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.

For the St Lucia Ground water monitoring document click here...

References

• Rawlins, B.K. (1991). A geohydrological assessment of the behaviour and response of the Zululand coastal plain to both environmental influences and human activity. Unpublished MSc dissertation submitted to the University of Zululand, January 1991. 150p.
• Taylor, R. (2006). Ecological responses to changes in the physical environment of the St Lucia Estuary. Dr. Scient. Thesis, Norwegian University of Life Sciences, Aas, Norway.
• Taylor, R., Adams, J. B., & Haldorsen, S. (2006). Primary habitats of the St Lucia Estuarine System, South Africa, and their responses to mouth management. African Journal of Aquatic Science, 31(1), 31-41.
• Tinley, K. L. (1971). Lake St Lucia and its peripheral sand catchment. Wildlife Society of South Africa, Pinetown, 62.