UPDATE: Draining of the St Lucia Narrows

THE phenomenon of Monday’s virtual emptying of the St Lucia Estuary Narrows was indeed a first time occurrence in this section of the estuary system.

‘The effect of wind on water levels in coastal lakes with enclosed water bodies like Lake St Lucia has been observed over time by scientists.

‘Winds are known to produce standing waves that are maintained by the wind force that drives water in the same direction as it is blowing, resulting in water being blown from one area to another,’ said iSimangaliso CEO Andrew Zaloumis.

While this phenomenon occurs in other parts of the system, Monday’s events were the first for the Narrows, the section of the estuary over which the bridge into St Lucia Town was built.

‘This effect has often been seen in Lake St Lucia where a southerly wind drives lake water towards the Mkhuze River mouth area of North Lake and a northerly wind drives water in the opposite direction towards Brodies in the south.

‘Stronger winds can change the depth at either end of the main lake by up to 50cm.’

Water levels in the Narrows are at their lowest since 2009, due to the drought and reduced input from rivers like the Mfolozi.

Zaloumis added that the effects of the strong southerly wind, in excess of 40 knots, were much more noticeable than they would have been had water levels been higher.

‘If we do not get good rains this summer and make sure the Mfolozi River flows into the Lake St Lucia system, conditions could well become extremely dire.’

Meanwhile, tour operators were counting the cost of having to cancel estuary boat trips on Monday and Tuesday.

The boats attempted to launch on Wednesday morning, but abandoned the effort as the water level was still too low.