Linking Two Systems
The strategy to allow the uMfolozi and Lake St Lucia estuary mouths to join to form a combined mouth is progressing well. The linking of the two systems via the beach spillway resulted in approximately 16.4 billion litres of fresh water reaching the Lake St Lucia estuary and lifting water levels at the end of the dry winter period.
The early spring rains and natural breaching of the uMfolozi mouth, which resulted from the one-in-five-year flood, have created a marine connection for the system. The recent events are both natural and positive and are part of the much broader long term strategy to restore estuarine function to this important nursery for fish and invertebrates.
Key to this is to allow these systems to function as naturally as possible. With the Lake St Lucia and uMfolozi systems joined, modeling shows that their combined mouth will be open more often than it is closed.
Long Term Process
However, it is unlikely that there will be a rapid recovery of the Lake St Lucia system – one of South Africa’s most important estuarine systems and Africa’s largest estuarine lake (approximately 32 000 ha). Together with reduced water inflow from nine years of below average rainfall, the lake has had little or no water from the uMfolozi river for the past 60 years.
The Lake St Lucia system requires large volumes of water before it is able to function within a range considered to be natural and indicative of a healthy system. Over the next two to three years the level of the water in Lake St Lucia will be highly dependent on rainfall, the amount of which will determine how quickly the level rises. This means that a large flood could fill the system quickly or that under average rainfall conditions, it could take a number of years.
Source: Andrew Zaloumis, Chief Executive Officer, iSimangaliso Wetland Park