Vízügyi Közlemények, 1935 (17. évfolyam)
Kivonatok, mellékletek - Kivonat a 3. számhoz
28 That is because the Triple-Körös has a very slight slope (on an average 0-03—0-05 per mille, and even less in some reaches), so that its recipient, the Tisza river, has a rebacking effect to a distance of about 120 kilometres. When there is a low stage in the Tisza, the water in the Körös river flows down with a great slope and low stage, while in the case of high water in the Tisza, the Körös flows with a small slope and a high stage. Figure 5 shows three different cases : the water levels are nearly the same in the upper reaches, but at the same time these differ from one another, farther down, by 1-5 metres, owing to the influence of the Tisza river. In consequence of these circumstances the usual form of discharge diagram affords no information as to the magnitude of water volume flowing down at a given stage. As a rule, the discharge diagram represents water volumes at the average slope ; but in the case of the Körös river the same volume can flow down at a slope ten times smaller than the average. (Figs. 10 and 11 show discharge diagrams at Gyoma and Szarvas. The full points indicate values measured at rising, the circles those at falling, and the stars those at culminating stages.) Therefore it has become necessary to prepare discharge diagrams taking into account the extraordinary variations in the slope conditions. In the method employed, the slope at the gauge in question lias been replaced by the difference of the prevailing stages at the next upper and lower gauges. This can be done, because these two outside gauges are at about the distance from the middle gauge, and so, however the water level may take its form between the two outside gauges, in the middle of this reach the tangent of the curve representing the water level may be regarded as the average slope obtained from the two outside gauges (fig. 14). The discharge diagram at Szarvas drawn on this principle actually is a row of curves (fig. 15), the abscissa of which is the local water stage, and the ordinate is the difference of water stages observed at the next upper and lower gauges (at Gyoma and Kunszentmárton), which gives the slope between the two latter gauges. In this figure the zigzag lines which connect the points corresponding to the prevailing slope and the local stage, represent the daily variations in the discharge of the river. In this way a perspicuous difference can be stated between the effect of the flood flowing down from the upper reach and the backing up effect coming from downstream. Both effects become apparent in rising stage at the gauge of Szarvas, but there are different cases. (1) When a flood is flowing down the Körös, and the stage in the Tisza is constant, i. e. both the stage and the local slope are increasing, the portion of the line which represents the variation of the daily discharge ascends from left to right, and its angle to the vertical «j < 90°. (2) When a flood is flowing down, and at the same time the Tisza is also rising, i. e. the local slope is decreasing on account of the backing up effect, the line indicating the discharge descends from left to right, and its angle to the vertical 90 0 < « 2 < 180°. (3) After the culmination of the flood — supposing no backing effect from the Tisza river — both the water stage and the slope are decreasing, so that 180° < a 3 < 270 0 (4) When both the Körös and the Tisza are subsiding, so that a draw-down effect is prevailing (decrease of stage and increase of slope), then 270° < » 4 < 360°. By means of this diagram we are able to state the approach of a flood in advance, when the local stage is still subsiding or constant In this case the portion of the diagram which represents the variation of the daily discharge, becomes ascending
