Seasonal increase in hydrological connectivity causes changing flow-concentration hysteresis patterns in headwaters of high mountain catchments.

Abstract

In the present work, we study the seasonal differences in the hydrological connectivity between a stream and the different hydrological compartments of a high mountain catchment, analyzing the hysteresis patterns during storm events. Stream water were sampled with autosamplers, to capture the entire rainfall event, at two sites at different altitudes during the snow-free season. Stream discharge (Q) – solute concentration (C) hysteresis patterns changed over the season, in parallel to indicators of the hydrological connectivity in the catchment. We present a numerical model based on three end-members (atmospheric water, shallow and deep groundwater), to reproduce the observed changes in hysteresis by simulating stages with increased connectivity. It has been observed that the hydrological connectivity of the catchment increases with precipitation and that it depends on the level of recharge of the non-surface compartments, with connectivity being greater the more recharged they are. Our results highlight the importance of groundwater in forming streamflow in high mountain catchments and how connectivity influences solute transport pathways.