Johannesburg – The water in Loskop Dam, Mpumalanga, was “deteriorating fast” with permanent bacteria visible on the surface, the Council for Scientific and Industrial Research (CSIR) said on Wednesday.
“The dam has permanent blooms of cyanobacteria visible on the surface water throughout the year since 2008,” CSIR limnologist Paul Oberholster said in a statement.
The algae, caused by high levels of nutrient enrichment, was up to 15m long and drifted down irrigation canals, clogging up control gates and crop sprayers.
Loskop Dam is fed by the Olifants River, described by the Loskop Irrigation Board (LIB) as heavily contaminated.
The dam was built in 1938 to supply irrigation water to the agricultural sector, supporting an export market to the EU valued at R1 billion a year. At present the bacteria had not filtered through into irrigation water and crops.
“A two-year study of the quality of irrigation water… in the Groblersdal areas has shown very low levels of E. coli and no detectable levels of other disease-causing bacteria,” CSIR spokesperson Tendani Tsedu said.
A research team funded by the LIB analysed fresh produce grown in the area including maize, citrus, grapes and wheat for traces of bacteria.
The LIB provides irrigation water to 16 000ha of agricultural land through channels with a total length of more than 550km.