The complexity of hydrological systems reflects the interaction of multiple factors. In addition to climatic, geological and physiographic variability, annual and seasonal variations in climatic forcings or catchment wetness conditions as well as changes in soil properties and land use often lead to changes in catchment states and to the modification of the dominant controls on hydrological responses. Particularly, contrasting catchment behaviours are found when non-linear and threshold effects occur. For instance, changes in wetness conditions may lead to changing directions in hysteretic storage/runoff loops, exceeding soil moisture thresholds can lead to the activation of subsurface flow patterns that dramatically increase streamflow, and marked changes in land cover may result in the alteration of specific flow pathways dominance. Unravelling such complexity is one of the current challenges in hillslope and catchment hydrology and represents an essential step toward a more accurate description and conceptualization of watershed functioning.

This session encourages contributions from experimental and numerical studies on:
i) The main controls on catchment behavior in different wetness conditions, above/below precipitation and other hydrological thresholds, before/after land use changes;
ii) Changing directions in non-linear and hysteretic relationships between storage/runoff, soil moisture/runoff, sediment concentrations/runoff, solute concentrations/runoff;
iii) Changes in spatial sources of runoff or dominant flow pathways at different time scales and under various conditions;
iv) Incorporation of thresholds and non-linearities in hydrological models


Solicited talk:

- Jerome Latron, Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona, Spain