Vízügyi Közlemények, 1997 (79. évfolyam)
4. füzet - Goda L.-Vasvári V.: A Felső-Rába vízjárásának statisztikai jellemzése
536 Goda L.— Vasvári V. VGI (Vízgazdálkodási Intézet): Magyarország vizeinek műszaki-hidrológiai jellemzése; Mosoni-Duna-ág, Rába, Vízgazdálkodási Intézet, Budapest, 1989. Wundt, W.: Die größten Abfluspenden in Abhängigkeit von der Fläche. Die Wasserwirtschaft 1949/50, Heft 2. 1949. Zsuffa /.. Műszaki Hidrológia. Tankönyvkiadó, Budapest 1985. * * * Statistical characterization of the flow regime of the Upper Rába river Dr. László GODA jr. and Dr. Vilmos VASVARI civil engineers The hydrological-statistical analysis of the catchment of the Upper Rába river of about 6,000 km 2 area, was carried out for obtaining knowledge on the flood characteristics of the basin as a whole and for that on the natural water resources. Calculations were made with a Hungarian software called the "Programme Package on Technical Hydrology". Results include probability distribution functions and hydrological longitudinal profiles and three-dimensional function "surfaces", derived from these functions. Time series of 25 gauging stations (See Figure I.) were utilized for this analysis. Description of flood conditions was based on the analysis of annual high flows (Table I.). Figure 2. shows and example of the probability distribution curves fitted to the annual high flow time series of each of the 25 stations. Extrapolation of the values obtained for the gauging stations was made in the form of longitudinal hydrological flood profiles. Flood flows of unknown stations were calculated by flood-equation 6. The exponent value of 0.77 of Eq. 6 and the flood coefficient apo / o were determined on the basis of Figure 3., which shows the 1 % probability flood values of monitoring stations in function of the drainage area. In order to check the results the longitudinal profile of flood coefficients can also be plotted (Figure 4.). High flows of 1., 3, 10 and 50% probability of exceedance have been plotted in the longitudinal flood profile of the River Rába (Figure 4.). Other characteristics of floods, such as the length and frequency of flood hydrographs can also be investigated by the means of mathematical statistics (e.g. with the „Crossing method"). Distribution of the annual longest floods is shown, in function of the base flow, in Figure 5. for the Feldbach station of the River Rába. This figure can be interpreted as for example the probability that the duration of the annuel longest flood will exceed 5 days is 2%, when one considers 40 m 3/s as the base flow. The potential water resource of the water courses were characterized on the basis of processing the time series of annual mean flow. The longitudinal profile of mean flow is also shown in Figure 4. More detailed analysis of available water resources was made on the basis of the time series of daily mean flow. Duration curves were determined for the whole year, for summer and winter half years, for the May-August period and for the months August and September. In selecting the representative periods Figure 7. provided an aid, showing the annual variation of the multiannual average of monthly mean flow. Water resources of the whole river system were estimated on the basis of the specific (unit area) water resource values of the monitoring stations (Table II.). The assumption of linearity between the natural water resource and the catchment area is jutified by Figure 8., showing the flows of 90% duration of the gauging stations in function of the drainage area (in double logarithmic scale). The intercept method, used for the more detailed analysis of floods, has also been used for investigation periods of water shortage. In this case, however, the analysis were made for the "valley" periods of the time series, that is for those falling below a specified flow Q 0 defined as the water demand. * * *
