Ground Water Resources Management
Groundwater resources have been a very important resource both for human consumption as well as ecosystem support. Zambia experiences one rainy season in a year running from around November through to March/April the following year. Many rivers and streams in Zambia are however perennial due to the contribution of groundwater from base flow. Groundwater also serves as an immediate source for rural populations as well as a source of water for municipal water supplies across the country. In Zambia, an average of 30% of municipal water supplies is drawn from groundwater. This entails that groundwater is an important and indispensable resource when it comes to contribution to the national growth domestic product. While groundwater occurrence and importance has been acknowledged in all sectors of the country, there has been no legal framework for its regulation from the time the country was colonized up until 2011 when the country reclassified groundwater as public water and hence amenable for regulation. It is this regulation that will provide the much needed information on groundwater abstraction and use. The country is now in the process of developing subsidiary groundwater regulation that will enforce the Water Resources Management (WRM) Act No. 21 of 2011.
The Zambian law now provides for registration of all boreholes. This is a process that has been embarked on by WARMA. The Authority currently has currently records of up to 16,000 groundwater points, 3,000 of which are not georeferenced. These are records for both commercial and domestic purposes.
Groundwater aquifers in Zambia is mainly composed of the carbonate, alluvial and schist aquifers. The carbonate aquifers are usually highly productive and form an important source domestic and industrial water supply. These aquifers are part of the kundelungu geological formation and span from the copperbelt though to Lusaka plateau following the famous Lufilian Arc orientation. The dolomite aquifer is generally unconfined with preferential horizontal flow direction. Most of the karsts are developed between 50 -90m below ground. The degree of fracturing and Karstification is progressively diminished below 90m above ground. This restricts significant flow process of groundwater below this depth. Transmisivities within the Kabwe dolomite range from 1100 to 4500m2/d). This scenario repeats itself in the carbonate rocks of Lusaka and Mpongwe. (Jones et al 1972 (Toepfer et al).
Zambia also boasts of vast stretches of alluvial aquifers indicated in the map . These are mainly found along on the banks of existing river channels as well as old river channels. Typical examples are the Barotse flood plains in the western part of Zambia, the Kafue flats and the Luapula basin in the Northwestern part of Zambia.
The schist aquifers are subordinate aquifers and are known to be generally poor in terms of water resources production. Geologically, the composition is mostly Schists, Phylites and shales of the Lower Roan formation series. It is a thick sequence which follows the basal group with no marked unconformity. It also exhibits common stripes of quartz veins. As mentioned earlier in-situ chemical weathering since the mid tertiary peneplanation has produced a thick saprolite layer from these rocks.
In some areas, the schist aquifers are composed of Feldspathic granitic gneiss with minor schists. This is a basement complex which is an unconformity. It is of Precambrian age with an isotope dating of 1200 to 3000 million years.
Documentation on groundwater abstractions remains a gigantic challenge for Zambia. This is because of the non-regulation of the groundwater sector since pre-colonial times. In 2015, WARMA recruited more staff in the groundwater Unit in order to pick up pace in the collection of Data. The WRM Act. Mandates WARMA to issue abstraction licenses for commercial entities. The Groundwater Unit participated in the stakeholder led process of development of a Pricing Strategy. Once adopted, the strategy will feed into the process of data collection through issuance of abstraction fees. As mentioned only pockets of abstraction data is available in the possession of a number of players in the groundwater sector.
Groundwater monitoring in Zambia is done using manual and data logging system. Currently, the country has an established network for Lusaka region and the upper Kafue catchment. The Lusaka groundwater network monitors water table and is spatially distributed as indicated in the map.
Groundwater network for Lusaka and surrounding area
The mapping of groundwater resources for Lusaka region showed that groundwater resources are on the decline for the past three years. This can be attributed to a number of factors, among which are increased abstractions to support human development, reduced recharge due to unfriendly environmental developments and sustained lower than normal precipitation.
The country has now established a monitoring network for the Upper kafue catchment. This is in an effort to expand the monitoring network. 10 sites have been constructed and are fitted with data logers which are recording hourly water levels, Electrical Conductivity, Total Dissolved Solids and Salinity. Below is the distribution network.
Ground water distribution