Wetland assessment and wetland delineation

Objectives:

The objectives of the wetland habitat assessment are to provide:

  • - An identification of major aspects of the hydro-geomorphic setting and terrain unit at which the wetland occur;
  • - An estimate of the size and roughness of the wetland
  • - An indication of the hydric soils at the site;
  • - An indication of erodability;
  • - An indication of the presence or absence of peat at the site;
  • - An outline of hydrological drivers that support the existence and character of the wetland;
  • - An assessment of the possible presence or absence of threatened or localised wetland plant species, wetland vertebrates and wetland invertebrates known from the region, at the site;
  • - A description of the functions provided by the wetland at the site;
  • - An interpretation of the priority of the wetland for local communities in the area;
  • - An interpretation of the priority of the wetland to biodiversity at the site;

Importance of wetlands

Ecosystem services which directly or indirectly benefit human well-being are of particular importance when wetlands are considered. Wetlands play a major role to enhance supporting services such as nutrient cycling and primary production, which in turn is the basis for other ecosystem services. Wetlands are very important to regulating services such as maintaining water flow and water quality by processing water and regulating water run-off, provisioning services such as providing freshwater, cultural services such as appreciating the landscape and biodiversity. Overall wetlands play a major role in the sustainability of land use from socio-economic and biodiversity conservation perspectives. The setting and function of wetlands at each site should therefore be evaluated to inform land use management.

Practical considerations:

Wetlands are defined by the National Water Act (Act 36 of 1998) as:

“land which is transitional between terrestrial and aquatic ecosystems 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 typically adapted to life in saturated soil”.

According to A practical field procedure for identification and delineation of wetlands and riparian areas (DWAF 2005) wetlands must have one or more of the following attributes:

  • • Wetland (hydromorphic) soils that display characteristics resulting from prolonged saturation
  • • The presence, at least occasionally, of water loving plants (hydrophytes)
  • • A high water table that results in saturation at or near the surface, leading to anaerobic conditions developing in the top 50cm of the soil

Wetlands, according to the definition of DWAF (2005) are at the interface of aquatic systems and the terrestrial environment. As such the characteristics of the surface water or near surface water in space and time at this interface between the terrestrial and aquatic environment are fundamental to understand the functioning of a particular wetland. At the higher elevations of South Africa surface water at wetlands are characterised by considerable contrasts between seasons and periodic precipitation events. Generally accepted definitions of wetlands which focus on the wetland attributes of soil and vegetation are therefore useful because of its consistency despite seasonal fluctuations.

However, a broader definition of wetlands, which is in line with the definition of the Ramsar Convention is the definition accepted by the proposed National Wetland Classification System for South Africa (SANBI 2009):

Wetland: an area of marsh, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water to the depth of which at low tide does not exceed ten metres.

The proposed National Wetland Classification (SANBI 2009) is likely to be of increasing importance in future and will be applied accordingly. SANBI (2009) also includes aquatic systems in the wetland assessments.