Scientists study northern aquiferExploration of the vast groundwater source known as the Ohangwena II Aquifer is proceeding slowly but surely. Hasty drilling could ruin huge water source 0 A group of German and local scientists have started testing the Ohangwena II Aquifer but they warn that careless drilling could spoil the giant groundwater source.Currently, a production well at Eenhana is being tested with the assistance of NamWater.
The well delivers a maximum yield of roughly 100 cubic metres (100 000 litres) per hour. The deputy director of geohydrology, Bertram Swartz, is the project coordinator.
The monitoring of the aquifer’s reaction will show the potential of this unique and immensely valuable resource.
The agriculture and water ministry estimates that the aquifer holds about 20 billion cubic metres of fresh water and has the potential to supply water to northern Namibia for the next 400 years.
“Once we are sure of a sustainable yield, we can start developing infrastructure and determine the costs thereof,” said agriculture spokesperson Margaret Kalo.
“There have been estimates but we will only know for sure once the aquifer is developed and supply has started. Monitoring of the aquifer’s movement will have to continue and therefore it is critical to have a good monitoring network.”
The project started in 2007 and will run until the end of May next year.
It is financially supported by the German Development Fund, the European Union (EU) and NamWater at a cost of N$25 million.
Information obtained from the EU revealed that after the aquifer was identified in Ohangwena, a groundwater hydro-census was conducted as a baseline study in 2007 to 2008, together with a transient electromagnetic (TEM) field survey that revealed potential freshwater horizons in the Ohangwena and Omusati regions.
Drilling campaigns were done between 2009 and 2010 and have verified the existence of a deep aquifer in the western part of the Ohangwena Region. Additional observation boreholes were drilled in 2011 to delineate the freshwater extent and to set up a groundwater monitoring network.
Preliminary results from extensive drilling campaigns, hydraulic tests, recharge calculations, water level and water quality monitoring revealed the huge potential of the Ohangwena II Aquifer (KOH II) for regional water supply.
Kalo said the aquifer stretches about 75km from the Ondobe Constituency towards the east and about 40km from the Angolan border to the south. It is part of the Cuvelai-Etosha Basin (CEB) - an extensive sedimentary basin which is part of the much larger Kalahari Basin covering parts of Angola, Namibia, Zambia, Botswana and South Africa.
The CEB is divided into six groundwater regions, based on geological units (Damara Sequence) and local occurrence (Kalahari Sequence).
One of the six regions is the Ohangwena Aquifer (KOH I and KOH II), a multi-layered, continuous porous aquifer system of the eastern Ohangwena and northern Oshikoto regions with a groundwater flow from Angola to the south.
The eastern part of the Ohangwena I Aquifer is being tapped through small-scale abstraction schemes for livestock and human consumption.
The newly discovered Ohangwena II Aquifer, which is being investigated in detail at the moment, underlies the brackish to saline western part of the Ohangwena I Aquifer. Careless drilling could, therefore, contaminate the fresh water with saline water.