Catchment and Eco-hydrology

Research carried out in densely equipped experimental catchments, Long-Term Ecological Research (LTER) sites, Critical Zone Observatories (CZO), and other test sites in Luxembourg has advanced our understanding of environmental processes. However, translating this knowledge into robust prediction tools for environmental systems undergoing significant changes remains a steep challenge. Across the Earth sciences community, there is now consensus on the need for research efforts to be better organized and harmonized across disciplines to tackle pressing issues (e.g. Blöschl et al. [2019] (1)). Key challenges include:

• Fundamental questions regarding (i) changes in the water cycle triggered by global change, (ii) water and life and (iii) clean water for human consumption and agro-ecosystems.
• A growing scientific interest in understanding how change propagates through space and time, and how the hydrological cycle may accelerate or decelerate. Here, the challenge lies in linking short-term local processes (as studied thus far in manifold field sites) to long-term global processes, and vice versa.
• Limited integration between environmental compartments (and disciplines, e.g. water chemistry, ecology, biogeochemistry), as well as among nutrient cycles – constituting a real bottleneck in the achievement of holistic system understanding.
• The intensifying human footprint, which raises a new set of questions related to human-water systems, such as long-term dynamic feedback, or contaminants causing increasing concern.

Objectives

The Catchment and eco-hydrology (CAT) group focuses on questions related to:

• How eco-hydrosystems collect, store, mix and release water, solutes and matter in the critical zone.
• The development of new environmental monitoring tools.
• Predictions related to water in the future, as expressed through floods and droughts, drinking water availability, and water for agriculture and ecosystems.

The group specializes in hydrological processes in small catchments, water quality in rural watersheds, and the hydrological functions of forests. Both basic and applied science goals drive the group’s research, based on the conviction that the major challenges posed by global change require both a new understanding of natural systems and immediate tools to manage them effectively. 

Major technological and research assets include:

• Long-term water flux datasets from streams and rivers in Luxembourg,
• Highly instrumented hydrological and ecological observatories in small catchments and forests,
• Well-equipped laboratories with instruments to develop and apply water flow techniques in catchments and plants, and to acquire and interpret biogeochemical and biological geochronologies,
• Colocation with diverse and capable colleagues at LIST, to accelerate the development of technological tools for new applications in research.

Scope of expertise

The Catchment and Eco-hydrology (CAT) research group leverages nearly two decades of hydrological process research in the unique experimental setting of the Sûre River basin, which exhibits contrasting physiographical characteristics and a homogenous temperate climate. Pioneering work is carried out on controlling mechanisms of the fundamental hydrological catchment functions of water, matter and contaminant collection, storage, mixing and release. New technological solutions for monitoring and modelling agro-environmental systems, which are increasingly under pressure from global change, are designed, built and tested. This includes the development of innovative field deployable sampling devices, which deliver water quality and isotope data with unprecedented temporal resolution. The newest telecommunication technologies (e.g. microwave antennas, IoT devices) are used to deploy environmental monitoring networks of unprecedented and flexible density. These transformational datasets are integrated into highly innovative modelling concepts to anticipate the response of hydro- and agro-ecosystems to global change – including long-term responses of water resources (e.g. surface- and groundwater) and vegetation (e.g. forests) to a changing climate, as well as short-term responses to extreme weather (e.g. flash floods).

A unique blend of experts in catchment hydrology, eco-hydrology, isotope hydrology, hydro-geochemistry, environmental chemistry, sediment transport and plant physiology characterize the water, matter and contaminant fluxes within and across the various compartments of the critical zone. Collaboration with the other groups in the unit enables the full potential of new in-situ and remote sensing technologies to be leveraged (some developed in-house), providing data with unprecedented spatial and temporal resolution. These data ultimately serve to calibrate and validate the newly designed forecasting and prediction tools for hydro- and agro-ecosystem responses to global change.

To overcome the pressing technological limitations of conventional tools and protocols, field and laboratory prototypes, and experimental set-ups and protocols are being designed, built and tested in collaboration with ENVISION’s Luxembourg Eco-hydrology Observatory (LEO). These solutions address demanding high-resolution and /or high-frequency sampling /sensing criteria. In addition, state-of-the-art field and laboratory infrastructures are utilized, including:

• Weierbach experimental catchment 
  operates from a long-term research perspective and focuses on CZ research (Weierbach timelapse)
• Water sampling 
  long-term grab sampling programs of surface & groundwater bodies, passive samplers, high-frequency event-based sampling of rainfall-runoff events with automatic sampling devices.
• Isotope laboratory 
  designs its own water extraction protocols (from soils, plants, regolith) and carries out subsequent O and H stable isotope analyses with laser spectrometers.
• Geochemistry laboratory 
  offers environmental sample mineralization and preparation for the determination of nutrients and trace-metal concentrations, as well as Sr-Nd-Pb isotopic ratio quantifications.
• Sediment characterization 
  turbidimeters, laboratory and field laser diffraction particle size analysers, sediment sampling devices, UV-VIS spectrometer probes and an underwater camera.
• Geophysics IRIS Syscal Pro 120 all-in-one multi-node resistivity and induced polarization imaging system for environmental and engineering geophysical studies (e.g. 2D and 3D characterization of subsurface geometry and properties).
• Numerical modelling tools
  HydroGeoSphere, Coupled Water Balance and Vegetation Optimality Model, Catchment Travel Time Distributions.

(1) Blöschl G., Bierkens M.F.P., Chambel A., (...), Pfister L., (…), Yilmaz K.K., Zhang Y.  2019. Twenty-three unsolved problems in hydrology (UPH)–a community perspective. Hydrological Sciences Journal 64: 1141-1158.