Capturing Hydrological and Sedimentological Connectivity from Cropland Plots to Catchments - Integrating Experimental Sites into a Multi-Scale Approach

In many European regions, the ecological cycles are changing significantly because of advancing climate change, the ongoing landscape transformation, and intensive agricultural use. Runoff components redistribute towards more surface runoff (more heavy rainfall, less snow cover, compaction, crusting) and thus significantly reduced groundwater recharge, faster runoff concentration (accelerated concentration, secondary water network through drainage ditches and drains, shorter and steeper flow paths), and thus a lower landscape retention capacity. As a result, more soil, nutrients and pollutants are eroded, especially from arable land, threatening the ecosystems and the associated ecosystem services along the watercourses.

The increasingly strict environmental legislation in the EU has recently led to farmers’ protests across Europe, and subsequently to a hasty softening at all governmental levels. The protest is also directed against environmental regulations, as their predicted effect in many cases cannot be substantiated with quantitative figures and there is a lack of coherent concepts for combining measures in small catchments, quantified combined effectiveness analyses, and an understandable roadmap towards the ecosystems’ sustainable use.

The existing data sets are often fragmented, short, focus on individual measures under strictly limited conditions. In particular, the results of studies evaluating agricultural management methods can only rarely be applied to entire catchment areas or landscapes, as neither the cross-scale processes are understood nor do corresponding data sets exist at the landscape scale. Hence, there is no basis for making informed decisions.

Two new open-air laboratories are currently being built in southeast Germany: the almost completed Erosion and Runoff Laboratory (EARL) uses long-term measurements of water and nutrient fluxes of 36 sloping (approx. 10%) agricultural plots (each 660 m²) to monitor the effect of different agricultural systems on the runoff components, soil erosion, as well as the discharge of nutrients and pollutants. The Water and Environmental Landscape Laboratory (WELL) focuses on the effects of management methods combined with measures, monitoring 22 similarly sloped sub-catchment areas (each 0.3 to 0.5 km²) predominantly used for arable farming. In combination with the nearby Hydrological Open Air Laboratory (HOAL), this results in a unique combination of three long-term experimental laboratories in the same natural entity: EARL on the plot scale, HOAL on the slope scale, and WELL on the landscape scale. We would like to present the status of the projects in order to facilitate cooperation for research applications at the European level.