Zhangjiakou city is a temperate continental monsoon climate. Its climate is characterized by: four distinct seasons, cold and long winter; Dry and windy in spring; Hot and short precipitation concentrated in summer; Autumn is warm and sunny. Because of the high terrain, the warm and wet air is blocked by Jundu Mountain and the head of the dam twice suddenly, the water vapor source is not rich, the precipitation is less, the annual precipitation is 330 ~ 400 mm. The distribution trend of dam discharge is closely related to topography and varies greatly among regions. Due to the lifting effect of terrain on warm and wet air, the mountainous area receives more precipitation, with annual precipitation of 400 ~ 500 mm.