Hydrogeology of Zambia

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

Authors

Professor Daniel CW Nkhuwa, School of Mines, University of Zambia

Mr Simon Kang’omba, Department of Water Affairs, Ministry of Mines, Energy and Water Development, Zambia

Mr Kolala C Chomba, Department of Geological Survey, Ministry of Mines, Energy and Water Development, Zambia

Emily Crane & Brighid Ó Dochartaigh, British Geological Survey, UK

Geographical & Political Setting

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

General

Estimated Population in 2013* 14538640
Rural Population (% of total)* 60%
Total Surface Area* 743390 sq km
Agricultural Land (% of total area)* 32.1%
Capital City Lusaka
Region Eastern Africa
Border Countries Democratic Republic of the Congo, Tanzania, Malawi, Mozambique, Zimbabwe, Botswana, Namibia and Angola
Annual Freshwater Withdrawal (2013)* 1572 Million cubic metres
Annual Freshwater Withdrawal for Agriculture* 73.28%
Annual Freshwater Withdrawal for Domestic Use* 18.45%
Annual Freshwater Withdrawal for Industry* 8.27%
Rural Population with Access to Improved Water Source* 49.2%
Urban Population with Access to Improved Water Source* 84.8%

* Source: World Bank


Climate

Broad description of Zambia – major topographical/geographical features e.g. mountain ranges, deserts, coastal areas etc... Climate classification of Zambia. Spatial variations in annual average rainfall and temperature.

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


Average monthly precipitation for Zambia showing minimum and maximum (light blue), 25th and 75th percentile (blue), and median (dark blue) rainfall Average monthly temperature for Zambia 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

General information about Zambia surface water – perennial/ephemeral – major rivers – discharge points.

River flow gauging is undertaken by Zesco, Zambia's power generating company, and the Zambezi River Authority (ZRA). Zesco's gauging stations are mainly on the Kafue River, while the ZRA gauges the Zambezi and stretches of the Kafue.

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

Soil

Soil Map of Zambia (For more information on the datasets used in the map see the soil resources section)
General information about Zambia soils.

Land cover

General information about Zambia land cover.
Land Cover Map of Zambia (For more information on the datasets used in the map see the land cover resources section)


Geology

The following section provides a summary of the geology of Zambia. More detailed information can be found in the key references listed below: many of these are available through the Africa Groundwater Literature Archive.

The geology map below was created for this Atlas. It shows a simplified version of the geology of Zambia at a national scale. The map is available to download as a shapefile (.shp) for use in GIS packages. File:Zambia Geology.png

More information on the geology of Zambia is available from the Geological Survey Department (GSD), including a detailed national geological map at 1:1,000,000 scale.

Geological Environments
Key Formations Period Lithology Structure
Alluvium
Alluvium and lacustrine deposits Recent (Quaternary) Unconsolidated alluvial soil, sands and gravels; and some clays near lakes
Kalahari Group
Zambezi Formation Tertiary - Recent Ferricrete, evaporites, conglomerate and gravel
Barotse Formation Tertiary Sandstone, Chert, Quartzite Sedimentary bedding
Upper Karoo Group and Karoo Basalts
Luano, Siavonga, Kato, Luangwa and Batoka formations Jurassic - Early Cretaceous Most of the sequence comprises consolidated sedimentary rocks: mudstone, sandstone, siltstone, coal, gritstone, tillite, mixtite and conglomerate. The uppermost Batoka Formation consists of basalt with interbedded sandstone, distinguished on the geology map above as Karoo Basalts. Sedimentary bedding, laminations and ripple marks
Lower Karoo Group
Siakandobo, Gwembe and Madumabisa formations Carboniferous - Jurassic Consolidated sedimentary rocks: sandstone, gritstone, siltstone, mudstone Sedimentary bedding, laminations and ripple marks
Katanga Supergroup
Including Upper Roan Dolomite, Lusaka, Kaleya, Chifumbu and Chafugoma formations and Kundelungu Limestone Precambrian (870-620 Ma) Variably metamorphosed mable, schist, argillite, quartzite, dolomite and limestone. Sedimentary bedding; metamorphic foliation and banding; folding
Muva Supergroup
Kankaluwe, Rufunsa and Chakwenga River formations Precambrian (1355+/-28 Ma) Metamorphic rocks: carbonatite, gabbro, amphibolite, granodiorite and schist Metamorphic foliation; jointing and folding
Chitobe, Kabweluma, Nsama and Mbala formations Precambrian (1355+/-28 Ma) Variously metamorphosed conglomerate, quartzite, limestone and carbonates Metamorphic foliation; jointing and folding
Basement Complex: Granite
Mainly older Precambrian Granite Quartz veins.
Basement Complex: undifferentiated
Mainly older Precambrian Metamorphosed rocks; gabbro, basalt, granite, dolerite, aplite, andesite. Quartz veins; faulted, folded and jointed

Hydrogeology

Aquifer properties

File:Zambia Hydrogeology.png Hydrogeology Key.png


Unconsolidated: Intergranular Flow

Named Aquifers General Description Water quantity issues Water quality issues Recharge
Kalahari Group (Tertiary) This aquifer comprises 20 to 40 m of unconsolidated sands, which are usually unconfined. Flow and storage are intergranular. The water table is usually at a depth of about 10 to 20 m below ground surface, but sometimes is as much as 30 m deep. Yields of 0.2 to 5 l/s are obtainable. Sometimes brackish. Largely direct recharge from rainfall.

Igneous

Named Aquifers General Description Water quantity issues Water quality issues Recharge
Karoo Basalts The aquifer comprises basalts with interbedded sandstone. It is characterised by a weathered zone up to 20 m deep. Below this are fractures that allow groundwater flow, which are more common above about 45 to 50 m depth. The aquifer is unconfined, and the water table varies from about 10 to 25m deep. Boreholes are usually between 45 and 50 m deep, to the base of the most fractured zone. One transmissivity value quoted for the aquifer is 5.7 m²/day. Borehole yields are usually low, less than 2 l/s. Higher yields may be encountered in zones where low permeability crystallised quartz horizons have created 'dams' and increased local groundwater storage, although such higher yields may not be sustainable in the long term as groundwater storage is used up. Usually good Recharge can occur through fractures

Upper and Lower Karoo Groups: Consolidated Sedimentary Aquifer with Intergranular & Fracture Flow

Named Aquifers General Description Water quantity issues Water quality issues Recharge
Upper and Lower Karoo Groups Sandstones in the Karoo sequence form high porosity, high permeability aquifers with significant intergranular flow. The aquifers are typically unconfined, but occasionally confined.The water table is often between 15 to 20 m below ground surface. Yields of up to 15 l/s are possible.

Shales, mudstones and other fine grained lithologies in the Karoo sequence typically form low productivity aquifers, with yields of 0.2 to 2 l/s.

Sometimes fresh, but in most cases brackish. Direct recharge.

Consolidated Sedimentary Aquifers with Fracture Flow

Named Aquifers General Description Water quantity issues Water quality issues Recharge
Katanga Supergroup: Upper Roan Dolomite and Kundelungu Limestone The Upper Roan Dolomite and Kundelungu Limestone of the Katanga Supergroup form highly productive aquifers in which fractures provide the dominant permeability and storage. The aquifers are mostly between 15 and 50 m thick. The water table is generally from 20 to 35 m below ground surface. The aquifers are usually unconfined. The maximum borehole depth is 50 to 70 m, with water occasionally struck at depths as great as 120 to 150 m. Transmissivity values of up to 800 to 1000 m²/day are reported (United Nations 1989). Yields are typically high: one study of 190 boreholes found an average yield of 6 l/s, with some boreholes known to yield 10-20 l/s and even more than 50 l/s. The highest yielding boreholes are in the areas of Lusaka, Ndola, Kobwe and Mpongwe. Good to very good yields in dolomites and limestones; lower yields in other lithologies. Sometimes hard water due to high dissolved calcium. Direct recharge; sometimes also focussed recharge from runoff from higher ground
Katanga Supergroup: Kundelungu and Lower Roan Quartzites; Muva Supergroup Other formations in the Katanga Supergroup, including the undifferentiated Kundelungu and Lower Roan Quartzites, and the formations of the Muva Supergroup, typically form locally productive aquifers. Yields typically between 0.1 and 10 l/s Direct recharge through fractures.

Basement Complex: Granite and undifferentiated

Named Aquifers General Description Water quantity issues Water quality issues Recharge
This aquifer is composed of crystalline basement rocks, mostly granitic, and sometimes gabbro and others. The aquifer properties of crystalline basement aquifers are controlled by the depth of the weathered profile (regolith) and the degree of fracturing of unweathered bedrock. Fractured bedrock alone cannot sustain usable yields without the storage capacity of the overlying regolith.

The regolith is typically 10 to 15 m thick, but can be up to 30 m thick. Below this, the unweathered bedrock can be fractured to depths of about 60 - 70 m (United Nations 1989). The water table is usually 20 to 30 m below the ground surface. Boreholes tend to be 50 to 60 m deep. An average transmissivity value of 5.7 m²/day is given. Yields are typically very low to low: between 0.2 and 2 l/s. One study reported the average yield from 106 boreholes to be 1.4 l/s, with 44% of the boreholes yielding less than 1 l/s and just 3% yielding 3 l/s or more (United Nations 1989).

Yields are typically low to very low: 0.2 to 2 l/s. Sometimes acidic but in most cases neutral Recharge is influenced by geomorphology, thickness of regolith, and depth to groundwater table.

Groundwater quality

The country’s groundwater is generally potable in igneous and basement areas, but in densely populated areas, groundwater quality is threatened by:

  • High rates of urbanisation that exceed infrastructure development, which usually leads to low access to safe and adequate sanitation.
  • Uncoordinated developments in the water supply and sanitation (WSS) sector.
  • Growth in water demand, especially for agriculture and hydropower.

Further, groundwater quality may be threatened by intense rainfall events, which result in frequent floods, and which is made worse by climate change. In this regard, worsening groundwater quality might increasingly undermine its important role in the country’s economic development.

A brief summary of the groundwater quality in Zambia is provided by Smedley (2001). This indicates that groundwater in Zambia usually has very low concentrations of dissolved constituents (total dissolved solids concentrations are typically less than 200 mg/l). The main pollution problems are expected to be associated with metal mining, which can lead to increased concentrations of trace metals such as copper, zinc, chromium, nickel, cadmium and arsenic. Urban and agricultural areas may be impacted by nitrate and other anthropogenic contamination. Iodine deficiency has been observed in Zambia, particularly in the Northwestern, Western, Central and Southern Provinces, where some areas had goitre rates in excess of 50% (Bailey 1991), suggesting low iodine concentrations in groundwater in these areas. There is now legislation requiring all salt to be iodised (ICCIDD, 2012).

Microbiological contamination is a widespread problem in urban areas and particularly affects shallow groundwater points.

Groundwater Status

The country’s aquifers are classified into three main types (JICA-MEWD 1995):

  1. Those where groundwater flow is mainly through fractures/fissures/discontinuities, which are classified as either highly or locally productive. Highly productive aquifers occur mostly in karstic limestones/marbles on the Copperbelt and stretching down into the Lusaka area;
  2. Those where intergranular groundwater flow is dominant, and which occur mainly in alluvial soils and Tertiary sand deposits; and
  3. Low yielding aquifers with limited potential, which are largely in the Basement complex.

Groundwater-surface water interaction is known to occur in valleys, where the groundwater table is shallow, and where the valleys act, in most cases, as discharge zones. However, there is a need for more in-depth knowledge of this interaction, in order to understand how groundwater discharge sustains flows in many perennial rivers and streams during the dry seasons. This knowledge is important for optimising conjunctive use of surface water and groundwater resources.

The country’s biodiversity is protected by 19 national parks, 35 Game Management Areas (GMAs) and 488 national and local forest reserves (covering 8%, 22% and 9.6% of the country’s land area, respectively). All of these have many groundwater dependent ecosystems.

Groundwater use and management

Groundwater use

There are currently inadequate data to make an accurate assessment of Zambia's groundwater availability and use. Personal experiences and estimates would put groundwater usage at about 60% – 70% of total national water supplies, although this is highly variable spatially.

The groundwater resource has greatly suffered from unregulated exploitation and exposure to pollution – aspects that may threaten it as an important source of water in the future.

The National Water Master Plan (JICA-MEWD, 1995) estimated that the breakdown of groundwater use was:

  • 30% irrigation
  • 27% rural water supply
  • 22% livestock
  • 13% urban supply.

Groundwater is accessed from a variety of sources: boreholes equipped with electric pump, hand-pumps, windmills, solar pump, diesel pumps and rope and bucket. There are no recent statistics on the different pump technologies employed, but a nationwide inventory carried out by government in 1998 produced an estimated total of 11,000 boreholes (electric and hand pump) and 22,000 protected wells in the country (National Water Policy 2010).

Groundwater management

The key groundwater institutions are:

  • Department of Water Affairs – for water policy formulation.
  • Ministry of Local Government and Housing – for rural water supply
  • Water Resources Management Authority (WARMA) – for water resources development, utilisation and management

The legal framework for groundwater monitoring in Zambia comprises the following:

  • The Revised National Water Policy of 2010
  • The Water Resources Management Act of 2011, which stipulates that there shall be no private ownership of water and that any permission to use water will be time-limited. The Act provides for permits to drill and abstract groundwater, but these have not yet been implemented. The greatest challenge to effective (ground)water resources management in the country is posed by poor institutional and legal frameworks; inadequate water resources data and information systems; poor coordination of various ministries, departments and institutions dealing with water; centralised management of water resources; and lack of monitoring and evaluation of programmes and projects relating to water (National Water Policy 2010).

Transboundary aquifers

Zambia has two transboundary aquifers identified by the SADC Hydrogeological Mapping Project (SADC, 2010). The "Medium Zambezi Aquifer" crosses the border with Zimbabwe, and the "Sands and gravel aquifer" crosses the border with Malawi.

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

Groundwater monitoring

Groundwater level measurements are taken automatically at some stations in Lusaka on a daily basis, while in other places, these are read fortnightly.

There is no national or regional groundwater quality monitoring.

References

Geology: key references

Thieme JG and Johnson RL. 1974/75. Geological map of the Republic of Zambia. Geological Survey Department, Zambia.

Ray AK. 1983. Lithostratigraphic succession of Zambia- under the recommendation of the Stratigraphic Committee, Geological Survey Department, Zambia; Lusaka.

Hydrogeology: key references

Bailey KV. 1991. Zambia: review of national IDD control programme. Summary of report to World Health Organisation/International Council for Control of Iodine Deficiency Disorders. IDD Newsletter, 7(3).

Chenov C D. 1978. Hydrogeological Map of Zambia. UNESCO/National Water Resources Research Project, Zambia; National Council for Scientific Research, Lusaka, Zambia.

ICCIDD. 2012. Zambia zeroes in on IDD elimination. IDD Newsletter, International Council for Control of Iodine Deficiency Disorders (Accessed from http://www.iccidd.org/newsletter/idd_aug12_zambia.pdf in May 2015).

JICA-MEWD. 1995. National Water Resources Master Plan for the Republic of Zambia. Final Report – Main Report. Yachiyo Engineering Co. Ltd.

Mpamba NH. 2006. Comparative Analytical Model for Groundwater Monitoring in the Urban and Rural areas of Zambia – Groundwater Resources Data and Information. The University of Zambia, Lusaka, Zambia.

Smedley PL. 2001. Groundwater Quality: Zambia. British Geological Survey. (Available for download from http://www.bgs.ac.uk/sadc/fulldetails.cfm?id=ZM4009).

African Groundwater Literature Archive (AGLA) references

For more references for the hydrogeology of Zambia please visit the African Groundwater Literature Archive's Zambia page.

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