Instrumentation
Measurements are continuously made at two sites: 'Büel' and 'Mosnang'. 'Büel' is equipped with meteorological instruments and hydrological runoff as well as ground water instrumentation. The data is recorded by several external page Campbell data loggers with at least an hourly time interval. Below the actual instrumentation is listed and a detailed description of the lysimeter is given. At 'Mosnang' the runoff of the whole Rietholzbach catchment is captured (external page runoff station operated by Federal Office for the Environment FOEN).
The long-term large lysimeter at 'Büel'
The lysimeter is a big 'plant pot' which is weighed. Additionally, the outflow at the bottom is measured. From this information precipitation and evapotranspiration values can be calculated by applying the water balance equation and information about infiltration and storage can be obtained.
The surface of the lysimeter at 'Büel' measures 3.14 m2 and is covered with grass. The plant composition, cutting intervals and fertilizer applications reflect the conditions of the area surrounding the measurement site. The lysimeter container has a depth of 2.5 m and is filled with a typical gley-cambisol resulting in an average weight of 14'000 kg. The container is positioned on the scales (composed of three elements) which has a resolution of 100 g, which corresponds to a water column of 0.032 mm.
The controlled tension weighing mini lysimeter at 'Büel'
The mini-lysimeter was installed in August 2015. It has a surface area of 0.071 m2 (0.3 m diameter) and a depth of 0.6 m. The soil column is monolithic and thus possess soil characteristics comparable to those in the undisturbed surroundings. As with the large lysimeter, the surface is grass-covered and reflects the conditions of the surroundings. At the lysimeter base, the soil matrix potential is continuously measured and compared to a reference tensiometer measurement at the same depth in the undisturbed surroundings. A bi-directional pump connecting a series of suction cups at the lysimeter base to an external drain water bottle is then used to adjust the lysimeter water content to equilibrate these records.