On the surface, the water is clear, apart from a patch of thriving green algae on the edge and some water striders scurrying around energetically.
Words by René de Klerk
But little bugs lurking underneath the surface of the Orange River are also of interest to scientists as they reflect a lot about the water quality.
Macroinvertebrates are one of the indicators that can reveal a lot about the quality in river systems. This is why the Northern Cape’s Department of Environment and Nature Conservation visited the /Ai/Ais-Richtersveld Transfrontier Park, just one of their sites just before spring to conduct surveys on the water quality of the Orange River during low flow.
Peter Ramollo, an aquatic scientist at the department says that their work is about much more than simply taking water samples and looking at the quality of the water. “We are assessing the ecological condition of the river ecosystem, through bi-annual monitoring,” he says.
To determine the ecological condition, there are a number of indicators to look at. Apart from the macroinvertebrates, scientists can also look at fish species. A third aspect is vegetation, not only growing in the water, but also on river banks. “We also look at the geomorphology which includes the physical structure inside and next to the river,” says Ramollo. “Here we look at erosion, the size of stones and the floodplain.” This, and diatoms together with the chemical composition of the water collectively then contribute to the interpretation of the river’s ecological health.
To find the macroinvertebrates, researchers disturb the rocks in flowing water with their feet and capture what escapes in a net. This then gets emptied into white trays and analysed. “Nothing dies in the process as everything is placed back in the river,” assures Ramollo.
Many of the species recorded are extremely sensitive to pollution and their presence suggests clean water. Species such as earth worms and leeches can live in severely polluted water, and therefore receive low point scores. Mayfly species, which were plentiful on the day of surveying, receive higher scores if they are present as they can’t live in polluted water. Apart from these, other species found on the day included freshwater shrimp, freshwater sprites, bugs, beetles and even snails.
While the water quality might differ between the seasons, it is fairly clean. “Overall the sites in the park are in good state,” says Ramollo. Apart from two sites inside the park, there are also numerous other sites upstream from te park along the Orange River where surveys take place. The water at many of these sites being impacted by agricultural activities.
The former Department of Water Affairs and Forestry started the former River Health Programme. Today, the Department of Water and Sanitation continues with the project known as the National Ecostatus Monitoring Programme. The project has been running for 23 years because of the need for information about the ecological state of aquatic ecosystems. It is collaboration with the Department of Environmental Affairs, Water Research Council and the Council for Scientific and Industrial Research.