Vízügyi Közlemények, 1958 (40. évfolyam)
4. füzet - VII. Kisebb közleménye
(83) THE DESIGN FLOOD-LEVEL FOR THE HORTOBÁGY—BERETTYÓ CANAL By J. Juhász (Figures on pp. 483 — 511 of Hungarian text) UDC. 627.4(439.16) The Hortobágy—Berettyó Canal (referred to subsequently as the Hortobágy Canal) is the main collector of excess surface waters for parts of the Hungarian Plains east from the Tisza River. Collected surface waters are conveyed by the main canal into the Körös River which is the main tributary of the Tisza River. In order to retain flood waters of the Körös River a flood gate has been erected at the mouth (Fig. 1). The investigation was conducted with the aim to determine the flood level of the Hortobágy Canal in its present and future state, occurring with a frequency of 0,5 per cent. However, stage and discharge records covering a period of 14 years were available for a but single control section — Ágota — and these were not considered satisfactory for the solution of the problem. Therefore, as a first step a discharge record covering at least SO years had to be established. This has been accomplished by graphical correlation ( Fig. 4 ) transformed to the cross section at the mouth. Stage records and the rating curve for the control section at Ágota (Fig. 2) as well as the time order of discharges constructed of on basis lysimeter data have been made use of for this purpose ( Fig. 3 and Table I ). Transformation to the section at the mouth has been carried out by considering the difference in catchment areas pertaining to the two sections, and the precipitation volume for the entire catchment. Flood profiles observed at the control section Ágota have also been transferred to the mouth on basis of the maximum discharge (Fig. 5) and duration (Fig. 6) occurring during the flood. It has been assumed, that the flood profile suffers no essential changes over the 60 km long reach in question. A time interval of four or five days has been assumed between the beginning of precipitation and the origin of the resulting flood wave. Those obtained in this manner were superimposed if partial overlapping was observed. Periods comprising the highest annual flood waves have been established as outlined above for the years 1901 to 1950 (Fig. 7 and Table II). Flood waves observed on the Körös River — the recipient of the Hortobágy—Berettyó Canal —• have also been entered into the figure. With the above information available flood waves carrying maximum discharges have been selected for each year which in general occurred coincident with the period of the maximum flood in the Körös River in the same year. Annual maximum discharges in the Hortobágy Canal and the Körös River, respectively, were found to occur at different times in but 7 cases during the 50 year period investigated. These differences, however, were insignificant. Therefore, annual maximum discharges of the Hortobágy Caned have been conservatively considered coincident with the annual maximum flood in the Körös River. Flood discharges having different specified probabilities were determined from these data using Curve III of Pearson and the empirical method (Fig. 8. and Table IV). Values obtained by the latter have been adopted which resulted for the 0,5 per cent frequency flood in a discharge of 92 cu.m/sec (Table V ). Stage relation curves have been constructed for the reach between Ágota and Mezőtúr on basis of stage observations and bed surveys (Fig. 17). Approximating extrapolation was only possible for the reach above Ágota no stage observations having been carried out there. Corresponding stages on the reach between Ágota and Mezőtúr have been determined by the aid of gage relation curves (Fig. 11). The time order of discharges has thereby been established for the section Mezőtúr which, in turn, permitted to determine Ihe time order of stages as elevations above Adriatic level in the Hortobágy Canal for the period of highest stages in the Körös River. In view of the fact, that on the reach downstream of Ágota surface waters are, instead of being discharged gravitationally, elevated by pumping into the recipient Hortobágy Canal, the maximum flow conveyed along the reach between Ágota and the mouth has been increased gradually according to the maximum volume pumped from successive bays as indicated in Table VI. Gage relation curves have again been made use of to determine
