Nauka Przyroda Technologie

Abstract. The paper presents the size and range of the oscillations of water stages (discharges) of the River Zgłowiączka triggered off by the Small Hydro-Electric Power Station (SHEPS) in Nowy Młyn. Oscillations of water stages were determined on the basis of the measurements carried out by the author at the correction step in Włocławek (16.22 km from the SHEPS), as well as the data of the Institute of Meteorology and Water Management (IMGW) collected at the gauge station in Włocławek Ruda (11.53 km from the SHEPS). The analysis was carried out between 2003 and 2005. The influence of the activity of the power station was mostly felt in the summer half-year. The time when oscillations appeared corresponded with the time when water shortages were recorded in the river basin. The amplitude of the extreme oscillations of the water stages at the correction step amounted from 11 cm (2003) to 17 cm (2005), which gave the discharge at the level from 1.83 m³s^-1 to 2.62 m³s^-1 respectively. The time intervals between culminations (retention time) were irregular. They depended on the amount of the water supplied to the reservoir and its capacity. In 2003 the culminations were recorded at the intervals of 2 to 5 days, while in 2005 at 2 to 12 days. The amplitude of the daily mean discharges at the Włocławek Ruda profile amounted from 0.78 m³s^-1 (2005) to 1.30 m³s^-1 (2003). The largest oscillations of water stages and the corresponding oscillations of discharges remained within low water stages. Daily oscillations of the discharges exerted their influence not only directly on the zone down the power station; they were also felt along the entire section of the River Zgłowiączka between the SHEPS and the river’s mouth to the Vistula.