The VegET model is a physically based, bucket-type hydrological model that simulates key water balance components such as evapotranspiration, soil moisture, surface runoff, and deep drainage at a spatial resolution of 1 km. The model is primarily driven by remote sensing data, including precipitation and Normalized Difference Vegetation Index (NDVI), which facilitates capturing the diverse hydrological processes across Africa (Figure 2). Precipitation data sources such as CHIRPS, ERA5, and MSWEP, alongside soil property data from ISRIC and vegetation data from MODIS, ensure robust and accurate simulation outcomes. Read more

The gridded runoff output from VegET is subsequently routed using the mizuRoute model, a vector-based river network routing tool (Figure 1). mizuRoute utilizes Hydrological Response Units (HRUs) sourced from the Hydrologic Derivatives for Modeling and Analysis (HDMA) database. To enhance the accuracy of discharge estimation, particularly in complex hydrological environments like tropical rainforests, deep drainage and surface runoff partitioning were applied using region-specific coefficients (Figure 2). This process involves a bias correction factor (β), which adjusts for underestimations observed in regions such as the Congo River Basin.

The performance and reliability of VegDischarge v1 were rigorously validated against observational data from the Global Runoff Data Centre (GRDC). Validation was performed at annual and monthly time scales, covering numerous stations across Africa, to ensure robust results (Figures 3, 4). At the continental scale, the model demonstrated strong performance with high correlation (R² = 0.5–0.9), Nash-Sutcliffe efficiency (NSE = 0.6–0.9), and Kling-Gupta Efficiency (KGE = 0.5–0.8), indicating its capability to accurately replicate observed hydrological patterns across diverse climatic and hydrological conditions. Read more