One needs to keep in mind the difference between water quality and river health. Water quality is defined as “to describe the physical, chemical, biological and aesthetic properties of water that determines its fitness for a variety of uses and for the protection of the health and integrity of aquatic systems” (SA Water Quality Guidelines)
River health on the other hand, comprises a far broader range which includes the entire ecological system and functioning of the river plus the adjacent interconnected land. Not only the water, but also the river bed and river banks as well as flora and fauna communities occurring in the river and on the banks. Should any one of these parts be negatively impacted, the health of the river declines.
Profile of the Aller River
Although in the upper reaches the water is clear,
much of the natural vegetation on the banks has been replaced by buildings, gardens, roads, lawn and pipelines. Remaining natural riparian vegetation on the river banks is inundated by invasive plant species which have, in some places, smothered the indigenous vegetation completely. Illegal dumping causes more destruction whilst storm water drains from nearby roads and gardens bring a cocktail of ingredients in the runoff.
In the middle reaches, the water becomes turbid and grey in colour from effluent.
Informal settlements have been erected on the river banks
and the invasive plant species continue. River banks are littered with faeces as are some rocks in the river and illegal dumping on the banks and into the river takes place on such a scale that in places the stench is similar to that of a landfill site.
Even when the water finally became clear, excessive algae indicated high nutrient levels.
In the lower reaches the indigenous vegetation is in far better condition
there are far fewer invasives and the only construction impacts are that of the sewer pipeline and inspection track that run alongside the river, eight causeways, and one area where a multitude of pipelines cross the river.
The only solid waste was a pile of used vehicle tyres thrown off the cliff above(!!!), and a few areas of plastic rubbish left behind by receding flood waters. The steep sides of the valley here seem to have discouraged people from settling, and what could thus be a beautiful wild belt in the heart of Durban
is instead the bearer of all the effluent dumped into the river higher upstream.
Mini SASS is a very simple and enjoyable way of determining the health of the river, and the results give an overall picture of river health that is often missed by laboratory tests, for the pure and simple reason that a lab test, if taken say a week after a chemical contamination, may not reveal any chemicals as they will have washed downstream whilst the Mini SASS gives an overall picture of the rivers health at any time. With Mini SASS, aquatic insects are caught, identified and classed according to tolerance levels to pollution and a simple scoring method results in an accurate picture of river health.
Due to the contamination of the river only one Mini SASS test was carried out close to the source of the Aller, and this produced a disappointing result of 5.3 indicating a river in poor condition right from the source area. The poor condition can be attributed to the disturbance of construction, invasive vegetation, contaminated storm water and illegal dumping
Methylene Blue is a handy test for the river walking team to conduct to either assist in determining the reasons behind a low Mini SASS score, or to use when contact with the river water is not advisable. A sample of river water is stained with Methylene Blue on site at the river (actually, it is the oxygen that gets stained).
If bacteria is present in the water, the bacteria will eat the oxygen and as a result the blue colour will fade. The time it takes to fade (from one to 5 days) indicates the levels of bacteria in the water and conversely indicates levels of oxygen in the water. For example a sample that fades in less than 24 hours has very little oxygen and a very high bacteria load, whilst at the other extreme, a sample which does not fade after 5 days has high oxygen levels and little to no bacteria. An additional sample is boiled and the Meth Blue added to this cooled boiled water. As boiling kills all bacteria, this sample will not fade and can be used to measure the degree that the other samples are fading.
Simple as a pudding! Hence the delay in getting this blog out – I have been checking the Meth Blue samples each morning.
The Meth Blue results indicate that with the exception of the sample taken near the source, the remaining samples indicate that much of the Aller River has unacceptably high bacterial levels which reduce oxygen in the water and result in a river with shocking health and water quality.
First Meth blue sample:
- The sample taken at the Mini SASS site just 300 metres downstream of the source barely changed colour, indicating that the low Mini SASS score is not due to bacterial levels (effluent). We surmise the most likely reason for the low score could be the infestation of invasive plants on the river banks; invisible ingredients such as garden fertilisers and pesticides and vehicle contaminants that have dripped onto roads and found their way to the water via storm water drains.
- The first sewage grey / sewage smelling water was seen 2.3 kilometres from the source in Claremont.
Second Meth Blue sample:
- 3.8 kilometres from the source
- 25 metres upstream of the New Germany Waste Water Treatment Works (WWTW – the sewage purification works) outlet.
- Water was again clear, although the river had algae and excessive levels of sludge on the river bed indicating elevated nutrient levels.
- This sample faded completely after four days indicating 60 – 80% oxygen and 20 – 40% bacteria.
Third Meth Blue sample:
- 25 metres downstream of sample site 2
- Taken at the WWTW outlet where the water was once again murkey and grey.
- Sample turned clear within 48 hours indicating high bacterial counts and little oxygen
- In a 2.4 kilometre section stretching downstream from Claremont Primary School, a total of seven sewer manholes showed evidence of recent surcharges
- 5.7km from the source the water had turned clear, albeit with low levels of white foam. A high infestation of snails indicates high nutrient levels
- 6km from source – surcharging manhole
- 6.1 km from source – surcharging manhole
- We did not see the river from 6.2km downstream of the source to 8.2km from source
- 8.2km from the source – water grey and smelly
Fourth Meth Blue sample:
- 8.6km from source
- Water murky, some foam
- Took 48 hours to turn clear. This indicates the possibility of an additional surcharging manhole between the WWTW and the sample site that we missed due to the steep terrain and extremely thick vegetation.
- From the fourth sample site the river remained murky until 10km from the source where it was once more clear.
- We did not see the last 200 metres of river, however at its confluence with the uMngeni the Aller was once again grey and smelling of sewage. We thus made the assumption that in the last 200 meters, a final sewer manhole was surcharging somewhere.
Fifth Meth Blue sample
- Taken at the Aller / uMneni confluence:
- Aller water murkey and smelling of sewage
- Sample was clear in 48 hours indicating high bacterial loads (and low oxygen levels)
Sixth Meth Blue Sample
- Taken at the Aller / uMneni confluence
- uMngeni water clear and no unpleasant smell
- The sample has remained unchanged as at 11 November 2015, indicating high oxygen levels and low bacteria levels
In addition to various negative impacts which include invasive plants, construction and invisible water contaminants, the Aller is contaminated with sewage for at least 8.5 kilometres of its 10 kilometre length. Be it River Health or Water Quality, the end result for the Aller and the folk who live along this small river is the same. With the province entering a severe drought, the Aller should be able to sustain neighbouring communities. They should be able to use its water without danger instead of watching this toxic stream flow by. Water, water everywhere and not a drop to drink – just another in the litany of trashed KZN Rivers which are tragically abused and disrespected.
On a positive note, the miracle of rivers which we have seen time and again, is that given enough length without impacts, rivers can and do heal. There is hope yet for the Aller River.