South Africa: Ecohydrological analysis of Vazi-wetlands

The Vazi-wetlands are situated in the province of KwaZulu-Natal in South-Africa at of 600-700 meters above sea level. They occur in inter-dunal depressions close to the eastern coastline (see maps). Some of the Vazi-wetlands have thick peat layers of up to 8 meters. Peatlands are rare in South-Africa. Around 60% of the mare situated in the eastern part of the country, called Maputaland, where annual rainfall is relatively high. The Water Research Commission (WRC) in South Africa has many projects related to the rehabilitation of peatlands. One of such projects (WRC K5/2346) deals with the best preserved peatland (Vazi-North), which is threatened by expansion of pine (Pinus) and blue gum (Eucalyptus) state-plantations on the surrounding dunes. These plantations use a lot of groundwater from the dune systems that supply the Vazi-wetlands with water. As a consequence the Vazi wetlands are drying out. Already in 1998 severe burning of the peat in Vazi-wetlands has been reported (Grundling & Blackmore, 1998). We are trying to investigate, which dune systems are most important for supplying the wetlands with groundwater. If that is known, it will be possible to target areas where pine and blue gum plantations should be banned in order to restore the flow of groundwater to the wetlands. Increased knowledge on the functioning of the hydrological system is urgent, because some peatlands have started to burn again in 2015 and this has led to an increased loss of peat and to almost the total destruction of the vegetation (see photographs of March and May 2015).


Photo: This photo reveals the underground springs with iron deposits, which have been exposed by the fires. The dried-out peat layer (black and grey) shows large shrink fissures.  (Photo A.P.Grootjans, March
2015).


Photo:This photo shows the burned springs with a wild fire in the background (Photo A.P.Grootjans, March 2015). 


Figure: This figure shows a conceptual model of how the Vazi-wetlands are supplied with groundwater. The groundwater originates from the high dunes with large pine and blue gumplantations (dark green). They enter the Vazi-wetlands via (underground) springs with much iron deposits (orange). The groundwater flows through the upper peat layers and infiltrates again feeding other low lying wetlands. Loss of groundwater due to increased evaporation in the forest plantations therefor affects the whole chain of wetlands.