Extreme Stream Flow in Hydrological Year 1965 in Bohemia

Abstract

In contrast to the preceding years 1963-1964 the hydrological year 1965 was characterized by extremely great stream flow. In the basin of the river Elbe it represents the fourth year with the greatest stream flow (from the viewpoint of annual average discharge) in the period 1850-1965 (after the years 1941, 1926, 1940). The annual average discharge on the Elbe in Děčín made 492 m3/s (i. e. 161 % of the long-time average). From the viewpoint of precipitation the hydrological year 1965 was also an above-average one (792 mm, i. e. 116 % of the long-time average). In the vegetation period 70 % of total precipitation in the hydrological year 1965 have fallen and in four months with the greatest stream flow (i. e. March till June) 62 % from the annual average discharge have flowed on the Elbe in Děčín, in June itself more than one fifth. Spring (i. e. March till May) with 277 mm orf precipitation (179 % of the normal) has contributed above all to extreme stream flow of the vegetation period and was the moistest one in the last 90 years. The period of abundant spring precipitation has followed immediately the period of the great melting of snow cover so that the high waterstages on the Bohemian rivers had the longterm character. Abundant precipitation in May (148 mm, 228 % of the normal, the moistest May in the period 1876-1965) and in June has caused several flood waves. In single cases the maximum flood was in July, owing to heavy downpours. October had the least stream flow and precipitation on the greatest territory of Bohemia. In the hydrological year 1965 in general the southern half of Bohemia was more humid than the northern one. From the viewpoint of the index of humidity by M. Konček (1955) the greater part of Bohemia was in the hydrological year 1965 humid, the highest parts of the border mountains perhumid, a little territory moistsubhumid.