Rainfall and Jukskei River Catchment Information

Rainfall features Witwatersrand and Edenvale area *

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

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 Edenglen *

The table shows Edenglen rainfall by month, year and season from 1983 to the 2016. The graphs show season to date rainfall for the last two seasons and the current season. The 2015/16 season started dry and the second half season was wetter, but at season as a whole was well below average. Unfortunately this distribution does not suit agriculture and it was seen a a drought year. The 2016/17 season started exceptionally wet and the second half season was also above average. Rainfall in the current season starting July 2017 is above average as at the end of December

Rainfall upper Jukskei River catchment 2016
  Cumulative rainfall for Edenvale July 2015 to June 2016, below average for the season
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

Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Season
1983 . . . . . . 9.0 7.0 18.5 73.3 133.5 206.5 . .
1984 80.5 33.0 72.9 4.5 0.0 2.5 13.0 0.5 13.5 87.9 78.0 91.0 477.3 641.2
1985 108.5 81.5 74.6 3.5 10.5 0.0 7.5 0.0 49.5 98.5 134.0 116.5 684.6 562.5
1986 84.3 71.2 54.2 38.2 0.0 0.0 0.0 11.0 1.5 110.8 161.1 144.0 676.3 653.9
1987 131.2 67.1 152.5 5.0 0.0 0.0 0.0 12.0 124.0 59.1 192.7 99.2 842.8 784.2
1988 90.0 60.4 144.3 36.0 2.1 12.3 3.0 0.8 49.1 70.1 68.4 84.7 621.2 832.1
1989 64.4 225.0 32.7 40.5 15.5 52.0 0.0 2.8 0.0 41.0 166.1 117.3 757.3 706.2
1990 50.7 97.9 91.2 135.0 6.5 0.0 2.3 28.8 0.0 30.0 54.5 124.5 621.4 708.5
1991 103.4 121.1 107.0 0.0 0.0 6.4 0.0 1.8 13.2 57.5 43.5 125.3 579.2 578.0
1992 72.3 42.5 26.0 34.7 0.0 8.0 0.0 13.5 5.8 30.6 133.0 53.7 420.1 424.8
1993 126.7 45.0 124.7 52.0 1.0 8.0 0.0 8.0 3.0 173.3 73.2 109.1 724.0 594.0
1994 103.3 167.9 67.1 29.0 0.0 0.0 0.0 0.0 5.0 98.7 43.7 169.2 683.9 733.9
1995 60.7 83.7 142.8 58.3 14.7 0.0 0.0 11.7 7.7 90.8 124.4 189.7 784.5 676.8
1996 169.1 221.4 39.2 51.0 22.2 6.5 0.0 5.5 2.0 62.4 58.4 146.3 784.0 933.7
1997 142.4 50.2 318.2 32.2 95.5 3.5 9.5 4.0 41.8 26.7 173.1 116.7 1013.8 916.6
1998 157.9 64.1 36.9 27.0 0.0 0.0 0.0 0.0 45.4 85.0 228.2 124.0 768.5 657.7
1999 120.0 59.6 55.9 37.7 51.8 5.8 0.0 0.5 18.4 25.8 79.3 129.1 583.9 813.4
Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Season
2000 153.6 322.6 191.7 39.8 18.7 2.4 0.0 4.2 33.0 128.4 86.2 167.2 1147.8 981.9
2001 65.9 96.8 54.8 8.3 56.2 0.0 0.0 15.5 73.7 95.9 106.8 91.0 664.9 701.0
2002 137.7 94.4 60.5 14.7 9.6 49.2 0.0 13.8 3.5 59.0 13.3 144.8 601.5 750.0
2003 96.6 62.4 68.6 10.3 0.0 15.6 0.0 1.5 12.8 70.0 49.5 43.4 430.7 487.9
2004 117.7 168.7 101.3 33.2 12.0 6.0 20.0 4.9 0.0 45.1 50.9 225.8 785.6 616.1
2005 175.6 71.0 60.9 102.6 1.9 0.0 0.0 0.0 4.0 65.3 121.6 120.3 723.2 758.7
2006 176.9 117.2 114.6 39.1 3.2 0.0 0.0 36.8 1.5 52.0 139.8 156.6 837.7 762.2
2007 68.5 17.2 39.8 55.9 0.0 43.0 0.0 0.0 34.0 137.4 79.3 112.2 578.3 611.1
2008 152.2 53.6 134.8 25.2 48.0 16.0 0.0 0.0 0.0 69.4 93.7 90.5 683.4 792.7
2009 204.2 152.7 174.0 0.7 24.5 16.3 0.0 1.0 22.5 127.6 135.3 122.0 980.8 826.0
Year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Year Season
2010 289.1 109.0 94.2 147.8 40.0 0.0 0.0 0.0 0.0 20.5 91.8 150.7 1024.1 1169.5
2011 196.2 97.0 202.0 104.7 18.5 30.0 0.0 0.0 2.5 10.3 98.8 201.0 961.0 911.4
2012 149.4 94.2 68.9 21.0 0.0 1.0 0.0 2.0 28.0 77.8 61.0 148.5 651.8 647.1
2013 105.9 34.2 33.6 117.4 15.4 0.0 0.0 6.8 1.6 87.3 129.2 175.6 707.0 623.8
2014 40.7 118.6 123.4 16.2 4.4 0.2 0.0 0.5 10.6 34.2 113.2 214.7 676.7 704.0
2015 153.0 45.1 76.9 27.0 0.0 1.8 9.5 0.0 33.5 25.0 46.5 77.5 495.0 677.0
2016 123.4 86.1 144.3 11.5 53.5 10.0 12.5 0.0 7.7 77.0 315.5 132.5 974.9 620.8
2017 163.0 202.0 72.0 53.0 41.0 0.0 1.0 0.0 1.5 127.5 109.5 175.2 945.7 1076.2
2018 57.0 115.0 36.0 16.0 19.5 0.0

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