Streamside vegetation forming narrow "corridors" in temperate regions, is typically dominated by deciduous tree species reflecting strong influences by human activities. Riparian woodlands depend on hydrological resources and have to adapt to rapid changes in water levels and soil moisture conditions. Three main water sources are typically present in the riparian zone: river water originating in the mountains, ground water and rainfall. Stable isotopes, such as oxygen-18, are useful tools which allow for water movement to be traced within the riparian zone and which help to identify water sources utilised by the trees growing in these areas.