Hydrogeology of Malawi
Africa Groundwater Atlas >> Hydrogeology by country >> Hydrogeology of Malawi
Malawi is one of the smallest countries in Africa, bordered entirely by other countries and to the east by Lake Malawi, which makes up about a third of Malawi’s area. After independence in 1964 the country saw one-party state politics until 1994. Since then, Malawi has seen multi-party government, with occasional political and civil unrest.
Malawi’s economy is based on agriculture, which accounts for over a third of GDP and 90% of export revenues. Agricultural exports are dominated by tobacco, tea and sugar, mostly from large commercial farms. Market liberalisation in the 1990s saw more smallholder farmers enter agricultural markets. Smallholder, mostly rainfed, agricultural production, particularly of maize, is a majority livelihood activity. In recent years Malawi has granted licenses for hydrocarbon exploration in the East African Rift Valley, including Lake Malawi, but to date there are no proven hydrocarbon reserves.
Malawi has abundant surface water resources, both Lake Malawi and many large perennial rivers flowing from the highland areas. However, most rural Malawians rely on groundwater for their domestic supply, and groundwater is increasingly used for irrigation by smallholder farmers. The country has also seen recent devastating floods (in 2015) and drought (e.g. in 2016), highlighting its lack of resilience to hydrological risk.
Authors
Dr Kirsty Upton, Brighid Ó Dochartaigh, British Geological Survey, UK
Brighton Chunga, Mzuzu University, Malawi & Cranfield University, UK.
Dr Imogen Bellwood-Howard, Institute of Development Studies, UK
Please cite this page as: Upton, Ó Dochartaigh, Chunga and Bellwood-Howard, 2018.
Bibliographic reference: Upton, K., Ó Dochartaigh, B.É., Chunga, B. and Bellwood-Howard, I. 2018. Africa Groundwater Atlas: Hydrogeology of Malawi. British Geological Survey. Accessed [date you accessed the information]. https://earthwise.bgs.ac.uk/index.php/Hydrogeology_of_Malawi
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Geographical Setting
General
Malawi has four main physiographic zones: highlands or uplands; plateau areas; the rift valley escarpment; and the rift valley floor/plains.
The highlands cover a relatively small area but can be 2000 m to 3000 m in elevation. The plateau areas cover much of the country, and are gently undulating surfaces from 750 m to 1300 m in elevation. They are cut into by wide valleys, or 'dambos', with grassy, swampy bases, which largely drain towards the rift valley floor. The rift valley escarpment consists of parallel faults with the land stepping down to the rift valley floor. The rift valley floor and plains extend along the shores of Lake Malawi and the upper Shire Valley; they have low relief and range from 100 m to 600 m in altitude.
Capital city | Lilongwe |
Region | Eastern Africa |
Border countries | Tanzania, Mozambique, Zambia |
Total surface area* | 118,480 km2 (11,848,000 ha) |
Total population (2015)* | 17,215,000 |
Rural population (2015)* | 14,399,000 (84%) |
Urban population (2015)* | 2,816,000 (16%) |
UN Human Development Index (HDI) [highest = 1] (2014)* | 0.4454 |
* Source: FAO Aquastat
Climate
Malawi has two main seasons: a wet season from November to April and a dry season from May to October. Rainfall is influenced by topography, with the highest rainfall in upland areas and on slopes explosed to the prevailing northeasterly wet season winds. Annual rainfall exceeds 800 mm over most of the country. Lake Malawi and the upper Shire Valley receive relatively low rainfall. There are large interannual variations in rainfall.
More information on average rainfall and temperature for each of the climate zones in Malawi can be seen at the Malawi climate page.
These maps and graphs were developed from the CRU TS 3.21 dataset produced by the Climatic Research Unit at the University of East Anglia, UK. For more information see the climate resource page.
Surface water
Lake Malawi is the largest water body in Malawi, and is the dominant control on the surface water drainage network in the country. The only river flowing out of Lake Malawi is the Shire River, which flows south into Mozambique, where it flows into the Zambezi River.
The main rivers flowing into Lake Malawi are the Songwe, South Rukuru, North Rukuru, Dwangua, Linthipe and Bua. The Songwe river marks Malawi's northern boundary with Tanzania, and flows into Lake Malawi at its northern end. The South Rukuru river is the main river in the Northern region of Malawi, flowing though the Nyika Plateau to the lake. The Bua and Dwangua rivers flow through central Malawi into the lake.
These major rivers typically drain wide 'dambos' in the plateau areas, which have steep valley sides that become less steep as they reach the rift valley. The upper Shire Valley has a wide alluvial plain, changing to a narrower valley with gorges and rapids in the lower part.
The next largest lake in Malawi is Lake Chilwa, which forms an internal drainage basin and mainly drains the northern uplands. Rivers flowing into the Chilwa basin tend to be ephemeral in their lower courses, losing water to permeable valley alluvial deposits.
Soil
Soil compositions tend to be closely related to the underlying geology. Sandy soils occur on many granitic areas of the basement complex, and at the edges of alluvial plains. Latosols, including ferrosols, are common. Many soils are lateritic, typically 1 to 3 m thick (Smith-Carington and Chilton 1983), and sometimes 5 to 20 m thick (BGS 2004). Other soils include lithosols on steep slopes of the uplands and rift valley escarpment; hydromorphic (water logged) soils, including vertisols, in dambos; and calcimorphic soils on alluvial plains (Smith-Carington and Chilton 1983).
Land cover
GeologyThis section provides a summary of the geology of Malawi. 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 resource page for more details). SummaryMost of the country is underlain by Precambrian to Lower Palaeozoic crystalline basement rocks. These are unconformably overlain in places, particularly in the north and south, by more recent sedimentary rocks or volcanic rocks. There is extensive Quaternary alluvium in valley bottoms and the rift floor plain. The main structural feature is the rift valley, which was formed by a subsidence fault during the Upper Mesozoic and Cenozoic, and is still active. Lake Malawi and the Shire Valley lie on the floor of the rift valley (UN 1989).
HydrogeologyThis section provides a summary of the hydrogeology of the main aquifers in Malawi. 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 overview of the type and productivity of the main aquifers at a national scale (see the Hydrogeology map resource page for more details). Malawi is also covered by the SADC hydrogeological map and atlas (2010), available through the SADC Groundwater Information Portal. .SummaryThe two most important aquifer systems in Malawi are (Chavula 2012):
There are only small occurences of other rock types. Although these can be important locally, relatively little is known of their hydrogeological properties.
Unconsolidated
Sedimentary - Intergranular Flow
Igneous Volcanic
Igneous Intrusive
Sedimentary - Fracture Flow
Basement
Groundwater StatusThe quality of groundwater in Malawi is highly dependent on aquifer lithology, and is highly variable spatially. Nationally, groundwater is generally suitable for drinking water (Chavula 2012). Groundwater in alluvial aquifers is genearlly more mineralised than that in basement aquifers, and a number of boreholes in alluvial aquifers have been abandoned due to high salinity (Chavula 2012). Chemical parameters that are elevated in different areas include fluoride, sulphate, iron, chloride and nitrate. Fluoride concentrations of more than 1.5 mg/l are common in groundwater in alluvial aquifers in the Salima/Nkhotakota and Karonga lakeshore areas (Chavula 2012). Generally, groundwater from boreholes is of better microbiological quality than groundwater from dug wells, which tend to be more vulnerable to contamination (Chavula 2012). An overview of in groundwater quality is given in Bath 1980, BGS 2004, and Water Department/UNDP (1986). Groundwater use and managementGroundwater useGroundwater is widely used across Malawi for both domestic and agricultural purposes. There were about 30,000 water boreholes and 8,000 protected hand dug wells in 2012 (Chavula 2012). Drought and poor water quality have meant more people are turning from hand dug wells to drilled boreholes. Estimates show that 65% of the population depends on groundwater for domestic supply: in rural areas, this rises to 82%, while in urban areas is it closer to 20%, although a number of towns or districts within towns get most of their water supply from groundwater (Chavula 2012). Groundwater is increasingly used for irrigation by smallholder farmers, often from hand dug wells, and increasingly using treadle pumps, particularly in dambo areas. There is also a large scale irrigation scheme in the Salima district, where groundwater from an alluvial aquifer is extensively used for horticultural crops and agro processing. Some farmers use groundwater for livestock watering (Chavula 2012). Boreholes fitted with hand pumps are standard for rural groundwater supplies. The use of motorised pumps is widespread, particularly by farmers; and treadle pumps are becoming more widely used.
Groundwater managementThe Water Resources Act of 1969 was replaced by the Water Resources Act of 2013. Part of the new Act was to establish the National Water Resources Authority. Since 2013, there has been ongoing development and reorganisation within government agencies concerning how groundwater, and other water, resources are managed. The Ministry responsible for water resource affairs, including groundwater, is currently the Ministry of Agriculture, Irrigation and Water Development. Within this Ministry, the Departments of Water Resources and Water Supply are responsible for groundwater development policy. The Department of Water Resources currently has three sections: the Groundwater Division, Surface Water Division, and Water Quality section. Formerly, the Water Resources Board formed a fourth section within the Ministry, but under the Water Resources Act of 2013 this has now been replaced by the National Water Resources Authority (NWRA), an autonomous government sponsored body. The NWRA have taken over the roles of the former Water Resources Board, and will eventually assume other roles carried out currently by the other sections of the Water Resources Department. The responsibilities of the NWRA include (but are not limited to) the following: - developing principles, guidelines and procedures for the allocation of water resources; - monitoring, and from time to time reassessing, the National Water Policy and the National Water Resources Master Plan; - managing water use permits; - regulating and protecting water quality from adverse impacts; - managing and protecting water catchments; - gathering and maintaining information on water resources and from time to time publishing forecasts, projections and information on water resources; - assisting the Minister in the coordination of hydrological and hydrogeological investigations; - coordinating the preparation and implementation of a water action plan.
The NWRA works alongside the Shire River Basin Management Board, which is a pilot board created under a World Bank project, the Shire River Basin Management Programme. Ultimately, the aim is that the NWRA will oversee river basin / catchment management authorities or boards across the country, based on the major river basins. In much of the country, the practical development of groundwater resources is currently dominantly carried out by NGOs, the donor community and the private sector, in collaboration with the NWRA and the Ministry Agriculture, Irrigation and Water Development (Chavula 2012). Groundwater monitoringGroundwater level monitoring is being carried out across a network of approximately 30 boreholes across the country, assisted by the use of automatic water level monitors. Some groundwater quality monitoring is also taking place. The monitoring network is currently being upgraded as part of a World Bank funded project on national hydrogeological and water quality mapping. Transboundary aquifersFor further information about transboundary aquifers, please see the Transboundary aquifers resources page
ReferencesThe following references provide more information on the geology and hydrogeology of Malawi. These, and others, can be accessed through the Africa Groundwater Literature Archive. Online resourcesSADC Groundwater Information Portal General information on surface water and groundwater resources in SADC
Geology: key referencesSmith-Carington AK and Chilton PJ. 1983. Groundwater resources of Malawi. Department of Lands, Valuation and Water; Republic of Malawi, Lilongwe. Hydrogeology: key referencesBath AH. 1980. Hydrochemistry in groundwater development: report on an advisory visit to Malawi. British Geological Survey Report WD/OS/80/20. BGS. 2004. Groundwater Quality: Malawi. British Geological Survey/WaterAid. https://www.wateraid.org/~/media/Publications/groundwater-quality-information-malawi.pdf Chavula GMS. 2012. Malawi, in Groundwater Availability and Use in Sub-Saharan Africa: a review of fifteen countries. Pavelic P et al. (Eds). International Water Management Institute, Sri Lanka. Smith-Carington AK and Chilton PJ. 1983. Groundwater resources of Malawi. Department of Lands, Valuation and Water; Republic of Malawi, Lilongwe. UN. 1989. Malawi: Ground water in Eastern, Central and Southern Africa. Natural Resources/Water Series No. 19, ST/TCD/6. United Nations Department of Technical Cooperation for Development. Water Department/UNDP. 1986. National Water Resources Master Plan. Malawi Government. NOTE this was replaced by an updated version, compiled by JICA, 2014. Return to the index pagesAfrica Groundwater Atlas >> Hydrogeology by country >> Hydrogeology of Malawi |