Summary:

Evaluation of the precipitation value causing summer floods in the Middle Odra basin was done on the basis of daily precipitation totals within the period of 1971–2005 recorded at 53 precipitation stations. The critical value of precipitation was searched among the values of 5-days precipitation totals with the probability of exceeedance (p) of 10% and lower. The functional relationships between precipitation values of the given p and the altitude of the stations were identified. They were used to estimate the range of precipitation values of given p for the altitude layers. For each year a number of 5-days precipitation totals of the following p: >10%, [10% – 5%), [5% – 2%), [2% – 1%), [1% – 0,1%), ≤ 0,1% was calculated. Arranging the obtained results by the number of events of p≤1% let to designate the years of the severe and extended floods in the middle Odra basin. While analyzing the relationship between mean areal value of precipitation and the number of critical precipitation incidences, the values of precipitation causing moderate and severe risk of summer flood were estimated.