Capital faces perpetual water shortages
Windhoek’s demand for potable water currently stands at roughly 30 million cubic metres per annum, which translates to about 82 200 cubic metres per day.To put this in perspective, the capacity of the Oanob Dam near Rehoboth is about 34.5 million cubic metres.
According to the Namibian Agricultural Union’s newsletter, NamWater supplies the City of Windhoek with around 75% of this potable water demand from surface water sources.
Windhoek’s water security is a perpetual concern due to its average approximate rainfall of 350mm and the distant location of the nearest perennial water source - some 700 kilometres away, the municipality said.
It bears the responsibility of managing water supply, sewerage collection and water treatment across the capital’s 22 localities, providing water access to around 90% of households and handling sewerage services for about 75%.
Diverse sources contribute to Windhoek’s water supply, the municipality said. The primary source is surface water from a three-dam system: Omatako, Swakoppoort and Von Bach, with the latter managed by NamWater.
This water undergoes treatment at the Von Bach water treatment plant near Okahandja before being conveyed to Windhoek via the Von Bach-Windhoek transfer scheme.
“During severe droughts, NamWater can supplement this system with groundwater from the Karst area through the eastern national water carrier,” the newsletter read.
Additionally, the City supplements NamWater’s supply with groundwater drawn from the Windhoek Aquifer through its own boreholes.
Unconventional resources
Furthermore, the City exploits various unconventional water resources which include direct potable water reclamation through the new Goreangab water reclamation plant, reclamation of semi-purified water for limited irrigation purposes and managed aquifer recharge of the Windhoek Aquifer using surface water.
It has the capacity to reclaim approximately 5.09 million cubic metres of water per year, the municipality said.
The daily demand for semi-purified water is around 4 000 cubic metres, with a maximum supply capacity of about 6 000 cubic metres per day.
“However, during summer, demand peaks to the point of surpassing the maximum supply capacity, highlighting the need for system improvements.”
A key constraint lies in a pipeline section from the old Goreangab water reclamation plant, which can be expanded to enhance the supply rate, the City said.
It stressed that its water supply resilience is vulnerable to both drought and intensified rainfall.
“Reduced rainfall and heightened evapotranspiration result in diminished water availability from surface and groundwater sources. Consequently, treated wastewater and reclamation potential suffer a reduction. Industries reliant on water may experience setbacks, with potential cascading effects on the economy.”
Meanwhile, higher rainfall intensity can damage catchment areas and lead to heightened siltation of surface water sources.
“Asset functionality can be directly impacted by flooding. Intense rainfall can overwhelm sewer systems, potentially causing hydraulic overload in wastewater treatment plants and contaminating downstream surface water.”
Looking ahead
The City highlighted that several projects are being explored at national and regional levels to ensure sustained and resilient water supply for central areas of Namibia.
NamWater is actively investigating significant projects to secure Windhoek's water supply, such as desalination, the transfer of water from the central coast to central areas and the abstraction of water from the Kavango River, linked to the eastern national water carrier.
In addition to these initiatives, the municipality is engaged in the investigation and potential future implementation of projects to bolster long-term water supply and resilience, including expanding the Gammams wastewater treatment plant to increase capacity.
It is also augmenting direct potable re-use capacity through reclamation facility expansion, enhancing the security of potable and semi-purified water supply and supporting local development, it said, adding that it plans to establish a managed aquifer recharge system to amplify the Windhoek Aquifer's sustainability.
The City also plans to introduce pre-treatment measures for certain borehole sources and to expand the semi-purified supply system to better harness capacity within Goreangab Dam.