In this method , on the assumption that inconsistent annual runoff series were composed of relatively consistent random component and inconsistent deterministic component ; firstly the random component and deterministic component were identified and tested by using genetic analysis method and statistic analysis method ; and the fitting calculation of deterministic component and the frequency calculation of random component were made separately ; secondly according to the theory of decomposition and composition in time series analysis , the deterministic forecasting value and stochastic design value were synthesized ; and the past and present as well as future frequency distributions were gained 該方法假設(shè)非一致性水文序列由相對一致的隨機性成分和非一致的確定性成分兩部分組成,采用成因分析法與統(tǒng)計分析法分別對確定性成分和隨機性成分進行識別與檢驗,并對確定性成分進行擬合計算,對隨機性成分進行頻率計算;根據(jù)時間序列分析的分解與合成理論,將確定性的預(yù)測值和隨機性的設(shè)計值進行合成,得到過去、現(xiàn)在和未來不同時期合成序列的頻率分布。