Calibration, validation and application of the SWAT model to determine the hydrological benefit of wetland rehabilitation in KwaZulu-Natal, South Africa

In South Africa, with highly variable and intense land-use practices, coupled limited soil fertility water resources, there has been a long history of encroachment arable lands (sugarcane timber plantations) into surrounding wetlands. Although wetland delineation within the sugar sectors is well-defined in policy, existing proposed legislation, are significant areas non-compliance. The spatially-explicit Soil Water Assessment Tool (SWAT) was adopted to investigate interactions climate, on water-use natural encroached This paper documents calibration, validation application SWAT model Quaternary Catchment (QC) U20G, which 498 km2 catchment that forms part uMngeni River basin. SWAT-CUP parameter sensitivity optimization tested daily observed streamflow data for this catchment. Parameters were modified using sequential uncertainty fitting (SUFI-2) analysis routine calibrate model. simulated flow had close fit regression coefficient (r2) 0.87 Nash-Sutcliffe (NS) 0.8. Through buffer scenario analysis, showed if 20-m be returned state, could 16% increase annual contribution, an upper limit 60% some hydrologic response units (HRUs). Thus would hydrological gain wetlands sensitive cleared commercial species sugarcane.