Flood risk is a very important subject in hydrology. Firstly, the exact meaning of flood risk has been discussed, and two concepts of flood risk in the current situation, time risk and annual risk, have been pointed out. In the former, Both risks resulting from annual maximum flood and submajor flood are considered simultaneously in the design. In the latter, only risk resulting from annual maximum flood is considered in the design. Secondly, frequency or probability is defined as flood risk degree in this paper. While time frequency corresponds to time flood risk degree, annual frequency corresponds to annual flood risk degree. Lastly, the analysis and calculation show that the standards for flood control of annual flood risk degree and time flood risk degree are different from each other. The difference between annual flood risk degree based on annual maximum flood value and that based on annual maximum and submajor flood value has been discussed. The former accords with current standard for flood control of water-related engineering, whereas the latter is not consistent fully with the current standard for flood control.

The manage-flood is very important for flood control safety and economic effectiveness of reservoir engineering. There are two approaches which can be used to calculate the manage-flood at present, i.e., one is based on Copula functions, and the other is based on the principle of total probability. The latter can be divided into direct method and indirect method. The direct method based on the principle of total probability is explored in this article. The flood data for calculation of manage-flood have been divided into three condition:Sufficient data condition, relatively sufficient data condition and insufficient data condition. For sufficient data conditions, the length of flood data series in main flood season is greater than 30 years and the length of flood data series in pre-main flood season and post-main flood season is no less than 20 years, respectively; For relatively sufficient data condition, the length of flood data series in main flood season is greater than 30 years and the length of flood data series in non-main flood season is no less than 20 years; For insufficient data condition, the length of flood data series in main flood season is greater than 30 years and the length of flood data series in non-main flood season is less than 20 years. The calculating methods of manage-flood for three flood data conditions have been presented based on the principle of total probability in this paper. For sufficient data condition, the mathematical expect formula of total probability has been adopted with frequency analysis; for relatively sufficient data condition, the mathematical expect formula of total probability with combined data in non-main flood season was applied; for insufficient data condition, the back calculation approach was presented, and the formula of manage-flood based on the principle of total probability has been suggested. The case studies for calculating of manage-flood in different flood data conditions have been given for different basins. The comparison of the suggested method to the method of Copula function has been discussed. The results have showed that the suggested method is better than the method of Copula function, and the designed value of manage-flood is reasonable.

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 fixed the limits water level of reservoir in flood period.

Engineering potential destruction risk caused by flood can be presented by the frequency of annual highest stages in front of engineering (Hm).A quantificational relational expression among annual highest stages,flood peak discharge (x) and flood volume (y) is established based on the condition that flood hydrograph was generalized into a triangle.And then,based on the stochastic simulation method,the annual highest stages (Hm) N are calculated according to the flood prevention standard.Therewith,the combinations of flood peak discharge and flood volume are analyzed by satisfying the standard.Results have shown that calculation was above the flood prevention standard on the condition of the combination that flood peak discharge and flood volume have the same frequency.In addition,the variation of engineering's characters of flood prevention have impact on Hm.

According to the study on flood hydrograph, the new concept of specific flood hydrograph and its connotation were pro-posed. Meanwhile, the external and essential implication of engineering flood prevention standard were expounded. And then the re-lationship that was the new concept of external frequency of flood hydrograph between specific flood hydrograph and flood preven-tion standard was drawn. The specific flood hydrograph of three types of transformation and its calculation method were elaborated. The advantages and disadvantages of the common multiple method and the common frequency method of specific flood hydrograph were pointed out. A brief introduction about the basic idea of new calculation method of specific flood hydrograph was given.

Bivariate return periods of floods,with peak flood discharge x and flood volume y as variables,are important to calculation and evaluation of flood control in hydraulic engineering.For a flood event,calculation of its return periods much depends on its components and how to match the demands.This paper discusses and calculates four types of return periods using the Copula function theories-univariate return period N1,OR-event return period N2,AND-event return period N3,and matching retum period N4 -focusing on the demonstration of N4.And the four return periods are compared in a case study of the Mabian hydrological station of the Mabian River,a branch of the Minjiang River.The results show that for a given set (x0,y0) of the bivariate variables,the values of these periods are quite different.When both x0 and y0 are large or small,they follow a decreasing order of N3＞ N4＞ N1＞ N2;when x0 is large and y0 is small or y0 large and x0 small,N4 could become possibly much larger than N3 or even smaller than N1.Thus,attention should be paid to the special properties of the Copula functions and we recommend the use of bivariate matching values N4 in flood control calculations.

The manage-flood, a new concept, is firstly proposed for reservoirs engineering management, and compared with the design-flood. The same and differences between the two kind floods have been analyzed in detail. Two standards for judging the rationality of the manage-flood has been proposed in this paper, one is about such condi-tions that are satisfied to some management demands, and the other is about flood control safety that is satisfied to the standards. This paper summarized two kinds of analysis methods about the manage-flood. One method is based on the maximum of seasonal flood, and the other based on the maximum of the annual flood. The two methods have respective advantages and disadvantages. The results of the former can′t conform completely to the flood control standards while the former has lower requirements for observed data. The results of the later can conform the flood control standards but the later has higher requirements for observed data and no application experiences.

In the definitions of water resources carrying capacity at the present stage, for the unpredictability of subject ( i. e. water re-sources) over time and the objects involved in water resources are too theoretical, abstract and general, calculation results about water resources carrying capacity are often difficult to guide practice. This paper integrates the concept of design into water resources carrying capacity, and proposes the exact definition on the design carrying capacity of water resources. Based on the design guarantee rate of wa-ter supply and development pattern, the corresponding amount of water supply and water consumption are respectively calculated, and the maximum number of population carrying capacity can be deduced on the basis of water supply and demand balance. The case study shows that the calculation method about design carrying capacity of water resources is simple and practical.

从确定性与不确定性的角度,探讨了相似预测的基本理念并论述其应用于水文学的基础,以此提出了从选取特征矢量到构造预测量的完整算法.重点分析构造预测量的方法,通过分析未来出现的数值可能围绕均值左右摆动的特性,并促使应用者主动考虑预测值的不确定性,提出平均区间和序位区间的概念,为区间预测方法研究提供参考.将此理念及方法应用于宜昌站1890-2010年的年平均流量资料进行检验,结果表明:该方法对宜昌站年径流量的预测效果较好,能较好地描述径流在年尺度的变化,又能促使应用者发挥主观能动性,主动考虑预测值的不确定性.

The concepts of time-risk and annual-risk were respectively presented based on the annual multi-samples method and the annual maximum sample method aiming at the inconsistent of return periods about design rainstorm in the municipal and water conservancy systems.The risk of municipal system was caused by the annual biggest flood or the second flood or others, but the risk of water conservancy systems was caused by the annual biggest flood.Taking the storm data in Guangzhou city as an example, the relationship between the two kinds return period was deeply analyzed.Results show that the return period of municipal system is not more than water conservancy system.The key to change the two return periods into accordance is unifying the two risk concepts and adopting the annual maximum sample method.

论述以下几个关键问题:①涉水工程防洪安全设计零风险理念导致极限洪水新概念;②极限洪水的四大特性;③可能极限洪水的新见解;④极限洪水和万年一遇洪水既对立又统一,不能孤立地对待;⑤在敲定极限洪水采用值时合理性分析至关重要.

The nearest neighbor method ( NNM) based on hydrological similarity is a data?driven prediction method, the use of which allows for avoiding making certain assumptions about the dependence and probability distribution forms of objects of study. One of the key factors that affect the quality of the predicted results using this method is the selection of the measure of the similarity in eigenvectors. In order to give consideration to the information about“direc?tion” and “quantity” while measuring similarity, this paper tries to couple Cosine distance and Euclidean distance to the technical indicator for similarity after thoroughly analyzing their differences and similarities. The nearest neighbor method based on coupled similarity indictor was used for the annual runoff prediction of Yichang hydrological station and Tangnaihai hydrological station, and the annual runoff data for different hydrological characteristics were used for checking. The results show that the nearest neighbor method based on the coupled indicator can appropriately predict annual runoff. It is an effective, feasible method.

水文现象具有确定性和不确定性,常用确定性方法和不确定性方法分析.这两种方法在水文学中广泛应用并愈来愈密切耦合.对这种耦合的背景、实质和途径等进行了初步分析.给出了水文学确定性方法和不确定性方法耦合的内涵;分析了耦合的客观背景,指出确定性和不确定性辩证的统一、不确定性和确定性在一定条件下相互转化是耦合的哲学基础;总结了耦合的三大主要途径:(1)简单混合.对某一个水文问题的解决分成两个部份,一个部份用确定性方法,另一个部份用不确定性法;(2)一般嵌入.指在某种分析法的总体框架下,局部或某些部分嵌入另一种分析法以达到提高分析可靠性之目的;(3)复杂的渗入.指两种方法相互渗透,充分发挥各自特色促使耦合效应独突.

The paper builds BP network predictive model of long-term variation of annual runoff of the middle and lower Yellow River by using improved algorithm of BP network and the time series of natural annual runoff of Shaanxian Hydrometric Station on the Yellow River in 531 years based on neural network theory and traditional analysis.It conducts predictive analysis on the variation trend of natural annual runoff of the middle and lower Yellow River during the period of 2001-2050 by using the model.The outcomes show that a) the general variation trend of natural annual runoff of the middle and lower reaches in the next 50 years is that wet time interval modest gains than that of dry time interval,undergoing relative wet time interval of 2001-2020,relative dry time interval of 2021-2026,relative wet time interval of 2027-2037 and relative dry time interval of 2038-2050 and;b) the general trend of variation of natural annual runoff of the middle and lower reaches is basically the same as that of the upper stream,but the continuous dry time interval happened in the middle and lower reaches is longer than that of the upper stream.

Based on the data of the flood losses in Sichuan Province from 1976-2006, a model for assessing the degree of flood disaster in Sichuan Province based on pursuit projection method is established. In the model, the population of disaster area, the number of dead, the comparative economic loss due to the floods and the stricken agricultural area by flood are the main indexes. The result indicates that Sichuan Province has been severely suffered from flood disaster, and the distribution of flood is similar every 10 years in recent 30 years. It also shows that disaster happens in each 10 years, in which 3 or 4 are severe. The degree of disaster does not change with time. The flood volume and the disaster grade are not compatible.

Abstract:In order to predominate comprehensively the abidance situation of water quality indexes of 12 representative inspection stations of main river in Sichuan Province, and to study the scheduling trend characteristic of water qualities, the article analyzed the pollution characteristic and scheduling trend characteristic. It is first time to use the runoff curve takes a period of time to study the continuance circs of each chemical index. By analyzing the water chemical indexes of each inspection station in Sichuan Province, it show that water quality characteristic analysis reflect the water quality of each inspection station, and water quality model of the runoff curve takes a period of time can reflect the river pollution continuance status preferably and intuitionisticly. Key words: water chemical element; pollution analysis; character analysis; scheduling trend analysis; the runoff curve model takes a period of time

Most traditional assessment methods, which have complicated mathematic formulas, are difficult for calculation and application in water resources system assessment. A new approach to water resources system assessment, the set pair analysis method (SPAM), has been proposed based on the principle of set pair analysis (SPA). The basic ideals and steps of SPAM are discussed. The proposed method can take fuzzy property of threshold values for grade standards into full account and avoid determining the discrepancy uncertainty coefficient i or i 1 , i 2 , i 3 , ... in SPA. The presented method is simple in concept, convenient to calculate and feasible for application. Two case studies of water resources assessment have been made. The results show that the proposed method is satisfactory.

The improved bayes model was proposed based on surface water quality assessment system.In the Bayes formula,the likelihood probability was calculated by sample error normal distribution principle.The Bayes model was applied to annual water quality assessment of 12 representative stations of 8 main rivers in Sichuan.After obtaining the results of river water quality in more than 30 years,the further analyses were performed for the durations of 1971-1988 and 1990-2004 respectively.The results show that the Bayes model reflects the true water status and pollution actuality of main rivers in Sichuan roundly and objectively,which provides a new approach to river water quality assessment.

Set pair analysis has demonstrated its unique advantage as a new evaluation method,but the connected weight coefficient value has been a perplexing problem.On the evaluation and class issues,this paper presents a simple way to gain the value of the connected weight coefficient.Then the assessment for the renew ability of water resources are studied by five-element connection number of the set pair analysis method.The study of practical examples shows that the method is simple and visualized.

Aiming at the chaotic time series,this paper presents the model of Kalman filter in the chaotic phase space combined with the chaotic theory and real-time adjustment technique of Kalman filter.The phase spots are looked as states and described in state space.Using Kalman filter model,the evolution law about the phase spots is predicted and revised on real-time.Then application on short term forecasting of daily power load of Sichuan province is discussed.Because it follows complex nonlinear locus well,the new combined model gets good forecasting precision.The prediction result shows that the method is effective.