Impact of Land Use and Runoff on Stream Quality

Climate changes, intensive agricultural production, and expanding urban areas make the study of runoff and its possible impact on stream quality increasingly important. In this study, we examined large datasets concerning catchment type, stream quality, and invertebrate composition in a comprehensive geographic information system study. The aim was to examine correlations between land use type and quality of the receiving waters to detect possible differences in anthropogenic impacts. The studied area covered 937 km 2 , and the dataset included 1672 stretches of streams and data from 468 fauna sampling stations. Runoff from agricultural areas more negatively influenced the stream quality than runoff from urban areas. Considering urban catchments, the areas with separate sewer systems generally influenced the stream quality less than catchments with combined sewer systems. In conclusion, the catchment of any specific stream must contain an area with a minimum of 20–30% without agriculture or urban areas to obtain good ecological status; when focusing only on the riparian zone (10 m on each side of the stream), a minimum of 40–55% is needed to create a good ecological status. Therefore, management focus on the entire catchment is important and separate sewers should be preferred rather than combined sewers.