Combining the fundamentals of the fuzzy sets with natural hydrological phenomena,a method offuzzy statistic analysis is given in this paper for computing hydrological parameters,analysing relations among va-riables and identifying systematical hydrological models.

The advanced hydrological conceptual model is adopted and modified by diving the catchment into sub units for calculation of runoff yield and flow concentration in order to consider the unevenness of hydrological phenomena.

Based on the physical principles of hydrological phenomena in small forested watershed, a mathematical model of rainfall-runoff process is proposed and validated in this paper. The model is used to analyze and predict runoff changes caused by clear-cutting or afforestation.

With the aid of some methematical formulas and computer techniques, the hydrological process of the system, which includes flow interception, surface flow, stared in soil, groundwater and the other hydrological phenomena, can be systematically simulated in a quantitative form.

Prediction of hydrological phenomena using self-organizing mathematical models

Bacterial concentrations varied widely in every reach due to fluctuations of loading and/or hydrological phenomena.

Earthquakes cause a variety of hydrological phenomena, including changes in the ground water levels in bore wells.

Study of hydrological phenomena by extreme value theory

The method of Relative Entropy with Fractile constraints (REF method) is explained and applied to model extreme compound hydrological phenomena, such as extreme sea levels under storm conditions.

This paper attempts to answer the following two questions: (1) Is it possible to derive the law of distribution of hydrological frequency theoretically(2) What type of distribution curve should be adopted as the model of hydrological frequency curve and how to determine their parameters? The results obtained may be summarized as follows: 1. Hydrological phenomena are time series with concealed periodic fluctuations. The results from statistical analysis based upon the current assumption that hydrological...

This paper attempts to answer the following two questions: (1) Is it possible to derive the law of distribution of hydrological frequency theoretically(2) What type of distribution curve should be adopted as the model of hydrological frequency curve and how to determine their parameters? The results obtained may be summarized as follows: 1. Hydrological phenomena are time series with concealed periodic fluctuations. The results from statistical analysis based upon the current assumption that hydrological phenomena are independent stochastic variables should be accepted with due considerations. 2. In view of the regional nature of hydrological phenomena, the current parctice of analyzing samples taking from a single station only is, in effect, to narrow the sampling field arbitrarily from a larger area to a point, thus reducing the accuracy of the statistical results. Hence, the synthetic utilization of the data of all stations within the hydrologically homo- geneous region is an important measure to increase the accuracy of statistical analysis. 3. The belief that the flood frequency obeys the binomial theorem or Poisson's theorem is but to mix up the priori with the empirical probability problem. The binomial theorem, being a powerful weapon to deal with the problems of priori probability, has not been adquately and properly utilized in the hydrologieal frequency analysis. 4. Analyses have been made of the nature of distribution of shydrologieal series on the basis of Kaptyen's derivation of the skew distribution, which indicate: (1) That the theoretical interpretation of the log-probability law of the hydrologic phenomena by V. T. Chow is not sound; (2) that hydrologic phenomena being results of very complicated meteorological and hydrological processes, it is impossible to derive theoretically the law of distribution for the hydrological series. 5. The view that the flood frequency obeys the Gumbel's distribution is theoretically not sound and also not verified by actual data. 6. According to the nature of the mathematical treatments applied, the method of description of the empirical probability can be classified into three systems: (1) The methods of the generalization of the characteristic factors of the distributions, such as Pearson's curves, Goodrich's curves, etc.; (2) The methods of the modification of a fundamental distribution by series and polynomials, such as Gram-Charlier curves. curves, etc.; (3) The methods of transformed functions, such as the log-probability law, curves, etc. It should be remarked that not only Pearson's and Goodrich's curves are frequency curves of empirical nature, but even the theoretical laws, such as the normal law and the log-probability law, will be aceepted as curves of empirical nature, when used as models for empirical probability problem. 7. Hydrological frequency analysis should not be mystified and made absolute. Instead of free selections, the models of hydrological frequency curve should be uniquely selected and specified. Statistical parameters should be determined not solely by the short period data of single station, but also by the synthetic utilization of the data of possible more stations. 8. It is recommended that one of the two types of distribution, i.e. the log-normal frequency curve with both sides limited and the Pearson's type Ⅲ curve, may be selected as unified models. The author suggests that the K-value corresponding to recurrence intervals of say 10~4, 10~5, or 10~6 years may be selected as the upper and lower limits for the log-normal curve. For Pearson's type III curves, C_s should be treated not as independent but as dependent variables of C_v. 9. The proper way to select and determine the model frequency curve is to see whether it fits well with the actual data of grouped stations (stations to be grouped by regions for rainfall data and by C_v for runoff data) and the reasonableness of the extrapolating part. 10. Suggestions on the method of determination of x and C_v: For point rainfall, iso-x map may be utilized, and the mean C_v for each hydrologicregion may be adopted in order to minimize the errors from single stations and to avoid the discrepancies in results obtained from the same region. With regard to flood frequency analysis, flood mark reconnaissance must be utilized to determine the magnitude and the recurrence interval of the unusual flood. The x and C_v values of the floods and runoffs of hydrologically similiar river basins may be compared. Besides, the reasonableness of the results of frequency calculations as well as of the statistical parameters adopted therein may be checked by comparing runoffs and point-rainfall values of the same frequency.

Based on the physical principles of hydrological phenomena in small forested watershed, a mathematical model of rainfall-runoff process is proposed and validated in this paper. The model is used to analyze and predict runoff changes caused by clear-cutting or afforestation. The results show that forest felling makes both runoff amount and peak flow increase and afforestion decreases the amount and peak flow. But these effects almost disappear when rainfall is extremely heavy.

In this paper, a mathematical model of the hydrological cycle of the forest set up on the basis of a man-made forest which originated from a bog land in the suburbs of Edinburgh in southern Scotland is described. The whole process is abstractly recognized as a forest ecosystem with 5 compartments, namely, trees, grasses, ditches, ditch slopes and ditch bottoms. With the aid of some methematical formulas and computer techniques, the hydrological process of the system, which includes flow interception, surface...

In this paper, a mathematical model of the hydrological cycle of the forest set up on the basis of a man-made forest which originated from a bog land in the suburbs of Edinburgh in southern Scotland is described. The whole process is abstractly recognized as a forest ecosystem with 5 compartments, namely, trees, grasses, ditches, ditch slopes and ditch bottoms. With the aid of some methematical formulas and computer techniques, the hydrological process of the system, which includes flow interception, surface flow, stared in soil, groundwater and the other hydrological phenomena, can be systematically simulated in a quantitative form. The amounts of rainfall and evaporation are put into the model and the runoff water is drained away from it- It is given here for an example to simulate the hydrological process of the system in 1986 and check the simulation efficiency. Through comparing the computed and observed flows of the forest ecosystem, it is found that the simulation efficiency is 93.5% on the daily basis and 85.1% on the two-hour basis.The model reveals the mechanism of the hydrological cycle of the forest. We can estimate the runoff by using the amounts of input pricipitation and evaporation only. It will be helpful to understanding the hydrological effect of the man-made forest which originates from a bog land.