Vízügyi Közlemények, 1975 (57. évfolyam)

4. füzet - Károlyi Csaba: Adathiányos vízgyűjtők vízkészlet meghatározása

552 Károlyi Csaba Estimation of water resources in catchments with limited data By Károlyi, Csaba, Civ. Ertgr. The objective of the present paper is to estimate the water resources in catchments which are little, or not at all explored hydrologically, or the parameters not of the distribution functions describing the water resources. The parameters are estimated on the basis of data available on discharge measuring sections having long records and representing

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4 small and medium catchments in the central, Hungarian part of the Danube Basin. For describing the catchments 13 parameters have been adopted, namely the area, average elevation, shape characteristic of the catchment, the length, average slope, highest point of the drainage channel, the difference of elevations at the two ends of the channel, the multiannual, monthly and antecedent monthly averages of surface water input per unit area, as well as for the total catchment. Instead of the monthly average precipitation, the water volume reaching the surface in liquid condition from the precipitation falling has been adopted for describing the hydrological input, this being termed the surface water input. In periods with 110 snow this is identical with the rain falling, whereas in periods of snow accumulation it is less, at melting higher than precipitation. For describing the monthly runoff the three-parameter log-normal distribution function has been adopted as the one fitting best, determined using the daily discharge data. The parameters of the distribution function were determined by the maximum likelhood method. In the course of data processing the x

0 parameter of the log-normal distribution was found to range from 0.004 to 25.5 m

3/sec, while the parameter m from —3.26 to +5.51, while the parameter о from 0.526 to 1.45. In addition, two commonly used discharge parameters were also determined, namely the expected value (0.081 to 305.1 m

3/sec) and the squared standard deviation (0.017 to 42 384). For exploring the relationship between the distribution parameters and the catchment characteristics and for ranking the dominant variables according to importance correlation computation and factor analysis were applied. The two different methods have yielded almost identical results. 01' the 13 factors examined the size and average elevation of the catchment, the average slope of the channel, the differential elevation in the channel, the monthly water input per unit area (or the specific values for the antecedent month, or for the year instead of the latter) were found acceptable as independent variables. For determining the discharge parameters, regression equations have been developed in different combinations. In determining the regression relations the following approach has been adopted: The variable most closely correlated with the target variable was identified and termed the explicative variable. Hereafter the partial correlation coefficients related to the standardized target variable were calculated and the explicative system was expanded successively by the variable showing a significant effect. 1. The best estimate of the parameter m was given by including the average elevation of the catchment, the differential elevation measured in the channel, the water intake per unit area during the antecendent month, the total annual intake, the monthly water intake per unit area, of the catchment and the average channel slope. 2. In the case of the parameter о there is no universally acceptable relationship for every month. The best result for the months May, July, August, October, November and December is obtained by including — the normal average total water input, the water inputs per unit area for the antecedent month, the month considered and for the year, for the months February, June and September — the size and average elevation of the catchment, the differential elevation in the channel and the normal average annual total water input, and for the months March, April and December — the size of the catchment, the normal average annual total water input and the monthly total water input.