Flood Modeling using SWAT and GR4J Models in the Oti River Basin in Togo (West Africa)

The Earth's climate evolution over the past few decades has been marked by global warming, leading to hydroclimatic variability and impacting water resource availability. Hydrological modeling has become a solution for reproducing river flows and is an essential tool for understanding watershed dynamics and mitigating natural disasters related to floods. The objective of this study is to reproduce flood flows in the management of floods in the Oti River Basin in Togo. To achieve this objective, the semi-distributed physically-based SWAT (Soil and Water Assessment Tool) and conceptual GR4J (Génie Rurale Quatre paramètres Journaliers) hydrological models were chosen as the base model to calculate flood hydrographs. The data used for this study consisted of a DEM, land use map, soil map, rainfall, temperature, flow, and PET observation data. Sensitivity analysis revealed the most significant parameters of the SWAT and GR4J models. The values of these parameters were determined during the calibration and validation phases. The Nash criterion value for the SWAT model is 0.83 and 0.78 for calibration and 0.72 and 0.81 for validation. Additionally, the KGE values of GR4J range from 0.73 to 0.85 during calibration and 0.62 to 0.81 during validation. These results show excellent performance of the SWAT and GR4J models in simulating flood flows in the watershed. However, the analysis of the results shows that the SWAT model is more efficient than GR4J in simulating high flows and could be used for flood management in the Oti River Basin.