We keep mentioning the miniSASS tests that we do during the walk. The theory behind these very simple, fun tests is that (believe it or not) river water is not ’empty’ – it teems with life – all sorts of tiny insects live in our rivers and streams
A river habitat is a mirror image of the more familiar landscape of for example, Mfolozi Game Reserve – teeming with predators and prey, herbivores and scavengers, each with his preferred home, be it under a rock, burrowed in the sand, swimming on or below the surface.
These tiny critters are the base of an intricate web which links rivers and the land and the sky – each one dependant on and impacted on by the other. They are also the base of river health – the plant eating …. Is eaten by the carnivorous…… who either dies and gets munched by the scavenging….. or is eaten by a fish who may then be eaten by an otter or a Fish Eagle…. and on ad infinitum.
Damage to the river habitat has the same impacts on the river inhabitants as does damage to the bush which will cause problems for the Lions, Impala and Hyaenas.
The state of the vegetation in and on the river banks impacts the water insects (food and shelter issues),
and for example, in an area like the Midlands grasslands, a stream would naturally be in full sunlight.
Once invasives such as Wattles shade the water,
they change the temperature of the water, as well as the acidity levels, which will impact the insects in the water – a sort of local aquatic climate change!
Too much silt in the water
(such as erosion caused by cattle carving a path in the river bank when they go for a drink),
or soil washing off roads during heavy rains) means gills get clogged (yup, some have gills like fish); the predators can’t see to hunt; and when the silt settles, it can either smother the insects living under the rocks and on the river bed, or can make their living spaces inaccessible.
Obviously, toxins will kill many of the insects, and pollutants such as overloads of nutrients from livestock dung and fertilizers attract either floating invasives which shade out the water course and slow the water flow,
or algae which use the oxygen in the water, robbing the insects of their ‘air to breathe’.
These excess nutrients also bring in the uglies – leeches, blood worms, rat-tailed maggots and snails – all of whom are the pariahs – seen as ugly and disgusting, they never-the-less munch up the ‘rubbish’ and help clean up the river.
So. The different river inhabiting insects have different levels of tolerance to pollution, and so, if you can catch and identify them, you can get a good idea of the health of the river. And that is what we do during the Mini Sass. We get to splosh around searching under stones and on the river floor,
scooping water striders off the surface, scooping fresh water shrimps from quiet side pools, netting dragonfly larvae from overhanging vegetation – its fun if it’s a hot day and the water isn’t filthy.
Once we have caught the insects they are tipped into a container and identified.
Each group has a different score depending on pollution tolerance, varying from the low score of 2 for worms and leeches up to the highest score of 17 for Stoneflies – wee beasties who look as if they are made up of a string of tiny beads tipped with head and tail.
The reason they are so sought after by us crazy river walkers (and anyone conducting miniSASS test) is that this ‘fussy’ little insect does not like to live in polluted water. Actually, he can’t survive in polluted water. Hence our ever constant hope of finding a Stonefly – Mama Rivers indicator of clean water.
The scores of the groups caught are added up, and divided by the number of groups caught and Hey Presto your final sum tells you how healthy (or not) the river is.
It is an amazingly simple exercise, and is based on the SASS5 that the scientists use – the results of which stand up in a court of law!
The miniSass results from our walk down the Dargle River showed us once again the Miracle of Rivers – their ability to heal when given a long enough length without negative impacts. We saw the miracle on the uMngeni River, we saw it on the Lions River and the Dargle River is no exception.
The Mini sass scores for the Dargle River, walked from source to the confluence with the uMngeni River; 9th to 12th January 2014 are as follows:
Site 1: 5.9 = Largely modified / Poor Condition
Site 2: 4.75 = Seriously / critically modified (Very poor condition)
Site 3: 4.9 = Seriously / critically modified (Very poor condition)
Site 4: 4.71 = Seriously / critically modified (Very poor condition)
Site 5: 7.5 = Largely natural / few modifications (Good condition)
Site 6: 5.1 = Largely modified (Poor condition)
Site 7: 6.6 = Moderately modified (Fair condition)
Sadly, the Dargle is not a healthy river!
The main causes as far as we could see are:
- Invasive alien plants causing poor condition of the river banks in the 32 metre buffers edge
- Heavy siltation in many areas where cattle access the river to drink
- Invasive Alien plants eliminating indigenous vegetation
- Too many nutrients (livestock manure, possible effluent)
- Rubbish: Dumping rubbish in the river and farm rubbish pits possibly too close to the river
Which leads me to the debate – what’s harder to find: a four-leaf clover or a stonefly? Preven and I raised this question in September last year during the Lions River walk. We despaired of ever finding a Stonefly. We did find a large patch of clover and spent a few minutes looking for a stalk with four leaves – to no avail! We have spent many, many more hours than that over a period of 39 full days of walking down rivers – the uMngeni, the Lions and the Dargle. Given Dargle’s Irish roots, I suspected that it might be a four-leafed clover… but it seems that the sought after clover leaf is indeed, the hardest to find!
The Stonefly Score so far:
uMngeni River: two Stoneflies at two sites
Lions River – no Stoneflies!
Dargle River: Stoneflies at two sites: three at one site, and TEN at the other!!!
So Dargle is Stonefly champ. The challenge is on, Indezi here we come.
The www.minsass.org website is live and filled with maps showing Mini sass results submitted by civilians – school learners, teachers, landowners etc, and the site gives a fascinating overall picture of the state of many of our local rivers. Our Dargle results have been submitted and will be posted after auditing.
The Mayday for Rivers Team would like to take this opportunity to thank:
- N3Toll Concession for the funding to walk the Dargle River
- Mahomed Desai of GroundTruth for mapping
- Carl Bronner for the awesome accommodation
- Will Griffin for carting us up to the source so early in the morning
- Midlands Conservancy Forum and Dargle Conservancy for all their assistance
- Dargle Conservancy for the delicious dinner
- All the Dargle River landowners for your enthusiastic support of our walk
You are most welcome to use this information – just credit the DUCT River Walk Team, please.