Changes in the lower Drava River water quality parameters over 24 years

The goal of this study was to analyse 13 physico-chemical and microbiological parameters of the Drava River water at three sampling sites in the lower Drava region (eastern Croatia) over two distinct periods: the pre-war period between 1985 and 1992 and the post-war period between 1993 and 2008. Over both periods, most parameters kept within the tolerable water quality limits, while NO3-N, NH4-N and BOD5 were higher. The lower Drava showed slight organic pollution with high concentrations of dissolved oxygen. High levels of total coliforms and heterotrophic bacteria in the post-war period were only found downstream of the town of Osijek. Upstream of Osijek, the river showed a tendency for improvement.