Extreme droughts, such as the 2003 drought in Europe, illustrate the importance of understanding climate and human impacts on low flows, for developing adaptation strategies and decision makings in water resources management. The aim of this study was to investigate the effects of climate variability and hydraulic engineering measures on the low flow runoff trends in Lower Austria. The time series of low flows (Q95), annual precipitation, annual snowfall depths, groundwater levels and air temperatures were compared with hydraulic engineering measures in four catchments of Lower Austria. The analyses include evaluation and attribution of low flow trends and their changes in the period 1976 - 2007. The results of the study show that the effects of hydraulic engineering measures on low flows in Lower Austria are generally smaller than the effects of climate variability. One exception is the Rußbach in the Marchfeld, where the combination of a dry climate and an associated increase in groundwater extractions led to declining groundwater levels. However, the discharge measurements started at a time, when the groundwater levels were already very low (1977), and changed very little until the Marchfeldkanal was constructed. With the flooding of the Marchfeldkanal in 1992, the low flow in the Rußbach increased from 0.07 to 1.4 m3/s which represents the largest impact of engineering measures in this regard.