Hydrologic Frequency Analysis For Inconsistent Annual Runoff Series

Due to the frequent human activities and the climate change, partial climate and underlying surface conditions were changed considerablly. All this change destroyed the consistence of natural hydrological data, which made it cannot use traditional frequency analysis methods. This research used three methods to calculate the frequency of inconsistent annual runoff serise in Shanbei and Guanzhong region, in hopes to provide hydrological design values for these regions. The main contents and the conclusions are as follows:(1) Comprehensive hydrology change point analysis. Adopt the comprehensive hydrology change point analysis method to determine the change-point of inconsistent annual runoff in the regions. Preliminary diagnosis includes the process line method, the differences of cumulative slope method and Hurst coefficient method. Detailed diagnosis includes trend detailed diagnosis and jump point for diagnosis of detailed. Three methods for trend detailed diagnosis were enployed: correlation coefficient method, Spearman correlation test and Kendall rank correlation test. Using 11 methods for jump detailed diagnosis: Lee-Heghinian method, orderly clustering method, two segmentation method of optimal information, R/S method, Brown-Forsythe method, sliding F method, sliding T method, sliding rank method, sliding run method and Mann-Kendall method. Comprehensive diagnosis includes trend integrated diagnosis and jump integrated diagnosis, and the change-point can be determined according to efficiency coefficients and practical survey analysis. Through analysis, there are 7 stations'annual runoff series hydrological changed: Zhaoshiyao belong to trend type, and the rest of the annual runoff series belong to jump type, and the change point is Shenmu 1979, Zaoyuan 1996, Huangling 1985, Linjiacun 1985, Zhangjiashan 1985 and Zhuangtou 1985.(2) For this 7 variation stations, using the inconsistent annual runoff frequency calculation method which based on random analysis, we can gain the statistical parameters of P-â…¢distribution in the past, present and future. And the results indicated that the annual runoff series reduced year by year.(3) Frequency calculation of inconsistent annual runoff series based on conditional probability. Firstly, according to change-point, classified inconsistent annual runoff series as two parts. Secondly, eatimate the probability weight and conditional probability(in this paper probability include LN(2)and P-â…¢). Finally, by use ABS, OLS and WLS standard test the goodness-of-fit, we can find the frequency curve fitting well. (4) Frequency calculation of inconsistent annual runoff series based on mixed distribution. Firstly, according to change-point, clasiified inconsistent annual runoff series as two parts. Assumpt this two series follow differently distribute, and the whole series follows mixed distribution(mixed-two lognormal distribution and mixed-two P-â…¢distribution). Secondly, use the simulated annealing algorithm estimate the parameters of mixed distribution. Finally, ABS, OLS and WLS standard were tested the goodness-of-fit, we can find the frequency curve fitting well.The mixed distribution contains statistic analysisy and casue-effect analysis, is more rational and flexibal than traditonal methods. Acorrding to calculation results, the mixed distributiom model is better than to conditional probability model.