以前期水量为条件的管运洪水推求

Floods encountered by a reservoir project during operation and management period are mainly determined by the volume of rainstorm and the previous flood volume of the river. For small watersheds, the latter plays a minor role which can be ignored. For large and medium watersheds, the latter has a greater impact and thus should be paid attention to. Based on the total probability formula the concept of quantificational characterizing this influence of flood frequency distribution of the annual maximum time period flood volume whose condition is previous flood volume is proposed, and the calculation formula is given. Two calculation methods for the manage-flood based on previous flood volume are established, i.e., the direct method and the indirect method. The paper divides the previous flood volume of the river into two states: less water and more water. The direct method is based on the measured flood data, and the conditional distribution of less water and more water is deduced by the principle of single variable frequency calculation principle. The direct method is simple and practical, but it requires more data. In the indirect method, the Copula function is first used to describe the two dimensional joint distribution of the maximum period flood volume of annual (such as annual maximum seven days flood volume) and the previous flood volume of the river. The key of this method is the choice of Copula function. By analyzing the correlation charts of the maximum period flood volume of annual and the previous flood volume of the river, the Clayton-Copula function is selected to deduce the conditional distribution. The indirect method can be used in lack of data, but the shortcoming is that the appropriate Copula function should be selected, and the calculation is more complicated. Finally, the proposed direct method and indirect method were applied to the calculation of channel flood in Zagunao River. The results showed that the overall benefit of the reservoir was higher than that of the original operation that fixedthe limits water level of reservoir in flood period.