Getting to grips with wetlands

Hannes Marais, Wetland Scientist, MTPA, shared some of his knowledge on a recent field trip.

By James van den Heever

Keeping your balance is important when exploring wetlands (Photograph: Paul van Vuuren)

One of the most important reasons for conserving Verloren Valei is the significant contribution it makes to securing South Africa’s precious water resources. The purpose of the field trip, on 6 November 2021, was to give participants an introduction to wetlands—what they are, how they work and so on—via practical examples. We were fortunate to have the services of Hannes Marais as an expert guide to introduce us to the subject.

The reserve covers 6055 hectares and yet this relatively small area feeds 11 streams which become four rivers. Given its great height above sea level, Verloren Valei is rich in unpolluted wetlands, natural springs and streams, which make up about 900 hectares of the total.

To give an idea of the kind of contribution the reserve makes in terms of water, recent measurements show that it discharges 14 million litres of water every 24 hours in the dry winter months, and 600 million litres of water every 24 hours in the wet months. Read more about these latest measurements.

The broad term “wetlands” describes many forms of aquatic system, including riverine floodplains, tree-covered swamps, high altitude rain pools and even saline lakes. Ponds, lakes, rivers, marshes, swamps and bogs, are also listed as wetlands. The National Water Act (36 of 1998) defines a wetland as ”land which is transitional between terrestrial and aquatic systems, where the water table is usually at, or near the surface, or the land is periodically covered with shallow water and which land in normal circumstances supports, or would support, vegetation adapted to life in saturated soil”.

It’s worth noting that 43% of South Africa’s wetlands are located in the Grassland biome. This fact, and the reality that grasslands are often much more effective carbon sinks than forests, shows just how important it is to protect our grasslands—perhaps particularly from the modern love of simple solutions which manifests as a kneejerk desire to plant trees indiscriminately.

“Services” provided by wetlands

  • Wetlands are among the most productive habitats in the world. They provide food, water, and shelter for fish, shellfish, birds, and mammals, and they serve as a breeding ground and nursery for numerous species of fauna and flora that is adapted to live in these conditions.
  • Flood Control. Wetlands act as protective natural sponges by capturing, storing and slowly releasing water over a long period of time thereby protecting downstream property owners from flood damage.
  • Sediment Traps. Wetlands improve water quality by acting as sediment sinks or basins. They are especially effective at trapping sediments in slow moving water.
  • Pollution Interception – Wetlands act as filters and sponges. Water that enters a wetland is filtered through the substrate and wetland plants, removing nutrients, i.e. nitrogen and phosphorous, and toxins.
  • Ground Water Recharge – Wetlands often contribute to groundwater and can be important in recharging aquifers

We visited several sites on the reserve to examine what the various types of wetland actually look like, and to discuss changing attitudes to managing them. The opportunity to handle peat and see with our own eyes just how much water can be squeezed out of a handful of the stuff was a powerful demonstration of why and how wetlands act as unparalleled water storage facilities.

Hopefully, Hannes will repeat this field trip next year!

Hannes Marais demonstrates the water-retention properties of peat (Video by Paul van Vuuren)

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