014 (Blue line) are compared with observations (red icons). In future years, several precipitation scenarios are examined.
Source:  Massoud, E., et al., Projecting groundwater storage changes in California’s Central Valley, Scientific Reports 8(1), August 2018. Doi:10.1038/s41598-018-31201-1
Highlights from Global Aquifer Hotspots: High Plains Aquifer (United States) #17 (The International Scale of the Groundwater Issue)
  • One of the largest gw aquifers in the world (8 states; 450,000 km2)
  • Provides drinking water for 2.3 million people
  • Extensively used for agricultural production
  • Storage decline from 1950-2007 accounts for 36% of total gw depletion during 1900-2008
  • Depletion is highly variable spatially; very high depletion rates in the southern and central HP, large areas of Texas and Kansas. Low/no depletion in the northern HP aquifer (#14)

November 1, 1998-October 331, 2016
The High Plains Aquifer, also known as the Ogallala Aquifer, is under stress. Farmers today have to drill ever deeper wells in order to pump water for irrigation, and one recent study found the aquifer to be under more strain than any other in the United States. About 30 percent of the water once stored beneath Kansas is already gone, and another 40 percent will be gone within 50 years if current trends continue.  The map at the left of this page shows irrigation frequency in the basin between 1999 and 2016. Areas watered nearly every year are purple; those watered only rarely are yellow. The extent of the Ogallala Aquifer is shown with gray. The second image highlights the variability in irrigation between center-pivot irrigation fields in an area along the Colorado-Nebraska border. The most widely grown crops in the basin are corn and wheat.  NASA Earth Observatory maps by Lauren Dauphin, using data from Deines, Jillian, et al. (2017). Story by Adam Voiland.
Highlights from Global Aquifer Hotspots: Northwest India (#23) The International Scale of the Groundwater Issue
  • India is the world’s largest consumer of gw
  • 1/3 of India’s aquifers are overexploited, semicritical, or critical
  • 70% of India’s agricultural production depends on gw
  • GW is the primary source (85%) of drinking water for rural areas
  • GW is typically extracted by tubewells (~15 million)
  • In Northwestern India (Rajasthan, Punjab, Haryana, including Delhi) gw has been unsustainably depleted between 2000-2008 in an amount equivalent to double the capacity of India’s largest surface-water reservoir (Rodell, et al., 2009)
  • This region has a population of approximately 114,000,000.
Highlights from Global Aquifer Hotspots: North China Plain (#29) The International Scale of the Groundwater Issue
  • Region supplies nearly half of China’s wheat and one-third of other cereal grains
  • Population is more than 200,000,000
  • Rapid groundwater depletion since the 1980’s
  • Saltwater intrusion into the freshwater aquifer due to groundwater depletion has salinized 44% of the total area between the coastal plain and Laizhou city.

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