The Upper Tisa Valley. Preparatory proposal for Ramsay

Figure 13. Mosaic map of flowage coefficients of the catchment area of River Tisa
areas at the end of March and the beginning of April. In April snow remains only on
high peaks and in hollows of cold locations, and only in small amounts. Every year
three major flood waves set off from the Upper Tisa. The first is caused by the melting
of snow, and it rarely reaches record heights, it is rather a sequence of several smaller
flood waves. The second, taking place at the end of spring and at the beginning of
summer, is called the "green flood", which is particularly noteworthy if it finds a
riverbed already filled by winter floods. The third is the autumn flood wave, which is
remarkable only at times of major autumn rainfall, and then mainly in the right
tributaries, to the north of River Tisa. The flood waves mentioned do not occur every
year, they may often fail to come about.
Out of the three flood waves of the Upper Tisa only the spring and the summer
floods are significant in the Middle-River Tisa section. These floods are substantially
prolonged because of the floods in the tributaries. The difference between the water
mass at low water mark and at high-water mark constantly decreases. At
Vásárosnamény, below the confluence with River Szamos the lowest water output
(average of many years) is 38 m 3 /sec, the highest is 3300 m 3 /sec (i.e. 87 times the
lowest). The abatement of the flood wave here still cannot be observed because of the
joint effect of the rivers Tisa and Szamos, but below Tokaj the lowest water output is
54 m 3 /sec, the highest is 4000 m3/sec, (i.e. 74 times the lowest).
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