The news ran like wildfire through the town: “No… really?” “Yes… after four years – to the day! Imagine!” And the people came in droves – mothers, fathers, children, dogs, cats, pet snakes, all making their way in haste to the Kleinmond lagoon to see it break through to the ocean. There was an air of anticipation, of mass celebration in the air. Children, unbelievably, rushed from the icy air into the icier water (“Children just don’t seem to feel the cold, do they?”). It seemed like the end of a long, hard drought.
And, in a way, it was. According to Pierre de Villiers, CapeNature’s Co-ordinator of the Western Cape Estuaries Programme, the opening of the mouth depends on fresh water inflow, which, in turn depends on rainfall. The mouth has not opened during the last four years due to the drought that the Western Cape experienced over this period. Under normal circumstances, it would open more frequently, he says.
Interestingly, the other, larger mouth of the Bot River estuary, at Meer-en-See, does not open naturally. “It needs to be opened by grader from time to time and this forms part of the mouth and estuary management plan. Legally-binding documents need to be approved before this can take place and these provide guidelines for the management of the system,” he adds.
Certain adverse circumstances militate against artificially opening either this mouth, or more specifically, the Kleinmond mouth during periods when this does not occur naturally. “Opening the mouth results in large volumes of water rushing out of the estuary,” Pierre explains. “This scours out sand and mud which is taken out to sea, providing an important source of sand and nutrients for the ocean and its species.
“However, if the mouth is artificially opened at a low water level, the impact will not be as great as it should be and much less nutrient-rich mud or sand will reach the sea. In addition, if the optimum amount of scouring does not occur, the mouth will close quickly, and without follow-up rains and fresh water, it will end up a very small shallow system.”
The interaction between the sea and the fresh water systems which originate in river catchment areas in the mountains has been developing since the beginning of time, he points out. “Estuaries form the interphase between fresh water and salt water. Special species have evolved to survive within these changing ecosystems. Most of them require some connection to the ocean to complete their life cycle. In fact, some estuarine fish species, like Steenbras and Kob breed at sea and then the young pass back into the estuaries to develop and grow.”
An inflow of salty sea water also has the effect of killing off some of the reeds which, during long static periods tend to develop into dense clumps near the mouth. However, when the estuary has been closed off for a long time, evaporation of the fresh water may also result in an increase in dissolved salts in the estuary, which will have the same effect.
Those Kleinmonders who rushed like lemmings to the sea when news of the breakthrough began spreading through town and who got there first remarked on the stench which occurred as the estuary water began to carve a channel to the sea. This, says Pierre, is because of the build-up of sand and mud in the estuary. The deeper one goes, the less oxygen penetration there is and anaerobic processes take place. As the mud begins to pass into the sea, the smell is released.
The short-lived smell notwithstanding, the people of Kleinmond continue to flock to the newly-created mouth with cameras clicking, to celebrate this miracle of nature which has been playing itself out for millennia and, beating all the man-made odds thrown in its path, continues to do so right on their doorsteps.