These research lines dominate the chair group's research agenda Mid-term Research Agenda (2011-2015). The related projects will require undertaking applied and fundamental research. The scale of integration varies significantly from lab-scale experiments to large scale hydrological modelling. In the lines on hydrological processes (no.1) and ecohydrology (no.2) experimental work is carried out to improve the understanding of dominating hydrological processes, and with the aim to develop process-oriented models that are able to make predictions for hydrological systems under current and future changed circumstances.
Hydrological processes near the earth's surface
This research line focuses in particular on improving the understanding of near-surface processes of the land phase of the hydrologic cycle (surface and shallow subsurface processes), in particular the movement of water and associated substances near the earth's land surfaces, the physical and chemical interactions with earth materials accompanying that movement, and the vegetation and biological processes that conduct or affect that movement. The nature of this type of research is experimental and field oriented, and attempts to assess the scales (spatial and temporal) and magnitude of processes in their natural environment, which includes arid to humid climates and cold to temperate and tropical regions, 'soft' and 'hard' rock areas, and natural to human affected habitats. Better understanding of related hydrological processes through experimental research provides the basis for improved process-based modeling - much needed in particular in the developing world to predict the impact of changes (e.g. climate, land use) on hydrological systems.
A main objective is to connect the knowledge of quantitative hydrology, i.e. groundwater dynamics, flow pathways, residence times and mixing of different water compartments etc., with the water quality. The main regional emphasis is on semi-arid conditions. This research is positioned in between the more fundamental sciences (e.g. physics, chemistry, biology), on the one hand, and the applied sciences (e.g. civil engineering, hydraulic engineering) on the other. This research line encompasses:
- Catchment and hillslope hydrology;
- Preferential flow systems (fissures, karstic limestone, and vadose zone);
- Evaporation, interception and transpiration;
- Hydrological systems analysis;
- Water balance evaluation; and
- Transport of pollutants in groundwater.
In order to study water fluxes, the driving forces of these fluxes and their causal relationships, we employ standard field data collection techniques focused on geology (e.g. mapping, auger drilling, electrical resistivity tomography), surface water discharge (e.g. stream discharge, water quality such as temperature, EC and natural isotopes), hydrometeorology, hydrogeology and flow field characteristics (e.g. piezometer installation, automated groundwater monitoring at various temporal scales), tracer methods (multiple artificial and natural tracers incl. DNA, bio-colloids and stable isotopes) and hydrochemistry (major and minor cations and anions). Experiments are carried out under controlled conditions in the lab (column experiments, lysimeters etc.) as well as in the field.
Ecohydrology is a widely recognized interdisciplinary science integrating hydrological, ecological, and biogeochemical processes. Ecohydrological processes regulate many environmental conditions within aquatic systems, maintaining water quantity and water quality within ranges suitable to native flora/fauna and the services they provide. Human interference in natural ecohydrological processes is the basis for many pressing environmental problems, including the most ubiquitous forms of water pollution (eutrophication, hypoxia, and acidification), related degradation of ecosystem services (loss of soil fertility, declines in fisheries, invasions of exotic species, and outbreaks of pathogens), and accelerating climate change (e.g. non-industrial emissions of greenhouse gases and carbon sequestration).
Ecohydrology addresses the underlying physical, chemical, and biological processes that manifest these problems as well as the processes that are the keys to ultimately solve them. In developed areas, knowledge of ecohydrological processes serves to enhance the highly engineered systems already in place, while in less developed areas ecohydrological processes may serve as the primary means for managing water quantity and quality through natural attenuation of contamination and natural regulation of flow levels. The science includes well developed methodologies of field sampling, laboratory analysis, experimentation, and computer modelling.
Research in this theme involves multidisciplinary field, laboratory, and modeling techniques. Direct measurements are made of surface water flows and groundwater levels, and chemical and isotopic tools are utilized to trace the spatial and temporal interactions of flowpaths, including uptake by plants (i.e. xylem water). Biogeochemical and ecological methods focus on measurement of flow-related processes such as nutrient and organic matter retention along surface and subsurface flow paths, hypoxia related to high and low flow events, and flow- and wetness-related controls on spatial and temporal patterns of productivity in river and wetland (including GDEs). A wide variety of modeling approaches are applied, including physically based modeling, cellular automata, and fuzzy logic. Emphasis is also placed on model-supported decision making.
Basin hydrology and global changes
With the increasing population, expanding urbanization, modernised lifestyles, climate changes and other global changes the pressure for sustainable planning and management of our finite water resources is more evident than ever. Consequently, the role and importance of hydrological research in river basin of various scales have increased. In particular, we are facing increased challenges in predicting the [future] state of the water resources in view of the impacts from climate and anthropogenic changes to hydrological system dynamics. The key objectives of this research theme contribute to the understanding of hydrological processes at basin scales and modeling of these processes to predict the space-time availability of water resources and water cycle dynamics, including impacts from global changes. We primarily focus our research to the river basin scale typically varying from a few thousand to several hundred thousand square kilometers.
Identification and quantification of the cause and effect relationships and predicting the impacts for the future at the large scale can only be achieved through process-based modeling. Large scale modeling typically encounters data requirements beyond the classical rainfall-runoff simulation. Therefore, representation of hydrological processes at appropriate detail and integration of comprehensive remote sensing and ground observations into the modeling system form the framework for our research methodology. Within this framework, it is also important to acknowledge possible sources of uncertainty, and to provide reasonable assessments of uncertainty in model results.