This study explores the relationship between low flows and large scale climate variability in France. To this aim, a national low flow reference network of near-natural catchments, consisting of 236 gauging stations, was set up. A subset of 220 daily streamflow records for the period 1968-2008 was used to detect trends in a number of severity and timing drought indices. In addition to testing temporal trends, correlations with four climate indices were also evaluated: the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO) and the frequency of two Weather Patterns corresponding to circulation types associated to wet (WP2) and dry (WP8) conditions over France. Due to their specific dynamics, NAO and WPs were also analyzed seasonally. Results show a consistent increase of drought severity in southern France.

This paper describes a trend analysis performed on 177 streamflow time series collected over the Alps in Central Europe. The analysis covers several facets of the Alpine hydrologic regimes, including winter droughts and spring snowmelt flows, both in terms of severity and timing of occurrence. Statistical trend tests are applied at a local scale (i.e. on a site-by-site basis) and at a regional scale (seeking a common trend for sites within the same hydroclimatic region). The overall results indicate a trend toward less severe winter droughts, and consistent changes in the timing of snowmelt flows. However, a more in-depth analysis at the scale of hydro-climatic regimes reveals more contrasted changes. While most glacial-and snowmelt-dominated regimes show a decreasing trend in the severity of winter droughts, contrasted trends are found for mixed snowmelt-rainfall regimes in the Southeastern Alps. Changes in the timing of snowmelt flows (earlier start and increased duration of the snowmelt season) mostly affect glacial-and snowmelt-dominated regimes. Lastly, glacial regimes show an increase in the volume and the peak of snowmelt flows.

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