When stream discharge is composed of baseflow only, the discharge shows diurnal variation; namely, the daily minimum discharge is observed at noon, and the daily peak discharge is observed in the afternoon. Diurnal variations of latent heat flux and discharge show a same phase. Solar radiation and relative humidity have also good correlation with discharge. It is considered that the diurnal variation of discharge is affected by the latent heat flux from watershed. The diurnal variation of discharge is observed during the warm season, especially in spring and autumn. This variation is influenced by evapotranspiration because of a rich solar radiation, relative humidity declines, and it is not observed the heavy rainfall in both seasons.