Vízügyi Közlemények, 1965 (47. évfolyam)

4. füzet - Rövidebb közlemények és beszámolók

<86) Both for winter storage and summer irrigation, sprinkling can be considered as most suitable irrigation method, applied during summer possibly by night and with a mistlike water application. Other known methods, however, may also be used. Water requirements of winter irrigation may be ensured from the winter water mass of rivers, unused up to now. After complying with the demands of drinkingwater and industrial water supply, as well as with those of navigation, by means of water amounts withdrawn from the rivers for irrigation purposes the irrigation needs of the agriculturally cultivable Hungarian territory can be met in an area of 5 million hectares, as shown in Fig. 3. As a matter of fact, not every soil type is suitable for storage. First of all cohesive soils or in general soil types of good water economy, with groundwater levels of at least 2 metres below ground surface, have to be taken into consideration. The accordance of combined irrigation with moisture demands of the plants is demonstrated in Fig. 4. Winter moisture resulting from average precipitation amounts to 152 mm, while summer moisture to 79 mm. This moisture amount is utilized by perennial plants with deep roots during the period from sprouting to ripening according to the curve a-b-c, expressing growth and water demand, respectively. Crop would be obtained even without summer precipitation. Without winter precipitation, however, at a summer rainfall amount of to 200 to 250 mm, the flora of the Hungarian temperate zone could not evolve. Consequently, the precipitation of the winter period is not only more considerable but also more important than that of the summer. This forms the basis of the water management of Nature and at the same time that of the combined irrigation. As shown in Fig. 4, winter moisture becomes exhausted in early July. Up to this time the plants satisfy their moisture demands simultaneously from below, i.e. from the soil, and from above, i.e. from summer rainfalls. From early July to the second third of the same month, however, the plants take their required moisture quantities from precipitation only. Growth is finished by that time, and during the remaining stage of ripening the moisture demands are gradually ceasing. This can be seen on the section a-b of curve No. 2 in Fig. 4. Curve No. 3 shows the growth conditions when a summer irrigation of 400 mm is applied. This rate of water application is decreased to half by combined irrigation, while bringing about an unchanged moisture amount of 76 mm. THE FLOOD OF THE TISZA RIVER IN 1964 By S. Baranyi, civ. eng. (For the Hungarian text see pp. 355) Author describes the flood of the Tisza River in March-April, 1964, as well

1 as the lessons to be drawn from the flood. On the Tisza reach above Tiszalök (524 river kilometres) the previously recorded highest stages were approximated, while on the reach between Tiszalök and Polgár (524 — 491 river kilometres) they were exceeded by this flood. On the reach below Polgár (491 river kilometres), however, the flood stage remained under the highest recorded values. The 1st Section of the paper discusses the antecedents of the flood, Section 2 deals with the river stages and Section 3 with discharges. The velocities of the passage of flood waves are presented and conclusions are drawn in Section 4. Maximum stages of the flood compared with previously recorded highest stages are compiled in Table I, discharge data in Table II, stream flows of the affluents in Table III, and finally travelling velocities at rising and falling stage, as well as at peak are given in km/day according to characteristic gauging stations in Table IV. Experiences and conclusions to be drawn from studying the development and subsidence of the flood are as follows : 1. A considerable flood can arise on the Tisza River only then and there, where the flood waves of the affluents meet those travelling on the Tisza.