Hydrologiczne i hydrauliczne uwarunkowania budowy zbiornika wstępnego w cofce zbiornika Słup

The study presents the research results of the water quality and flows of the Nysa Szalona river which supplies the Słup drinking water dam reservoir. The research was carried out in the years 2005-2008 with the purpose to determine the potential for construction of a pre-dam reservoir in the backwater of the existing Słup reservoir. Maintenance of good water quality in this reservoir is of high importance due to the purposes it serves. It balances the outflow from the Nysa Szalona River basin to ensure appropriate volume of water at the intake on the Kaczawa River situated in Przybków. The data collected during the studies demonstrated poor quality of water. The analysis of the Nysa Szalona River water supplying the reservoir showed that from the eutrophication viewpoint, the hydrochemical conditions existing in the basin of the Słup reservoir were unfavourable, mainly due to high concentrations of biogenic substances, especially phosphorus. Analysis of the data on water quality inflowing to the Słup reservoir demonstrated that due to high concentrations of phosphorus the BOD5· values exceeded the water quality limits set up for surface water bodies in natural river courses applying to class II. At the same time the concentration of nitrates, pH and total suspension were within the limits of class II water quality. To protect the Słup reservoir against pollutants transferred from the basin of the Nysa Szalona River, construction of a pre-dam reservoir in the backwater of the Słup reservoir was investigated taking into account the existing hydrological and hydraulic conditions. A capacity of 2 mln m3. was proposed for the pre-dam reservoir. Construction of a pre-dam reservoir would contribute to the improvement of the quality of water supplying the main reservoir reducing thus the content of inorganic nitrogen by ca 40% and phosphates by ca 50% in the Słup reservoir. The study also showed that a construction of a biological filter with macrophyte plants on the inflow to the pre-dam reservoir would effectively increase its performance. The presented results also confirmed the potential of using the hydrological and hydraulic criteria for the dimensioning of the pre-dam reservoirs.