The term ‘accumulated streamflow’ is defined as the runoff (i.e. stormflow plus baseflow) from a specific catchment plus the runoff from all catchment areas upstream of the specific Quinary catchment in question. From these, the accumulated streamflows were derived and mapped.
Daily values of local runoff and hence accumulated streamflows, were computed for all 1 401 Quinary catchments within the Western Cape with the daily time-step and process-based ACRU simulation model (Schulze, 1995; 2004 and updates). All computations utilised the 50 years of daily climate plus soils and land cover inputs from the Quinary Catchment Database (Schulze et al., 2010). A baseline land cover of natural vegetation was used, represented by Acocks’ (1988) Veld Types, the hydrological attributes of which were described by Schulze (2004), and using soils attributes from Schulze and Horan (2010).
Mean annual accumulated streamflows were calculated for the historical climate and simulated with the ACRU model for present (mid-1990s) climatic conditions using 6 bias-corrected CMIP5 GCMs used in a current (as yet unpublished) WRC Project at the Centre for Water Resources Research at the University of KwaZulu-Natal.