A new model called the two-dimension Gumbel mixed model was created to analyze how rainfall and reservoir inflow are related. By using this model, researchers were able to figure out how often certain amounts of rainfall are linked to specific levels of reservoir inflow. They tested the model using real data from Gangnan reservoir and found that it accurately represents the connection between rainfall and reservoir inflow. This model can help solve problems related to changes in water levels caused by rainfall, making it a valuable tool for understanding and managing water resources.