Vízügyi Közlemények, 1974 (56. évfolyam)

1. füzet - Kovács György: A felszíni lefolyás általános vizsgálata és az árvizek előrejelzése

52 Dr. Kovács György as the most important requirements. In this latter domain field- and laboratory studies of considerable interest have already been started. It is expected from the data to indicate the correct choice of the parameters that are of greatest influence on the full process of gathering. These efforts should be continued with unchanged effort. A fundamental condition for the selection of the most relevant models is the comparison of analytical and observation results. As an interesting advancement in this domain a double check (on discharge and time difference) for the simulated and observed data series (records) has been suggested. Moreover, no check can be run and no systems analysis performed, unless an observation network of the necessary density is available , which is capable of yielding the essential, corresponding data at sufficiently short time intervals. Fundamental studies (e. g. concerning the spacing of observations in time) have been performed in part, or are under way. The most important task related to model formulation is thus the modernization of the observation network. These model have a wide variety of potential uses, including the replacement, or completion of past and incomplete records, the determination of parameters dominating surface runoff, further the estimation of potential consequences of any contemplated interference, wTien planning water projects. The most important field of application is nonetheless the prediction of hydrological characteristics in periods with extreme water regimes. If it is intended, however, to increase the time advance of forecasts and to use the models for flood forecasting on the basis of precipitation data, a limiting factor is encountered, in that the volume of the generating rainfall must be known as the input value to the model. It is therefore deemed desirable to intensify research on quantitative rain forecasting. The results attained thus far are already of great interest and often complement each other organically, but sometimes parallel research is conducted unnecessarily by several research groups operating individually. It is thus suggested to establish the possibility of regular discussions on such problems, as primary objectives of which the practical applications of models and the discussion on the formulation of operative models can be mentioned. 3. The base flow of rivers Unfortunately very little data are available which would yield information of the interrelations between rivers and groundwater. Thus the level of research directed at the determination of base flow, the exploration of the dependence thereof on physico-geographical parameters and on climatical processes is below the desired standard and the results fail to meet the demands of practice. From the foregoing it will be perceived that a fundamental prerequisite for further research work is the commencement of more detailed, more reliable data collection work, organized specifically for the exploration of the interrelation mentioned before. In designing the network reconstruction contemplated allowance has already been made for these requirement. Thus the first-order stations along rivers will be provided with a group of groundwater wells permitting the groundwater inflow to the river, or the supply to groundwater therefrom to be estimated. Over experimental sections between first-order river stations continuous flow measurements are suggested in low-water periods. The changes in streamflow between the stations would vield information on variations in base flow. An important method of data collection involves the regular and continuous observation of the concentration of natural radioactive isotopes present in the water. Such observations have been started with an experimental character and with promising results. Direct research work has resulted thus far in largely negative conclusions. It was demonstrated that the simple exponential discharge curves widely suggested in the relevant literature are not applicable, because of their poor accuracy to the great rivers in Hungary. Owing however, to the complexity of the process, this conclusion was anticipated. In a single section, namely Vásárosnamény on the Tisza River, W'e succeeded in establishing a double-exponential relation, which described fairly well the reduction in streamflow, but owing to differences in environmental conditions along the successive river sections, no generalization of this result appears per-