Convenient use of electrical conductivity measurements to investigate hydrological processes in Alpine headwaters

Developing effective hydrological models for streamflow generation in Alpine catchments is challenging due to the inherent complexity of the intertwined processes controlling water transfer from hillslopes to streams and along the river network. Over the past decades, studies have proposed complementing traditional hydrological information with environmental tracer data, e.g. stable isotopes or electrical conductivity (EC), for different purposes such as the separation of streamflow components or the estimation of catchment mean residence time. In particular EC has been applied in Alpine environments mainly for hydrograph separation but also, more recently, considered as a possible proxy for streamflow (Q) prediction. The reason is simple: EC data loggers are convenient because of their relative low cost, easiness of installation and low maintenance, unlike traditional water stage gauges. However, EC time series require careful interpretation since electrical conductivity is influenced by a number of geochemical processes not always introduced in the analysis since these can be difficult to parametrize. Likewise, the relationship between EC and Q is very complex because it is characterized by hysteresis loops and often site specific. This study shows how the continuous monitoring of EC in Alpine catchments can be useful specifically for: hydrograph separation, including a proper quantification of uncertainty; process understanding of catchment functioning through the interpretation of hysteresis loops and time lags between EC and Q signals; and finally, water discharge estimation through calibrated functional EC-Q relationships. We discuss advantages and limitations of the use of EC in hydrology and provide information to encourage its use in studies dealing with streamflow generation dynamics in snow-dominated catchments.