The main water-course on the territory of Bratislava is the Danube. Its quality of water in a large measure is influenced by the degree of pollution coming from outside the territory of our county. In our country water quality is influenced by the water quality of the river Morava that is polluted by sugar Works (but in the course of the last 10 years the pollution fell to 1/3) and the waste water of industrial plants and housing estates in Devínska Nová Ves and Stupava. In location Karlova Ves communal waste waters empty into the river, similarly as near the bridge SNT and ČA. Other resources of pollution are the port and waste waters from the Slovnaft and ChZJD. The Danube is polluted also by the housing estates of Petržalka. The Small Danube is polluted especially by Slovnaft from where leaks cca 500 t petroleum. However the trend of the development of the quality of surface water in Bratislava is positive.