Salinity refers to the saltiness of water caused by the dissolution of minerals in rocks, soils and decomposing plant material. The level of salinity in a river, for instance, depends on the geological and climatic environments through which the river flows. Salinity increases downstream, as salts are continuously added through natural and anthropogenic processes such as mining, industry and agriculture, but are only minimally removed through technological interventions or diluted by precipitation (du Preez et al. 2000).
Salt encrusted soil.
Source: Reed 2009
( click to enlarge )
High levels of salinity can lead to the "salinisation of irrigated soils, diminished crop yields, increased scale formation and corrosion in domestic and industrial water pipes, and changes in the biotic communities." 1 000 mg/L is considered moderate salinity and is generally tolerated by humans; however, at levels above 3 000 mg/L (high salinity) fatal intestinal damage and renal damage can occur (DEAT 2009).
According to several studies undertaken within the Lower Kunene region, the data availability concerning water quality issues in this area is slightly better than in any other part of the basin. Chemical water analysis shows that the mineralization and thus the salinity of the Lower Kunene River water, downstream of Ruacana, is very low. However, rainfall may triple the content of total dissolved solids, sodium chloride and sodium sulphate (Hannan 1995).
