High stream intermittency in an alpine fluvial network: Val Roseg, Switzerland

More than one-third of the world's rivers cease to flow and go dry on a periodic basis-so-called intermittent rivers. The frequency and duration of flow intermittency in running waters are increasing due to climate change and water demands for human use. Intermittency effects on stream biodiversity and ecosystem functioning are dramatic and are expected to become increasingly prevalent in alpine landscapes in the near future. This project used modified field sensors to measure flow intermittency, temperature, and water origin (groundwater, precipitation, glacier) at high spatio-temporal resolution throughout an alpine fluvial network (Val Roseg, Switzerland). We continuously recorded water presence in 30 tributary streams and validated sensor performance with field-collected measures. Three different flow regimes were observed in the network, including periodically intermittent, seasonally intermittent, and permanently flowing streams. Twenty-four streams (80% of recorded streams) dried at least once during the sampling period. Principal components analysis along with generalized additive models showed alpine streams with low average temperature and high conductivity (groundwater-fed) were prone to permanent flow, whereas streams with higher average temperature and low conductivity (glacier-fed) typically had intermittent flow. The field sensors proved precise for simultaneously measuring flow intermittency, temperature, and water origin at high resolution throughout the river network. Overall, this approach provides an effective way to develop eco-hydrological models that examine the effects of flow intermittency on biodiversity and ecosystem functioning in riverine networks.