TC Zambia: Groundwater Resources for Southern Province

Report of the project:

• Sambia – Grundwasserressourcen für Lusaka und ausgewählte Einzugsgebiete (Phase III)
• Zambia - Groundwater Resources Management Support Programme (GReSP)

Fig. 1: Location of project area Source: BGR

Background
The Southern Province covers an area of approximately 85,500 square kilometres and is known to form one of the most drought-prone regions within Zambia (Figure 1). The tropical continental highland climate is characterised by a cool and hot dry season lasting from May to October and a wet season between November and April. Rainfall totals are the lowest in the country with mean annual rainfall ranging from 650 mm to 800 mm. The distribution of rainfall during individual rainfall events and rainy seasons is very unpredictable. Due to these climatic conditions rain-fed agriculture is highly undependable.

The Southern Province has a share in two of Zambia’s major water courses, the Zambezi River including the Kariba reservoir at its southern and eastern boundaries and the Kafue River to its northern margins. During prolonged dry periods however, the discharge of most tributary rivers ceases (Figures 2a + 2b) and the large majority of the population of the Southern Province depends on water supply from small dams or groundwater. Groundwater constitutes therefore the only reliable and safe water source available throughout the year.

Despite of its importance, the use of groundwater is currently not regulated. Groundwater management regulations are incorporated in the proposed Water Resources Management Bill which is yet to be enacted.

Methodology
Accurate and updated information on both surface and groundwater resources is required to regulate its use and to establish an integrated and sustainable management of the Nation’s water resources. For underground water, this includes a comprehensive assessment of the groundwater resources and their current use, an improved understanding of the groundwater systems and their interactions with surface water as well as a continuous and extended monitoring of groundwater levels and quality.

Fig. 3: Groundwater information system Source: BGR

The Project was launched in May 2005 with the objectives to facilitate an effective groundwater resource planning and management in the Province and to strengthen the capacities in the Zambian water sector. As an integral part of this Project a professional groundwater information system at the DWA is developed consisting of a groundwater database and a Geographic Information System (GIS) (Figure 3). The database stores information on over 3,000 water points including hand dug wells, boreholes, springs and unsuccessful groundwater exploration drill sites. The database includes the information of all major hydrogeological investigations carried out since the mid- 1970s and combines general information (e.g. location, type and purpose of water point) with comprehensive and detailed technical information on groundwater hydraulics, borehole design, geology and groundwater quality.

Fig. 4: Groundwater contour map Source: DWA/BGR

Three hydrogeological maps at scale 1:250,000 covering about 75% of the Province, and another more detailed map at scale 1:100, 000 were developed. The maps show water usage as well as lithological characteristics and potential of aquifers. The design and legend of the maps follow international guidelines and can be adopted as a national standard for groundwater maps of other regions. Other thematic maps produced show the regional groundwater flow (Figure 4) and surface water catchments (Figure 5) that were derived from a Digital Elevation Model (resolution: 90 by 90 meters). The developed groundwater information system and the thematic maps support efforts on exploring, managing and protecting the groundwater resources.

Results
The groundwater related information assembled was assessed and interpreted in order to identify groundwater systems and their potential.

Fig. 5: Surface water catchments Source: DWA/BGR

About two thirds of the Province is made up of hard rocks including Precambrian basement rocks as well as clastic deposits and basalts of Karoo (Permian to early Jurassic) age. The remainder is covered by unconsolidated deposits consisting of alluvial deposits and Kalahari sands. Most of the rock formations have been characterised as heterogeneous, i.e. their potential to host and produce groundwater is extremely variable. This seems to be one of the reasons why about one out of five boreholes drilled during larger exploration campaigns was unsuccessful. Careful planning using the groundwater information system and possibly the use of advanced geophysical methods could considerably improve success rates during exploration.

Fig. 6: Major aquifer systems Source: DWA/BGR

The comprehensive statistical analysis of available hydrogeological data showed that the potential of groundwater in the Province is overall limited (Figure 6). In some areas, namely regions within the Karoo sandstones and basalts, the alluvial deposits of the Kafue Flats and the calc-silicate rocks in the Mazabuka/Magoye area, groundwater conditions are more favourable. The groundwater quality is overall good although concerns must be raised over microbiological contamination near major settlements due to poor sanitary conditions. In general, potential groundwater production from aquifers is insufficient for larger development such as irrigation schemes. Despite these limitations extractable groundwater volumes are sufficient to assure long-term water supply to rural areas and smaller settlements if used sustainably.

Literature:

Reports:

• BÄUMLE, R., NEUKUM, C., NKHOMA, J. & SILEMBO, O. (2007): The Groundwater Resources of Southern Province, Zambia. - Technical report Vol. 1, prepared by Department of Water Affairs (DWA), Zambia & Federal Institute for Geosciences and Natural Resources (BGR); Unpubl. report, BGR archive no. 0127518, 132 p., 64 fig., 27 tab.; Hannover - Lusaka. (PDF, 6 MB)
• BÄUMLE, R., NKHOMA, J., SILEMBO, O. & NEUKUM, CH. (2007): Groundwater resources for Southern Province, Zambia – A brief description of physiography, climate, hydrology and groundwater systems of the Southern Province. - Department of Water Affairs (DWA), Zambia & Federal Institute for Geosciences and Natural Resources (BGR); 53 pp; Hannover - Lusaka (Printech). (PDF, 5 MB)
• NKHOMA, J. & BÄUMLE, R. (2007): Groundwater resources for Southern Province, Zambia – A manual with explanations for the use of the hydrogeological maps. - Department of Water Affairs (DWA), Zambia & Federal Institute for Geosciences and Natural Resources (BGR); 20 pp; Hannover - Lusaka (Printech). (PDF, 2 MB)

Hydrogeological Maps:

• BÄUMLE, R., NKHOMA, J. & SILEMBO, O. (2007): Hydrogeological Map of Zambia, Southern Province: Map Sheet Kafue Flats and Southern Tributaries 1:250,000. - Department of Water Affairs (DWA), Zambia & Federal Institute for Geosciences and Natural Resources (BGR); 1st ed.; Hannover - Lusaka.
• BÄUMLE, R., NKHOMA, J. & SILEMBO, O. (2007): Hydrogeological Map of Zambia, Southern Province: Map Sheet Northern Kariba Lake and Kafue Gorge 1:250,000. - Department of Water Affairs (DWA), Zambia & Federal Institute for Geosciences and Natural Resources (BGR); 1st ed.; Hannover - Lusaka.
• BÄUMLE, R., NKHOMA, J. & SILEMBO, O. (2007): Hydrogeological Map of Zambia, Southern Province: Map Sheet Southern Kariba Lake and Kalomo 1:250,000. - Department of Water Affairs (DWA), Zambia & Federal Institute for Geosciences and Natural Resources (BGR); 1st ed.; Hannover - Lusaka.
• BÄUMLE, R., NKHOMA, J. & SILEMBO, O. (2007): Hydrogeological Map of Zambia, Southern Province: Map Sheet Lusitu Catchment 1:100,000. - Department of Water Affairs (DWA), Zambia & Federal Institute for Geosciences and Natural Resources (BGR); 1st ed.; Hannover - Lusaka.
  
  Printed copies of the Hydrogeological Maps of Zambia can be ordered at the Internationales Landkartenhaus (ILH) Stuttgart.