The ATHYS model was used to simulate rainfall-runoff in the Fengle catchment of Lake Chao to help manage erosion, flooding, and water quality. The model divided the catchment into small sections based on elevation, land use, and soil type, using data from rain gauge stations. By calculating runoff and routing it to the outlet, the model generated hydrographs and discharge volumes. Key parameters like STO, INF, and ω were used to estimate reservoir volume and infiltration rates. The study focused on a 1500 km2 area with various land uses, including rice fields. After calibrating the model with five years of discharge data, the researchers were able to accurately simulate runoff for ten years.