Method for estimating flow during freezeup period of cold region river through stage-discharge relation during flowing period

The invention provides a method for estimating flow during a freezeup period of a cold region river through a stage-discharge relation during a flowing period. The method comprises the following steps that during the flowing period of the river, a target section is selected, and the stage-discharge relation of the target section during the flowing period is built; during the freezeup period of the river, measure points are arranged on the target section, and the average effective water depth of water flow under an ice sheet of the section is measured and determined; the average relative water depth lambda of the point with the maximum water flow flowing speed under the ice sheet away from a bed surface is measured, and r is calculated and obtained through lambda; the water depth ratio (please see the formula in the specification) of an ice sheet layer and a bed surface layer is calculated; and the convert coefficient of the flow during the freezeup period is calculated through the stage-discharge relation dur