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Controls on water storage, mixing and release dynamics across multiple spatial and temporal scales : open challenges, new experimental approaches and modelling avenues
Convener: Laurent Pfister  | Co-Conveners: Theresa Blume , Peter Chifflard , Tonie van Dam , Ingo Heidbüchel 
 / Thu, 12 Apr, 08:30–12:00
 / Attendance Thu, 12 Apr, 17:30–19:00

The apparently inextricable natural diversity of streamflow generating mechanisms still often derails our efforts to anticipate how water quality and supply are and also will be impacted by land use and/or climate change. Understanding fundamental catchment functions of water collection, storage and release are recognized as the way forward to overcome this current status quo.
Storage dynamics essentially reflect the balance between water entering (e.g. incident precipitation) and leaving (e.g. streamflow, evapotranspiration) the hydrological system. Storage dynamics and subsequently also residence time distributions, as well as solute export to the stream network, are dependent on (i) the dynamic connectivity of these storages to the stream network, (ii) physiographic catchment properties and (iii) past and future inputs of precipitation.
Essentially due to technological limitations, the direct determination of catchment water storage remains difficult. Very often, storage dynamics in the unsaturated and saturated zones can only be determined locally. Eventually, the information retrieved from this type of observations lacks spatial and temporal representativeness. The advent of new monitoring technologies (in situ, air- and space-borne), operating at unprecedented spatial and temporal scales, has generated new opportunities for going beyond the current status quo in water storage assessment.
Subsurface runoff, the link between subsurface storages and the stream network is unfortunately particularly difficult to observe, to quantify and characterize. Consequently, scaling, modeling and prediction are problematic (with respect to its occurrence in space but also in time, as it is often governed by threshold processes).
This session focuses on contributions that relate to direct or indirect assessment approaches of lumped catchment storage dynamics on the one hand and individual dynamics of storage in the unsaturated and saturated zones on the other hand. For example, while catchment storage dynamics may be approached through water balance calculations, recession analysis, or gravimetric measurements, other - multi-sensor based - approaches may focus at determining unsaturated zone dynamics from both in situ measurements and satellite-borne microwave remote sensing of soil moisture. Moreover, we present experimental and modeling studies that analyze the role of catchment storage, catchment mixing, subsurface runoff and hyporheic exchange fluxes and determine how they control hydrologic and hydrochemical catchment response in time and space.