The WRF-lake, as a one-dimensional (1D) lake model popularly used for coupling with the Weather Research and Forecasting (WRF) system and modelling lake atmosphere interactions, does not consider the heat exchange caused by inflow outflow, which is an important characteristic of large reservoirs and can affect the energy budget and reservoir-atmosphere interactions. We evaluated the WRF-lake model by applying it at a large dimictic reservoir, Miyun Reservoir, in northern China. The results show that the WRF-lake model, though ignoring inflow-outflow, yields good surface water temperature simulation through reasonable parameterization. The Minlake model, as a better physically-based model in reservoirs, was used to test the effect of inflow-outflow, including heat carried by inflow-outflow water exchange and water level change on the 1D model’s performance. The effect of heat carried by inflow-outflow is mainly in summer, negatively correlated with hydraulic residence time and positively correlated with temperature difference between inflow and outflow. For a reservoir with hydraulic residence time of 3 years and temperature difference between inflow and outflow about 10 ° in summer, the heat carried by inflow-outflow is far less than the heat exchange through the surface (< 2 %), therefore, has little influence on total energy balance. The effect of water level change is mainly on latent heat and sensible heat in unit area, rather than outgoing longwave radiation. Though influencing the temperature in deep layers, the water level change does not have a significant impact on the surface temperature.

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