Groundwater still a mystery
Officials involved in the Ohangwena underground aquifer project are unable to say whether the water can be safely used in the long term.
Both the agriculture ministry and the German Federal Institute for Geosciences and Natural Resources (BGR) have remained mum on the outcome of the testing that took place on the Kalahari Ohangwena aquifer (KOH-2) January 2011 and May 2017.
The German embassy and the agriculture ministry did not respond to repeated requests for information.
From what could be surmised, the aquifer is not responding well to the abstraction of water from its main body and thus, it is not yet operational although it was said it would be up and running this month.
A well-placed source that spoke to Namibian Sun on condition of anonymity, said the latest results reveal the aquifer has a huge potential of supplying fresh underground water in the country, however, during and after the tests, the aquifer did not react well.
The experts still do not know how much water can sustainably be taken from the aquifer without any permanent damage to the resource.
“The ministry and its partners cannot say anything at this stage. During the tests, the aquifer could not react positively as it was expected to. The aquifer should have been operational by June this year, but now has to wait,” the source said.
Namibian Sun is reliably informed the geological setting of the Ohangwena 1 and 2 aquifers was translated into a conceptual hydrogeological model.
Extensive drilling, hydraulic tests, recharge calculations, water levels and water quality monitoring provided information to parameterise the conceptual model and to develop a numerical groundwater model. This model is being used as a decision tool for the planning of groundwater abstraction schemes.
Several abstraction scenarios have been calculated and the impact on the resource, or aquifer, visualised.
“The problem lies with the determination of the sustainable yield of the aquifer and the conceptualisation of water abstraction. The production well of Eenhana town does not prove that the aquifer is sustainable. More tests are still needed and this will take more time.”
The aquifer's viability was verified after drilling campaign tests between 2009 and 2014 verified the existence and spatial extent of the KOH-2 aquifer in the Ohangwena Region.
Additional observation boreholes were drilled between 2011 and 2014 to delineate the freshwater extent and to set up a groundwater monitoring network.
According to the ministry, the aquifer has a store volume of freshwater of about 20 billion cubic metres which could supply water to the northern parts of the country for 400 years.
A production well that is currently supplying water to Eenhana town delivers a maximum yield of about 100 cubic metres an hour.
It was opened in 2011.
NamWater and the ministry, along with technical support from Germany are supervising the project, while the European Union has provided funds of approximately N$25 million.
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 the locally occurring 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 tested in detail at the moment, underlies the brackish to saline western part of the Ohangwena I aquifer. Careless drilling could, therefore, contaminate the large body of fresh water with saline water, destroying the natural value of the resource.
ILENI NANDJATO
The German embassy and the agriculture ministry did not respond to repeated requests for information.
From what could be surmised, the aquifer is not responding well to the abstraction of water from its main body and thus, it is not yet operational although it was said it would be up and running this month.
A well-placed source that spoke to Namibian Sun on condition of anonymity, said the latest results reveal the aquifer has a huge potential of supplying fresh underground water in the country, however, during and after the tests, the aquifer did not react well.
The experts still do not know how much water can sustainably be taken from the aquifer without any permanent damage to the resource.
“The ministry and its partners cannot say anything at this stage. During the tests, the aquifer could not react positively as it was expected to. The aquifer should have been operational by June this year, but now has to wait,” the source said.
Namibian Sun is reliably informed the geological setting of the Ohangwena 1 and 2 aquifers was translated into a conceptual hydrogeological model.
Extensive drilling, hydraulic tests, recharge calculations, water levels and water quality monitoring provided information to parameterise the conceptual model and to develop a numerical groundwater model. This model is being used as a decision tool for the planning of groundwater abstraction schemes.
Several abstraction scenarios have been calculated and the impact on the resource, or aquifer, visualised.
“The problem lies with the determination of the sustainable yield of the aquifer and the conceptualisation of water abstraction. The production well of Eenhana town does not prove that the aquifer is sustainable. More tests are still needed and this will take more time.”
The aquifer's viability was verified after drilling campaign tests between 2009 and 2014 verified the existence and spatial extent of the KOH-2 aquifer in the Ohangwena Region.
Additional observation boreholes were drilled between 2011 and 2014 to delineate the freshwater extent and to set up a groundwater monitoring network.
According to the ministry, the aquifer has a store volume of freshwater of about 20 billion cubic metres which could supply water to the northern parts of the country for 400 years.
A production well that is currently supplying water to Eenhana town delivers a maximum yield of about 100 cubic metres an hour.
It was opened in 2011.
NamWater and the ministry, along with technical support from Germany are supervising the project, while the European Union has provided funds of approximately N$25 million.
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 the locally occurring 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 tested in detail at the moment, underlies the brackish to saline western part of the Ohangwena I aquifer. Careless drilling could, therefore, contaminate the large body of fresh water with saline water, destroying the natural value of the resource.
ILENI NANDJATO
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