Water level trends in the ponds of Siemianice Experimental Forest Farm

The results of a long-term water level monitoring in three forest ponds are presented in the paper. The ponds are located in the Wielisławice and Laski forest districts in South Wielkopolska, Poland. Two of the analysed ponds are natural ones supplied by precipitation and the third now is disused artificial fishpond of throughflow water management. Systematic water level measurements, as well as measurement of basic meteorological conditions – precipitation and air temperature – were carried out in the 2000–2016 hydrological period. The basic statistics as well as the trends in long-time changes in water levels, were determined using the nonparametric Mann–Kendall test were calculated. The results obtained were statistically inconclusive, but they indicated downward trends in water levels in the natural ponds and upward trends in water levels in the artificial pond. Although a statistically significant downward trend was observed in only one natural pond, it may suggest some negative changes occurring in the catchment of ponds in general.