Shen Guoting (front), chief of Toudaoguai hydrologic station, measures water level of the Yellow River in Tuoketuo County, north China's Inner Mongolia Autonomous Region, Jan. 20, 2020. Although the Yellow River has entered its frozen period, hydrological workers here still stuck to their posts. They usually start their work before daybreak in the temperature of minus 20 degrees Celsius. (Xinhua/Bei He)