Zandvlei Trust

Salinity

Compliance with conditions of the Zandvlei Estuary Mouth Maintenance Management Plan
DEADP Reference E12/2/4/7 A5/328 CJ2142/11.

Schedule of PROVISIONAL DATES for mouth management.

  • Note that these provisional dates have been compiled using the tide tables.
  • However they are subject to weather conditions which may necessitate
    adjustments to these dates or the introduction of additional dates.

Zandvlei Estuary mouth planned opening and closing dates.

               rubble weir is 0.4m above M.S.L.

Date
Open.
Date
Close.
M.S.L
 in metres.
Chart Datumn.
09/12/2016 15/12/2016 1.87 1.027
11/11/2016 18/11/2016 1.63 0.787
13/10/2016 20/10/2016 1.63 0.787
- 20/09/2016 1.81 0.967
03/06/2016 - - Will remain open for winter period
04/05/2016 10/05/2016 1.63 0.787
04/04/2016 11/04/2016 1.62 0.777
07/03/2016 14/03/2016 1.64 0.797
08/02/2016 12/02/2016 1.72 0.877
21/01/2016 27/01/2016 1.62  0.777
20/11/2015 30/11/2015 1.48 0.637
23/10/2015 03/11/2015 0.477 1.32
23/09/2015 02/10/2015 0.797 1.64
- 07/09/2015 0.437 1.28
01/07/2015 - - Will remain open for winter period
15/05/2015 21/05/2015 0.757 1.6
16/04/2015 22/04/2015 0.757 1.6
17/03/2015 23/03/2015 0.907 1.75
16/02/2015 25/02/2015 0.647 1.49
19/01/2015 27/01/2015 0.697 1.54
01/12/2014 05/12/2014 0.927 1.77
03/11/2014 07/11/2014 1.027 1.87
06/10/2014 10/10/2014 1.047 -
- 12/09/2014 0.967 -
11/06/2014 - - Will remain open for winter period
12/05/2014 16/05/2014 0.907 -
24/04/2014 30/04/2014 0.877 -
26/03/2014 31/03/2014 0.997 -
25/02/2014 03/03/2014 0.997 -
27/01/ 2014   31/01/ 2014 1.087 -
02/12/2013 05/12/2013 0.957 -
01/11/2013 05/11/2013 1.007 -
14/10/2013 18/10/2013 1.017  -
- 20/09/2013 1.077 -
24/06/2013 - 1.057 Will remain open for winter period.
23/05/2013 27/05/2013 0.947 -
22/04/2013 26/04/2013 0.977 -
11/03/2013 13/03/2013 0.917 -
08/02/2013 13/02/2013 0.857 No opening in January for public safety reasons.
10/12/2012 14/12/2012 1.027 -

 

Opening the mouth of the Zandvlei estuary.

Zandvlei estuary mouth opened.


photograph by Michael Lambrecht.

...and sometimes "stuff happens" as on 16/09/2014.

General notes.

  • The above tables are supplied by City of Cape Town - Stormwater Catchment Management and are planned dates for opening and closing the mouth. Note - these are planned dates and may change with weather conditions and other factors.

  • The vlei mouth is opened and closed mechanically at full moon and spring tides where the tide is generally in excess of 1,8 meters.This is to get as much sea water into the estuary as possible. The rainfall in the catchment is monitored electronically.With telemetry the responsible Managers are notified of the rising and falling water levels in the catchment rivers.

  • Mouth will remain open in the winter months, unless there is very little rainfall. Officials monitor the forecasts daily.

  • The Zandvlei Catchment Forum and Zandvlei Protected Areas Advisory Committee (City of Cape Town, Provincial and National government officials and other interested stakeholders) regularly review in and out flows of Zandvlei, as there are a number of critical factors which have to be maintained. ie. water levels for flood management  for the residents and waterbody user groups, also the salintity levels need to be maintained so that the estuary may function to an optimum for aquatic fauna and flora.

  • Martin Thompson has produced a pamphlet;
    Zandvlei - Factors concerning Water Level Management.

This pamphlet sets out the background information in priority order for;
Flooding
Salinity
Revetment stability (concrete walls around the vleis edge)
Fish migration
Recreation

         

             Read the content.                                       Read the content. 

 


This graph indicates the monthly average or mean salinity collected at 2 points in Zandvlei.
The readings are taken on a weekly basis.

  • This information was collected and supplied by Timm Hoffman. It is only part of the information and should not be used to draw any conclusions or make deductions.

  • The data may not indicate the current months readings but will be updated regularly.

  • Royal Road bridge about 50 meters from the mouth of Zandvlei as it enters the sea, and

  • Rutter Road about 2 kms away near the confluence of the Westlake and Keysers Rivers on the western side of the railway line. This water body is fresh, it is located out of the main river flow entering the main water body.


Long-term salinity trends in Zandvlei estuary (Western Cape, South Africa) and implications for dominant macroalgae.  
by
S Muhl, JJ Bolton (corresponding author) and TM Hoffman.

Read this reference document.


                                                                                                                                               

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