A large scale study on the dependence of time lag of runoff on snow depth and stratigraphy was carried out in a watershed. The time lag in peak runoff was found to be increased by 1.5 - 4 h per I m increment in snow depth. Although the data were widely scattered, it was found that the time lag series converged in a line every year and that discrete layers in the snow cover composed in a warm winter, accelerated meltwater flow.Subtracting the time of propagation through a snowcover from the total time lag, the effect of size of a watershed on a delay in runoff was rearranged, as follows: where Tf is the time lag in min after discharge from a snow cover, A the area of a watershed in km2, Re the effective snowmelt in mm/hr. The time lag Tf increases only by 1.5 times when an area of a watershed is increased by a factor of ten.