NBA2018_Rivers

To determine the threat status and protection level (i.e. headline indicators) of river ecosystems across the country using the proportion of each river ecosystem type in a natural/near-natural condition against a series of thresholds. This GIS layer also represent examples of river ecosystem types that are intact from source to mouth (i.e. free-flowing and flagship rivers).

Department: Water Affairs and Forestry (DWAF). 2006. The construction of a hydrologically-correct, annotated 1:500 000 spatial dataset of the rivers of South Africa and contiguous basins, Report Number N/0000/00/REH/0701. DWAF: Resource Quality Services. Pretoria, South Africa.

Department of Water and Sanitation (DWS). 2014. A desktop assessment of the present ecological state, ecological importance and ecological sensitivity per subquaternary reaches for secondary catchments in South Africa. Department of Water and Sanitation. Compiled by RQIS-RDM. Available at: http://www.dwa.gov.za/iwqs/rhp/eco/peseismodel.aspx.

Driver, A., Sink, K.J., Nel, J.L., Holness, S., Van Niekerk, L., Daniels, F., Jonas, Z., Majiedt, P.A., Harris, L. and Maze, K. 2012. National Biodiversity Assessment 2011: An assessment of South Africa’s biodiversity and ecosystems. Synthesis Report. South African National Biodiversity Institute and Department of Environmental Affairs, Pretoria.

Skowno, A.L., Poole, C.J., Raimondo, D.C., Sink, K.J., Van Deventer, H., Van Niekerk, L., Harris, L.R., Smith-Adao, L.B., Tolley, K.A., Zengeya, T.A., Foden, W.B., Midgley, G.F. and Driver, A. 2019. National Biodiversity Assessment 2018: The status of South Africa’s ecosystems and biodiversity. Synthesis Report. South African National Biodiversity Institute, an entity of the Department of Environment, Forestry and Fisheries, Pretoria. pp. 1–214.

Moolman, J. 2008. River long profiles aid in ecological planning. PositionIT Jan/Feb (43-45).

Nel, J.L., Murray, K.M., Maherry, A.M., Petersen, C.P., Roux, D.J., Driver, A., Hill, L., Van Deventer, H., Funke, N., Swartz, E.R., Smith-Adao, L.B., Mbona, N., Downsborough, L. and Nienaber, S. 2011. Technical report for the National Freshwater Ecosystem Priority Areas project. WRC Report No 1810/2/11, Water Research Commission, Pretoria, South Africa.

Nel, J.L. and Driver, A. 2012. National Biodiversity Assessment 2011: Technical Report. Volume 2: Freshwater Component. CSIR Report Number CSIR/NRE/ECO/IR/2012/0022/A. Council for Scientific and Industrial Research, Stellenbosch.

Rowntree, K.M., Wadeson, R.A., 1999. A Hierarchical Geomorphological Model for the Classification of Selected South African Rivers. Water Research Commission Report No 497/1/99, Water Research Commission, Pretoria.

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. and Snaddon, K. 2018. South African National Biodiversity Assessment 2018: Technical Report. Volume 2a: South African Inventory of Inland Aquatic Ecosystems (SAIIAE). Version 3, final released on 3 October 2019. Council for Scientific and Industrial Research (CSIR) and South African National Biodiversity Institute (SANBI): Pretoria, South Africa. Report Number: CSIR report number CSIR/NRE/ECOS/IR/2018/0001/A; SANBI report number http://hdl.handle.net/20.500.12143/5847.

Van Deventer, H., Smith-Adao, L., Collins, N.B., Grenfell, M., Grundling, A., Grundling, P-L., Impson, D., Job, N., Lötter, M., Ollis, D., Petersen, C., Scherman, P., Sieben, E., Snaddon, K., Tererai, F. and Van der Colff, D. 2019. South African National Biodiversity Assessment 2018: Technical Report. Volume 2b: Inland Aquatic (Freshwater) Realm. CSIR report number CSIR/NRE/ECOS/IR/2019/0004/A. South African National Biodiversity Institute, Pretoria. http://hdl.handle.net/20.500.12143/6230.

Completed

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There are no access limitations for this item.

None

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)

The GIS layer of origin is the 1:500 000 rivers data layer (DWAF, 2006) that the Department of Water Affairs (DWA) ran the first geomorphological zonation process on (Rowntree and Wadeson, 1999; Moolman, 2008). Only minor river arc edits (e.g. deleting duplicate vertices) were performed during the NBA 2018 (Van Deventer et al., 2018). The Counsel of Scientific and Industrial Research (CSIR) subsequently used this layer to add information during the NPEPA project (Nel et al., 2011). This included the 97 1:50 000 coastal rivers from the Department of Land Affairs: Chief Directorate of Surveys and Mapping (DLA:CDSM), now the Department of Rural Development and Land Reform: National Geo-spatial Information (DRDLR:NGI) which were associated with missing estuaries along the coast line mapped for the NBA 2011 (Van Niekerk and Turpie, 2012).

Other attributes attached to the rivers GIS layer, for example, included the river ecosystem type and river condition (Nel et al., 2011; Nel and Driver, 2012). River ecosystem types were developed by the NFEPA project and also used in the NBA 2011. They represent the diversity of river ecosystems and are components of rivers with similar physical features such as climate, flow and geomorphology. The river ecosystem types used in the NBA 2018 (Van Deventer et al., 2019; Skowno et al., 2019) remains largely unchanged from the previous NBA (Driver et al., 2012). The NFEPA river network spatial layer was coded using 31 Level 1 ecoregions, flow variability (permanent to not permanent) and geomorphological zones or slope categories (mountain stream, upper foothill, lower foothill and lowland river) to produce 223 river ecosystem types. These were reduced to 222 types in the NBA 2018 (i.e. deletion of a subtype located outside South Africa) (Van Deventer et al., 2019).

The methods used for assessing the ecological condition of the river ecosystem types differed from the NBA 2011 in that Present Ecological State (PES) categories were not modelled in the NBA 2018. The river condition data was determined by using DWS (2014) Present Ecological State/Ecological Importance/Ecological Sensitivity (PES/EI/ES) (also referred to as PES/EIS) data, which included mainstems and tributaries at a sub-quaternary level. These desktop data were updated with data that became available between 2011 and 2017 from Reserve or Ecological Water Requirement (EWR) and Water Resource Classification System (WRCS) studies. The ecological category was either updated or remained unchanged depending on which assessment was most recent (Van Deventer et al., 2019).

Free-flowing rivers were also expertly reviewed and updated during the NFEPA project in 2011 following set criteria (Nel et al., 2011). This included for example selecting permanent or seasonally flowing intact rivers (AB rivers) and rivers with no instream dam throughout its length. The PES of rivers was updated during the NBA 2018 process, which included the free-flowing and flagship rivers. The artificial wetland GIS layer was also updated and together with the DWS dams 2016 dataset the free-flowing and flagship rivers were reassessed using the same criteria identified during NFEPA. Where dams and artificial wetlands intersected with the free-flowing and flagship rivers and condition change occurred. River condition in free-flowing rivers also changed after the confluence with a degraded tributary. In these cases the free-flowing/flagship rivers’ PES status was updated to reflect the change resulting in some free-flowing/flagship rivers being removed from the list identified during the NFEPA process. However, where the free-flowing river was identified in the expert consultation process, regardless of the “C” PES condition, the river remained free-flowing/flagship. Where no river condition changes were recorded the free-flowing/flagship rivers remained unchanged.

SANS 1878

FGDC-STD-001-1998

http://hdl.handle.net/20.500.12143/6230