Tuesday, 11 July 2006

Innovation in Lysimeter Techniques.

Ralph Meissner1, Holger Rupp1, Juliane Seeger1, and Manfred Seyfarth2. (1) UFZ Centre for Environmental Research Leipzig-Halle, Department of Soil Science, Lysimeter Station, Dorfstrasse 55, Falkenberg, 39615, Germany, (2) UGT Environmental Measuring Techniques Ltd., Eberswalder Strasse 58, Muencheberg, 15374, Germany

Exact information about the soil water balance is needed to quantify water and solute transfer within the vadose zone. Different methods exist for measuring water and solute flux in and below the root zone. In principal it is grouped into indirect (water balance estimates, physically-based methods, environmental tracer methods) and direct (drainage-type lysimeter, water fluxmeter) methods. In the last years, particulary in Europe, direct lysimetry methods are being used more and more for studying water and solute migration in soil. In general, a lysimeter consists of a container filled with soil and a mechanism to collect and quantify the amount of solutes contained in it. Only lysimeters permit a direct determination of the amount of water percolating through a soil profile and of the type and amount of solutes contained in it. If the lysimeter is weighable, the actual evapotranspiration can be obtained from the weight change. Due to these charcteristics lysimeters are an excellent tool to derive or calibrate water and solute transport models. A large weighable lysimeter is the best method for obtaining reliable data about seepage water quantity and quality but it is connected with relatively high investment and additional expenses for maintanance. To solve these problems new lysimeter techniques have been developed. The poster will inform about the progress in lysimeter technology. It focused on new technologies to obtain large undisturbed soil monoliths and newly developed types of monolithic weighable lysimeters. Furthermore, a container lysimeter unit will presented which is much more cheaper as a conventional steel or concrete cellar to locate the lysimeters. A substantial progress concerning the extraction of cylindrical lysimeter monoliths is obtained by development of a vertical extraction technology, which cuts out the outline of the soil monolith by a rotating milling tool. This technology has been used successfully for different soil types (from sand to gravel to clay) respectively sites (agricultural and forest land, flood plains, contaminated sites, dump soils) and for different lysimeter sizes (surface area of 0.5 to 2 square meter and depths from 1 to 3 m). Furthermore, a special device for the horizontal cutting of undistrubed soil monoliths (surface area 4 square meter, width 1.0 m and depth 1.5 m) will presented. This technology has been used successfully to obtain undisturbed soil cores under wet site conditions (for example moore lands). The newly developed gravitation lysimeter is equipped with an improved weighing device. Besides recording precipitation and seepage, its weighing precision makes it possible to register mass input by dew, fog or rime. It also permits a very accurate calculation of actual evapotranspiration. Because the precise measuring of pedohydrological parameters in floodplains itself (that serve for obtaining drinking water from bank filtrate) is very difficult a weighable groundwater lysimeter was developed. It is the basis for recording the water balance quantities precipitation, evapotranspiration, groundwater recharge, capillary rise, and interaction with the water course. The function of the lysimeter and the measuring procedure will explained in detail. In the last years enhanced activities were carried out for the preservation and revitalization of the still existing fen sites (Histosols) by re-wetting. But re-wetting may be connected with eutrophication of adjacent surface waters. At this time there is inadequate knowledge about lateral transport processes in fens available. With a newly developed weighable fen lysimeter it is possible to measure water and solute fluxes in fen soils with high temporal and spatial resolution as well as to simulate this processes. The schematic of this lysimeter type and first results will presented. Lysimeters are usually located at special lysimeter stations with an access for functional inspection as well as for the accomodation of measurement, control and weighing devices. To reduce cost and secure mobility, a polyethylene-(PE-HD)-lysimeter station as a container was developed, where 4 lysimeter vessels are located in a clover-leaf arrangement around the access. Variations regarding the amount and arrangement of lysimeter vessels are possible (at present from 1 to 4 lysimeters at one station). The poster contains an evaluation of the newly developed lysimeter techniques and conclusions for further research.

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