Rietspruit Mini SASS / River Health results
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 taking in the entire ecological system of the river and interconnected land; of not only the water, but also the physical river (river bed and river banks) as well as flora and fauna communities in the river and occurring on the banks.
During the walk, all impacts were recorded and photographed, and regular Mini SASS, Methylene Blue and Turbidity tests were undertaken. Mini SASS is a general indicator of river health, Meth Blue indicates levels of bacteria & oxygen (the higher the level of bacteria the lower the amount of oxygen in the water) and turbidity indicates levels of suspended solids in the water.
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 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 of pollution and a simple scoring method results in an accurate picture of river health.
Mini SASS scores are broken down as follows:
- Under 5.3 = Seriously / critically modified, very poor condition
- 5.3 – 5.6 = Largely modified / poor condition
- 5.7 – 6.1 = Moderately modified / fair condition
- 6.2 – 7.2 = Largely Natural / few modification GOOD condition
- +7.2 = Unmodified / Natural condition
Our Rietspruit walk included the main river plus three tributaries however apart from one Mini SASS test on the most eastern tributary, all the remaining tests were carried out on the main stream. As Mini SASS can only be done where the river is accessible, has flowing water and pools and riffles (areas comprising rock and fast running water), there were long stretches on the Rietspruit where natural conditions were not conducive to Mini SASS. Added to these were areas either completely encroached by vegetation and inaccessible due to log jams, wattle sapling thickets and drainage ditches.
Mini SASS # 1: Upper reaches of Rietspruit +- 1.5km from source
- Surrounding land use: Timber and veld cattle grazing camps
- Banks & buffer: Steeply sloping vegetated with indigenous grasses
- Beyond buffer: Indigenous grassland
- Upstream negative impacts: Timber plantations, invasive vegetation, dam, Euclyptus logs and branches in stream bed
- Site negative impacts: 2 young Eucalyptus trees
- Siltation: None
- Turbidity: Clear
Mini SASS Score: 5.6 Largely modified – Poor condition
The water was crystal clear, the river bank buffers and beyond were undisturbed beyond two small Eucalypts. We thus attribute the low score to the impacts immediately upstream of the site. The log jam would not be difficult to clear – it would make a good supply of firewood – and the young Eucalypts can be easily removed. Once indigenous vegetation has recovered after the removal of the dead Eucalypts, there is no reason why the river should not improve to at least Fair condition (Moderately modified)
Mini SASS # 2 : Upper reaches of Rietspruit +- 2km from source
- Surrounding land use: Timber and veld grazing cattle camps
- Banks & buffer: Steeply sloping vegetated with indigenous grasses and bush
- Beyond buffer: Indigenous grassland & bush \ timber
- Upstream negative impacts: None noted
- Site negative impact: Light bank erosion and light layer of silt on river bed from cattle accessing river
- Siltation: Excess silt on river bed
- Turbidity: Clear
Mini SASS Score: 7 Good, largely natural, few modifications.
The water was crystal clear, although there was some silt on the river bed itself. The river bank buffers and beyond were undisturbed apart from one Bug Weed. The score of 7, (Good) is an improvement on the previous score of 5.6 (Poor condition). This is due to a lack of negative impacts on site plus a farther distance downstream from the impacts mentioned at Mini SASS site 1.
Mini SASS # 3: N3 highway crossing Rietspruit +-13.4km from source
- Surrounding land use: Intense agriculture and N3 highway bridge and road
- Banks & buffer: Mainly concrete, comprising overhead highway bridge which forms a tunnel for the river to flow through. Some indigenous aquatic plants
- Beyond buffer: Highway, road
- Upstream negative impacts: Agricultural lands, wetland drainage ditches, weir, highway bridge over river
- Site negative impacts: Lack of sunlight, invasive Canna plants on bank, rocks covered in algae, Water Cress in water compacted bank immediately downstream from site
- Siltation: Heavy silt load on river bed and stones
- Turbidity: Slightly turbid
Methylene Blue: test indicated elevated levels of bacteria which may originate from slurry irrigation or cattle accessing the river.
Mini SASS Score: 4.8 Seriously / critically modified Very poor condition
The low score is not surprising considering the location of the site. The presence of Water Cress and algae are an indicator of elevated nutrient levels in the river which correlate with the Methylene Blue results indicating elevated bacteria. Other impacts range from the draining of the original wetland some 100 years ago resulting in a deep incised river channel, to the intense agricultural practices and the construction of the highway in more recent decades, as well as water extraction by means of a tanker causing river bank compaction and oil and diesel contamination of the water.
Mini SASS # 4: 5km North of N3 highway +-18.5km from source
- Surrounding land use: Dairy farm
- Banks & buffer: Trampled by cattle and stream bed scoured by dam overflows
- Beyond buffer: Overgrown kikuyu pastures
- Upstream negative impacts: large earth walled dam and road crossing
- Site negative impacts: erosion, bank trampling by cattle
- Siltation: Heavy silt load on river bed and rocks
- Turbidity: Clear
Methylene Blue test indicated slightly elevated levels of bacteria which we attribute to the cattle that access the river at the test site for drinking purposes.
Mini SASS Score: 4.5 Seriously / critically modified Very poor condition
The major causes of the low score comprise the dam and road and the trampling of the banks and river bed by cattle. Interestingly, although the dam shows signs of eutrophication, and the Meth Blue indicated elevated nutrient levels, the usual indicators of such a nutrient overload (aquatic plants such as Water Cress) were not in evidence downstream of the wall. Presumably the excess nutrients in the dam are being processed by the reed beds and other flourishing aquatic invasives that occur therein.
Mini SASS # 5: +- 16km from source
- Surrounding land use: Natural grassland and bush – not being actively farmed
- Banks & buffer: Natural grassland and bush with some annual invasives (Thistle and Clover)
- Beyond buffer: Natural grassland and bush with signs of past overgrazing
- Upstream negative impacts: Uncontrolled wattle groves in buffer, bank erosion, Unnatural flows from Umgeni Water pipeline, heavy bramble infestation 200 metres upstream
- Site negative impacts: None visible
- Siltation: Medium to heavy on river bed and submerged rocks
- Turbidity : Clear
Methylene Blue: test indicated slightly elevated levels of bacteria.
Mini SASS Score: 5.9 Moderately modified / Fair condition
The low score was initially surprising as the area seems almost pristine, with little invasive vegetation, no obvious contaminant in the water, nor visible sources of contamination. On closer investigation we note’d the following:
- The Umgeni pipeline tunnel sometimes overflows into a small tributary of the the Rietspruit approximately 300 metres upstream of the test site – on our first visit on day 3 (16 December 2016) it was overflowing increasing the river’s flow. On our return on day 4 (18 December 2016), there was no tunnel “overflow” and the river flow was much lower. These erratic, unseasonal flows are unnatural and problematic.
- There are excessive turbidity levels in the river: some close to the site likely caused by erosion from the Umgeni tunnel “overflows”as well as excess turbidity at each of the first three waterfall plunge pools (two upstream and one downstream of the pipeline tributary and Mini SASS site) plus elevated silt levels on at least 50% of river rocks between the large upstream dam and the mini sass site. As we are in a drought and there has been little rain, the amount of silt could be from a lack of scouring by a flooding river.
- Bacterial levels of unknown origin were slightly elevated
- There are areas close to the site that have been overgrazed in the past and are choked with invasive annual weeds.
- Just upstream of the test site, one river bank buffer is entirely inundated for approximately 200 metres by dense Bramble
As one of the landowners we interviewed had previously done mini SASS test which had scored higher: in the category Largely Natural / Good condition, we surmise that the major impact is due to the drought and the resultant silt levels.
Mini SASS # 6: Eastern tributary near Hilton
- Surrounding land use: Timber plantations
- Banks & buffer: Natural grassland
- Beyond buffer: Natural grassland
- Upstream negative impacts: Earth wall dam, dirt road, bridge
- Site negative impacts: None visible
- Siltation: on river bed and submerged rocks
- Turbidity: Slightly turbid
Mini SASS Score: 5.7 Moderately modified / Fair condition
The earth walled dam, dirt road and bridge immediately upstream of the site are the likely causes of the low score, as the area has in the past been rehabilitated via removal of all timber to a line well past the buffer zone, resulting in natural grasslands surrounding the stream
This was another upside down back to front river that proved that there are no definitives regarding beautiful healthy areas and impacted areas along rivers. Four of the rivers we have walked have gone from good to bad: beautiful, lightly impacted (if at all) at the source, with degradation and damage accumulating proportionately the farther downstream they go. The uMngeni, Lions, Dargle and Indezi all begin life in beautiful surrounds of either wetlands or grasslands, some followed by beautiful indigenous forests prior to the start of the impact and degradation –agricultural in the case of the Lions, Dargle and Indezi and a mix of urban, agriculture, rural and industrial in the case of the uMngeni . All four end tragically impacted and trashed.
Images of Dargle and Lions Rivers
Images Indezi and uMngeni Rivers
Then the Merrivale, Aller and Rietspruit do the exact opposite – they all start in conditions that are far from satisfactory: the Merrivale and Aller in small holdings and residential areas followed by industry and the Rietspruit in timber planted ex-grasslands followed by agriculture: who would have realised that the Cedara Flats were once a vast wetland, drained over 100 years ago?
Images of Mpofana and Aller Rivers
Now I finally understand why the river is called the Rietspruit!
But here is the thing: the last three all end spectacularly – not only spectacular scenery, but with spectacular unexpectedness: improved, healthier river banks and water courses plus either less contaminated water (Merrivale and Rietspruit) or water where the potential to eliminate the contamination source is completely achievable (Aller) a3. The last few kilometres of the Aller run through an undeveloped, beautiful valley in the heart of Durban. A2 During the last few kilometres of both the Merrivale and Rietspruit the rivers drop dramatically into the deep valley of the uMngeni River downstream of the Howick Falls. M2 Possibly due to the sudden change in altitude, invasive riverbank vegetation seems to stop, and the waters flow down over waterfalls and steeply sided thickly vegetated wild places where there is little to no negative human impact.
The lessons are two fold:
Rivers can and do heal, if given the opportunity
These wild untamed valleys we have witnessed need to be treasured and protected as if gold – they are a remnant of the wild places that are so rapidly disappearing; they are soul food, for the fortunate people who get to see them as well as mother earth. And they ensure that the water that joins the uMngeni river is cleaner than it could have been – a dilution for the dirty water in the main river, and a constant reminder to us of what can be.
Once we have collated all the data from the walk, we will post the information on the blog. This will include details of indigenous Fauna and Flora and invasive plants identified, and a detailed list of impacts recorded along the Rietspruit. Our findings and recommendations will be posted at a later stage.