Long overlooked, low fl ows-both in terms of discharges and water levels-are becoming increasingly important to hydrologists as well as public authorities and the overall population. This new awareness is the consequence of the ever-growing pressure placed on the water resources of streams and rivers. It also stems from the fact that water availability and needs rarely coincide due to the random nature of climate and its seasonal variability. Our society is therefore obliged to orient its activities according to available resources.