[D] Spatio-temporal dynamics of water storage, mixing and release
The baffling diversity of streamflow generation still largely jeopardizes our efforts to anticipate how water quality and supply will be impacted under a potential future climate change. Recent work has suggested that a better understanding of how catchments collect, store and release water is the way forward in this respect. However, descriptors of water storage, flowpaths and release can be subject to considerable spatial and temporal variability. The complexity of this mixture is highly time-variant, as it is controlled by multiple factors: precipitation intensity, complexity and length of flowpaths, infiltration, soil and bedrock type, soil moisture, groundwater levels, etc. In this project we aim at answering at the following research questions: (i) How much water do catchments store?, (ii) How do catchments apportion water in space and time? and (iii) How are the hydrological functions of water collection, storage and release inter-connected? Our nested catchment set-up located in the Attert River basin provides a unique opportunity to investigate these pressing science issues with a plethora of hydrometric, geochemical and isotopic data across a large range of spatial scales and physiographic settings.
Fig 1. Schematic representation of the different water storage reservoirs in the Roudbach catchment (44 km2, sub-catchment of the Attert River basin) and approximate values of the residence time of water in each reservoir.*
We propose to leverage the research into hydrological processes carried out in the framework of the 1st phase of the CAOS project (Project H) focusing on the 46 cluster sites and the nested catchment experiments for improving our understanding of what are the dominant controls on the spatial and temporal variability of catchment functioning. Relying on a multi-tracer (geochemicals, stable isotopes of O and H, tritium) and multi-sensor (e.g. in situ and satellite-borne monitoring of soil moisture) approach, we intend to contribute answering fundamental research questions on spatio-temporal variance of storage and water apportionment.
More specifically, we intend to investigate through our nested catchment set-up located in the geologically contrasted Attert River basin (Luxembourg):
- the spatio-temporal dynamics of catchment storage and its compartments (i.e. saturated and unsaturated zones);
- the links between catchment characteristics, storage dynamics, temporal dynamics of transit times and end-member contributions;
- regionalisation of our newly gained understanding of hydrological processes by combining hydrological mapping of dominant processes with process-based hydrological modelling.