In a presentation on Wednesday at the second Botswana Society public forum series on what the future holds for Botswana’s water supply, Permanent Secretary in the Ministry of Minerals, Energy and Water Resources Boikobo Paya said water rationing will continue into the future as a form of supply management until the water situation in the country improves. Gaborone Dam is expected to fail in the next couple of weeks while Bokaa dam will fail by March 2015 if they do not receive inflows, Paya has said. Gaborone dam currently stands at 9.4% of the 141.4 million cubic metres (MCM) capacity which sustain supply for until October 2014.
In 2013/14 rainfall season most parts of the country received above normal rainfall. Only Gaborone and south-west Kgalagadi , experienced extremely below normal rainfall, which has negatively affected Gaborone dam. The Ngamiland district experienced good rains throughout the season leading to good vegetation performance compared with average conditions.
Paya however assured that his ministry are managing the water supply efficiently to ensure sustainability going forward. Statistics show that currently Gaborone, Molatedi, Bokaa, Letsibogo, Nnywane and Ramotswa dams supply a total 167.4 million litres per day, out of the normal supply capacity of 202 million litres per day.
Due to a relatively flat topography with low rates of surface runoff and deep (>250 m) overburden, there are no more dam sites in Botswana, which has forced the country to aggressively pursue Chobe-Zambezi transfer scheme, and the Lesotho Highlands transfer to Botswana, and other negotiations with riparian states for trans boundary usages.
While most of the developed dams in Botswana are concentrated along the eastern corridor, it has also emerged that there are no more dam sites available in the country. Therefore Botswana is currently actively pursuing Chobe-Zambezi transfer scheme, and the Lesotho Highlanders transfer to Botswana, and other negotiations with riparian states.
To address deficits and ensure a sustainable water supply, Paya said there is need for conjunctive use of surface and groundwater resources in the eastern corridor because of availability of dams/reservoirs. To this end, phase II of the North-South Carrier proejct to connect the southern parts of the country to dams in the north. He said the 26 km problematic stretch to the north of Palapye has been succesfully rectified with the use of steel pipeline in the North-South Carrier project. "The next phase will be to connect Palapye to Gaborone and the rest of the areas in the south," he said.
He said groundwater should be used as back-up since surface water is lost to evaporation processes. This will allow aquifers to recover during wet seasons. He said Botswana could also explore artificial recharge of aquifers with excess runoff as an alternative. Of greater importance, he said, is the water demand management (water conservation). Other alternatives to augment sustainable water supply include the utilisation of effluent-waste water recycling up to potable and the use of saline groundwater where possible, like Debswana, and the construction of water transfer schemes.
Botswana receives and average rainfall of 450 mm, with temperatures ranging from below zero in the south and can be greater than 40 degrees. The Topography is relatively flat with low rates of surface runoff and deep (>250 m) overburden. The country experiences low rates of recharge to its groundwater with about 40 mm in small areas in the Chobe District in the north and over most of the Kalahari region at 18mm or approaches zero.
Developed surface water resources in Botswana have a yield of 88 680 000 m3 per year, while
potential new surface water resources/ undeveloped stand at an estimated 72 680 000 m3 per year.
Developed ground water resources (excluding wellfields that are operated by mines and other privately owned boreholes) yield 46 306 000m3/ year while potentila new ground water resources/ undeveloped stand at 5 501 500 m3/ year. The quantity of saline groundwater resources and the groundwater recharge rates is unknown.
Paya was presenting on the topic: What is Botswana’s existing water infrastructure? Storage? Conveyance? Treatment? The aim of the public forum quarterly series is to sustain dialogue on an issue of national importance, in this case water, in a manner that generates factual knowledge and reasoned opinions to inform the public and relevant government policy-makers.