The quality and usability of water in the Wilga River water were assessed in order to determine whether it can be stored in a projected small retention reservoir. The Wilga catchment up to the gauging section under study has an area of 19.67 km2 and is situated in the Wieliczka county (Małopolska province). Hydrochemical studies were carried out from March 2006 to February 2007. Water temperature, pH, dissolved oxygen concentration and conductivity were measured on site, whereas total suspended solids, total dissolved substances, biogenic compounds (NH⁺, NO₂^–, NO₃ ^- , PO₄ ^3–) and mineral constituents (SO₄ ^2–, Cl^–, Mn²⁺, Fe^2+/3+, Mg²⁺, Ca²⁺) were determined in a laboratory. In terms of nitrate, iron and manganese concentrations, the Wilga River water flowing out of the catchment was classified into the 3rd purity class, i.e. into the waters of satisfactory quality. The projected reservoir may serve recreational purposes because the water fulfills the requirements posed for bathing sites. After a typical physical and chemical treatment it may also be used to provide water supply for the local community (category A2). Because of very high nitrite concentrations, however, the water creates an unsuitable environment for fish to live in.

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