Vízügyi Közlemények, 1986 (68. évfolyam)

2. füzet - Nováky Béla: Kisvízfolyások vízhozamadatainak területi és időbeli elemzése

184 Nováky Béla » Pintér A.: A növénytermesztés vízháztartási feltételeinek vizsgálata. Tájékoztató a Vízgazdálkodási Intézet 1980. évi munkájáról. Budapest, 1980. Szesztay K.: A vízgazdálkodás vízháztartási adottságai Magyarországon. Vízügyi Közlemények LXIII. évfolyam, 3. füzet 1980. Szokotovszkij. D. /.. Recsnoj Sztok. Gidrometizdat, Leningrad, 1968. VGI: Magyarország természetes felszíni vízkészletét jellemző hidrológiai adatok gyűjteménye. (Témafelelős: Szalay M . kézirat). Budapest. 1979. Zsujfa I: Műszaki hidrológia. Tankönyvkiadó. Budapest, 1984. * * * Spatial and temporal analyses of discharge data of small rivers by B. NOVÁKY, Hydrologist Engineer Hydrographical activities were extended to the measurement of discharges of 150 small rivers in the country during the past 30 years. Length of the corresponding time-series is mostly less than 30 years. Spatial and temporal analyses of these discharge values, and of characteristics derived from this information could be expanded in time with due consideration on certain climatic elements which were observed usually for a much longer period in a much denser network. The author was engaged first in the analysis of interrelations between annual average flow and climate, and their areal distribution. Correlation between the climatic elements (X- annual average precipitation in mm, T- annual average temperature in °C) and the value of point runoff from an elementary catchment ( Y- in mm) is represented by Eq.(2). The catchment was subdivided into squared elementary areas by aid of an orthogonal grid. The meteorological characteristics for the calculation of runoff according to Eq.(2). in an elementary area are obtained from climatological maps by spatial discretization of the isoline values. The elementary runoff values of elementary catchments are summed up for a given outlet according to Eq.(l); where e,j is an elementary catchment in row i-k and column j, and N

u is the set of elementary catchments above e

y. In Eq.(2)a is a parameter to characterize the topography in a comprehensive way. It can be calibrated in a given area by minimizing the difference between calculated and observed runoffs, (e.g. in the catchment of the Zagyva River the average relative error amounted to 8-9 percent when a was 1.95). The second part of the paper is in charge of temporal analyses in climate-runoff interrelations. In the values of annual runoff one can often discover statistically relevant inhomogeneity (Fig. 2.) dated back necessarily to the impact of human interferences, or of climatic fluctuations. For the characterization of climatic elements: annual mean temperatures, annual precipitation and the seasonal fluctuations of precipitation are compared in Fig. 3 for the periods 1953-77 and 1928-52 on the basis of data taken from 28 meteorological stations. From Eq.(2) the expected changes in mean annual runoff are estimated from these climatic fluctuations (Fig. 4). Due to the extremely short observation periods of our small rivers the changes in runoff - caused by climatic fluctuations - were checked only in 3 catchment areas. Calculated and measured discharges displayed a fairly acceptable agreement. This was a proof of the climatic influences explaining partly the changes in runoff in these 3 basins. The common analysis of hydrographical time-series and of climatic data is a prerequisite of well-founded investigations and of more usable conclusions. It is advisable and necessary therefore, that our hydrographical observations should be pursued in the entire area of the waterhousehold covering every element thereof.