The case of extreme hydrologic drought downstream from reservoirs in Quebec (Canada): The intermittent flow

Abstract

Intermittent flow is a hydrological phenomenon observed at all latitudes. This phenomenon is characterized by a complete or partial interruption of flow in time and/or space in channels. In Quebec, even though the climate is humid, intermittent flow occurs downstream from headwater reservoirs. These reservoirs store water during spring and summer (from April to September) and release it in winter to supply hydroelectric power plants located downstream. During the water storage period, intermittent flow is common (discharges falling to <1 L/s/km 2 ). The goal of the study is to analyse the characteristics (magnitude, frequency, and duration) of this flow downstream from 3 reservoirs built in the Saint-Maurice River watershed, during the period from 1930 to 2010. Downstream, the contribution (magnitude) of intermittent flow to total altered flow is less than 2%. Intermittent flow frequency ranges from 24 to 65 days per year downstream from the 3 reservoirs. As far as duration is concerned, intermittent flow persists on average from 40 to 128 consecutive days. Canonical correlation analysis revealed that the frequency of intermittent flow is correlated with the North Atlantic Oscillation and its magnitude and negatively correlated with the Southern Oscillation.