After the rain: Swartvlei and Touws River (Wilderness)

Park Manager for the Garden Route National Park, Paddy Gordon has expressed relief that breaching was as closely aligned to the management.

Wilderness Marine Rangers, Carel van der Merwe & Jonathan Britton

He affirmed the significance of keeping the mouth closed until the correct time and level of water measured above mean sea level. Swartvlei was ranked number 7 in South Africa by independent researchers for its biological diversity. ‘Managing the system is complex but water measured yesterday facilitated the decision made to breach/ open both the Swartvlei and Touws River mouths’ he says.

Touws River estuary breached in Wilderness

Both the Swartvlei and Touws River estuaries were breached subsequent to rainfall yesterday.  The Swartvlei Estuary system was monitored for 24 hours and rainfall was recorded:

  • In Farleigh till 07:00 on the 15th of November 2017 – 48.0 mm
  • Sedgefield – 63.0 mm

Water height before the rain was at 1.74meters above mean sea level. However at 18:00 – 1.79 and at 22:00 – 1.79 – 01:00 – 1.79  but at 06:30am = 1.80

  • Touw River – 24 hour rain at Buffelskop till 07:00 -33.0mm and water level at Ebb & Flow rest camp – 1.99
  • Goudveld (forest)-54mm of rain measured.
  • Diepwalle (Knysna forest) – 50mm
  • Knysna (Thesen Island jetty)-35mm

Residents from Sedgefield came out in numbers to witness the breaching of the Swartvei estuary. Channels were reportedly prepared days before and machinery on standby as reported by Jonathan Britton, marine ranger for Wilderness.

Scientist Dr. Ian Russel cautions against opening the mouth too soon as during the open and closed phase there is a unique ecological process that collectively works together to maintain a delicate foodweb. The estuary mouth will generally close naturally during the low rainfall periods as there is a reduction of the inflow of freshwater.

The closed phase is a time of ‘rest and recovery’ when some interesting and important ecological processes come into play.

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