一、问题的提出我国东北地区冬季气候十分寒冷,天然河流一般均结成很厚的冰盖。但水电站下游河道却有一段距离不封冻,水流呈明流状态。从电站尾水到下游封冻冰缘之间明流段的长度我们定义为不封冻距离L_f(见图1)。在整个冬季,封冻冰缘是不断变化的,在其增长和消退过程中,必有一距电站最近的位置,这时L_f达到最 First, the issue put forward Northeast China’s winter climate is very cold, the natural rivers are generally formed a thick ice sheet. However, there is a certain distance downstream of the hydropower station is not frozen, the water flow was Ming flow state. From the tailrace to the downstream frozen ice edge between the length of the Ming stream we define not frozen distance L_f (see Figure 1). Throughout the winter, frozen ice edge is constantly changing, in its growth and dissipation process, there must be a location closest to the power plant, when L_f reaches the most