Modderfontein Stream

Modderfontein Stream and RiverWatch *

The Modderfontein Stream (also called Modderfonteinspruit) can be viewed in two sections: the Upper Modderfontein (in Ekurhuleni Metro) and the Lower Modderfontein (in Johannesburg Metro). The boundary is the Modderfontein Road (R25).

Upper Modderfontein Stream

Modderfontein stream perspective map
Modderfontein Stream with main features

The Modderfontein Stream arises in the Isandovale area in Ekurhuleni. Two streams known as the Kevin Stream and the Sebenza Stream flow through the industrial area of Sebenza meet in the powerline servitude. The Illiondale Wetland extends from there to the R25 road bridge. The Key Issues in this area are channeling of the stream and degradation of the wetland, loss of habitat and pollution of the water.

The Lower Modderfontein Stream

The course of the stream continues through the Modderfontein Golf Course where there are a number of small dams, the Modderfontein Estate with the Modderfontein No 1 Dam, and the Modderfontein Reserve where there are two further dams. This was the original property of the AECI dynamite factory. Modderfontein Reserve is a private nature reserve managed by Endangered Wildlife Trust for the owners, and much time and expense has been invested in restoration and eliminating invader plants. There are many wetlands in this area. Finally the stream flows through undeveloped open grassland in Buccleuch to join the Jukskei River.

RiverWatch Vision for the Modderfontein Stream: A continuous riparian corridor providing habitat for biodiversity, recreation for people and hydrodynamic benefits.

RiverWatch Action for the Modderfontein Stream: Monitor changes in the course of the stream and related wetlands and record trends. Use the information to support more informed decision-making. Encourage landowners to improve the habitat and eliminate breaks. In particular work towards connecting the Modderfontein Reserve and the Illiondale Wetland.

Upper Modderfontein Stream and Illiondale Wetland *

In the early days the suburb of Illiondale was developed on land that would not be considered suitable today, including buffer zone, wetland, flood plain and hillside seeps. It appears the channel was excavated to drain the wetland. As development continued problems with flooding and erosion arose.

In 2010 the “Isandovale Soil Erosion Management” Project (Gaut 002/07-08/NO946) was implemented to fix these problems. The capacity of four bridges between Driefontein Road and Cecil Awret Road were increased. Six or more concrete/gabion combination structures were built in the wetland between Cecil Awret and Margaret Roads to slow the flow and reduce erosion. The structures in the wetland all failed, in the first wet season according to residents. Rubble and soil removed was added to the west bank in places as a berm to protect from flooding. This increased flooding and erosion on the east bank, threatening homes.

Modderfontein Stream Illiondale failed gabion #3
Failed 2010 Gabion in Illiondale Wetland

A project in 2013 attempted to improve the stability of the channels at the Cecil Awret Road Bridge and the Margaret Road Bridges by constructing gabions both upstream and downstream of the bridges.  The contractor abandoned the site without completing the work, leaving the upper gabion at the Margaret Road Bridge unbuilt although the channel was excavated. The gabion on the east bank below Cecil Awret Bridge collapsed within three months. In July 2015 a sewage spill collapsed a wing of the Cecil Awret Road Bridge. In May 2016 a new contractor was appointed who replaced the failed gabions at the Cecil Awret Road Bridge and repaired the damage.

Modderfontein Outfall Sewer Project: Waste water for Sebenza and Illiondale feeds into the Ekurhuleni system for processing. To achieve this, sewage is allowed to flow downhill along the line of the Modderfontein valley and when reaches the Ekurhuleni/Johannesburg border it is pumped back over the divide to the east. This system has become overloaded and unreliable. The new Modderfontein Outfall Sewer will overcome this by linking into the Johannesburg sewer system by gravity. The pipeline will be laid along the west perimeter of the Illiondale Wetlands, through the Modderfontein Golf Course and ending downstream of the Modderfontein No 1 Dam. Environmental assessment (GAUT:002/08-09/N0584) was done by Seaton Thompson & Associates and environmental authorization was given in 2009. Work started in 2011 but was abandoned in 2012 due to contractor problems. The Ekurhuleni tender process has failed a number of times since then, and work is finally restarted early 2018. As at may 2018, the project appears to be on hold.

In the years of delay the pollution from sewage increased. In September 2015 there were six major sewage spills direct into the river. In a six week period starting mid-April 2016 Edenvale RiverWatch reported 17 sewage spills which flowed for a total of 46 days (some were concurrent). The amount of sewage entering the river was limited by vigilance and quick reporting, but from July pollution monitoring by volunteers was halted because of safety concerns. As a result spills in August and September have continued for longer periods. This has led to a sharp drop in the health of the stream in September 2016 (see bio-monitoring below).

Illiondale Wetland Restoration Project: The wetland will be restored between Cecil Awret Road Bridge and the R25 Modderfontein Road.  The work is planned in two phases. The first phase was to repair problem structures (but not the failed concrete/gabion structures) and remove the major stands of invasive plants. The second phase will slow the flow and raise the water table, landscape the area making it attractive for recreation. Environmental Authorization was received in April 2016.

Phase 1  was carried out  first half of 2017 but with a greatly reduced scope. Removal of alien invader plants was ineffective. Above ground growth of some of the gray poplar and giant reed at the end of the 2016/17 growth season was cut down and carted away away. There was no attempt to eradicate by addressing the underground roots and stems. In Spring new growth started as normal, continued through the 2017/18 summer season. The photo below shows regrowth of gray poplar, giant reed and bugweed one year after clearing. 

Photo showing growth of invasive plants in Illiondale June 2018, one year after clearing
Regrowth of invasive plants in Illiondale June 2018, one year after clearing

There is no indication as to when Phase 2 will take place.

Water Quality, Pollution and River Health Monitoring *

The Modderfontein Stream water quality, pollution and the health of the stream are being recorded by three sets of measurement:

  • RiverWatch Pollution Tracker using the smartphone app
  • Quarterly Water Quality Reports by the two local authorities (Ekurhuleni and Johannesburg Metros)
  • Bio-assessment of River Health using MiniSASS

Pollution Tracking: Volunteers use the RiverWatch smartphone app to record the condition of the stream almost daily. The reports raise an alarm when there is pollution and the source is investigated and reported to the local authority. A plot of the data monthly and weekly gives a picture of what has happened over time.  The graphs below shows the massive rise in pollution in September 2015 when there were six large sewage spills in about three weeks and again since about April 2016. It also shows that in 2015 most problems were in the Sebenza branch and in 2016 the Kelvin branch experienced the most spills. 

Map of the Modderfontein Stream in Illiondale, Ekurhuleni, showing the location of the water quality test sites
Water Quality Test Sites Modderfontein Stream, Illiondale, Ekurhuleni
Modderfontein Stream pollution tracker by month
Modderfontein Stream pollution by month 2015/2016
Modderfontein Stream pollution by week 2015/2016

Ekurhuleni Water Quality Reports: Counts for fecal coliforms per 100 ml taken from the quarterly reports show sewage pollution trend over the last 6 years. From a low base in 2013 pollution increased rapidly and then moved between about 10 000 and 400 000 counts per 100 mL to March 2019. In April 2019 the Modderfontein Outfall Sewer will be complete. Monitoring will show what impact there is on the river.

Graph showing trend in coliform counts per 100 ml for Modderfontein Stream 2013 to March 2019 from Ekurhuleni Water Quality Reports, showing high level sewage contamination.
High level sewage pollution in Modderfontein Stream for six years to March 2019

In addition, the largest and most frequent spills of sewage take place near the sewage pump station near Modderfontein Road Bridge (R25). This is downstream from the Ekurhuleni monitoring point at Margaret Road and the impact does not show in the water quality reports. The RiverWatch Pollution Tracker graph below shows how great the pollution is at the R25 Bridge compared to the Margaret Rd sampling site. The photo shows the recurring sewage spill at the R25 site.

Modderfontein Stream pollution at Margaret Rd and Modderfontein Rd (R25) compared

River Health Bio-assessment: Modderfontein Stream has been assessed for river health by SASS methodology at a number of sites since 2007. The results shown here are for a site the Margaret Road Bridge. The results show the river health to be in the lowest ecological category “Very Poor” throughout this period. It has been fairly stable over time but with a sharp decline in September 2016. This is due to the unrelenting sewage spills in the months leading up to the September 2016 assessment.

Graph showing River Health trend for Modderfontein Stream at Margaret Rd Bridge from 2007 to 2018, with a sharp decline in the last year
River Health Modderfontein Stream at Margaret Rd Bridge 2007 to 2018

Three Major Pollution Risks in the Upper Modderfontein Stream *

The three major risks of pollution spills into the Modderfontein Stream in Illiondale are:

  • Sewage pollution from blockages and broken infrastructure. These are taking place more days than not. This has deteriorated over the last three years and we are told the Modderfontein Outfall Sewer will fix this.
  • The risk of silt pollution from Kelvin Power. Fly-ash is managed with water and pumped into dams on top of the dumps. Over the weekend of 29 August 2014 there was a release of silt that covered the Modderfontein Stream bed from Sebenza to the Modderfontein Golf Course. The silt was removed from the stream bed manually, a massive undertaking with serious impact on the ecology of the area. The ongoing accumulation of fly-ash managed by a water process is an ever present risk to the catchment.
  • Industrial pollution from Founder’s Hill South in Johannesburg flows into the Modderfontein Stream a few meters upstream from the R25 Modderfontein Road Bridge. There is a report in the Bedfordview Edenvale News from August 2009 concerning this discharge. Since then the stream channel has become overgrown and the site is not easily viewed. The problem was taken up by Edenvale RiverWatch in May 2015.  A time lapse video was taken on 8 February 2016 showing at least 14 discharges took place. In spite of repeated inspections by officials from Johannesburg City and Joburg Water the problem is not resolved as at September 2016.
Modderfontein Stream Kelvin silt Alpine Road
Modderfontein Stream Kelvin Silt Pollution September 2014
Modderfontein Stream industrial discharge
Industrial discharge Modderfontein Stream 6 July 26 July 2015

Habitat and Structure Upper Modderfontein Stream *

The Modderfontein Stream is being monitored by Fixed Point Photo Monitoring. The sites selected will record changes due to construction of the Modderfontein Outfall Sewer, the Illiondale Wetland Rehabilitation Project, and specific sites vulnerable to erosion or invader vegetation.There are more than 20 sites and about 50 camera views recorded. 

Map of Illiondale Wetland showing Edenvale RiverWatch photo monitoring sites as at June 2018
Edenvale RiverWatch photo monitoring sites in Illiondale Wetland June 2018

This time sequence video shows the history of the view downstream from the Cecil Awret Road Bridge from April 2014, and also a comparison with the view in October 2009. The view monitored shows the increase in capacity of the channel to accommodate increasing run off with each construction project as well as a view of stands of invader plants further downstream.

Wildlife *

There are open areas along the Modderfontein Stream, in particular the Modderfontein Reserve. To some extent wildlife can move along the water course. The presence of wildlife recorded by camera trap and other signs, and verified by the University of Cape town Animal Demography Unit, includes Duiker, Large Spotted Genet, Blacked Back Jackal, Water Mongoose, Slender Mongoose, Serval and Greater Cane Rat.  This was outside the Modderfontein Reserve, which reports steenbok, reedbuck, duiker, black-backed jackals, Cape clawless otter, Spotted-necked Otter, hedgehogs, and four varieties of mongoose.

Water mongoose at headwaters of Modderfontein Stream December 2019
Photo of Duiker in Longmeadow, Modderfontein, December 2016
Duiker in Longmeadow, Modderfontein, December 2016
Photo of large Spotted Genet in Longmeadow, Modderfontein, December 2016
Photo of Large Spotted Genet in Longmeadow, Modderfontein, December 2016
Photo of Black backed Jackal in Longmeadow, Modderfontein, January 2017
Black backed Jackal in Longmeadow, Modderfontein, January 2017
Photo of Water Mongoose in Longmeadow, Modderfontein, December 2016
Water Mongoose in Longmeadow, Modderfontein, December 2016
Photo of Slender Mongoose in Longmeadow, Modderfontein, January 2017
Slender Mongoose in Longmeadow, Modderfontein, January 2017
Photo of a Serval in Westlake Wetland Modderfontein, January 2018
Serval in Westlake Wetland, Modderfontein, January 2018

Illiondale Wetland supported two species of mongoose, greater cane rat, gerbils and large numbers of grassland birds in 2013. They have disappeared in the last few years, except the water mongoose and gerbil greatly reduced numbers. This is because 2014 Ekurhuleni started cutting vegetation regularly and indiscriminately. Vegetation is cut to the water’s edge leaving little habitat for wildlife. The natural grasses are cut as the seed is forming and then removed leaving no attraction for grassland birds and rodents.

Small mammals are recorded with trail cameras and the photos uploaded to the UCT MammalMap database where the identity of the animals is confirmed by experts. Some examples.

Photo of Gerbil burrows in the upper Illiondale wetland
Gerbil burrows in upper Illiondale Wetland
Water Mongoose Illiondale Wetland
Water Mongoose Illiondale Wetland May 2014
Water Mongoose Illiondale Wetland
  Water Mongoose Illiondale Wetland November 2014
Cane Rat evidence of feeding in the Illiondale Wetland
Cane Rat feeding Illiondale Wetland February 2014

Lower Modderfontein Stream  and Modderfontein Estate *

The Modderfontein Stream flows through the Modderfontein Golf Course. There are a number of small dams which settle some of the pollution and silt. The stream from Esther Park in the east enters at this point. This stream flows past a decommissioned AECI ash dump. At the time of decommissioning around 2009 a retention dam was built on this stream near Centenary Road. The dam almost immediately filled with silt and no longer has capacity. The result is repeated deposits of silt in the golf course. This is most likely the source of silt leading to the loss of open water in Modderfontein Dam No 1 – see video “Silting up of the Modderfontein Dam 2001 to 2016”