在均质土坝设计中，水位骤降通常是拟定上游边坡时需控制的工况。水位降落期浸润线位置判别和确定，为大坝稳定计算提供依据，合理判别水位降落速度是浸润线计算的关键步骤，为此，用k/μv表示库水位相对于渗流自由面下降的速度，以区别库水位是缓降、快降还是骤降，并以此来判别和计算浸润线。渗透系数k值一般可通过试验给出比较精确的数值；给水度μ是确定浸润线位置的关键参数；黏性土μ值的研究目前还没有比较完善的确定方法。此次研究采用了公式计算和查表对比的方法确定合适的给水度值，并用不同公式进行了水位下降快慢的判别，提出了水位骤降期坝型调整和稳定计算指标合理性问题。

 In the homogeneous earth dam design, reservoir water level sudden drawdown is often a control condition of the upstream slope. The judgment and determination of the wetting front location will provide a basis for dam stability calculation during reservoir water level lowering and a reasonably judging lowering rate of water level is a key step for calculating wetting front. The k/μv represents the rate of reservoir water level being relative to seepage free surface decline, which is used for distinguishing different drops of water level： gradual drop, quick drop or sudden drop, and from this value, the saturation line can be calculated. The permeability coefficient k can be given precisely by the test；the storativity μ is a key parameter to determine the saturation line location, but there is no perfect method to identify μ, and then this paper uses a suitable contrast value obtained from the formula calculation and relative table；the rate v to determine the pace of water level decline is given by different formulas. So, an issue on the reasonable judgment of damtype and the rational choice of stability calculation indexes during water level sudden drop is proposed.