Vízügyi Közlemények, 1962 (44. évfolyam)

4. füzet - IX. Könyvismertetés

(20)* SURFACE DRAINAGE OF THE HORTOBÁGY REGION By G. Kienitz (For the Hungarian test see pp. 103) The plains commonly referred to as the Hortobágy Puszta lie east from the Tisza River, in Hungary. The region has been opened up to intensive agricultural production by building irrigation canals. The efficient removal of unwanted precipitation waters, of excess surface waters became mandatory for uninterrupted production. The planning activities aiming at this"surface drainage are described in the present paper. The general plan of the region is shown in Fig. 1. The detailed survey of hydrological conditions furnished the basic facts for planning work. The stage, respectively discharge hydrographs for the gage Ágota, on the Hortobágy Main Canal draining the runoff waters from the area, were first established. Hereafter the site data for major inundations in the past were collected. Using the latter, so-called inundation curves were prepared, one of which, the combined curve, indicates the relationship between the inundating water volume and the magnitude of the inundated area, while the others indicate the extension of areas of different soil types inundated within part catchments (Fig. 2). The combined inundation curve has been used to determine the shape of the flood hydrographs at Ágota, which could have been observed if the drainage system would have been developed in an ideal manner and to an ideal degree. The mass curve of the actual flood wave was plotted side-by-side with the mass curve of ideal runoff (Fig. 3), which, on Ihe other hand, was determined on the basis of precipitation data. The runoff coefficient of ideal runoff was not available and a method of successive approximation was therefore used for its determination. The differences between the ordinates of the two curves represent the daily water volumes supplying the inundating water mass. Daily losses could be calculated from the inundation curve and evaporation data, and the stepped curve indicated in the figure could be constructed. The runoff coefficient of ideal runoff was correctly assumed when A coincided with A'. Using this method, corresponding pairs of actual and ideal flood hydrographs have been prepared for the Ágota gage. The elements defining Ihe mass curves of these flood waves (Fig. 4) showed a relationship lo exist with the mass of the flood wave. Thus e.g. a relationship could be established for different degrees of development of the drainage system, between the mass of the flood wave and the design discharge of the sysLem (Fig. 5). Similar relationships were relied upon for completing on the basis of precipitation data the pairs of flood hydrographs for the Ágota gage into a 50 year record. Two hydrographs pertaining to two intermediate degrees of development (q

0,

3o and q

0>4

0) were interposed between the actua 1 (q

0 2

0) and the ideal (q

0,5

0) flood hydrographs. The 50 year flood records were used to derive the empirical probability curves of 1) the peak annual specific discharges (Fig. 6) for different degrees of development q, and 2) the excess water masses (Fig. 7 ), and 3) the damage caused by excess surface water. The difference between the ordinates of the mass curves for any degree of development and for q

0 50 (Fig. 8) represents the inundation due to the insufficient development of the system. Discharge data were used when investigating the structures to be designed for flood protection with an adequate factor of safety, while mass data provided the necessary storage space to be taken into account for designing reservoirs, and the damage data furnished the information for determining the economical degree of development of the drainage system. A degree of development involving an overall optimum in various economic characteristics was eventually proposed by the author and his collaborators. The peak runoff to be removed is 0,40 I s. ha (about 0,006 cfs/acre) on the average for the entire region, and a corresponding degree of development has been suggested. (Translated by Z. Szilvássy struct, eng.)