Summary:

Changes of underground waters quality in the intakes located in the intensive industrialization and mining area are caused by anthropogenic activity. The type of quality changes is essential to use these waters in water-supply systems. It also allows for accepting proper solution of extension of intake or introduce possible protection relatively to source evoking these changes (bring about changes). The subject of research presented in this article is variability of selected quality parameters such as dry residuum, total hardness, concentration of sulfate, chloride, calcium and magnesium ion concentrations of underground waters from four intakes located in eastern part of Zapadlisko Górnośląskie. Dobra 1 and 2, Bielany and Galmany intakes include six drilled wells of 88,0-101,5 meters depth and discharge about 700,0-800,0 m³*d^-1 taken water from Triassic formation and ventilating-filling shaft J. Dąbrowski of 103,0 meters depth and 2000 m³*d^-1 capacity that takes water from Carbon formation. Detailed analysis of chemical composition variability indicates big changes of dry residuum in Triassic waters intake Galmany, smaller in Bielany and Dobra 1. High variability of water hardness and Ca, SO₄ and Cl ion concentrations was affirmed in Dobra 1 intake and Cl and SO₄ occurred in Bielany. Considerable variability of all analysed components occurred in Dobra 1 intake, Cl and SO₄ in Dobra 2, dry residuum, SO₄ and Cl in Bielany intake and dry residuum in Galmany. In case of carbonate water taken from Dąbrowski shaft, high variability concerned only magnesium ions.