Rainfall and Jukskei River Catchment Information

Rainfall and run-off in the Jukskei River Catchment *

There are some important features of rainfall in the Edenvale and upper Jukskei River catchment, which lies in a summer rainfall region:

  • Rainfall is higher on the Witwatersrand Ridge than the surrounding area
  • Rainfall is usually higher over a city, but the relationship can be more complicated
  • Highveld rainfall follows an 11 year cycle of wetter and drier periods
  • Peak flow volumes in the Jukskei River have increased 10-fold over the last 50 years

Rainfall at six sites local from 1971/72 to 2015/16 roughly follows the 11 year pattern (first graph below). This places us now at the end of a dry phase, and peak of the next wet phase will be around 2020.

Rainfall by season Edenvale Bedfordview Jukskei Catchment
Rainfall Edenvale Bedfordview Area – six sites 1971 to 2016

The first  figure below shows the positions of the six rainfall sites in relation to the Witwatersrand ridge, looking north. The graph that follows shows the average seasonal rainfall for the 23 year period from 1991/92  to 2013/14 that are common to five sites. Rainfall declines as one moves west to east. This could be due to the influence of the city to the west, or the ridge since the there are two ridges to the west and they are higher.  Compared to Kensington which is on the ridge, rainfall is 8% lower in Glendower and 19% lower in Edenglen. The five sites are in approximate order of distance from the ridge. 

Rainfall sites from Kensington to OR Tambo International Airport
Edenvale Bedfordview rainfall sites in relation to Witwatersrand Ridge. Looking north
Edenvale rainfall by season 1971 to 2016
Rainfall Edenvale and upper Jukskei River catchment by season

Rainfall in Edenglen *

The chart below shows Edenglen rainfall by season to from 1983/38 to 2017/18. The season of 2016/17 was exceptionally wet and included the flood of 16 November 2016.

Graph of rainfall by season in Edenglen from 1983/84 to 2017/18, showing a cyclical trend
Rainfall by season in Edenglen from 1983/84 to 2017/18

The charts below show the cumulative rainfall to date for the 2018/19 Season and the two previous seasons. The chart for 2016/17 shows the exceptional rain that started from November but continued through the season. The current season started dry and the second half season was wetter, with the April cumulative total already above average.

Graph of cumulative rainfall for Edenvale from July 2016 to June 2017, compared to average, showing an extremely wet season
Cumulative rainfall for Edenvale July 2016 to June 2017 showing an extremely wet season
Cumulative rainfall for Edenvale July 2016 to June 2017 showing a drier second half season and season end below average
Graph of cumulative season rainfall for Edenvale from July 2018 to April 2019, compared to average. It shows a dry first half season and a rapid catch up to average from January
Season to date Edenglen 2018-2019 to April

Jukskei River Peak Flow Trend *

The Department of Water and Sanitation maintains hydrological stations on major rivers that measure the volumes and levels of flow. There is only one station on the Jukskei that is still functioning and that is Nietgedacht A2H023. This station has continuous monthly peak flows and levels for 50 years. The trend is to higher peak flows (see below). Statistical modelling of the data shows the peak flows have risen 10-fold over 50 years andwill increase 30% in the five years to 2020. This is roughly when the next wet phase will peak.

Jukskei peak flow
Peak flow by month in the Jukskei River – 50 years trend

Acknowledgements *

Those who provided rainfall data are Alan Clark – Kensington, Costa Polous -Glendower, Irwin Juckes – Edenglen, Judi Dragan – Isandovale and Robert Rotteveel – Buurendal