Geography of the World’s Groundwater: A Hierarchical Approach to Scale-Dependent Zoning

Abstract

The description and analysis of local, regional or global groundwater conditions are of practical use only if the groundwater information is properly linked to well-defined geographic locations or zones. Most hydrogeological maps do so by presenting values or patterns of hydrogeological variables superimposed on a simplified topographic map. For various purposes, however, it is helpful to relate the groundwater information to predefined spatial units or zones with hydrogeologically meaningful boundaries. Such zones can be defined at different scale levels, according to the geographic dimensions of the case considered and the spatial resolution required. In this chapter, a hierarchical approach to scale-dependent groundwater zoning is presented. It includes three levels: (1) ‘aquifers’ or ‘aquifer systems’ at the local level; (2) ‘groundwater provinces’ at the intermediate level; and (3) ‘global groundwater regions’ at the macro-level. Each of the delineated 36 global groundwater regions is subdivided into a number of the 217 proposed groundwater provinces. Each of the latter, in turn, includes one, several or many of the aquifer systems present on Earth. The proposed zoning system has potential to contribute to organising, deepening and disseminating knowledge on the World’s groundwater.

Appendices

Appendix 1: Brief Description of the Global Groundwater Regions

North and Central America & The Caribbean

Global Groundwater Region 1: Western mountain belt of North and Central America

This region, the westernmost zone of the continent, includes highly elevated folded areas of North and Central America, belonging to the Pacific and Cordilleran Belts. Sedimentary and metamorphic rocks underlie the region. After these belts were formed, extensive less deformed basins dominated by volcanic rocks superimposed them. There are large variations in climate: above-average rainfall in mountain zones, low rainfall in arid zones, permafrost conditions in the North and tropical temperature regimes in the South.

The region is subdivided into the following groundwater provinces:

• 1.01 Alaska

• 1.02 Cordilleran Orogen of Canada

• 1.03 Pacific Mountain System

• 1.04 Columbia Plateau

• 1.05 Basin and Range

• 1.06 Colorado Plateau

• 1.07 Rocky Mountains System

• 1.08 Central American ranges (including Mexican Sierras)

Groundwater resources are variable. In the mountains they are associated with glacial and fluvial aquifers in faulted troughs or with intermontane basins. The volcanic regions in Central America contain some of the most productive aquifers. Coastal aquifers are present in structural basins filled with marine and alluvial sediments.

Global Groundwater Region 2: Central plains of North and Central America

This region is located in the heart of North America and includes topographically low areas with gently rolling to flat topography. Except at its Northern edge, there is no boundary with the sea. Thick sequences of sediments deposited in marine, alluvial, glacial and eolian environments cover the Precambrian Basement. Climate is predominantly dry. Permafrost is present in the North.

The region is subdivided into the following groundwater provinces:

• 2.01 Interior Platform of Canada

• 2.02 Interior Plains of USA

• 2.03 Interior Highlands

• 2.04 Sierra Madre Oriental

Groundwater resources are abundant and the region is characterised by large volumes of stored groundwater. Large regional aquifers occur in porous or fractured consolidated sediments and in large alluvial areas (e.g. High Plains or Ogallala aquifer in USA). Glacial sediments in the Northern parts may form local aquifers.

Global Groundwater Region 3: Canadian shield

This region includes the low to moderately elevated areas of the Canadian Shield. The region’s topography is mainly a result of the effects of glacial action. Precambrian crystalline rocks cover most of the region. Locally remains of sedimentary covers (mainly limestone) are found. Region receives moderate precipitation (often as snow). Continuous permafrost is present in the Northern half.

The region is subdivided into the following groundwater provinces:

• 3.01 Seven geological provinces of Canadian shield

• 3.02 Innuitian Orogen

• 3.03 Hudson Bay Lowlands

• 3.04 Arctic Platform

• 3.05 St. Lawrence Platform (including Laurentian Platform of USA)

• 3.06 Greenland

Groundwater resources are limited. Groundwater is restricted to local pockets of weathered or fractured consolidated rocks or to shallow layers of fluvial and glacial sediments. Certain areas are susceptible to arsenic contamination.

Global Groundwater Region 4: Appalachian highlands

This region includes the high-elevated Eastern part of North America belonging to the Appalachian Orogenic belt. Metamorphic and igneous rocks are present. After the belt was deformed extensive less deformed basins dominated by sedimentary rocks superimposed it. Climate is predominantly humid.

The region is subdivided into the following groundwater provinces:

• 4.01 Appalachian Orogen in Canada

• 4.02 Appalachian Highlands in USA

Groundwater resources are variable. The principal aquifers are found in carbonate rocks and sandstones (e.g. Valley and Ridge aquifers). The high-elevated areas have limited groundwater resources with local surficial aquifer systems in sand and gravel deposits of glacial and alluvial origin.

Global Groundwater Region 5: Caribbean islands and coastal plains of North and Central America

This region includes the low, flat areas along the Atlantic coast and the Gulf of Mexico, associated with the Ouachita tectonic depression. The coastal plains are huge seawards-thickening wedges of unconsolidated sedimentary rocks lying on consolidated limestone and sandstones. The sediments are of fluvial, deltaic and shallow marine origin. The Caribbean island arc (several thousand islands) is a partially submerged cordillera, having a nucleus of igneous rocks overlain by sediments and volcanics. The region receives abundant precipitation.

The region is subdivided into the following groundwater provinces:

• 5.01 Atlantic Plains (incl. Florida Peninsula)

• 5.02 Mexican Gulf Plains (incl. Yucatan Peninsula)

• 5.03 Caribbean Plains

• 5.04 Caribbean Islands Arc

Groundwater resources are abundant. Large regional groundwater systems are developed in unconsolidated and (semi-)consolidated sediments (e.g. Coastal lowlands aquifer system and Mississippi River Valley aquifer system). Karst aquifers are frequently found (e.g. Florida and Yucatan aquifer systems). Large islands have combined unconsolidated (alluvial), carbonate and volcanic aquifers. Sea water intrusion is a major problem, especially on islands with shallow freshwater lenses.

South America

Global Groundwater Region 6: Andean belt

This region includes the high-elevated areas of South America belonging to the Andean Mobile Belt. There are many wide valleys of tectonic origin and valleys that resulted from fluvial erosion.

The region is composed of heterogeneous rocks. Frequently, a core of granitic and metamorphic rocks is surrounded or partially covered by folded and fractured sedimentary rocks (marine limestone and continental conglomeratic sandstones). On many locations, volcanic rocks (pyroclastic material and lavas) have been ejected or have flowed out. Large variation in climatic conditions is reflected by an above-average rainfall in mountains alternating with arid zones.

The region is subdivided into the following groundwater provinces:

• 6.01 Andes

• 6.02 Altiplano

• 6.03 Coastal

Groundwater resources are variable. Groundwater is typically associated with colluvial aquifers in faulted troughs or basins within mountains. The volcanic zones are very important groundwater sources. High fluoride concentrations are common in these zones. Coastal aquifers occur in structural basins filled with marine and alluvial sediments. These aquifers are prone to seawater intrusions.

Global Groundwater Region 7: Lowlands of South America

This region includes the low to moderate elevated, flat areas of South American sedimentary basins, relatively unaffected by tectonic events.

Thick sedimentary sequence is composed of consolidated (mainly conglomerates and sandstone) and unconsolidated sediments of alluvial, lacustrine and eolian origin transported from neighbouring high-elevated areas. The region receives moderate to very high precipitation.

The region is subdivided into the following groundwater provinces:

• 7.01 Orinoco basin (Northern Llanos Basins)

• 7.02 Amazon basin

• 7.03 Pantanal and Gran Chaco

• 7.04 Pampas with Rio de la Plata estuary

• 7.05 Parana Basin

• 7.06 Patagonia plains

Groundwater resources are abundant. The unconsolidated alluvial sediments, deposited by the major rivers (e.g. aquifers in the Amazon basin and the Puelches Aquifer) and sandstones (e.g. the Guarani aquifer system) form the most important aquifers. Saline water and high concentrations of arsenic and fluoride are common.

Global Groundwater Region 8: Guyana Shield

This region includes the moderate elevated, flat topped, Guyana Shield in North-Eastern part of the continent. Crystalline rocks cover almost whole area. The region has a warm and humid climate with annual rainfall in the range of 1000–2000 mm. Groundwater resources are restricted by geological conditions, except for relatively narrow sedimentary zones along the coast. Based on these different hydrogeological conditions, the region is subdivided into two groundwater provinces:

• 8.01 Guyana Shield province: mainly Precambrian igneous and metamorphic rocks with low potential for storing and transmitting groundwater.

• 8.02 Guyana Coastal province: deltaic multilayer sandy aquifer systems in the coastal lowlands. They are the main aquifers of the region.

Global Groundwater Region 9: Brazilian Shield and Associated Basins

This region includes the low to moderate elevated, predominantly flat Brazilian Shield with associated younger sedimentary basins. The Brazilian Shield is mainly composed of crystalline rocks. The associated basins contain a sequence of sandstone, volcanic rocks and unconsolidated sediments. Region receives high precipitation.

The region is subdivided into the following groundwater provinces:

• 9.01 Brazilian Shield (North, Central, East and South)

• 9.02 Parnaiba Basin

• 9.03 Sao Francisco Basin

• 9.04 Brazilian coastal

Groundwater resources are variable. Groundwater in the crystalline rocks is restricted to local pockets of weathered or fractured zones or to shallow layers of sediments. In the sedimentary basins, both sandstones and unconsolidated sediments can form large aquifers. The volcanic areas (predominantly basalts) have limited groundwater potential.

Europe

Global Groundwater Region 10: Baltic and Celtic shield

This region includes the low to moderate elevated, predominantly flat areas of Baltic Shield and Ireland-Scotland Platform. Included are also higher elevated areas of Norwegian Caledonides and Iceland and Massif Armoricain which have more pronounced relief. The Baltic Shield, the Scotland Platform and Massif Armoricain are mainly composed of crystalline rocks. The Ireland Platform is composed of sedimentary rocks, while Iceland is built almost exclusively of young volcanic rocks, predominantly basalts. Region receives medium to high precipitation.

The region is subdivided into the following groundwater provinces:

• 10.01 Baltic Shield

• 10.02 Norwegian Caledonides

• 10.03 Island of Iceland

• 10.04 Ireland-Scotland Platform

• 10.05 Massif Armoricain

Groundwater resources are limited. Groundwater in crystalline rocks is restricted to local pockets of weathered or fractured hard rocks. The only widespread aquifers with inter-granular permeability are found in the Quaternary deposits (glacio-fluvial deposits). Local karst aquifers occur in Ireland (e.g. the Waulsortian aquifer). The recent volcanoclastics are highly permeable and can form local aquifers in Iceland.

Global Groundwater Region 11: Lowlands of Europe

This region includes the low-elevated, flat areas of European sedimentary basins. The higher elevated areas, associated with the Uralian Orogenic Belt, are included in this region as an administrative boundary between Europe and Asia. Thick sedimentary sequence is composed of consolidated and unconsolidated sediments of marine, eolian and alluvial and origin. Region receives medium to high precipitation.

The region is subdivided into the following groundwater provinces:

• 11.01 Anglo & Paris Basin

• 11.02 Aquitaine Basin

• 11.03 London & Brabant Platform

• 11.04 Dutch Basin

• 11.05 Northwest German Basin

• 11.06 German-Polish Basin

• 11.07 Russian Platform

• 11.08 Ural Mountains

Groundwater resources are abundant. The unconsolidated sediments form the most important aquifers in the deltas of main rivers (e.g. in the Netherlands). Glacial and eolian aquifers are of local importance. In south-western and northern basins, limestone aquifers are found (e.g. the Chalk Aquifer). The central and eastern parts of the regions have also extensive sandstone aquifers. The Ural Mountains, composed of crystalline rocks, have limited groundwater resources. All coastal aquifers are prone to saline intrusion.

Global Groundwater Region 12: Mountains of Central and Southern Europe

This region includes the high-elevated areas of Europe belonging to the Hercynian and Alpine Orogenic Belt. Also included are low to medium elevated sedimentary basins associated with these tectonic structures. The folded areas have complex lithology with alternating crystalline, volcanic and sedimentary rocks. Western sedimentary basins contain thick sequence of predominately carboniferous rocks. The eastern basins are covered with thick layers of unconsolidated sediments. Large variations in climate are reflected by an above-average rainfall in mountains alternating with dry zones in the lowlands.

The region is subdivided into the following groundwater provinces:

• 12.01 Iberian Massifs (a.o. the Hesperian Massif)

• 12.02 Iberian Basins

• 12.03 Pyrenees

• 12.04 Massif Central

• 12.05 Jura, Vosges and Ardennes

• 12.06 Southern German Basins

• 12.07 Alps

• 12.08 Po Basin

• 12.09 Apennines

• 12.10 Bohemian massifs

• 12.11 Pannonian Basin

• 12.12 Carpathian Mountains

• 12.13 Dinaric Alps

Groundwater resources are variable. Groundwater in crystalline rocks is restricted to local pockets of weathered or fractured hard rocks. Alluvial and colluvial fill of relative flat areas form local aquifers in the mountains. In the sedimentary basins, limestone, sandstones and unconsolidated sediments can form large interconnected aquifer systems (e.g. Po Plain aquifers and Hungarian Plain aquifers).

Africa

Global Groundwater Region 13: Atlas mountains

This region includes the elevated areas of the Atlas Mountains, created during the Alpine orogenesis in Northwestern Africa. The Northern part is composed of folded sedimentary rocks (mainly limestone). In the Southern part, basement crystalline rocks are covered by shallow marine and alluvial sediments. Precipitation shows large spatial and temporal variation. The Southern areas are subject to desert influences.

The region is subdivided into the following groundwater provinces:

• 13.01 Northern Atlas mountain range (Anti, High, Middle and Tell Atlas)

• 13.02 El-Shatout depression

• 13.03 Saharan Atlas mountains in the South

Groundwater resources are limited to alluvial sediments in the mountains, karstic aquifers in the Northern part and shallow aquifers at the North and North-West coast.

Global Groundwater Region 14: Saharan basins

This region includes the North African Craton. It comprises a Precambrian basement unconformably overlain by a thick sequence of continental and marine sediments (clastic sediments covered by carbonates), structured into a number of low to medium elevated flat basins separated by higher elevated zones. The flat areas are covered by aeolian sand and locally by alluvial deposits.

The region has an arid climate and is subdivided into the following groundwater provinces:

• 14.01 Tindoef Basin

• 14.02 Grand Erg/Ahnet Basin

• 14.03 Trias/Ghadamedes Basin

• 14.04 Hamra Basin

• 14.05 Sirte Basin

• 14.06 Erdis/Kufra Basin (Nubian sandstone)

• 14.07 Dakhla Basin (Nubian sandstone)

• 14.08 Nile valley and delta

• 14.09 Senegal-Mauritanian Basin

• 14.10 Regubiat High

• 14.11 Taoudeni Basin

• 14.12 Hoggar High

• 14.13 Iullemeden Basin

• 14.14 Chad Basin

• 14.15 Tibesti (Quadai) Mountains

• 14.16 Ennedi-Darfour Uplift

• 14.17 Sudan interior basins (Nubian sandstone)

• 14.18 Ougarta Uplift

Groundwater resources are variable. Groundwater in crystalline rocks is restricted to local pockets of weathered or fractured zones or to shallow layers of fluvial sediments. In the sedimentary basins sandstone and limestone layers form important regional aquifer systems. Some of these aquifers are deep and receive no modern recharge (e.g. The Nubian Sandstone Aquifer). Other systems are recharged in the river valleys (e.g. Iullemeden Aquifer System). Large alluvial aquifers developed along the river Nile and in its delta.

Global Groundwater Region 15: West African basements

This region includes low to moderate elevated, flat areas of the West African Shield and sedimentary basins associated with large rivers. Narrow coastal strip containing unconsolidated sediments is also included. The Shield areas are dominated by outcropping crystalline Basement rocks. Region has a humid climate in the Northern parts along the coast and a dry climate in the South and the Northern strip along the Sahara.

The region is subdivided into the following groundwater provinces:

• 15.01 Eburneen Massif

• 15.02 Volta Basin

• 15.03 Niger Delta

• 15.04 Nigerian Massif

• 15.05 West Congo Precambrian Belt

• 15.06 Damer Belt

Some areas have high fluoride concentrations. Deltas of large rivers (Volta, Niger) have more favourable groundwater conditions. High arsenic concentrations are found locally.

Global Groundwater Region 16: Sub-Saharan basins

This region includes large inland depressions in basement rocks of Central and Southern Africa that have been filled by sediments of various origins. The sedimentary areas are moderate elevated and have flat relief. Topographical high of crystalline rocks, which separate two Southern basins, is included in this region. Region has a humid climate in the Northern parts and a dry climate in the South. Groundwater resources are abundant.

The region is subdivided into the following groundwater provinces:

• 16.01 Congo basin

• 16.02 Kalahari-Ethosha Basin

• 16.03 Kalahari Precambrian Belt

• 16.04 Karoo Basin

• 16.05 Cape Fold Belt

• 16.06 Coastal Basins of Mozambique

Large regional aquifers are found in unconsolidated sediments (e.g. in Congo basin) and fractured sandstones (e.g. Karoo Aquifer system). Limestone and dolomite layers (e.g. Katanga System) form local aquifers. Shales and crystalline rocks are poor aquifers. Some of the aquifers receive limited modern recharge.

Global Groundwater Region 17: East African basement and Madagascar

This region includes moderate elevated, flat areas of the East African Shield, affected in the Eastern parts by rifting. The region is dominated by outcropping crystalline Basement rocks, with local occurrence of volcanic rocks and sediments. Climate is humid in the Northern parts and dry in the South. Groundwater resources are limited.

The region is subdivided into the following groundwater provinces:

• 17.01 East Congo Precambrian Belt

• 17.02 Luffilian Arch (Katanga system)

• 17.03 East Kalahari Precambrian Belt

• 17.04 East Africa Basement (including rifted zones)

• 17.05 Tanzania coastal basin

• 17.06 Sediments of Madagascar

• 17.07 Basement of Madagascar

Groundwater resources are limited. Groundwater in crystalline rocks is restricted to local pockets of weathered or fractured zones or to shallow layers of fluvial sediments. Coastal sediments (e.g. Karoo Sandstone in Tanzania) have favourable groundwater conditions. High fluoride concentrations occur locally.

Global Groundwater Region 18: Volcanics of East Africa

This region includes the moderate to high-elevated part of the East African Craton that has been affected by rifting and volcanism. In the rifted zone, large fault escarpments and steep slopes of volcano’s dominate the relief. Arid to semiarid climate prevails, with humid zones in higher elevated areas. Groundwater resources are variable.

The region is subdivided into the following groundwater provinces:

• 18.01 Amhara Plateau

• 18.02 Eastern Branch of East African Rift Valley

Groundwater in crystalline rocks is restricted to local pockets of fractured and weathered zones or shallow layers of alluvial sediments. In volcanic areas groundwater occurs in fractured zones and in the sediments interbedded between successive lava flows (‘old land surfaces’). Groundwater may contain high concentrations of fluoride and is often hot and brackish in the Rift Valley.

Global Groundwater Region 19: Horn of Africa basins

This region includes large depressions in basement rocks that have been filled by sediments of various origins. Locally isolated uplifted Basement complexes occur. Southern en central parts are flat and moderate-elevated. Northern parts have more pronounced relief. Arid to semiarid climate prevails, with humid zones in higher elevated areas. Groundwater resources are variable.

The region is subdivided into the following groundwater provinces:

• 19.01 Ogaden Basin

• 19.02 Somali Coastal Basin

Groundwater resources are variable. Groundwater in crystalline rocks is restricted to local pockets of fractured and weathered zones or shallow layers of alluvial sediments. The sedimentary rocks have variable groundwater potential. Sandstones and fractured limestones are permeable and have good yields, although water levels are in place deep. Interbedded silt and clay horizons form barriers to groundwater flow. The best aquifers are found in coarse Quaternary alluvial sediments in the floodplains of major rivers. Dissolution of evaporates occurring in central horizons of sediments causes increased salinity of groundwater.

Asia

Global Groundwater Region 20: West Siberian platform

This region includes the low to moderate elevated, flat areas of West Siberian craton that has been rifted and filled by thick sedimentary sequences. Upper part of these sequences consists predominantly of alluvial-lacustrine sediments. Climate is cold and dry. In the Northern parts of the region is a belt of permafrost. Groundwater resources are abundant.

The region is subdivided into the following groundwater provinces:

• 20.01 Yenisey Basin

• 20.02 West Siberian Basin

• 20.03 Turgay Depression (basin)

Groundwater resources are abundant. Unconsolidated sediments show large variations in grain size. Main aquifers are associated with layers of coarse material in alluvial sediments. Fractured sandstones form local aquifers.

Global Groundwater Region 21: Central Siberian plateau

This region includes the moderate elevated areas of Central Siberian craton, including large basins separated by uplifted highs and arches of crystalline rocks. Numerous rivers have further modified the relief of the region. Climate is cold and dry. In the Northern half of the region is a belt of permafrost.

The region is subdivided into the following groundwater provinces:

• 21.01 Tunguska Basin

• 21.02 Cis-Sayan Basin

• 21.03 Lena-Vilyuy Basin

• 21.04 Anabar-Olenek High

• 21.05 Nepa-Botuoaba Arch

• 21.06 Aldan uplift

Groundwater resources are moderate. Alluvia associated with large rivers (e.g. Lena) and fissured limestone and sandstones form potential aquifers. Crystalline rocks have a low groundwater potential restricted to weathered zones. Groundwater distribution is greatly influenced by permafrost.

Global Groundwater Region 22: East Siberian highlands

This region includes the moderate to high-elevated areas of East Siberian craton. The craton now is largely covered by thick sedimentary sequences of marine and continental sediments. The relief of the region is related to anticlinal structures in sedimentary rocks. In the Eastern parts of the region, also crystalline rocks crop out in the folded structures. Climate is cold and dry. Almost entire region belongs to the permafrost zone.

The region is subdivided into the following groundwater provinces:

• 22.01 Verkhoiansk Range

• 22.02 Cherskii Range

• 22.03 Kolyma Plain

• 22.04 Yukagir Plateau

• 22.05 Anadyr Range

Groundwater resources are limited. Groundwater occurrence is restricted to fractured or weathered zones in crystalline rocks and consolidated sediments. Locally aquifers in unconsolidated alluvial sediments may occur. Groundwater distribution is greatly influenced by permafrost.

Global Groundwater Region 23: Northwestern Pacific margin

This region includes the moderate to high-elevated areas of Northwestern Asia associated with the unstable island arch of West Pacific (Circum-Pacific Belt). These areas have pronounced relief, related to uplift of sedimentary rocks and volcanic activity. The sedimentary formations consist mainly of marine sandstones and mudstones, which are intercalated by limestone and granitic intrusions. The climate varies from cold and dry to hot and moist.

The region is subdivided into the following groundwater provinces:

• 23.01 Kamchatka Peninsula

• 23.02 Kuril Islands

• 23.03 Japan

• 23.04 Philippines

Groundwater occurs in fractured and fissured sandstones and limestone. Porous volcanic rocks and locally thick unconsolidated sediments form productive aquifers (e.g. Tokyo Group Aquifer System). Thermal zones, associated with volcanic activity, affect the groundwater composition.

Global Groundwater Region 24: Mountain belt of Central and Eastern Asia

This region includes the high-elevated areas of Central and East Asia associated with Palaeozoic Mobile Belt. As result of intensive folding, the region has a steep relief. Crystalline rocks dominate the surface in the Northern half of the region. In the Southern half, crystalline and volcanic rocks alternate with consolidated and unconsolidated sediments.

The region is subdivided into the following groundwater provinces:

• 24.01 The Altay-Sayan Folded Region (Central Siberia-Mongolia Border)

• 24.02 Mongol-Okhotsk Folded Region

• 24.03 Baikal-Paton Folded Region (surroundings of Lake Baikal)

• 24.04 Aldan Shield in Eastern Siberia

• 24.05 Yinshah Da and Xia Hinggannling Uplift (Yablonovy and Khingan ranges)

• 24.06 Sikhote-Alin Folded Region (South-East Siberia)

• 24.07 Korean Peninsula

Groundwater resources are limited to moderate. Local aquifers occur in intermontane alluvial systems, fractured volcanic rocks, and karstified carbonates. Crystalline rocks have a low groundwater potential, restricted to the thickness of the weathered zone. Highlands have low precipitation and high evaporation, while coastal areas have a moist climate. Groundwater resources are limited to moderate.

Global Groundwater Region 25: Basins of Central Asia

This region includes the low to moderate elevated, relatively flat areas of West and Central Asia. Low-elevated Western part of the region is associated with huge geo-syncline containing a thick sequence of sedimentary rocks. In Western parts, the sedimentary basins are separated by more elevated areas containing crystalline rocks. Unconsolidated alluvial and eolian deposits cover large areas. Climate is arid to semiarid.

The region is subdivided into the following groundwater provinces:

• 25.01 Central Kazakhstan Folded Region

• 25.02 Syr-Darya basin

• 25.03 Tian Shan Foldbelt

• 25.04 Junggar Basin

• 25.05 Tarim Basin

• 25.06 Altushan Fold Belt

• 25.07 Jinguan Minle Wuwei Basin

• 25.08 Ordos Basin

• 25.09 Shauxi Plateau

• 25.10 Taihang Shan Yanshan Fold Belt

Groundwater resources are variable. Regional aquifers occur in fractured sandstones, karstified limestone (e.g. Erdos Basin aquifer) and alluvial sediments. Groundwater in extensive loess deposits is associated with the presence of permeable paleo-soils. These horizons are an important water source. Modern recharge is very limited.

Global Groundwater Region 26: Mountain belt of West Asia

This region includes high-elevated areas of West Asia, belonging to the Alpine-Himalayan Mobile Belt (Taurus Mountains, Anatolian Plateau, Caucasus, Central Iranian Basins, Elburz Mountains and Zagros Fold belt and Trust zone). Also included are medium elevated sedimentary basins associated with tectonic structures. The folded areas have complex lithology with alternating crystalline, volcanic and sedimentary rocks. Sedimentary depressions containing predominately marine sediments (carboniferous rocks and sandstones). Basins are locally covered with thick layers of unconsolidated sediments. Climate is predominantly dry, with some moist zones in the higher altitudes.

The region is subdivided into the following groundwater provinces:

• 26.01 Taurus Mountains

• 26.02 Anatolian Plateau

• 26.03 Caucasus

• 26.04 Central Iranian Basins

• 26.05 Elburz Mountains

• 26.06 Zagros Fold belt and Trust zone (Zagros Mountains)

Groundwater resources are low to moderate. Alluvial and colluvial fill of relative flat areas form local aquifers in the mountains. In the sedimentary basins, karstified limestone (e.g. Midyat Aquifer in Turkey) are major groundwater sources. Fractured sandstones and unconsolidated sediments can also form interconnected aquifer systems. The groundwater yield of unconsolidated sediments is high in the alluvial deposits directly connected to the riverbeds.

Global Groundwater Region 27: Himalayas and associated highlands

This region includes high-elevated areas of Central Asia, belonging to the Himalayan Mobile Belt. It is continuation of the West Asian part of this belt (Region 26). The folded areas have complex lithology with altering crystalline, volcanic and sedimentary rocks. Climate varies from warm and humid to cold and arid. Large areas are covered by glaciers or seasonal snow.

The region is subdivided into the following groundwater provinces:

• 27.01 Hindu Kush

• 27.02 Pamir High

• 27.03 Tibetan Plateau

• 27.04 Himalayas

• 27.05 Sichuan Basin

• 27.06 Tenasserim Mountains

Groundwater resources are limited. Alluvial and colluvial fills in relative flat areas might form extensive aquifers (e.g. Kathmandu Valley) in the mountains. Local aquifers also occur in karstic limestone and fractured sandstones.

Global Groundwater Region 28: Plains of Eastern China

This region includes the low to medium elevated areas of Great Plains of Eastern China. Thick sequences of alluvial and aeolian sediments were deposited in sedimentary basins. Region receives low to medium precipitation.

The region is subdivided into the following groundwater provinces:

• 28.01 Manchurian Plain

• 28.02 North China Plain

• 28.03 Middle and Lower Chang Jiang (Yangtze) River Basin

Groundwater resources are abundant. Extensive alluvial aquifers (e.g. Huang-Hai-Hai Plain) store large volumes of groundwater. This region obtained its separate status also due to a very high population density. The bulk of the population of East Asia lives in this region.

Global Groundwater Region 29: Indo-Gangetic-Brahmaputra plain

This region includes the low elevated and flat reaches of large Asian rivers draining the Himalayas. Thick layers of sediments accumulated in the foredeep, which underlie the Ganges Plain and neighbouring plains. Climate varies from arid to humid as the mean annual rainfall increases from west to east.

The region is subdivided into the following groundwater provinces:

• 29.01 Indus Basin

• 29.02 Ganges Basin

• 29.03 Brahmaputra Basin

• 29.04 Irrawaddy Basin

Groundwater resources are abundant. Extensive alluvial aquifer system, associated with major rivers draining the Himalayas, is one of the largest groundwater reservoirs in the world.

Global Groundwater Region 30: Nubian and Arabian shields

This region includes the low-elevated coastal plains, associated with the Red Sea depression, and moderate high areas belonging to the Nubian and Arabian Shields. High-elevated, rift-related, volcanic areas are also included in this region. Climate is arid to semiarid. Red Sea Hills in Africa (including parts of Sahara and Ethiopian Highlands).

The region is subdivided into the following groundwater provinces:

• 30.01 Red Sea Hills in Africa

• 30.02 Red-Sea coastal plains (e.g. Tihama Plains)

• 30.03 North Western Escarpment Mountains (Midian & Hiraz)

• 30.04 Asir Mountains

• 30.05 Arabian Shield (e.g. Najd Plateau)

• 30.06 Yemen Highlands

Groundwater resources are variable. Crystalline rock areas have limited groundwater potential, restricted to local weathered zones. Larger aquifer systems are associated with unconsolidated sediments underlying plains (e.g. Tihama aquifer) and river deltas (e.g. Abyan). Fractured sandstones, limestone and volcanic rocks, underlying the Yemeni Highlands, can form important aquifers.

Global Groundwater Region 31: Levant and Arabian platform

This region includes the low to moderate elevated, predominantly flat areas of the Levant region and Western parts of the Arabian Peninsula. More elevated areas in Oman are also included. Large rift basins were successively filled with sediments of different origin. Climate is arid.

The region is subdivided into the following groundwater provinces:

• 31.01 Sinai

• 31.02 Euphrates-Tigris Basin

• 31.03 Al Hasa Plain in (Saudi Arabia)

• 31.04 Central Arch with Tuwaig Mountains

• 31.05 Rub Al Khali Basin

• 31.06 Marib and Shabwa basins in Yemen

• 31.07 Masila-Jeza Basin (with wadi Hadramawt)

• 31.08 Mountains and plains of Oman

Groundwater resources are abundant in terms of stored volumes, but limited in terms of replenishment. Large regional aquifer systems are found in sandstones (e.g. Mukalla Aquifer System) and fissured carbonates (e.g. Umm-Er-Rhaduma Aquifer System). Unconsolidated alluvial sediments along main wadis form local aquifers.

Global Groundwater Region 32: Peninsular India and Sri Lanka

This region includes low- to moderate-elevated areas of the Indian craton. The region is predominantly composed of crystalline rocks. Volcanic (basalt) rocks belonging to the Deccan Trap cover a large area in the Western part of the peninsula. In coastal areas, sedimentary rocks (predominantly sandstones) occur. These rocks might be covered by thick accumulation of unconsolidated sediments especially in the deltas of larger rivers. Climate varies from arid to humid.

The region is subdivided into the following groundwater provinces:

• 32.01 Precambrian basement areas in southern and eastern India

• 32.02 Precambrian basement area of Aravalli Range in Rajasthan

• 32.03 Precambrian basement and sediments of Sri Lanka

• 32.04 Deccan Trap

• 32.05 Coastal sedimentary areas

Groundwater resources are low to moderate. Groundwater in crystalline rocks is restricted to local pockets of fractured and weathered zones or shallow layers of alluvial sediments. Sedimentary intercalations between lava flows (intertrappeans) are important groundwater sources in volcanic areas. Major deltaic and coastal aquifers, particularly along the East coast, have the highest potential. The coastal zones are prone to seawater intrusion.

Global Groundwater Region 33: Peninsulas and Islands of South-East Asia

This region includes low- to moderate-elevated areas of peninsulas and islands of South-East Asia associated with the Circum-Pacific Belt. Tectonic activity in this area produces a complex geological setting. The region is characterised by outcrops of old crystalline rocks, deep sedimentary basins and recent volcanic eruptions. Climate is humid.

The region is subdivided into the following groundwater provinces:

• 33.01 South China Fold Belt

• 33.02 Truong Son Fold Belt

• 33.03 Thailand Basin

• 33.04 Khorat Platform

• 33.05 Tonle Sap-Phnom Penh Basin

• 33.06 Malay Peninsula

• 33.07 Sumatra/Java Magmatic Belt

• 33.08 Sumatra Basin

• 33.09 Sunda Platform

• 33.10 Barito-Kutei Basin

• 33.11 Sulawesi Magmatic Arc

• 33.12 Irian Basins

• 33.13 New Guinea Mobile Belt

Groundwater resources are variable. Groundwater in crystalline and volcanic rocks is restricted to local pockets of fractured and weathered rocks. Unconsolidated sediments (e.g. in Jakarta Groundwater basin) and fissured sedimentary rocks (e.g. karstic zones in Vietnam) form regional aquifers. The groundwater in volcanic areas has a high fluoride content.

Australia & The Pacific

Global Groundwater Region 34: Western Australia

This region includes low to moderate elevated, predominantly flat basement blocks of Australian Craton, separated by deep sedimentary basins. Sedimentary basins contain thick layers of sandstones and karstified limestone and local alluvial sediments. Climate is semiarid to arid.

The region is subdivided into the following groundwater provinces:

• 34.01 Pilbara Block

• 34.02 Yilgarn Basement Block

• 34.03 Carnarvon Basin

• 34.04 Canning Basin

• 34.05 Officer Basins

• 34.06 Eucla Basin

• 34.07 Kimberly Basement Block

• 34.08 Musgrave Basement Block

• 34.09 McArthur Basin

• 34.10 Wiso and Georgina Basins

Groundwater resources are low to moderate. Groundwater in crystalline and volcanic rocks is restricted to local pockets of fractured and weathered zones or shallow layers of alluvial sediments. Fissured sandstones (e.g. Canning Basin) and limestone (e.g. Eucla Basin) form large regional aquifers. The amount of renewable groundwater is small in comparison to the total storage. Palaeochannel sands (representing former riverbeds) are also prospective aquifers in the region, though the groundwater salinity is high.

Global Groundwater Region 35: Eastern Australia

This region includes low- to moderate-elevated, flat areas of East Australian sedimentary basins. The older consolidated sediments are frequently overlain by extensive alluvial fans. Uplifted areas in the Eastern margin (Great Dividing Range), belonging to the Tasman Mobile Belt, are also included. Climate is arid to semiarid.

The region is subdivided into the following groundwater provinces:

• 35.01 Gawler Ranges

• 35.02 Great Artesian Basin

• 35.03 Murray Basin

• 35.04 Great Dividing Range

• 35.05 Australian Alps

• 35.06 Tasmania Island

Groundwater resources are moderate to high. Thick layers of sandstones form one of the world’s largest aquifer systems (The Great Artesian Basin Aquifer System). Fissured limestone aquifers also occur (e.g. Murray Group Aquifer). Extensive alluvial aquifers, associated with the large rivers draining the uplifted areas, are important shallow groundwater source. Uplifted areas themselves have only local aquifers found in the fractured rocks.

Global Groundwater Region 36: Islands of the Pacific

This region includes small islands of South-Eastern Pacific and New Zealand, belonging to the Circum-Pacific Belt. Pacific islands West of the American continents are also included. The region has large variation in elevation and relief. Volcanic rocks are found in the Northern part. The Southern part (New Zealand) includes also crystalline rocks, uplifted by orogeny, and thick sequences of sedimentary rocks. Climate is humid.

The region is subdivided into the following groundwater provinces:

• 36.01 Bismarck -New Hebrides Volcanic Arcs

• 36.02 Fiji Islands

• 36.03 Orogenic belt of New Caledonia

• 36.04 Axial tectonic belt of New Zealand

• 36.05 Sedimentary basins of New Zealand

• 36.06 Pacific islands West of the American continents

Groundwater resources are variable. Some recent volcanic rocks are highly porous and contain large volume of water. Karstified limestone and porous calcareous formations in coastal areas are also important aquifers. Shallow aquifers occur in unconsolidated alluvial sediments. Freshwater lenses are usually shallow and saline water intrusions are very common.

Appendix 2: Proposed Groundwater Provinces

(See Figs. 7, 8, 9, and 10)

Fig. 7

Groundwater provinces in North & Central America and in Europe (reproduced with permission from IGRAC)

Fig. 8

Groundwater provinces in South America and in Africa (reproduced with permission from IGRAC)

Fig. 9

Groundwater provinces in Northern Asia and in Western & Southern Asia (reproduced with permission from IGRAC)

Fig. 10

Groundwater provinces in Eastern Asia and in Ocania (reproduced with permission from IGRAC)

WESTERN MOUNTAIN BELT OF NORTH & CENTRAL AMERICA

• 1.01 Alaska

• 1.02 Cordilleran Orogen of Canada

• 1.03 Pacific Mountain System

• 1.04 Columbia Plateau

• 1.05 Basin and Range

• 1.06 Colorado Plateau

• 1.07 Rocky Mountains System

• 1.08 Central American Ranges

CENTRAL PLAINS OF NORTH & CENTRAL AMERICA

• 2.01 Interior Platform of Canada

• 2.02 Interior Plains of the USA

• 2.03 Interior Highlands

• 2.04 Sierra Madre Oriental

CANADIAN SHIELD

• 3.01 Seven geological Provinces of the Canadian Shield

• 3.02 Innuitian Orogen

• 3.03 Hudson Bay Lowlands

• 3.04 Arctic Platform

• 3.05 St. Lawrence Platform

• 3.06 Greenland

APPALACHIAN HIGHLANDS

• 4.01 Appalachian Orogen in Canada

• 4.02 Appalachian Highlands in the USA

CARIBBEAN ISLANDS AND COASTAL PLAINS OF NORTH AND CENTRAL AMERICA

• 5.01 Atlantic Plains

• 5.02 Mexican Gulf Plains

• 5.03 Caribbean Plains

• 5.04 Carribean Islands Arc

ANDEAN BELT

• 6.01 Andes

• 6.02 Altiplano

• 6.03 Coastal

LOWLANDS OF SOUTH AMERICA

• 7.01 Orinoco Basin

• 7.02 Amazon Basin

• 7.03 Pantanal and Gran Chaco

• 7.04 Pampas with Rio de la Plata Estuary

• 7.05 Parana Basin

• 7.06 Patagonia Plains

GUYANA SHIELD

• 8.01 Guyana Shield

• 8.02 Gyuana Coastal

BRAZILIAN SHIELD AND ASSOCIATED BASINS

• 9.01 Brazilian Shield

• 9.02 Parnaiba Basin

• 9.03 Sao Francisco Basin

• 9.04 Brazilian Coastal

BALTIC AND CELTIC SHIELDS

• 10.01 Baltic Shield

• 10.02 Norwegian Caledonides

• 10.03 Island of Iceland

• 10.04 Ireland-Scotland Platform

• 10.05 Massif Armoricain

LOWLANDS OF EUROPE

• 11.01 Anglo and Paris Basin

• 11.02 Aquitaine Basin

• 11.03 London and Brabant Platform

• 11.04 Dutch Basin

• 11.05 Northwest German Basin

• 11.06 German-Polish Basin

• 11.07 Russian Platform

• 11.08 Ural Mountains

MOUNTAINS OF CENTRAL AND SOUTHERN EUROPE

• 12.01 Iberian Massif

• 12.02 Iberian Basins

• 12.03 Pyrenees

• 12.04 Massif Central

• 12.05 Jura, Vosges and Ardennes

• 12.06 Southern German Basin

• 12.07 Alps

• 12.08 Po Basin

• 12.09 Appennines

• 12.10 Bohemian Massif

• 12.11 Pannonian Basin

• 12.12 Carpathian Mountains

• 12.13 Dinaric Alps

ATLAS MOUNTAINS

• 13.01 Northern Atlas Mountains

• 13.02 El-Shatout Depression

• 13.03 Saharan Atlas Mountains

SAHARAN BASINS

• 14.01 Tindoef Basin

• 14.02 Grand Erg/Ahnet Basin

• 14.03 Trias/Ghadamedes Basin

• 14.04 Hamra Basin

• 14.05 Sirte Basin

• 14.06 Erdis/Kufra Basin

• 14.07 Dakhla Basin

• 14.08 Nile Valley and Delta

• 14.09 Senegal Mauretanian Basin

• 14.10 Regubiat High

• 14.11 Taoudeni Basin

• 14.12 Hoggar High

• 14.13 Iullemeden Basin

• 14.14 Chad Basin

• 14.15 Tibesti (Quadai) Mountains

• 14.16 Ennedi-Darfour Uplift

• 14.17 Sudan Interior Basins

• 14.18 Ougarta Uplift

WEST AFRICAN BASEMENT

• 15.01 Eburneen Massif

• 15.02 Volta Basin

• 15.03 Niger Delta

• 15.04 Nigerian Massif

• 15.05 West Congo Precambrian Belt

• 15.06 Damer Belt

SUB-SAHARAN BASINS

• 16.01 Congo Basin

• 16.02 Kalahari-Etosha Basin

• 16.03 Kalahari Precambrian Belt

• 16.04 Karoo Basin

• 16.05 Cape Fold Belt

• 16.06 Coastal Basins of Mozambique

EAST AFRICAN BASEMENT AND MADAGASCAR

• 17.01 East Congo Precambrian Belt

• 17.02 Luffillian Arch

• 17.03 East Kalahari Precambrian Belt

• 17.04 East Africa Basement

• 17.05 Tanzania Coastal Basin

• 17.06 Sediments of Madagascar

• 17.07 Basement of Madagascar

VOLCANICS OF EAST AFRICA

• 18.01 Amhara Plateau

• 18.02 Eastern Branch of East African Rift Valley

HORN OF AFRICA BASINS

• 19.01 Ogaden Basin

• 19.02 Somali Coastal Basin

WEST SIBERIAN PLATFORM

• 20.01 Yenisey Basin

• 20.02 West Siberian Basin

• 20.03 Turgay Depression

CENTRAL SIBERIAN PLATEAU

• 21.01 Tunguska Basin

• 21.02 Cis-Sayan Basin

• 21.03 Lena-Vilyuy Basin

• 21.04 Anabar-Olenek High

• 21.05 Nepa-Botuoba Arch

• 21.06 Aldan Uplift

EAST SIBERIAN HIGHLANDS

• 22.01 Verkhoiansk Range

• 22.02 Cherskii Range

• 22.03 Kolyma Plain

• 22.04 Yukagir Plateau

• 22.05 Anadyr Range

NORTHWESTERN PACIFIC MARGIN

• 23.01 Kamchatka Peninsula

• 23.02 Kuril Islands

• 23.03 Japan

• 23.04 Philippines

MOUNTAIN BELT OF CENTRAL AND EASTERN ASIA

• 24.01 The Altay-Sayan Folded Region

• 24.02 Mongol-Okhotsk Folded Region

• 24.03 Baikal-Patom Folded Region

• 24.04 Aldan Shield in East Siberia

• 24.05 Yinshah Da and Xia Hinggannling Uplift

• 24.06 Sikhote-Alin Folded Region

• 24.07 Korean Peninsula

BASINS OF WEST AND CENTRAL ASIA

• 25.01 Central Kazakhstan Folded Region

• 25.02 Syr Darya Basin

• 25.03 Tian Shan Fold Belt

• 25.04 Junggar Basin

• 25.05 Tarim Basin

• 25.06 Altun Shan Fold Belt

• 25.07 Jinquan Minle Wuwei Basin

• 25.08 Ordos Basin

• 25.09 Shanxi Plateau

• 25.10 Taihang Shan Yanshan Fold Belt

MOUNTAIN BELT OF WEST ASIA

• 26.01 Taurus Mountains

• 26.02 Anatolian Plateau

• 26.03 Caucasus

• 26.04 Central Iranian Basins

• 26.05 Elburz Mountains

• 26.06 Zagros Fold Belt and Trust Zone

HIMALAYAS AND ASSOCIATED HIGHLANDS

• 27.01 Hindu Kush

• 27.02 Pamir High

• 27.03 Tibetan Plateau

• 27.04 Himalayas

• 27.05 Sichuan Basin

• 27.06 Tenasserim Shan

PLAINS OF EASTERN CHINA

• 28.01 Manchurian Plain

• 28.02 North China Plain

• 28.03 Middle and Lower Chang Jiang River Basin

INDO-GANGETIC-BRAHMAPUTRA PLAIN

• 29.01 Indus Basin

• 29.02 Ganges Basin

• 29.03 Brahmaputra Basin

• 29.04 Irrawaddy Basin

NUBIAN AND ARABIAN SHIELDS

• 30.01 Red Sea Hills in Africa

• 30.02 Red Sea Coastal Plains

• 30.03 North Western Escarpment Mountains

• 30.04 Asir Mountains

• 30.05 Arabian Shield

• 30.06 Yemen Highlands

LEVANT AND ARABIAN PLATFORM

• 31.01 Sinai

• 31.02 Euphrates-Tigris Basin

• 31.03 Al Hasa Plain in Saudi Arabia

• 31.04 Central Arch with Tuwayq Mountains

• 31.05 Rub Al Khali Basin

• 31.06 Marib and Shabwa Basins in Yemen

• 31.07 Masila-Jeza Basin

• 31.08 Mountains and Plains of Oman

PENINSULAR INDIA AND SRI LANKA

• 32.01 Precambrian Basement in Southern and Eastern India

• 32.02 Precambrian Basement of Aravalli Range in Rajasthan

• 32.03 Precambrian Basement and Sediments of Sri Lanka

• 32.04 Deccan Trap

• 32.05 Coastal Sedimentary Areas

PENINSULAS AND ISLANDS OF SOURH-EAST ASIA

• 33.01 South China Fold Belt

• 33.02 Truong Son Fold Belt

• 33.03 Thailand Basin

• 33.04 Khorat Platform

• 33.05 Tonle Sap-Phnom Penh Basin

• 33.06 Malay Peninsula

• 33.07 Sumatra-Java Magmatic Belt

• 33.08 Sumatra Basin

• 33.09 Sunda Platform

• 33.10 Barito-Kutei Basin

• 33.11 Sulawesi-Banda Magmatic Arch

• 33.12 Irian Basins

• 33.13 New Guinea Mobile Belt

WEST AUSTRALIA

• 34.01 Pilbara Block

• 34.02 Yilgarn Basement Block

• 34.03 Carnarvon Basin

• 34.04 Canning Basin

• 34.05 Officer Basins

• 34.06 Eucla Basin

• 34.07 Kimberly Basement Block

• 34.08 Musgrave Basement Block

• 34.09 McArthur Basin

• 34.10 Wiso and Georgina Basins

EAST AUSTRALIA

• 35.01 Gawler Ranges

• 35.02 Great Artesian Basin

• 35.03 Murray Basin

• 35.04 Great Dividing Range

• 35.05 Australian Alps

• 35.06 Tasmania Island

ISLANDS OF THE PACIFIC

• 36.01 Bismarck-New Hebrides Volcanic Arc

• 36.02 Fiji Islands

• 36.03 Orogenic Belt of New Caledonia

• 36.04 Axial Tectonic Belt of New Zealand

• 36.05 Sedimentary Basins of New Zealand

• 36.06 Pacific Islands West of the American Continents