Some time ago the closing of some plantations was mentioned in the George Herald, but then it was also mentioned that the private sector might carry on with planting of the plantations.
Seems the reason for closing the plantations is due to water shortages because the pine trees use a lot of rain water.
Question: Will the pine trees stop using water if managed by a private company? At Beervlei plantation there is a natural fountain in the mountain that supplied water to several farmers.
The Forestry Department now stopped the supply to these farmers and diverted the supply to only one milk dairy.
Why are the farmers not allowed to take water from the rivers or the lakes or need to pay for water when the water is allowed to flow into the sea basically every three months?
The farm workers also say that the plantations will be sold off as a game farm, avocado farm and for planting of nut trees?
Why is SANParks opening the river mouths to allow the river water to run out into the sea if there is not enough water to sustain the plantations?
Nandi Mgwadlamba, regional communications manager of SanParks, responds:
SANParks manages indigenous forest areas and also "exit areas". These are declared of no commercial use by timber companies and set aside to manage for conservation after the companies exit. The closing and opening of estuary mouths has nothing to do with plantations at all.
Breaching of estuaries
'Estuaries have many natural states (open and closed, high and low levels of inflow of both fresh and marine waters). During spring high tides, the upper estuary is filled to a high water level which causes strong outflow during spring low water.' (Howards Williams & Allanson, 1979.)
Both the Swartvlei and Touw River systems have estuaries and estuarine lakes. Estuaries are globally understood to be 'enclosed' coastal bodies of brackish water (resulting from a mixture of freshwater and seawater) with one or more rivers or streams flowing into them, with a connection to the open sea.
Why open and close the mouth of the estuary (also called breaching)?
The presence and height of a sandbar determines open / closed phases of the mouth of the estuary.
During open phases during high tides, water moves from the sea to the estuary, ensuring a combination of both fresh and sea water. This is important for fish species dependent on the opening of the estuary mouth in order to facilitate recruitment of larvae and post-larvae into the system from the sea.
Closed phases are natural and can be highly productive for a variety of estuarine biota including plants, zooplankton, macrobenthos and fish.
This allows a whole range of juvenile forms of estuarine-dependent and estuarine-associated marine species to be recruited inside their sheltered and productive reaches, where they complete their growth to maturity.
Whitfield and Bate (2007) indicate that annual migrations of postlarvae into temporarily opened and closed estuaries (also known as TOCEs) 'indicate that these life stages act as the dispersal phase for this species, allowing it to spread into areas where it is otherwise unable to breed successfully. Mud prawn larvae require a marine phase of development and are often absent from intermittently open estuaries (also known as IOEs) that are, on average, closed for more than 50% of the time. This observation illustrates the importance of the open mouth phase for these and other zoobenthic species with marine larval phases.'
When is the mouth opened?
The method used for this is 'periodic artificial breaching' of the estuary mouth. The set standards for breaching are when water levels in the estuary reach two metres above mean sea level (amsl) for Swartvlei and between 2,1 and 2,4 metres for the Touw River.
Breaching is done by SANParks, the custodians of the system. Changes in water exchanges could influence the physical and chemical properties of water.
SANParks scientists have closely measured the temperature of the system, salinity, total dissolved solids, dissolved oxygen and others since 1991.
A response from the media desk of the Department of Environment, Forestry and Fisheries is being awaited.