大型水利枢纽,施工期一般均需数年。在此期间,必须进行各阶段的水文计算,以确定一系列的水文要素作为施工的依据。施工期的水文计算的主要特点就是时段的划分要仔细得多。这是由于河流的特性,在一年之中,迳流必然有着较固定的丯枯时段,必须分析出在各个时期所可能出现的水文数据。施工部门为了施工安全经济,往往要求得出分季、分月、甚至分旬的情况。但水文现象是不稳定性,洪水出现可能提早或推迟,提供这些数据就感到有一定困难。另外, Large-scale water control project, the construction period generally takes several years. During this period, hydrological calculations at various stages must be conducted to determine a series of hydrological elements as a basis for construction. The main feature of hydrologic calculations during construction is that the time period is divided much more carefully. This is due to the nature of the river. During the year, it is inevitable that there must be a relatively constant period of stagnation and the hydrological data that may emerge at various times must be analyzed. In order to construct a safe and economical economy, the construction department often requires the conclusion of sub-quarters, sub-months and even sub-ten-days. However, the hydrological phenomenon is unstable and floods may be delayed or delayed. There are some difficulties in providing these data. In addition,