Difference between revisions of "Hydrogeology of Mozambique"

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Mozambique can be divided into three major hydrogeological provinces (DNA 1987). These are:  
 
Mozambique can be divided into three major hydrogeological provinces (DNA 1987). These are:  
  
1. Basement Complex
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1. Sedimentary Basins.
  
 
2. Volcanic (and other igneous) terrains
 
2. Volcanic (and other igneous) terrains
  
3. Sedimentary Basins.
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3. Basement Complex
  
The most significant sedimentary basin is the Mozambique Sedimentary Basin to the south of the Save River, in southern Mozambique. Other, smaller, sedimentary basins include the Mozambique Sedimentary basin to the north of the Save River; the Northern/Rovuma Sedimentary Basin which has a narrow linear outcrop in the northeast of the country; the Middle Zambeze Sedimentary Basin, in the centre-west of the country; and the Maniamba Sedimentary Basin, which has a very small outcrop in the northwest of the country.  
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A fourth province is unconsolidated aquifers, which are sometimes in hydraulic continuity with underlying bedrock aquifers.
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 +
The sedimentary  basins comprise mainly Cretaceous-Tertiary rocks, with small outcrops of older Mesozoic-Palaeozoic rocks, mainly Karoo-type. The most significant sedimentary basin is the Mozambique Sedimentary Basin to the south of the Save River, in southern Mozambique. Other, smaller sedimentary basins are the Mozambique Sedimentary basin to the north of the Save River; the Northern/Rovuma Sedimentary Basin, with  which has a narrow linear outcrop in the northeast of the country; the Middle Zambeze Sedimentary Basin, in the centre-west of the country; and the Maniamba Sedimentary Basin, which has a very small outcrop in the northwest of the country. The sedimentary rocks form variably local/discontinuous to regional/continuous aquifers, typically with a mixture of intergranular (porous) and fracture/fissure permeability.
 +
 
 +
Large areas of the country are overlain by unconsolidated sediments, particularly in valleys, dune fields and the coastal plain. These form variably local/discontinuous to regional/continuous aquifers. The unconsolidated aquifers are described separately below, but where they overlie bedrock aquifers, they can be in hydraulic continuity with the underlying aquifer. This is particularly the case for consolidated sedimentary aquifers, but can also occur over basement and igneous aquifers.  
  
  
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|Named Aquifers||General Description||Water quantity issues||Water quality issues||Recharge
 
|Named Aquifers||General Description||Water quantity issues||Water quality issues||Recharge
 
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|-
|Unconsolidated aquifers cover a large part of the Mozambique basin, especially south of the Save River; and occur in river valleys and in some dune and coastal areas across the country.
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|Unconsolidated sedimentary aquifers cover a large part of the Mozambique basin, especially south of the Save River; and occur in river valleys and in some dune and coastal areas across the country. They form variably local/discontinous and, in some areas, more regional/continuous aquifers. Groundwater in the unconsolidated aquifers may be in hydraulic continuity with underlying bedrock aquifers.  
  
 
Key aquifers include sand layers within clayey alluvium; loamy silty to medium grained aeolian and beach/marine sands; and areas of weathered fine grained clayey sands overlying consolidated rocks. Less frequent, but highly productive, are thick sandy and gravelly alluvium in valleys.  
 
Key aquifers include sand layers within clayey alluvium; loamy silty to medium grained aeolian and beach/marine sands; and areas of weathered fine grained clayey sands overlying consolidated rocks. Less frequent, but highly productive, are thick sandy and gravelly alluvium in valleys.  
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Significant thicknesses of alluvium have been developed along the main river valleys, and may form productive, stratified aquifers with good water quality. The aquifer layers can be confined or unconfined, depending on local circumstances. The central reaches of the Limpopo and Incomati have especially high-yielding prospects, with specific yields of up to 20 m³/h/m.  
 
Significant thicknesses of alluvium have been developed along the main river valleys, and may form productive, stratified aquifers with good water quality. The aquifer layers can be confined or unconfined, depending on local circumstances. The central reaches of the Limpopo and Incomati have especially high-yielding prospects, with specific yields of up to 20 m³/h/m.  
 
  
 
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|}
 
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==== Sedimentary - Intergranular Flow====
 
{| class = "wikitable"
 
|Named Aquifers||General Description||Water quantity issues||Water quality issues||Recharge
 
|-
 
|
 
||
 
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|}
 
  
 
==== Sedimentary - Intergranular & Fracture Flow====
 
==== Sedimentary - Intergranular & Fracture Flow====
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====Igneous====
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{| class = "wikitable"
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|Named Aquifers||General Description||Water quantity issues||Water quality issues||Recharge
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|-
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|Volcanic/extrusive rocks: phonolites; trachytes and similar rocks; rhyolites; basalts
 +
Intrusive rocks: syenites; granites and similar rocks; gabbros and similar rocks
 +
||Igneous rocks typically form local, small and dispersed aquifers, with limited productivity and without significant groundwater resources. Weathering variable, but there can be a 10 to 20 m thick weathered mantle. Weathering in basalt terrain is often more enhanced, but here weathered material tends to be very clayey and almost impermeable. Some shallow groundwater can be found where the weathered mantle is thick enough and permeable enough, but generally primary and secondary fractures are the most important water-bearing features. Groundwater frequently appears in spring zones. The most productive areas are along fault zones, and talus slopes where weathering is enhanced.
 +
 +
Typical borehole yields are less than 1 m³/hour. Where there is a well-developed, permeable weathered zone, yields from this zone can be higher, but typically not more than 3 m³/hour. Intergranular permeability is very low to zero. The aquifer is generally unconfined. Borehole depths typically vary between 30 and 100 m.
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||Aquifer zones are typically small and dispersed, and therefore there is limited groundwater storage.
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||Water quality is usually good
 
|}
 
|}
  

Revision as of 10:36, 30 July 2015

Africa Groundwater Atlas >> Hydrogeology by country >> Hydrogeology of Mozambique

Authors

Lucas Chairuca, National Directorate of Water, Mozambique

Arjen Naafs, WaterAid, UK

Ivo van Haren, WE Consult, Mozambique

Kirsty Upton and Brighid Ó Dochartaigh, British Geological Survey, UK


Geographical Setting

Map of Mozambique (For more information on the datasets used in the map see the geography resources section)

General

The Zambezi River divides Mozambique into two topographical regions: to the north, a narrow coastal strip gives way to inland hills and low plateaus; and further west to highland areas including the Niassa, Namuli or Shire, Angonia and Tete highlands and the Makonde plateau. To the south of the Zambezi River, the lowlands cover a larger area inland from the coast, rising to the Mashonaland plateau and Lebombo Mountains located in the deep south.

Estimated Population in 2013* 25,833,752
Rural Population (% of total) (2013)* 68.3%
Total Surface Area* 786,380 sq km
Agricultural Land (% of total area) (2012)* 63.5%
Capital City Maputo
Region Eastern Africa
Border Countries Malawi, South Africa, Swaziland, Tanzania, Zambia, Zimbabwe
Annual Freshwater Withdrawal (2013)* 884.2 Million cubic metres
Annual Freshwater Withdrawal for Agriculture (2013)* 78.0%
Annual Freshwater Withdrawal for Domestic Use (2013)* 19.2%
Annual Freshwater Withdrawal for Industry (2013)* 2.8%
Rural Population with Access to Improved Water Source (2012)* 35%
Urban Population with Access to Improved Water Source (2012)* 80%

* Source: World Bank


Climate

Mozambique has a tropical climate, with a general wet season (October to March) and dry season (April to September). However, local climate varies significantly according to altitude. The highest rainfall is in coastal areas, decreasing to the north and south. Annual precipitation varies from 500 to 900 mm across the country.

Rainfall time-series and graphs of monthly average rainfall and temperature for each individual climate zone can be found on the Mozambique Climate Page.


Average monthly precipitation for Mozambique showing minimum and maximum (light blue), 25th and 75th percentile (blue), and median (dark blue) rainfall Average monthly temperature for Mozambique showing minimum and maximum (orange), 25th and 75th percentile (red), and median (black) temperature Quarterly precipitation over the period 1950-2012 Monthly precipitation (blue) over the period 2000-2012 compared with the long term monthly average (red)

For further detail on the climate datasets used see the climate resources section.

Surface water

The country is drained by five principal rivers and several smaller ones. The largest and most important is the Zambezi River. There are four significant lakes: Lake Niassa (or Malawi), Lake Chiuta, Lake Cahora Bassa and Lake Shirwa, all in the north.

The Regional Water Administrations (or Regional Water Boards) / Administracao Regional de Aguas (ARAs) are responsible for operational water management, including collecting river level and flow data, in Mozambique. More detail on the ARAs and their mandate is given in the section on Groundwater management, below.

There are gauging stations on all main rivers. In 1986 there were 14 hydrometric stations in 14 river basins, each station generally gauging a catchment area ranging from around 5,500 km² to around 50,000 km², but in three cases between 100,000 km² and 1,200,000 km². Since the establishment of the ARAs (starting with ARA-Sul in 1996), the number of gauging stations has gradually been increased. Information about the stations and flow records can be obtained from the ARA’s.



Surface Water Map of Mozambique (For more information on the datasets used in the map see the surface water resources section)

Soil

Soil Map of Mozambique (For map key and more information on the datasets used in the map see the soil resources section)

Land cover

Land Cover Map of Mozambique (For map key and more information on the datasets used in the map see the land cover resources section)


Geology

This section provides a summary of the geology of Mozambique. More detail can be found in the references listed at the bottom of this page. Many of these references can be accessed through the Africa Groundwater Literature Archive.

The geology map on this page shows a simplified version of the geology at a national scale (see the Geology resources page for more details). The map is available to download as a shapefile (.shp) for use in GIS packages.

A more detailed geological map at higher resolution was published in 2008 (see Geology: key references, below, for details).

Geological Environments
Key Formations Period Lithology Structure
Unconsolidated sedimentary
Coastal sand dunes; Alluvium; Interior aeolian sand dunes; Lacustrine limestones; Marine reef and bioclastic sediments; Sand sheets with local gravel Quaternary Almost 70% of the area underlain by sedimentary basins in Mozambique has a cover of unconsolidated sediment. This is very commonly a 5 to 10 m thick weathered layer of clayey sand, sometimes overlain by valley (alluvial) sand, aeolian sand, and rare colluvial deposits. Particular deposits are:

Coastal beach and dune sands.

Alluvium: alluvial sand, sandy soil, silt, gravel, lacustrine saline maud, pebble-bearing debris, estuarine and tidal flat sediment and back-barrier sediment.

Interior dune and red aeolian sand, including the Topuito Formation.

Lacustrine limestone.

Marine reef, coral and bioclastic sediment.

Sand sheets with local gravel.

Sedimentary - Cretaceous-Tertiary
Many, including Mazamba Formation; Jofane Formation; Inhaminga Formation; Cheringoma Formation; Mangulane Formation; Mapai Formation; Sena Formation; Lupata Group (Mazambulo Formation; Tchazica Formation) Cretaceous (Tchazica Formation of Lupata Group is partly Jurassic) and Tertiary (Palaeogene-Neogene) Sedimentary rocks of Cretaceous-Tertiary age occur mainly in two separate Cenozoic sedimentary basins in the southeast and northeast of Mozambique:

The Southern or Mozambique Sedimentary Basin, covers much of the southeast of Mozambique, and about 32% of the country as a whole, reaching a maximum width of 440km.

The Northern or Rovuma Sedimentary Basin, extends along a narrow outcrop from the Tanzanian border south to Ilha de Mozambique, and has a maximum onshore width of 120km.

Both sedimentary basins were subject to several marine transgressions, the main one of which occurred in Upper Cretaceous and Tertiary. The sedimentary sequences are characterized by predominately continental series of arkosic sandstones in the western parts of the basins; and mainly marine sandstones, limestones and calcarenites, in the coastal .

Some Cretaceous-Tertiary sedimentary rocks also occur in the smaller Middle Zambeze Basin in the west of the country.

Some of the main formations are:

Mazamba Formation (Neogene): arkosic sandstones, in part conglomeratic

Jofane Formation (Neogene): sandstone and conglomeratic sandstone members, locally silicified. The Cabe Member comprises calcarenite, conglomerate and quartzite. Some limestone, occasionally karstified.

Inhaminga Formation (Neogene): sandstone

Cheringoma Formation (Tertiary): limestone and calcarenite

Mangulane Formation (Palaeogene): sandstone and limestone

Sena Formation (Cretaceous): conglomerate and minor sandstone (including a thorium sandstone member), with a basal conglomerate member

Lupata Group (Jurassic-Cretaceous): Monte Mazambulo Formation - conglomeratic sandstone; Tchazica Formation - sandstone and conglomerate.

Post-Karoo sedimentation was largely controlled by the development of the East African Rift System and related tectonic events. The Tertiary saw subsidence along deep N-S oriented troughs along the axis of the Mozambique Channel, in which sedimentation occurred. The sedimentary rocks are sometimes intensely faulted, but only slightly folded, with slightly developed arched structures. The best developed rift valleys are the Chire-Urema and the Funhalouro-Mabote grabens (the latter is part of the larger Mazunga Graben).
Sedimentary - Mesozoic-Palaeozoic
Upper Karoo Group (Lualadzi Formation, Zumbo Formation), Magoe Formation Jurassic to Cretaceous Sedimentary rocks of the Karoo sequence were deposited throughout Jurassic to Lower Cretaceous times, largely in the relatively small Middle Zambeze Basin in the west and the Maniamba Basin in the north of the country. The lower sequence of Karoo sedimentary rocks contains mainly very fine grained (largely mudstones), and sometimes contain carbonaceous beds. The upper sequence is more sandy.

Key formations are:

Magoe Formation (Jurassic/Cretaceous) - limestone and sandstone

Zumbo Formation, Upper Karoo Group (Triassic) - sandstone and silicified sandstone

Lualadzi Formation, Upper Karoo Group (Jurassic) - red sandstone, locally silicified


Post-Cambrian crustal development was characterised by the break up of the supercontinent Gondwana. From Permian to Jurassic, rifts developed along the E-W trending Limpopo and Zambeze Belts, where deep troughs were filled with continental Karoo sediments, forming the Middle Zambeze Basin. In the north of Mozambique, the Maniamba Basin and smaller outcrops of Karoo sedimentary rocks form part of a larger Karoo basin in Tanzania.
Igneous
Karoo volcanic rocks and Post-Karoo largely intrusive igneous rocks, including the volcanic Movene Formation, Umbeluzi Formation (including Basalt Member), Rio Nhavudezi Formation, Bangomatete Formation, Rio Mazoe Formation; and intrusive igneous Gorongosa Suite and Rukore Suite Jurassic to Early Cretaceous The Karoo terminated with a period of intensive volcanic activity, dominated by basaltic and rhyolitic outflows, with the resulting rocks including basalt, rhyolite, andesite, tuff, ignimbrite and volcanic breccia. The volcanic sequence consists of a number of superposed lava flows, emerging from tension faults and fissures along the margins of the Basement Complex and along the widening Zambeze and Limpopo Basins. A line of outcrops is found along these margins, of which the Libombo Range in the southwest is the most important. The outcrops continue in a narrow strip to the north of the Zambeze. The basalt along the coast of Nampula province is considered to form part of the same system.

After Karoo volcanism, local igneous activities continued along borders of the East African Rift System and the Zimbabwe and Kaapvaal Cratons. The Post-Karoo igneous phenomena are dispersed and produced rocks with a wide variety of composition, genesis and age, including granite, syenite, gabbro, feldspar porphyry and mafic dykes. The late Jurassic to early Cretaceous batholith of the Serra da Gorongosa, consisting of gabbroic and granitic rocks, and the Middle Cretaceous alkaline lavas of the Lupata region are the most important features. More dispersed examples are the Cretaceous syenitic plutons of Milange, Chiperone and Derre and the carbonatite complexes and Upper Tertiary vents of basic to ultra-basic composition in the Sena region.

Precambrian Basement Complex
Archaean to Proterozoic Many named groups and formations The Precambrian Basement Complex occupies Manica, the western part of Sofala and almost the entire region north of the Zambeze. The formations of the northern part of Mozambique (a large part of the provinces of Zambezi, Nampula, Cabo Delgado and Niassa and the northern part of the province of Tete), comprise of high-grade metamorphic rock, forming part of the Mozambique Metamorphic Belt. This belt is dominated by gneiss and a gneiss-granite-migmatite complex with local meta sediments, charnockite series and a gabbro-anorthosite complex in the center of Tete province. In the Manica region (the Mozambican Province in the centre of the country, bordering Zimbabwe) one finds remnants of the Early Precambrian Zimbabwe Craton, dominated by greenschists.

The Basement Complex includes many metamorphic and meta-igneous rock types, including granite, granofels, granodiorite, gneiss (including leucocratic gneiss, quartz-feldspar gneiss, orthogneiss, paragneiss, migmatitic paragneiss, granitic gneiss, calc-silicate gneiss, biotite-gneiss, mica gneiss, augen gneiss, magmatic gneiss and garnet gneiss), quartz diorite, tonalite, , gabbro, pyroxene diorite, garnet-sillimanite, metasiliciclastic sedimentary rocks, metagranite, hornblende gneiss, amphibolite, amygdaloidal andesitic lava, orthoquartzite, quartzite, arkosic quartzite, mafic metavolvanics including meta-tuff, siltstone, claystone, marble, meta-sandstone, muscovite-biotite schist, mica schist, arenaceous mica schist, migmatite, mylonite.


Hydrogeology

This section provides a summary of the hydrogeology of the main aquifers in Mozambique. More information is available in the references listed at the bottom of this page. Many of these references can be accessed through the Africa Groundwater Literature Archive.

The hydrogeology map on this page shows a simplified version of the type and productivity of the main aquifers at a national scale (see the Aquifer properties resource page for more details). The map is available to download as a shapefile (.shp) for use in GIS packages.

A more detailed hydrogeological map was published by DNA (1987).

File:Mozambique Hydrogeology.png Hydrogeology Key.png

Summary

Mozambique can be divided into three major hydrogeological provinces (DNA 1987). These are:

1. Sedimentary Basins.

2. Volcanic (and other igneous) terrains

3. Basement Complex

A fourth province is unconsolidated aquifers, which are sometimes in hydraulic continuity with underlying bedrock aquifers.

The sedimentary basins comprise mainly Cretaceous-Tertiary rocks, with small outcrops of older Mesozoic-Palaeozoic rocks, mainly Karoo-type. The most significant sedimentary basin is the Mozambique Sedimentary Basin to the south of the Save River, in southern Mozambique. Other, smaller sedimentary basins are the Mozambique Sedimentary basin to the north of the Save River; the Northern/Rovuma Sedimentary Basin, with which has a narrow linear outcrop in the northeast of the country; the Middle Zambeze Sedimentary Basin, in the centre-west of the country; and the Maniamba Sedimentary Basin, which has a very small outcrop in the northwest of the country. The sedimentary rocks form variably local/discontinuous to regional/continuous aquifers, typically with a mixture of intergranular (porous) and fracture/fissure permeability.

Large areas of the country are overlain by unconsolidated sediments, particularly in valleys, dune fields and the coastal plain. These form variably local/discontinuous to regional/continuous aquifers. The unconsolidated aquifers are described separately below, but where they overlie bedrock aquifers, they can be in hydraulic continuity with the underlying aquifer. This is particularly the case for consolidated sedimentary aquifers, but can also occur over basement and igneous aquifers.


Unconsolidated

Named Aquifers General Description Water quantity issues Water quality issues Recharge
Unconsolidated sedimentary aquifers cover a large part of the Mozambique basin, especially south of the Save River; and occur in river valleys and in some dune and coastal areas across the country. They form variably local/discontinous and, in some areas, more regional/continuous aquifers. Groundwater in the unconsolidated aquifers may be in hydraulic continuity with underlying bedrock aquifers.

Key aquifers include sand layers within clayey alluvium; loamy silty to medium grained aeolian and beach/marine sands; and areas of weathered fine grained clayey sands overlying consolidated rocks. Less frequent, but highly productive, are thick sandy and gravelly alluvium in valleys.

A belt of dune sands is developed along the entire coast of southern Mozambique, south of the Save River. These porous aeolian sands form a regional unconfined aquifer which can be very productive, as shown by boreholes in the Ponta de Ouro and Tofo aquifers, and can contain fresh groundwater. Permeability decreases from the coast inland, as a consequence of increased clay content. These unconsolidated sands are frequently underlain by more productive deeper consolidated aquifers, and there can be hydraulic continuity between the upper unconsolidated and deeper consolidated aquifer. For example, dune sands along the Inhambane coast overlie very productive limestones of the Jofane Formation, except in the area around Inharrime, where the dunes cover the low productive argillaceous sandstones of the Inharrime Formation.

Significant thicknesses of alluvium have been developed along the main river valleys, and may form productive, stratified aquifers with good water quality. The aquifer layers can be confined or unconfined, depending on local circumstances. The central reaches of the Limpopo and Incomati have especially high-yielding prospects, with specific yields of up to 20 m³/h/m.

In most areas of the southern dune belt, the nearness of the aquifer to the sea, and sometimes to lagoonal inland depressions, means that the aquifer often contains brackish to saline water, which limits its use. However, there is fresh groundwater between Homoine and Massinga.

In alluvial aquifers along the main river valleys, groundwater is generally of good quality. However, in the lower reaches of the main main valleys increased groundwater mineralization is often seen, as a consequence of occasional marine inundations or longer term sea-water intrusions near the river mouth.

In the centre of the Incomati valley, the good prospects are offset by the existence of highly mineralized groundwater.


Sedimentary - Intergranular & Fracture Flow

Named Aquifers General Description Water quantity issues Water quality issues Recharge

Sedimentary - Fracture Flow

Named Aquifers General Description Water quantity issues Water quality issues Recharge


Igneous

Named Aquifers General Description Water quantity issues Water quality issues Recharge
Volcanic/extrusive rocks: phonolites; trachytes and similar rocks; rhyolites; basalts

Intrusive rocks: syenites; granites and similar rocks; gabbros and similar rocks

Igneous rocks typically form local, small and dispersed aquifers, with limited productivity and without significant groundwater resources. Weathering variable, but there can be a 10 to 20 m thick weathered mantle. Weathering in basalt terrain is often more enhanced, but here weathered material tends to be very clayey and almost impermeable. Some shallow groundwater can be found where the weathered mantle is thick enough and permeable enough, but generally primary and secondary fractures are the most important water-bearing features. Groundwater frequently appears in spring zones. The most productive areas are along fault zones, and talus slopes where weathering is enhanced.

Typical borehole yields are less than 1 m³/hour. Where there is a well-developed, permeable weathered zone, yields from this zone can be higher, but typically not more than 3 m³/hour. Intergranular permeability is very low to zero. The aquifer is generally unconfined. Borehole depths typically vary between 30 and 100 m.

Aquifer zones are typically small and dispersed, and therefore there is limited groundwater storage. Water quality is usually good

Basement

Named Aquifers General Description Water quantity issues Water quality issues Recharge

Groundwater Status

Recharge

Reliable information on natural aquifer recharge in Mozambique is very scarce. Only a few studies have been conducted, in a few small areas. Recharge to sandy soils around Maputo was studied by IWACO in 1985 and was found to be somewhere between 140 and 185 mm per year, which is around 20% of the total precipitation. In other areas with sandy soils and higher precipitation, recharge was found to be higher, for example, 210 and 350 mm per year, or around 30% of annual rainfall, near Pemba. In drier areas with less permeable soils, such as the semi-arid Chitima region near Tete, recharge values of less than 10 mm per year were estimated (IWACO 1985, DNA 1987).

Groundwater quantity

There are many potential problems linked to the use of groundwater in Mozambique. Little information exists on the present status of groundwater quantity, and there is no quantitative information on groundwater use and recharge. Before groundwater can be used on a large scale for irrigation or other uses, extensive research is needed (DNA 1987; British Geological Survey 2002).

Groundwater has a significant role to play in the supply of drinking water, but is currently only used sparsely for irrigation due to the following factors:

• Mozambique still has enough areas that can be developed for irrigation using surface water resources. • There is limited to no information on the potential of aquifers and yields of individual boreholes. • Large areas in southern Mozambique are deemed unsuitable for groundwater abstraction due to salinity issues. The exact extent of these areas is undetermined.

It seems that the lack of information (which means there is an unknown risk of drilling low yielding boreholes and/or incurring high drilling costs) is a larger constraining factor than the actual potential of the groundwater. As well as this, there is a general consensus that surface water is more cost-effective for irrigation than groundwater. The potential for, in particular, large surface water irrigation schemes is still present in Mozambique, and thus the interest for groundwater is low. Furthermore, the following can be concluded: 1) There is little knowledge of groundwater use around non-perennial rivers 2) Groundwater for irrigation is mainly used for subsistence farming, except for certain labour intensive areas around Maputo. 3) Legislation of groundwater abstraction is in its infancy in Mozambique. Capacity is very limited presently. Technical assistance and capacity training in this area is essential. 4) Groundwater is probably underutilised at present, as potential users do not have knowledge of or access to the groundwater potential in their area.


Groundwater quality

Little information is available on the quality of groundwater in the aquifers of Mozambique. The available information suggests that the groundwater is for the larger part fresh and of acceptable quality, though often of limited quantity, especially in the aquifers of the Basement Complex and the Volcanic Terrains.

Significant salinity problems are experienced in some parts of the Tertiary aquifers in the south, as a result of natural seawater intrusion, forming areas with brackish groundwater. In large parts of Gaza, Maputo and Inhambane Province, groundwater in the main aquifer (from 20 – 80 m depth) has Electrical Conductivity values well above the WHO drinking water standards of 2000 µS/cm. These values also make the groundwater unsuitable for many crops and for livestock watering. In some particular instances (e.g. at Chokwe and Chibugo), extra deep boreholes (100-150 m) have been drilled to reach fresh water in aquifers. Such boreholes are, however, too expensive to consider for irrigation (particularly as proper sealing of the upper saline aquifer needs to be achieved).

There is risk of pollution in the vicinity of industrial and urban developments, including from sewage effluent, from centres of petroleum and chemical manufacture, and from ports, as well as from agricultural activity. Pollution incidence is likely to be greatest in the coastal lowlands (DNA 1987, British Geological Survey 2002).

Localized groundwater pollution is known to be occurring in the Chokwe (Gaza Province) area, where extensive irrigation has taken place (using surface water) since the 1930s. This has raised the local groundwater table and has led to increased levels of salinity. An estimated 2,000 hectares (of the 30,000 irrigated) has already been lost for normal crop production (Interview with Eng. Rui Brito UEM, Faculty of Agronomy and Forestry).

Pollution by heavy metals is rarely measured or recorded. A recent GAS meeting indicated that after a relative extensive groundwater quality study led by UNICEF in the centre of Mozambique, only in some areas (around Gorongosa mountain) was mercury (Hg) found at levels above WHO standards (Minutes of meeting GAS, October 2009).

Groundwater use and management

Groundwater use

Groundwater is the main source of domestic water for most rural areas, and for the towns of Quelimane, Pemba, Tete and Inhambane. Groundwater is also used in part of Maputo (Private Small System). The Census of 2007 showed that groundwater is used by at least 60% of the population. It is mostly extracted through hand-pump mounted boreholes (14.1%) and open shallow wells (46.8%), for used for drinking water in rural areas. Piped water to taps (to individual houses and public tapstands) (20.6%) is also partly produced from groundwater. Surface water from rivers and lakes is only used by 17.1% of households.

As there is no form of monitoring or control of groundwater use, there is no quantitative information on total quantities or quality. Reliable estimates on the resources available are also non-existent (ADB 2007). A prognosis by DNA (RWSS 2005) indicated there were over 17,000 boreholes throughout the country in 2010.


Groundwater management

The National Water Directorate is responsible for water resources planning and development.

The Regional Water Administrations (or Regional Water Boards) / Administracao Regional de Aguas (ARAs) are responsible for operational water management in Mozambique. Their mandate is to:

- Ensure participatory water resources development and management in the basins; - Guarantee protection and sustainable use of water resources; - Administer and control of use, licensing and management of water rights for public water use; - Approve and supervise construction and operations of water resources infrastructure developments; - Develop, own and operate water resources infrastructures; - Develop, maintain and operate water resources monitoring network; - Resolve and minimise conflicts between and among water users; - Control and impose sanctions when water users use the water without the appropriate license; - Define and administer water resources protection zones as given in the law; - Identify and register unregistered water, river and lake users.

In total there are 5 ARAs: ARA-Sul (South), ARA-Centre, ARA-Zambeze, ARA-Centro-Norte (Centre-North), ARA-Norte (North).

The most relevant national laws and regulations relating surface and groundwater resources in Mozambique are:

Water Policy, Resolution No. 46/2007, of 30 October, and the Water Law, Law No. 16/91, of 3 August;  National Environmental Policy, Resolution No. 5/95, of 6 December, and the Environmental Law, Law No. 20/97, of 1 October, which relates to any activities that could have impacts on the environment;

Regulation for Environmental Quality Standards and Effluent Emission, Decree No. 18/2004, of 2 June (as amended by Decree No. 67/2010, of 31 October). The regulations define environmental quality and effluent emission standards for receiving water bodies;

Regulation for Water Quality for Human Consumption; Ministerial Diploma No. 180/2004 of 15 September (Ministry of Health);

Regulation for Waste Management, Decree No. 13/2006, of 15 June.  The EPA 2009 National Recommended Water Quality Criteria for freshwater and marine waters. The water quality criteria were designed for the protection of aquatic life and human health in surface water and include values for both acute and chronic risks. In this report, the most conservative value for each parameter has been used.

The Mozambican Water Quality Regulations on Water Quality for Human Consumption (Ministerial Order No. 180/2004 of 15 September 2004), was also reviewed as part of the data assessment.

Issuing permits for drilling and groundwater abstraction is part of the mandate of the ARAs. However, up to now, only ARA-Sul has made a start with registration of groundwater users and issuing permits for drilling and groundwater abstraction.

ARAs are also responsible for the delineation of groundwater protection zones. However, to date no protection zone has been established yet.

Treatment of waste water is the responsibility of the municipalities.


Groundwater monitoring

There are no national groundwater level monitoring programmes, and only one regional groundwater monitoring network, established by ARA-Sul for the Greater Maputo Aquifer. This aquifer stretches from Maputo to Magude, with an aquifer width of about 40 km and length about 120 km. ARA-Norte is monitoring the groundwater well field for the supply of Pemba, while ARA-Zambeze is responsible for the monitoring of the groundwater well field for the cities of Tete and Quelimane. The piezometers of the networks are not monitored ate a regular basis. At present, the ARAs are mainly focused on measuring surface water flows, and attention to groundwater monitoring in the well fields is just begining.

ARA-Sul is also measuring groundwater quality (a limited number of parameters) in the Greater Maputo Aquifer, but not on a regular basis. For the Greater Maputo aquifer ARA-Sul has 25 monitoring points.

Transboundary aquifers

Transboundary surface water management is an important issue in Mozambique. The country shares 9 river basins with neighbouring countries and in nearly all cases Mozambique is the downstream country. However, there are no significant transboundary aquifers.

For further information about transboundary aquifers, please see the Transboundary aquifers resources page


References

The following references provide more information on the geology and hydrogeology of Mozambique. These, and others, can be accessed through the Africa Groundwater Literature Archive.

Geology: key references

A revised national geological map was published in 2008, as part of the Mineral Resources Management Capacity Building Project:

Republica de Mocambique - Ministerio dos Recursos Minerais – Direccao Nacional De Geologia. 2008. Carta Geologica Escala 1:1,000,000.

The Map Explanation has 4 volumes:

GTK Consortium. 2006. Carta Geologica Escala 1:1,000,000: Map Explanation, Volume 1. Describes the area south of the Save River

GTK Consortium. 2006. Carta Geologica Escala 1:1,000,000: Map Explanation, Volume 2. Describes the central part of Mozambique.

GTK Consortium. 2006. Carta Geologica Escala 1:1,000,000: Map Explanation, Volume 3. Describes the eastern-central part of Mozambique (Zambezi Province).

GTK Consortium. 2006. Carta Geologica Escala 1:1,000,000: Map Explanation, Volume 4. Describes the western-central part of Mozambique (Tete Province). Report_B6_f1_screen


Hydrogeology: key references

The main source of hydrogeological information for Mozambique is:

Ferro and Bouman / DNA. 1987. Explanatory Notes to the Hydrogeological Map of Mozambique: 1:1,000,000.

This map is largely based on the 1978 national geological map (Afonso 1987), and limited hydrogeological field data. The national geological map was updated in 2008 (see Geology: key references, above), but the 1987 national hydrogeological map has not yet been updated.


Other hydrogeological references are:

African Development Bank (ADB). 2002. Mozambique Water and Sanitation Sector Review. Prepared by SEED, May 2002.

African Development Bank (ADB). 2005. Rapid Assessment of Rural Water Supply and Sanitation. Mozambique Requirements for Meeting the MDGs, March 2005

African Development Bank (ADB). 2007

British Geological Survey (BGS). 2002. Groundwater Quality: Mozambique.

DNA. 1999. Water resources of Mozambique.

Government of Mozambique (GOM). 1995. Política Nacional de Águas, Resolução do Conselho de Ministros nº 7/95 de 8 de Agosto, Boletim da República no. 34, 1ª Série de 23 de Agosto de 1995.

IWACO. 1985. Study of groundwater to supply Maputo.

RWSS. 2005.

World Bank. 2007. Mozambique Country Water Resources Assistance Strategy: Making Water Work for Sustainable Growth and Poverty Reduction


The DNA (National Water Department), together with donors, particularly UNICEF, have carried out several drilling programs. Drilling reports from these programmes provide lithological information (typically simple but relatively accurate descriptions); borehole information (depth, location filters etc); and hydrogeological information (water levels, main water strikes, some water quality parameters). Proper pumping tests data are rare: most constant discharge tests were less than 1 hour, and in most cases only air-lift tests were done. This information from drilling programmes is not available in one report or single database: the DPOPH (Provincial Departments of Public Works and Housing) have databases with hydrogeological data per province.

Particular drilling programmes were:

ASNANI. 2004-2008. Executed by DNA and financed by ADB. Hundreds of boreholes drilled in Nampula and Niassa Provinces.

MCA (Millenium Challenge Account. 2008-2012. Hundreds of boreholes drilled in Nampula and Cabo Delgado Provinces.

UNICEF One Million Initiative. 2008-2012. Hundreds of boreholes drilled in the Tete, Manica and Sofala Provinces.


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Africa Groundwater Atlas >> Hydrogeology by country >> Hydrogeology of Mozambique