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Home The River Basin People and the River Governance Resource Management
The River Basin
 Introduction
Geography
Climate and Weather
Hydrology
Water Quality
 Principles of Water Quality
 Human Impacts on Water Quality
 Groundwater
Agricultural Effluent & Eutrophication
 Industry and Mining
 Salinity
 Hardness
 Microbiological Organisms and Pathogens
 Heavy Metals
 Persistent Organic Pollutants
 Water Temperature
 Radio-nuclides
 Waste Management
Ecology & Biodiversity
Watersheds
 References

 



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Agricultural Effluent and Eutrophication  

The Kunene River is relatively unpolluted and the water quality is considered to be good, with a low concentration of phosphorus as well as other nutrients (ERM 2009). The main reason for such good water quality can be seen as being a combination of low industrial development, urbanisation and a barely developed (irrigated) agriculture sector within the basin. One indicator for the low concentration of nutrients in the Kunene River is the low fish production.

Agriculture in the Upper Kunene basin is generally extensive with a low potential to impact upon water quality.
Source: AHT GROUP AG 2009
( click to enlarge )

During the period of civil war, the agriculture area under irrigation in Angola decreased dramatically. In 2005 the area under irrigation (340 000 ha) was still less than the irrigated area before independence (400 000 ha). Given, however, the huge irrigation potential in the country the government of Angola has recently developed a programme to rehabilitate and extend existing irrigation areas as well as develop new schemes. By 2025 a total of over 600 000 ha of land in the Kunene River basin along are earmarked for irrigated agriculture.

The expansion of large scale irrigated agriculture will have a dramatic impact on the availability of water in the river as well as on the quality of surface and ground water due to an increased use of agrochemicals such as pesticides and fertilizers. High concentrations of nitrogen and phosphorus lead to eutrophication and increased oxygen demand.

The potential routes for agrochemicals to contaminate surface water bodies or aquifers can be characterised as being either point or non-point source. In areas with irrigated agriculture the water pollution may originate mainly from the effluent of drainage water as a point source.

The pollution from non-point sources through erosion increases in areas with high rainfall, steep terrain and sparsely developed vegetation as a result of deforestation and non-conservational cultivation techniques. This kind of landscape is mainly predominant in the northern mountains of the Upper Kunene basin.

The Lower Kunene River is considered of high wilderness and conservation value. The low amount of organic matter (up to 0.9 %) contained in the sediments of the Kunene River mouth reveals the past and present (high) water quality of the river (Burmeister & Partners 1993). The area is sparsely populated and the only cultivation of land takes place through seasonal gardening adjacent to the banks of the lower Kunene River. There is no irrigation of land used for gardens and once a plot has been used the land is left fallow for a few years. These small scale subsistence agricultural activities of local Himba communities have no measurable influence on water quality.

 

 



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