The Global Runoff Data Centre (GRDC), operated by the German Federal Institute of Hydrology (BfG) under the auspices of the World Meteorological Organization (WMO), maintains the world's largest archive of river discharge data. Contains data from over 9,800 gauging stations worldwide, with approximately 435,000 station-years of daily and monthly river discharge records. Data is provided in WaterML2 format and can be accessed through web-based tools and data portals. Particularly valuable for accessing discharge data from countries where national data portals are limited or unavailable — in the Incomati Basin context, GRDC provides access to Mozambican and Eswatini river flow data that may not be readily available through South Africa's DWS system. Supports transboundary hydrological analysis, model calibration, and long-term trend assessment. Free access for non-commercial use after registration.