CHANGES IN PROSNA WATER LEVELS (BOGUSŁAW PROFILE) IN 1973-2017

The paper presents long-term changes in water levels of Prosna, one of the main rivers in Wielkopolska, i.e. the region which is widely regarded as one of the least abundant in water in Poland. It was established that during the last 40 years the average annual water levels of Prosny showed a downward trend at the level of 7.8 cm-dec-1 and were statistically significant at the level of p=0.05 and also p=0.01. In all months a decrease in the water level was noted, although it was statistically significant in seven cases. The highest decrease in average monthly water levels (statistically significant, p=0.05) occurred in August and December and progressed at a rate of 13.2 and 12.3 cm-dec-1. The consequence of the ongoing trend may be, among others, worsening of ichthyofauna living conditions or worse quality of Prosny's water.