Vízügyi Közlemények, 1961 (43. évfolyam)

4. füzet - IX. Képek a Föld különböző részeinek vízépítési munkáiról

(37 > The time of occurrence of the flood peak i. e. the travel time t can be forecast on the basis of the appropriate combinations of the following data: the peak stage H observed at the upstream station, or forecast for the downstream station, the travel time V observed over an upstream reach, and the rise Ah forecast for the downstream station (Figs. 12 and 13). For preparing continuous, daitg discharge, or stage forecasts for a longer river reach, a practicable start can be made by compiling the profile of changes in discharge during unit time [Figs. 15 and 10, Eqs. (8) to (13)]. For preparing the forecasts the relationships characterizing the changes in shape and the progress during unit time of the waves must be established (Figs. 17 and IS

) [13]. The forecasts are prepared by shifting from time unit to time unit a few characteristic points of the waves (Fig. 20). In order to issue continuous forecasts on the basis of precipitation data, the rainfall vs. runoff relationship characteristic for the catchment under consideration, and the unit flood-hydrograph must be determined (Figs. 21, 22 and 23). Continuous forecasting of snowmelt runoff is illustrated in Figs. 24 and 25. The initial step in forecasting the highest spring stage of lakes consists of the determination of the relationships existing between the autumn-winter precipitation (C), the water surplus of the antecedent year (Fe), the mean temperature of the winter months (/) and the total annual rise of the lake level (Ah) (Figs. 20 and 27). Separate forecasts should he- prepared for several assumed precipitations, or for such adopted as significant (Fig. 28). III. Forecasting average and extreme values The long-range forecast of summer runoff relies on the indices representing water accumulation during the winter [see Eqs. (17) to (20)] [10]. The weighting ratios a, b and с characterizing the periodical and areal distribution of precipitation data can be determined by correlation (Table I, Figs. 29 and 31). The forecast which is in general issued at the beginning of April (Fig. 30) can be improved from month to month (Fig. 32). Instead of the indices according to Eqs. (17) and (20) the problem can be solved also by correlation diagrams involving several variables (Fig. 33). Instead of the total annual runoff it will be found frequently expedient to include the underground runoff determined according to Fig. 2 into lhe evaluation. By separating the surface and underground runoff, a possibility is offered for the long-range forecasting of summer low-water discharges as well [17]. Smallest discharges and lowest stages to be anticipated after the passage of flood waves can be forecast by investigating the recession curves. Information on the expected lowest values can be gained by determining the lower envelopping line of the recession curves (Fig. 34). The more detailed procedure according to Fig. 35 includes allowance for the actual water regime, and the forecasts can be gradually improved thereby. In the "concluding part of the paper a review is given on the development and present state of Lhe forecasting service in Hungary (Table II.). (Author's summary translated by '/.. Szilvássg struct, eng.) EINIGE METHODEN DER VORHERSAGE DER ABFLUSSVERHÄLTNISSE von Dr. K. Szesztag (Ungarischer Text Seite 249) Diese, von der Ungarischen Akademie der Wissenschaften preisgekrönte Arbeit fasst die Ergebnisse einer mehrjähriger Arbeit zusammen, welche zwecks Förderung des ungarischen hydrologischen Vorhersagedienstes in der Forschungsanstalt für Wasserwirtschaft durchgeführt wurde. Kapitel I. und IV. geben einen kurzen Überblick der hydrologischen Grundlagen der Organisierung des Vorhersagedienstes und der Entwicklung desselben in Ungarn. Kapitel IL, der bedeutendste Teil der Abhandlung, beschäftigt sich mit der Vorhersage einzelner Abflussereignisse (Vorhersage der Hochwasserwellenscheitel, fortlaufende tägliche Vorhersagen der Wasserstände und Abflussmengen von Flüssen, Vorhersage der höchsten Früh-