Przepływy i odpływy maksymalne w środkowej Polsce

Abstrakt

In the article presented above the seasonal and multiannual variation and spatial differentiation of a few parameters were studied. These specifications were obtained on the basis of maximum discharges registered for 71 water-gauges in central Poland in the second half of the 20th century (1951-2002) (Table 1). In particular, seasonal and spatial regularities of maximum outflows, maximum discharges (WWQs and WWQs) and Françou-Rodier Flood Ratings (K) appearance were established. The greatest number of WWQs (WWQs) in central Poland was registered during the cold half-year (months: January and March) and in the summer (July and August). In autumn and early winter months (from September till December) maximum outflows were not registered. In central Poland the maximum unit runoffs are not very differentiated as they range from 23 to 228 dm3∙s-1.km-2. These values can be assumed as the representatives of the regional extremes. Regression equations between catchment surface areas and maximum discharges (unit runoffs) were also calculated - equation 1 (Fig. 4) and equation 2 (Fig. 6). In the catchments of the region, the maximum unit runoffs values (WWQ) decrease very slowly with increasing catchment areas (compare with Fig. 6). Spatial differentiation of Françou-Rodier Flood Indexes (K, equation 3) was under investigation. Moreover, the regional equation of the relationship between WWQ and K (equation 4, Fig. 8) was computed. Due to the Françou-Rodier Flood Indexes (K), the risk of precipitation and snowmelt/rainfall floods in the small and large central Poland river valleys is of minor importance. In general, some previously identified patterns, which describe the relationships between WWQ, WWQ, K and A in the global, continental and national scale are also visible considering the regional scale (central Poland area). The aim of this study was also to investigate the multiannual variability of the Flood Indexes (IWW K) – equation 5 and Fig. 9, which were calculated for central Poland area. In the second half of the 20th century the IWW indexes, which were determined in this region were continuously declining. It proves that the scale and the frequency of floods in the rivers of the particular area are getting reduced. The relationships and linkages between annual North Atlantic Oscillation Indexes (NAO) and Flood Indexes (WWQ) were also studied, and it can be stated that they are unclear and statistically insignificant (Fig. 10) and cannot be treated as simple statistical correlations.