| Hydrological series are the uppermost and the most direct resources of information for human to understand the hydrological mechanism. We rely on these information all along to infer and explain the phenomenon in hydrological cycle. But during the recent decades, the physical background has changed a lot duo to climate changes and human activities, and result in the hydrological alteration. The most direct effect of hydrological elements’spatiotemporal variation is that the hydrological series lost their consistency. How to uncover the regulations of hydrological alteration in the inconsistent hydrological series, select a best Inconsistent Hydrological Frequency Calculation Method (IHFCM) to the certain alteration condition, and analyze the uncertainty of the frequency calculation results, have become one of the fundamental and critical theoretical problems. The relevant research works were opterated from3aspects to solve the problem, first of all, the regional temporal and spatial scale hydrological alteration regulations were studied, then the uncertainty of IHFCM was analyzed, finally, the best chosen research of IHFCM was conducted.(1) Summarize of researchThe research background and meanings of regional water resources assessment problem in the changing environment were introduced, based on the internal and international study progress, the problem still exist and the research ideas was put forward, the contents of this paper was presented at the same time.(2)Regional temporal and spatial scale hydrological alteration analysisBased on the alteration formation and degree of hydrological series alteration diagnose results from the Hydrological Alteration Diagnose System (HADS), the general methods ofregional hydrological alteration regulations analysis at the scale of temporal, spatial and annual allocation were put forward. With the alteration results of difference temporal scale runoff series of Fengzhen and Cetianshuiku hydrological station located at the third grade region Upstream of Cetian Reservoir at Yongding River, the alteration regulations of temporal scale was uncovered, the results show that:the main factor that impact the altreration formation of annual, drought/flood and seasonal scale is the proportion of monthly runoff series included. The precipitation and runoff series of the third and fourth grade region in Upstream of Cetian Reservoir at Yongding River were chosen to study the spatial regulations, the results uncover that:the closest and most relevant fourth grade to the third grade is Datong and Shuozhou. Four indexes were chosen to study the annual allocation alteration regulations, they are Gini Coefficient GI, Consentration Degree Cd, Consentration Area D, Ununiform Coefficient Cv, the conclusion of the four indexes alteration results of Fengzhen and Cetianshuiku hydrological station show the uneven tendency of annual allocation.(3)The principle and methods of inconsistent hydrological frequency calculationThe principle of inconsistent hydrological frequency calculation assumes the inconsistent hydrological series was conposed with two components, one is relatively consistent random component, and the other is inconsistent deterministic component. The inconsistent component reflected by the deterministic regulations, and the consistent component reflected by the random regulations. Five IHFCMs were introduced based on this principle, and the characteristics were analyzed in the paper.(4)Uncertainty of IHFCM with the influence of linear tendency componentEnlightened by the parameters uncertainty research of hydrological model, the way to study the uncertainty of7IHFCMs under the influence of linear tendency componet was summarized, and based on that, the best chosen method of7IHFCMs was also put forward.The conclusions of abundant experimental statistics as follow:at the past condition, to the inconsistent time series with linear tendency component, the uncertainty degree of IHFCM that based on the jump analysis was the biggest, the other IHFCMs’uncertainty degree were very close to each other. At the telquel condition, because of the impact from deterministic component, the uncertainty of all7IHFCMs increased, the uncertainty degree of IHFCM that based on the jump analysis was still the biggest, the other IHFCMs’uncertainty degree were still very close to each other. Meanwhile, the value change of slope K would not disturb the distribution area of7IHFCMs.Considering uncertainty degree could not tell the good or bad of the7IHFCMs, the synthesized best chosen index based on the upper limit and lower limit of90%confidence interval was put forward in this paper. Synthesized best chosen index includes2parts; one is the best chosen index at the past condition, the other is the best chosen index at the telquel condition. The synthesized best chosen index results of the7IHFCMs show that, with the influence of linear tendency component, the IHFCM that based on the jump analysis was not good all the time, the other IHFCMs’ synthesized best chosen indexes were very close to each other. Based on the synthesized best chosen indexes results, the table of best chosen method was summarized in this paper, from that a best hydrological frequency calculation method could be chosen by the series length and slope if the linear tendency alteration appears in the inconsistent hydrological series.Because of the linear decrease tendency alteration happened in the hydrological series from the year of1956to2000, the third regionalization Upstream of Cetian Reservoir of Yongding River in the first regionalization Haihe River was chosen as an example. Based on the linear slope and series length, the IHFCM based on the exponent non-linear tendency method was chosen as the best method, to assess the water resources quantity at the past and telquel condition. The assessment results show that, the probability of Average Relative Tolerance (ART) between the calculation results and the reality value at the past condition in the interval from2.55%to18.40%was90%, the uncertainty degree was15.85%. While at the telquel condition, the probability of ART between the calculation results and the reality value in the interval from1.54%to20.75%was90%, the uncertainty degree was19.21%.(5)Uncertainty of IHFCM with the influence of non-linear tendency componentIn order to adjust the non-stationary and non-linear characteristics of hydrological series, the exponent non-linear tendency component was chosen to study the uncertainty and synthesized best chosen index. By the results of experimental statistics, among the hydrological frequency calculation results, the uncertainty degree of IFHCM based on jump analysis was biggest, the other IHFCMs’ uncertainty degree were very close to each other. At the telquel condition, because of the impact from deterministic component, the uncertainty of all7IHFCMs increased, the uncertainty degree of IHFCM that based on the jump analysis was still the biggest, while the uncertainty degree of IHFCM that based on the Hilbert-Huang Transform (HHT) and Wavelet Analysis changed much, the other4IHFCMs’ uncertainty degrees close to each other. Meanwhile, the value change of exponent parameter B would not disturb the distribution area of7IHFCMs.Because of the linear decrease tendency alteration happened in the hydrological series from the year of1956to2000, the third regionalization Upstream of Cetian Reservoir of Yongding River in the first regionalization Haihe River was chosen as an example. Based on the linear slope and series length, the IHFCM based on the exponent non-linear tendency method was chosen as the best method, to assess the water resources quantity at the past and telquel condition. The assessment results show that, the probability of Average Relative Tolerance (ART) between the calculation results and the reality value at the past condition in the interval from2.75%to21.35%was90%, the uncertainty degree was18.60%. While at the telquel condition, the probability of ART between the calculation results and the reality value in the interval from0.89%to21.58%was90%, the uncertainty degree was20.69%.(6)Uncertainry of IHFCM with the influence of jump componentThere are some difference between jump and tendency component, in order to adjust the characteristics of jump component, the Standard Jump Coefficient (SJC) was put forward to analyze the uncertainty degree of7IFHCMs with the influence of jump alteration, and based on that, the synthesized best chosen indexes of7IFHCMs were also brought forward.By the results of experimental statistics, the uncertainty degrees of7IFHCMs at the past condition were all less than15%, so the stability of all IFHCM is well. While the SJC equals to1%, the uncertainty degree of IFHCM based on the jump analysis was the biggest, but as the SJC increasing, its uncertainty degree recede rapidly and keep a low steady level. On the contrary, the uncertainty degrees of the other6IFHCMs were small when the SJC was little, as the growing of SJC, the uncertainty degrees mount up fluctuately.By the value of SJC of inconsistent hydrological series with jump alteration, the biggest synthesized best chosen index of7IHFCMs could be confirmed to calculate the hydrological frequency. The results show that, if SJC≤2%, the IHFCM based on the exponent tendency is best, while SJC>2%, the IHFCM based on jump analysis is best all the time.Because of the jump increase alteration happened in the hydrological series from the year of1956to2000, the third regionalization Jimunaizhu River in the first regionalization Northwesten Rivers was chosen as an example. Based on the value of SJC, the IHFCM based on the jump analysis was chosen to assess the water resources quantity at the past and telquel condition. The assessment results show that, the probability of ART between the calculation results and the reality value at the past condition in the interval from0.04%to0.61%was90%, the uncertainty degree was0.57%. While at the telquel condition, the probability of ART between the calculation results and the reality value in the interval from0.15%to1.93%was90%, the uncertainty degree was1.78%. The synthesized best chosen index results of the7IHFCMs show that, with the influence of exponent non-linear tendency component, the IHFCM that based on the jump analysis was not good all the time, the other IHFCMs’ synthesized best chosen indexes were very close to each other. Based on the synthesized best chosen indexes results, the table of best chosen method was summarized in this paper, from that a best hydrological frequency calculation method could be chosen by the series length and exponent parameter if the exponent tendency alteration appears in the inconsistent hydrological series. |
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