Hydrology Rhine Transect

The intensification of agriculture, changes in the forestry sector, and increasing urban land use in Germany after World War II have likely led to large-scale changes in the water and heat balance of landscapes, the extent of which has not yet been examined in detail or quantified. There is ample evidence that land-use changes have significantly altered the water balance of urban and rural areas. At the same time, these measures have had a lasting impact on the landscape’s thermal behavior. The goal of the interdisciplinary Rhine Transect project is to identify potential trends in the water and heat balance components resulting from changes in land use and to evaluate them in the context of the future impacts of climate change. This raises the question of whether imbalances in the water and heat balance expected as a result of land-use planning measures can be at least partially mitigated. Our studies focus on the northern Upper Rhine Plain and the regions to its west and east. This part of southwestern Germany is characterized by highly diverse natural and regional climatic conditions. For example, agriculture is practiced particularly intensively in the northern Upper Rhine Plain, and due to the comparatively dry conditions in the rain shadow of the Palatinate Forest, crop farming often relies on irrigation. In the highlands of the northern Black Forest, on the other hand, precipitation is very high year-round, and since the Middle Ages, people have used the grinden (wet heathland areas) for extensive grazing. The project region also includes the Rhine-Neckar area, one of the most densely populated regions in Germany.

The research conducted as part of the Rhine Transect project aims to use experimental studies in agricultural and forested areas managed in different ways within the project area to improve our understanding of these processes. These findings are then incorporated into the further development of existing simulation models, which are subsequently applied to the entire region to quantify the effects of land-use changes on the water and heat balance, for example. These large-scale analyses are supported by remote sensing methods and cellular automata to reconstruct historical land-use changes and project future ones. Through the integration of basic research and application-oriented methods, the project is designed to foster collaboration between universities, research institutes, and state and federal agencies. The project is designed as a long-term initiative in order to obtain the longest possible time series of environmental parameters documenting ongoing environmental change, and to analyze them accordingly.

Rhine Transect was launched in 2012: In October 2012, the first study site was inaugurated at Queckbrunner Hof near Speyer, an experimental farm operated by the state of Rhineland-Palatinate (Fig. 1). One of the devices installed there was an eddy covariance station (Fig. 2). Using these sensitive micrometeorological instruments, it is possible to analyze high-frequency water vapor and carbon dioxide fluxes to investigate phenomena such as land surface evaporation or the response of the observed vegetation to water stress. Our station is part of a global network of such measurements (FLUXNET). Furthermore, the station’s instruments can record precipitation, air temperature, humidity, wind speed, wind direction, albedo, and short- and long-wave radiation components.

In addition to using the Geography Institute’s own funds and project funding, our research receives financial and logistical support from the state of Rhineland-Palatinate, in particular from the following agencies:

• State Office for the Environment, Water Management, and Industrial Safety (LUWG)
• State Geological Survey
• Service Center for Rural Areas (DLR)
• Competence Center for Climate Change Impacts

In addition, there are collaborative partnerships with various departments at Heidelberg University, in particular with:

• Heidelberg Center for the Environment (HCE)
• Institute for Environmental Physics