Canopy conductance, a crucial factor in estimating evapotranspiration, is influenced by plant health and environmental conditions like sunlight and humidity. A new model was created that considers these factors' changes over time, especially how plants respond to sunlight and humidity. By using this model, accurate estimates of surface conductance and evapotranspiration were achieved in two river basins in China. The model performed well even with most parameters assumed to be constant, except for two specific ones. This improved model can help predict canopy conductance and water use efficiency in different climates and surface types in Northern China.