Vízügyi Közlemények, 1948 (30. évfolyam)

2. szám - VII. Szakirodalom

(4) HYDROLOGICAL DESIGN OF LARGER STORAGE RESERVOIRS.

1) By E. MOSONYI. (See Pages 13—101 in the Hungarian text.) D. C. 627.81. IV. NECESSARY CAPACITY FOIt STEADY CONSUMPTION OF DEFINITE CHARACTER AND INTENSITY.

2) 1. Uniform Consumption. a) Annual Reservoir. In connection with the determination of storage capacity for an annual reservoir, it is the 12 month period subsequent to the melting of the snow that is to be taken into consideration. To distinguish this period from the years both calendar and hydrological, in the following the term of ,,storage year

" will be introduced. The storage year in the Carpathian Basin begins usually in the month of March. The decisive storage year for an annual reservoir is the one among rhe driest 12 month periods where distribution of run-off proves to be the most unfavourable (Figure 18.). Consequently: 1. the dry 12 month periods of the past years are to be selected and 2. out of these the ones where distribution of run-off happens to be of the most irregular character (i. e. where discharges following the spring flood are showing a falling tendency in general) are to be examined. Examination of two groups of easily available meteorological records may largely simplify the work of selection. It is satisfactory if the year-groups selected with regard to the annual precipitation and to the mean temperature of winter months (JanuaryMarch) in the subsequent year are drawn under thorough examination in the form of detailed hydrographie treatment. Selection of the decisive year means a great deal of work, especially when we bear in mind that for getting a satisfactory result, examination of an at least 30—40 year period is wanted. In areas with sporadic observing stations or in case of lacking records, the examination is entirely impossible and the hydrograph of the decisive storage year in many cases cannot be reconstructed at all. Determination of total run-off in the decisive storage year is somewhat easier, because in a 40 year period there are several dry years where run-off is almost or entirely equivalent to that of the decisive dry year, even if in view of distribution of discharges an essential difference prevails. In his examinations one of the author's aims it was to find the laws of the decisive hydrograph. For this purpose the meteorological and hydrographical conditions of 1942—43 were exceptionally favourable. On the basis of long-period hydrographe for the Eastern Carpathian Basin it has become obvious that in 1942—43 minimum and mean discharges of several streams were below the corresponding figures of the well-known arid year of 1904. Consequently the storage year beginning in the spring of 1942 was decisive as far as total run-off is concerned. Based on records for certain streams systematically observed in the past 40 years (Table V.J the author proves that for the examined area the aforementioned storage year can be regarded as decisive even in view of temporal distribution of discharges. The most unfavourable hydrograph for determinating necessary storage capacity is approximated by a parabolically decreasing curve based on the author's theoretic conceptions as shown in Figure 19. and in Formulae (22) and (23) where I and q denote the two variables: time and discharge respectively. Introducing the m index of extreme discharges (Formulae 24 and 25) and the relation between annual total run-off and variable discharges we come to Formulae (26) and (27). In computing storage capacity it is advisable to draw up the mass curve of the discharge-function, ordinates of which are given by 1 Chapters I —III have been published in Nos. 1 — 4 of 1947 of this periodical. 2 Chapter IV/la of this study is a dissertation for doctor's degree approved by the Board of civil engineers, University of Technical Sciences (Budapest).