| dc.description.abstract | North Central Namibia which is home to almost half of Namibia‟s estimated 2 million
people, like the whole of Namibia is heavily dependent on water sources from
neighbouring countries for secure water supplies. A good example is the Calueque-
Oshakati Canal which was built to convey water to the Region from the Kunene River
in Angola. Due to population expansion, traditional sources of water could no longer
meet the water demand in the Region and they increasingly became susceptible to
pollution and contamination. There are four water purification plants (Olushandja,
Ombalantu, Ogongo and Oshakati) abstracting water from the Canal and distributing
it to the surrounding villages and urban centres. The Canal is however exposed to
pollution due to poor sanitation and other land use activities in the basin.
The objective of this study was to assess the impacts of pollution on water quality and
its subsequent effects on the water suitability for the various intended uses
(Aquaculture, irrigation and potable use) and its implications on the water purification
processes. Water samples were collected at four points along the Canal from February
to April 2008 with the furthest sampling point upstream situated at the Canal entry
into Namibia borders and furthest point down stream located at the end of the Canal.
The following physico-chemical and biological parameters were determined:
temperature, dissolved oxygen, pH, turbidity, total dissolved solids, sodium, Calcium,
Magnesium, total hardness, Nitrate, and Escherichia coli. Water treatment plant
performance data for the year 2006/2007 of the four water purification plants were
obtained from NAMWATER with monthly average values of pH, turbidity,
coagulants and chlorine used, and the cost of chemicals used. Jar tests were also
carried out to confirm the impacts of pollution on water purification process.
Water samples were collected at four points along the Canal from February to April
2008 with the furthest sampling point upstream situated at the Canal entry into
Namibia and furthest point down stream located at the end of the Canal. Temperatures
at all stations averaged between 24oc and 26.7oc, dissolved oxygen averaged between
3.9 and 4.7mg/l at all sampling stations, pH values averaged between 6.9 to 7.6,
turbidity averaged 111NTU upstream and 243NTU down stream. Total dissolved
solids concentrations were 43mg/l upstream and 68mg/l down stream, total hardness
was 15mg/l as CaCo3 upstream and 24mg/l as CaCo3 downstream while nitrate
concentrations both up stream and down stream were below 0.1mg/l. and E.coli
averaged 4 Most probable number per 100ml (MPN/100ml) upstream and 42
MPN/100ml. Jar test results indicated that chemical dosages increased from upstream
to down stream treatment plants, Olushandja, 16mg/l, Ombalantu 18mg/l, Ogongo 29
mg/l and Oshati 38mg/l.
Despite the increase in parameters concentration from upstream to downstream, most
parameter concentrations were within the permissible limits of NAMWATER
standards and the WHO guidelines for drinking water and the water was found to be
suitable for the various intended uses except, as a direct source of potable water. The
jar test results shows that treatment plant further downstream use high dosages of
coagulants to purify the water compared to those further upstream, this could be
attributed to the cumulative impacts of pollution. | en_ZW |
