WHILE wet and dry weather cycles are natural, the drought is taking its toll on iSimangaliso Wetland Park, with a growing awareness of human impact on water resources.
Gale force winds earlier this year that pushed the water into St Lucia estuary’s Narrows section northwards, exposing mud flats, is testament to the current drought.
On 5 November, when the winds subsided, water returned to the affected area and tour boats resumed operations.
Coupled with the prolonged separation of the Mfolozi River mouth from the estuary system, the drought has resulted in low lake levels and higher salinity levels, especially in the estuary’s northern sections.
Commercial plantations and other human activity place further strain on the park’s water resources.
Water levels in lake basins are currently well below mean sea level, owing to the disappearance of links between the Narrows and lake basin compartments.
Water levels in the Narrows have just reached mean sea level.
A lack of incoming fresh river water during dry winter months, coupled with relatively warm weather conditions causing evaporation, causes salinity levels to rise.
Salinity
Currently, False Bay is at 60–100 parts per thousand (ppt) salinity, while southern sections of the estuary system are still below sea salinity, at 35ppt.
This causes species’ diversity to decrease as the conditions reach tolerance limits of normal estuarine invertebrates.
Flamingos, however, take advantage of higher salinity levels and are flocking to the estuary’s shallow areas.
‘Because of the reconnection with the Mfolozi River (via the spillway), Lake St Lucia is in a better state in this drought than during the previous one,’ said iSimangaliso CEO Andrew Zaloumis.
‘Conditions will become dire if we do not have good rains and get Mfolozi River water into the Lake St Lucia system this summer’.
