Vízügyi Közlemények, 1947 (29. évfolyam)

1-4. szám - VI. Szakirodalom

(17) гпеад discharge. Table I in this study is giving q

0, qk and Qk values for some investigated areas in the Carpathian Basin. Indexes derived from these values are characteristic for meteorological, topographical and geological conditions prevailing in the watershed area. The hydrograph must be fixed through a carefully plotted discharge curve with regard to modifications of the river bed subsequent to floods and well aware of the laws of runoff in winter time (Methods of STOUT or of KOLUPAILA). Owing to lack of hydrographical data, characteristic discharges are often to be determined, at least approximately, from precipitation data. Figure 3 shows a map of precipitation for the Eastern mountainous region of the Carpathian Basin. (The isohyetal lines are based on the average rainfall of 30 years.) The author, after having elaborated the readings of 121 observing stations (Table II), comes to the conclusion, that in the Carpathian Basin the ratio of annual precipitation of an average year to that of the most arid year may be regarded as constant, numerically: 1,56 (Formula 7). In Table II ja run-off coefficients, characteristic for arid years, are given in the function of both the geological characteristics and altitude of the drainage area. Average annual values of the run-off coefficient are given after BOGDÄNFY, LAUTERBURG and KENESSEY and in conclusion the author gives an account on the values computed on the basis of his own observations. In case of mountainous drainage area, modification of rainfall according to altitude (31) is also to be taken into consideration and for its computation for the Carpathian Basin the correction formula of HAJÓSY (Formula 8) is used. The formula in question gives, however, merely the normal increase of precipitation from which, according to topographical conditions and to the cardinal points, a certain deviation of positive or negative character can be observed. Mountains in general are showing a deviation of positive, while valleys in general are showing a deviation of negative chai acter. A map of rainfall isanomalia for the area in question has been prepared by HAJÓSY. If the hydrograph has been drawn up, this way or the other, for detailed study of the storage effect the mass curve is highly appropriate. Its graphical treatment is shown in Figure 4. Determination of evaporation and seepage losses belongs also to the sphere of hydrological investigations. Evaporation and seepage losses in reservoirs (Jq) are given in m

3/sec by Formula 10, where p means annual evaporation in mm, F means average surface of the lake and ш means annual seepage in m

3. According to readings and observations made by the Water Power Office and by the Meteorological Institute, evaporation losses in arid years in the Viso valley amount to 1,0—1,5 per cent. b) Topographical Conditions of Storage. Topographical conditions of the basin are characterized by the storage curve, giving the relation of storage level (height of dam гщ) to capacity (S) (See Figure 5). This function in case of the Visó reservoir is given by the author also in mathematical form as shown in Formula 11. The height of the dam is dependent on the distance of the dam site from the outlet of the basin and on the slope in the narrow section. Under unfavourable conditions the lowest — unuseful — part of the dam may happen to be very large. The situation is shown in Figure 6. Type and size of the dam are determined by the topographical conditions in the narrow, having thereby a great bearing on costs of stored water. Topographical conditions may be imperative for the upper limit of technically or economically realizable basin stinting thereby the output of the reservoir. In Figure 7 characteristic cross sections of the dam site are shown, where the corresponding volumes of dam — with presupposition of a gravity dam — are given in Formula group 12. c) Geological Conditions of Storage. The geological conditions are having a twofold effect upon the size of reservoirs: 1. The geological factors are modifying run-off and thereby the necessary storage area, 2. Geological conditions are effecting the size of technically or economically realizable basins. Drainage areas in the Carpathian Basin, with regard to the character of flow, may be divided into three groups (grouping is based principally on geological conditions, although there are other factors: topographical conditions, forestation, winter temperature etc. which are equally eftective): 2