Hydrological Gene-based Flood Frequency Analysis Considering Double Inconsistency In Lancang River

In recent decades,the hydrological series show variant characteristics or laws since natural water cycle processes in many river basins have been destroyed with the impacts of climate change and human activities.Thus,these hydrological series cannot meet the requirements of the consistency of the samples,making the traditional flood frequency analysis method no longer applicable.The inconsistency of the hydrological series is caused by interannual or(and)intra-annual variability of hydrological series,which reflects that significant changes have occurred in the hydrological series with the interannual/intra-annual time scale.From the perspective of hydrological components,an inconsistent hydrological series contains one or more of variant components,i.e.,trend,jump,period and dependence,which leads to the interannual variant characteristics.Meanwhile,there may exists intra-annual variant characteristics because of the differences in the generation mechanism of a hydrological series in a year.In order to comprehensively consider the hydrological inconsistency caused by interannual/intra-annual variability,the moments of hydrological variables are defined as hydrological genes,which are the basic units of the expression of the hydrological information.The hydrological genes are constructed and expressed by regular moments and probability weight moments,and the basic principles of hydrological genes are expounded.In this paper,the measured daily flow series of Yunjinghong station is selected as the research data.These data are firstly diagnosed whether there exist interannual/intra-annual variant characteristics.On the basis of this,the inconsistent flood frequency analysis is carried out by using hydrological gene approach to verify the applicability of this new approach.The main results of this research are as follows:(1)Taking P-? type distribution as an example,the numerical simulation experiments are carried out to simulate the process of transcription and translation of hydrological genes.The impacts of the jump,trend,period and dependence on the hydrological probability distribution function and the density function are described from perspective of genes.The results show that the variant components in the hydrological series make the hydrological gene change with time,further resulting in the change of "character",i.e.,the hydrological probability distribution function and the density function.(2)The diagnostic system for full hydrological components is used to diagnose interannual variability of hydrological series,and the intra-annual hydrological variability is diagnosed by the KS test,the rank sum test and the F test.The results show that there exist jump and periodic components in the 1-day maximum flow series in spring at Yunjinghong Station,and jump components in the 1-day maximum flow series in summer and the whole year,respectively,while the 1-day maximum flow series in autum and winter do not contain variant components.Meanwhile,there are significant differences among the 1-day maximum flow series in spring,summer,autumn and winter at Yunjinghong Station.(3)For the interannual inconsistent hydrological series,the hydrological genes with genetic and variant information are constructed,and the hydrological frequency analysis(HFA)can be fulfilled through the expression process of hydrological genes;For the intra-annual inconsistent hydrological series,the HFA can be fullfilled by the weighted synthesis of the distribution functions of different periods;For the interannual and intra-annual inconsistent hydrological series,the weighted synthesis of the internal distribution function is regarded as the combination of the expression of the interannual inconsistent hydrological genes.The results show that the pressure of the flood control with the current environment is lower than that in the past for floods of which the recurrence period is less than 50 years,while the pressure of the flood control with the current environment is higher than that in the past for floods of which the recurrence period is more than 50 years.(4)The Bootstrap method is used to estimate the uncertainty of sampling,and the Bayesian method is used to estimate the uncertainty of the calculation of parameters.The results show that the uncertainty of the hydrological design value is smaller with the middle design frequency;The uncertainty of the hydrological design value becomes greater when the design frequency is closer to both ends.Besides,the uncertainty of hydrological design values can be reduced when considering the inconsistency of hydrological series.