St Lucia

Background

Situated in the Kwazulu-Natal Province of South Africa, the St. Lucia system forms part of the iSimangaliso Wetland Park. It enjoys both UNESCO World Heritage and Ramsar Site status and is considered the most economically and ecologically important estuary within South Africa. The recent history of the system with respect to human interventions is well documented (iSimangaliso Wetland Park Authority, 2011). There has been active research in the area since the 1950's. This research has established a reasonable and growing conceptual understanding of the functioning of the system. The significant body of data and understanding of the system presents a solid foundation on which to build long-term ecological research programmes.

A Water Theme

Water is a central theme in SAEON, given it's life giving properties. St Lucia is a place where we can evaluate the effects of people on water systems. In 1971 Tinley wrote, “The St Lucia Lake System is condemned to death by thirst – lack of freshwater – and it can be reprieved only by securing one entire river catchment to flush out the lake periodically, and by re-establishing the peripheral, onetime perennial, freshwater resources from the high water table sands.” The lake receives water from the Mfolozi, Nyalazi, Mpahti, Hluhluwe and Mkuzi catchments as well as the Maputaland coastal aquifer. While the lake catchments provide the largest volume of river runoff to the lake, the ecological resilience of the lake is critically dependent on the ground water contribution through perennial seepage flows that sustain micro-habitats along the lake shoreline (Taylor, et. al., 2006. Published in Volume 31 of the African Journal of Aquatic Science, pp31-41). Surrounding land uses, the management of the Mfolozi mouth and the estuary mouth are all factors impacting on the quality and quality of water entering the system. Groundwater, physio-chemical and water quality monitoring were prioritized for long-term ecological research. Monitoring these parameters will help refine the model on the system functioning. These parameters have been reiterated as a priority by Whitfield (2014) and more recently by the iSimangaliso Authority's scientific studies which have refined our understanding of the Lake. SAEON is interested in building on long term datasets and providing additional critical parameter data required to understanding the variability within this system to explore the impact that human activity is having on the area relative to climate impacts and possible sea level rise. We are exploring observations linked to both the quality and quantity of water in the system in collaboration with Department of Water Affairs and iSimangaliso Authority.

Water quality

Baseline information and long-term data on the spatial and temporal variability of water quality, in relation to requirements of the estuarine biota, is one of several issues identified as requiring investigation with the St Lucia system (Whitfield et al. 2000). Improving the temporal and spatial data on the water quality in St. Lucia will contribute to a more complete understanding of the relative impacts of linked catchment land use, management interventions success and global change drivers Taylor (2013). Furthermore knowledge of physico-chemical parameter dynamics will not only aid in explaining the distribution of the fauna and flora (Perissinotto et al. 2013(a)(b)) but will also contribute to an understanding of the effect of the different drivers, natural or artificial (Perissinotto et al. 2013b). The Department of Water Affairs (DWA) is in the process of implementing water quality monitoring programs in key estuaries in South Africa. Given the size and complexity of the St. Lucia system however, routine approaches may not be suitable. It has been agreed that preliminary data is required to rationalise and direct longer term monitoring initiatives. SAEON, through the Grasslands, Forests and Wetlands and Elwandle Nodes, in collaboration with the and Department of Water Affairs and Sanitation (DWAS), is therefore undertaking a pilot project focused on enhancing our understanding of the spatial and temporal variability of water quality using biotic and abiotic water quality variables. This pilot study is intended to run for at least one year, with five sampling trips planned. The first field trip was successfully completed in June 2014. It is anticipated that the sampling results will be useful for informing components of a long term monitoring platform for both DWA and the iSimangaliso Authority.

Groundwater

Groundwater is one of the key ecosystem drivers in the Maputaland coastal areas (Rawlins, 1991; Taylor, 2006; Taylor et al., 2006; Kelbe, et al., 2013). In the primary aquifer, the synergy between the groundwater system and coastal lakes is a feature that is common along the east coast of Africa. These coastal lakes and surrounding wetlands are systems where the groundwater fluxes continually move through their shorelines to create groundwater-dependent ecosystems. The low lying topography in the coastal plains means that the groundwater is generally close to the topographical surface, creating a shallow phreatic zone that strongly influences the terrestrial ecology. Given the importance of ground water as one of the drivers of ecological resilience of the Lake St Lucia, particularly in dry times, and its influence on terrestrial ecology, changes in the groundwater dynamics in relation to shifts in adjacent land use practices around the protected area, climate change and sea level rise are important to monitor in the global change context. There is concern regarding the potential impact of extensive afforestation in the primary aquifers combined with habitat transformation of natural swamps and wetlands taking place within the system. Outside of the protected area the extent, nature and tipping points of these impacts on ground water resources on the system are not well understood. The importance of monitoring the ground water resource in relation to these threats was recognised by Tinley's (1971), who’s report led to the start of a groundwater monitoring program on the Eastern Shores in 1973 under the aegis of SCADCO (the St Lucia Scientific Advisory Council). Since then the infrastructure for monitoring of the groundwater storage (water level) has progressively been expanded for individual studies, resulting in a very fragmented and ageing network of piezometers, boreholes and wells that are in need of a radical revision. To establish a purposeful monitoring program it is essential to review the existing network of current and potential monitoring sites and then establish a clearly defined aim for the monitoring program. With this in mind, SAEON GFW node has implement a pilot study with the purpose evaluating the existing monitoring wells to determine if should be used for the long term deployment of monitoring equipment and of identifying the specific groundwater resources (aquifers) that need to be monitoring on a long term basis. This study will identify those sites that are currently being used for monitoring, those sites that could possibly also be used to enhance the monitoring and those that may not be suitable for monitoring. Seven loggers were deployed on eastern shores in January 2013. These have been downloaded on a regular basis. An additional logger was deployed on western shores in a DWA well. Many of these wells are in a dilapidated state and require refurbishment. Funding has been secured through the DAE-NRM program to facilitate this and is planned for the 2015/16 year.