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Namibia: Govt Plans Dam Project
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New Era (Windhoek)
11 April 2008
Posted to the web 11 April 2008
Wezi Tjaronda
Windhoek
The Ministry of Agriculture, Water and Forestry will in the next three years excavate earth dams into which to pump excess water.
About N$18 million has been budgeted for various small dams, which will be constructed in 12 of Namibia's 13 regions.
Permanent Secretary at the Ministry of Agriculture, Water and Forestry, Andrew Ndishishi, told New Era recently that this was one of the plans the ministry has devised to save water and use it when it is needed most.
So far, floodwater running into millions of cubic metres is going to waster because it is not being harvested for future use. Yet, due to Namibia's proneness to drought, this water could be banked and utilised in the future.
Apart from providing enough moisture for crop production, growing of grazing for livestock and bringing an abundance of fish to the north and northeastern regions affected by the floods, the water is largely unused.
Ndishishi said the ministry was caught unawares by this year's unexpected floods and could not implement the project.
"This year, there is water all over and we cannot excavate the dams. As soon as the water subsides, we will start the work," he said.
He added that water was already being pumped into one of the dams in the north, which was empty and the ministry was looking for other empty dams into which to pump excess water. The ministry is currently looking for consultants to investigate the feasibility of identified sites in the 12 regions for the construction of various small dams.
Plans are also underway to construct a bigger dam in the Karas region. The Neckertal Dam will be constructed this financial year once a feasibility study is completed. The ministry this week advertised for consultants to tender to review feasibility studies undertaken for the construction of the Neckertal Dam and make recommendations on future actions and design.
In a related development, the ministry is evaluating a report, which will determine the way forward for recharging underground water supplies (artificial recharge) for later use in the country.
Ndishishi said the study into artificial recharge was conducted and was now being discussed in government circles. The ministry's website says artificial recharge of groundwater is presently being considered as one of the cost-effective alternatives for augmenting the water supply of Windhoek and Rehoboth.
Artificial recharge has been a common practice in many countries for many years and is considered when there is a gap between water demand and water availability, when there is sufficient surface water and when there is sufficient underground storage capacity.
Pressures of the modern world to increase water resources has led to the concept of enhancing these natural rates of recharge so that groundwater can be used more widely.
According to the Global Change System for analysis, Research and Training (Start) changes in rainfall levels and increased hazards from floods and droughts will further impact recharge and groundwater stocks.
In addition, global warming is expected to increase evapo-transpiration of surface water, and in turn make groundwater storage and artificial recharge a more attractive option than surface water storage.
The initiative is not new in Namibia. In 1996, Windhoek City was one of the four pilot projects where preliminary results of a study into artificial groundwater recharge indicated that it is feasible to 'bank' vast quantities of water underground for later use.
According to Engineering News, the four projects undertaken with funding from the Water Research Commission indicated that storing water underground could provide a cost-effective and reliable water source for semi-arid South Africa.
The projects were also implemented in Calvinia and Kharkams in the Northern Cape and Pietersburg in Northern Province South Africa.
The projects focussed on artificial recharge to hard-rock aquifers, which make up 90 percent of South Africa's aquifers.
The Windhoek study, the largest scheme of the four involved pumping fully treated water into selected boreholes.
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The highest injection rate achieved was 214 kl/h, with the longest test running 195 kl/h, where 289 000 kl was injected into a single borehole.
These results demonstrated that large volumes of water can be stored in the subsurface, and that it can be injected at high flow-rates, according to Engineering News.
Windhoek at that time used 17 million kilolitres a year on average, and the study found that about five-million kilolitres a year could be injected into the area that was targeted for research (about a third of the city's yearly consumption).
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