 Nearly all of Croatia's groundwater aquifers are top quality, unlike the available surface water; the latter's quality varies in terms of biochemical oxygen demand and bacteriological water analysis results.As of 2008, 80% of the Croatian population are served by the public water supply system, but only 44% of the population have access to the public sewerage network, with septic systems in use.Adriatic Sea water quality monitoring between 2004 and 2008 indicated very good, oligotrophic conditions along most of the coast, while areas of increased eutrophication were identified in the Bay of Bakar, the Bay of Kaštela, the Port of Šibenik and near Ploče; other areas of localised pollution were identified near the larger coastal cities.