Appendix
THE FIRST SELECTED G@GPS “FLAG BASINS”
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Map of the largest groundwater aquifers in the world (modified after Atlas of Transboundary Aquifers, UNESCO-IHP, 2009), showing the
location of the first G@GPS “flag basins”
SHORT GEOLOGICAL DESCRIPTION OF THE FIRST G@GPS “FLAG BASINS”
Africa: North West Sahara Aquifer System (NWSAS)
Complexe Terminal Aquifer:
The Complexe Terminal is a multi-layer aquifer which consists of Upper Cretaceous
formations and sandy formations of the Eocene and the Mio-Pliocene. Artesian discharge
disappeared due to the intensive exploitation of this aquifer. Only some drills situated in the
low zones are still artesian.
Sources:
-Samir K 2011: Recharge of the plio-quaternary water table aquifer in Tunisian chotts region
estimated from stable isotopes Environ. Earth. Sci. 63:189–199.
Continental Intercalaire Aquifer:
The CI aquifer is shared between Algeria, Tunisia and Libya. The groundwater reservoir of the
Continental Intercalaire is contained in the continental formations of the lower Cretaceous.
This geological succession is differentiated into several units of detrital sediments separated
by clay-rich strata, giving rise to a degree of heterogeneity in the heart of the CI aquifer.
Sources:
-Abid K, Zouari K, Abidi, B Identification and characterisation of hydrogeological relays
of continental intercalaire aquifer of southern Tunisia. Carbonates, Evaporites 25: 65–75
-Samir K, Younes, H, Chkir N, Zouari, K 2008: The hydro geochemical characterization of
ground waters in Tunisian Chott’s region Environ Geol 54:843–854.
North America:
North America: High Plains Aquifer (HPA)
The High Plains aquifer (HPA) consists of near-surface sedimentary deposits of Tertiary and
Quaternary age that form six hydraulically connected hydrogeologic units of the regionally
unconfined aquifer. The Tertiary sediments include the Brule Formation, Arikaree Group,
Ogallala Formation, and alluvial deposits of Pliocene age. The deposits of Quaternary age
include glacially derived sediments hydraulically connected to the Tertiary units and local
alluvial, loess, dune-sand, and valley-fill deposits. Bedrock units that underlie that HPA range
in age from Permian to Tertiary. The most extensive and productive of the hydrogeologic
units is the Ogallala Formation that underlies approximately 77% of the system. The Ogallala
was deposited by aggrading streams that filled and buried valleys eroded into pre-Ogallala
rocks. Braided streams flowing eastward from the ancestral Rocky Mountains deposited a
heterogeneous sequence of clay, silt, sand, and gravel. Locally cemented zones consisting of
calcium carbonate (caliche), and sometime silica, occur near the top of the formation,
forming escarpments that mark the boundary of the central and southern HPA. The caliche
caprock is most prominent across much of Texas and New Mexico and is as much as 18 m
thick. Extensive clay layers are present locally within the saturated zone of the Ogallala
Formation, sometimes causing locally confined conditions. The saturated thickness of the
High Plains aquifer ranges from less than 1 m to more than 300 m and averages about 60 m.
Depth to water ranges from 0 to approximately 150 m, and averages about 30 m. Depths to
water are greatest in the central and southern HPA, whereas the saturated thickness is
greatest in the northern HPA. Water-table elevations in the HPA indicate that regional
groundwater flow is generally from west to east; however, local variability in hydraulic
gradients can result in different directions of groundwater flow, particularly near highcapacity pumping wells and major rivers like the Platte, Republican, and Arkansas.
Sources:
-Gurdak, J.J., McMahon, P.B., Dennehy, K.F., and Qi, S.L., 2009. Water quality in the High
Plains Aquifer, Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas,
and Wyoming, 1999–2004: U.S. Geological Survey Circular 1337, 63 p. ;
http://pubs.usgs.gov/circ/1337/.
-McMahon, P.B., Dennehy, K.F., Bruce, B.W., Gurdak, J.J., and Qi, S.L., 2007. Water-quality
assessment of the High Plains aquifer, 1999-2004, USGS Professional Paper 1749, 212 p. ;
http://pubs.usgs.gov/pp/1749/.
South America :
Guaraní Aquifer System (GAS)
The Guarani Aquifer consists primarily of sandstones deposited by fluvial and aeolian
processes during the Triassic and Jurassic periods, with over 90% of the total area overlain
by low-permeability basalt, acting as an aquitard.
Sources:
- Montaño J, Tujchneider O, Auge M, Perez M, Paris M, D´elia M, Fili M, Inagy M, Colllazo M
y Decoud P 1998. Acuíferos Regionales en América Latina. Sistema Acuífero Guaraní.
Capítulos Agentino y Uruguayo. Universidad Nacional del Litoral, 216 pp. ISBN 987-508-0330.
Asia :
North China Plains Aquifer (NCPA)
http://siteresources.worldbank.org/INTWRD/Resources/GWMATE_English_CP_08.pdf
The North China Plains Aquifer is bounded by the Taihang Mountains to the west, the Yanshan
Mountains to the north, the Bohai Sea to the east, and the Yellow River to the south (Fig.1). The plain
was formed through fault–subsidence since the Cenozoic and deposition of Quaternary sediment,
which are 400–600 m thick by the Yellow River and other main rivers.
In the western part of the plain close to the piedomont, the aquifer is mainly composed of
Quaternary cobbles, gravel, sand, and laminated or lensed clay to a depth of 400–500 m and is
separated into four groups: holocene (Q4, up to 10 m thickness), upper pleistocene (Q3, 20–70 m
thickness), middle pleistocene (Q2, up to 20 m thickness) and Lower Pleistocene (Q1, no thickness
data available) (Yang et al., 2001). In the eastern part of the plain affected by the lower reach of the
Yellow River, three main layers were found: yellowish loamy sand (0–15 m) with discontinuous thin
layers of clay, silty clay, and silt; reddish–whitish (15–22 m) and yellowish 27–50 m) sand with about
5–6 m of sand and loamy sand in the middle; and silty clay and clay (50–55 m), which serves as an
impermeable layer (Zhang, 1988).
Sources :
-Yang YS, Lin XY,Elliot T, Kalin RM, 2001.Anatural-gradient field tracer test for evaluation of pollutanttransport parameters in a porous-medium aquifer. Hydrogeology Journal 9 (3), 313–320.
-Zhang YZ (1988) Boundary integral equation for groundwater modeling and determination
parameters. In: Liu CM, Ren HZ (eds) Air, surface, soil and groundwater interactions – experiment and
calculation analysis (in Chinese). Science Press, Beijing, pp 287–312
Europe:
The Baltic Artesian Basin (BAB)
The Baltic Artesian Basin’s large platform structures include the southern slope of the Baltic
shield, the Baltic syneclise, and the Byelorussian anteclise. The region is composed of a
complex of metamorphic and igneous Archean and Proterozoic rocks and strata of
terrigenous and carbonate rocks from the Cambrian to the Anthropogenic. There are two
layers of subterranean water. The lower layer includes the Cambrian-Wendian aquiferous
horizon, and the upper layer encompasses the Cambrian-Ordovi-cian and overlying
aquiferous horizons. The two layers are separated from each other by a thick and persistent
bed of Cambrian clays.
Sources:
-A Zuzevičius 2010: BALTICA Vol 23, 1: 1-12 The groundwater dynamics in the southern part
of the Baltic artesian Basin during the Late Pleistocene
Oceania :
Great Artesian Basin (GAB)
Triassic sandstones and conglomerates and clay beds underly thicker sandstones. Cretaceous
marine mudstones form the confining beds overlying the artesian aquifer.
Sources:
-Collon P, Kutschera W, Loosli HH, Lehmann B, Purtschert R, Love AJ, Sampson L, Anthony D,
Cole D, Davids B, Morrissey DJ, Sherrill BM, Steiner M, Pardo RC, Paul M et al. 2000: 811Kr in
the Great Artesian Basin, Australia: a new method for dating very old groundwater, Earth
and Planetary Science Letters, 182, 103-113.
Sydney basin aquifers (SBAs)
The Triassic Hawkesbury sandstones form the most widespread regional aquifers and the
main hydrogeological units within the Sydney Basin. The Hawkesbury sandstone aquifers can
be generally described as semi-confined, but they are confined in some areas where the unit
is overlain by shales.
Sources:
-Cendón, D I, Hankin, S, Williams JP, Dimovski, C, Meredith KT, Hughes CE, Hollin SE 2009:
Groundwater residence time in the Kulnura-Mangrove Mountain Plateau (Gosford, NSW,
Australia). In: 10th Australasian Environmental Isotope Conference & 3rd Australasian
Hydrogeology. Research Conference, edited, p. 6, Perth, WA.
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