Message from Cassy...

Document from Department: Water & Sanitation; Scientific Services Branch
Sample Date: 2010-10-21
Sampling LocationFaecal coliforms /100mlE. coli /100ml
Zandvlei- north, surface <10 <10
Zandvlei- centre (opp. Imperial Yacht Club), surface390190
Zandvlei- south (opp. Playwaters), surface1010
Outlet channel near Royal Road bridge, surface6900044000
Westlake Wetland opp. Rutter Road570290
Zandvlei at rubble weir50003700
METHOD: Membrane filtration followed by incubation on m-TEC agar for 2 hours at 37C then at 44C for 22 hours followed by an in situ urease test. .
KEY: nd - no data; nr - no result; og - overgrown; E.coli - Escherichia coli
GUIDELINE: South African National 1996 Water Quality Guidelines (Recreational Use) for intermediate contact (not swimming): 3-month median (50%ile) limit of 1000 faecal coliforms/100ml in fortnightly samples.
WEATHER: Overcast with rain
The water sampling takes place once a month by Scientific Services. Their next sampling is taking place tomorrow, so I will only get the results next week, probably Monday or Tuesday. The last results for October were good at the north and south section. The guidelines for contact swimming is 100e coli per 100ml of water. The guideline for intermediate contact (recreational sports like yachting and canoeing) is 1000e coli per 100ml. The levels at the yacht club area last month were 390e coli/ml. The Royal Road bridge area was very high, due to another problem encountered at the sewerage line under the bridge, which has been reported to the authorities, so they may fix it.

Generally in summer the water quality is very good, especially if there has been good flushing of salinity at the mouth when it is open to wave action from the ocean. Unfortunately I cannot give you an indication of what the water is doing right now because we don’t have a more recent sample.

On other news at Zandvlei, yesterday I witnessed an interesting avian interaction. I watched a red breasted sparrow hawk chase and catch a feral pigeon and fly off with it, only to be chased by a pied crow. The sparrow hawk let go of the pigeon, which was still alive. The pied crow then continued to chase the pigeon just like the sparrow hawk did and for well over a km, wheeling and careening up and down in pursuit of the pigeon. Eventually when almost out of site, the crow gave up.

It is interesting as pied crows hardly ever actively hunt and this was a very novel and opportunistic way to try and secure a fair sized meal.
Cassandra Quinton Sheasby
Reserve Manager
Greater Zandvlei Estuary Nature Reserve
ph/fax: 021 701 7542
Guess this means we should swim with our mouth closed.

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