Improving the national wetland inventory.

Mapping the locality of wetlands is essential so that they may be classified into the different wetland ecosystem types across the country, which in turn can be used along with other data to identify wetlands of conservation significance.

Van Deventer, H., Smith-Adao, L., Mbona, N., Petersen, C., Skowno, A., Collins, N.B., Grenfell, M., Job, N., Lötter, M., Ollis, D., Scherman, P., Sieben, E. & Snaddon, K. 2018. South African National Biodiversity Assessment 2018: Technical Report. Volume 2a: South African Inventory

This layer is a static NWM2 dataset. The latest versions of the National Wetland Map can be viewed on the South African Inventory of Inland and Aquatic Ecosystems project page on BGIS.

There are no access limitations for this item.

There are no use limitations for this item. The latest version of the National Wetland Map is available on the South African Inland Inventory of Aquatic Ecosystems project page on BGIS.

WGS 1984

Projection: Albers

False_Easting: 0.0

False_Northing: 0.0

Central_Meridian: 25.0

Standard_Parallel_1: -24.0

Standard_Parallel_2: -33.0

Latitude_Of_Origin: 0.0

Linear Unit: Meter (1.0)

Wetlands and waterbodies categories from an improved version of the NLC2000 dataset were used to derive NWM2 in March 2008. Upon request of SANBI and the Water Research Commission (WRC), both NWM2 and the National Wetland Probability Map (NWPM) (Thompson et al. 2002) were provided to GeoTerraImage (GTI) for the assessment of accuracy (GTI 2008). The assessment considered congruency between the dataset and reference data which primarily consisted of features mapped by the former Department of Land Reform: Chief Directorate Surveys and Mapping (DLA:CDSM) for the topographical maps, as well as data from the Mpumalanga and KwaZulu-Natal provinces.

The majority of the reference datasets represented non-wetland categories and few included fine-scale mapped wetlands and were not mapped by wetland specialists. The congruency assessment found that both NWM2 and the NWPM had an overall agreement of between 30% and 90% for both the wetland and water classes (GTI 2008). A high commission error was also observed for both datasets, in relation to the reference datasets. A number of recommendations were made to improve the NWM2, including the use of a new range of multi-seasonal images and higher spatial resolution imagery. A confidence index was also produced, ranking the suitability of the Landsat imagery for each topographical map sheet, as well as the result of confidence in the mapping of wetland extent.

Subsequent to the report, NWM2 was updated using polygons of dams and lakes and the rivers network (line) data supplied by the former Department of Water Affairs and Forestry (DWAF date unknown). The resultant layer constituted of a number of GIS layers: wetlands, natural waterbodies and artificial waterbodies.

SANS 1878

FGDC-STD-001-1998