Using Simple Bucket Models to Analyze Solute Export to Subsurface Drains by Preferential Flow
A. Kohler*,a,
K. C. Abbaspourb,
M. Fritschc and
R. Schulind
a Federal Office for Water and Geology, Hydrological Survey, 3003 Bern, Switzerland
b Swiss Federal Institute for Environmental Science and Technology (EAWAG), 8600 Dübendorf, Switzerland
c Partners GmbH, Blaufahnenstrasse 14, CH-8093 Zurich, Switzerland
d Swiss Federal Institute of Technology, Department of Soil Protection, Grabenstrasse 3, 8952 Schlieren, Switzerland

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Fig. 1. Schematic of the experimental site in the study area. Shaded region shows the Br- application area.
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Fig. 2. Pictures of a dye infiltration test with high (bottom) and low (top) infiltration rates (after Gada and Felber, 1996). The total amount of infiltration was equal to 40 mm for both tests. The dimensions of the grids are 10 by 10 cm.
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Fig. 3. Schematic representation of surface-trigger and subsoil-trigger models used to analyze the conditions for triggering of preferential flow.
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Fig. 4. Measured (solid lines) and calculated (symbols) water contents by the subsoil-trigger model at depths of 0.3 and 0.6 m.
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Fig. 5. Time course of drainage discharge and Br- concentration (left) and Br- concentration vs. discharge (right) for the period of 25 Aug. 1995 to 12 Feb. 1996.
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Fig. 6. Time course of drainage discharge and Br- concentration (left) and Br- concentration vs. discharge (right) for the period of 13 Feb. 1996 to 8 June 1996.
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Fig. 7. Time course of drainage discharge and Br- concentration (left) and Br- concentration vs. discharge (right) for the period of 9 June 1996 to 8 Aug. 1997.
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Fig. 8. Partitioning of drain discharge into matrix and preferential flow for the event on 18 Nov. 1995. (a) Measured drainage discharge. (b) Measured (symbols) and interpolated (thick line) Br- concentration of drainage effluent as well as the interpolated matrix flow concentration. (c) Cumulative export of Br- in the drainage effluent due to preferential and matrix transport.
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Fig. 9. Partitioning of drain discharge into matrix and preferential flow for the event on 3 May 1996. (a) Measured drainage discharge. (b) Measured (symbols) and interpolated (thick line) Br- concentration of drainage effluent as well as the interpolated matrix flow concentration. (c) Cumulative export of Br- in the drainage effluent due to preferential and matrix transport.
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Fig. 10. Measured drainage discharge and Br- concentration for the period of 24 Aug. 1995 to 8 Aug. 1997. The symbols indicate the timing at which preferential flow was predicted by the surface-trigger (triangle) and the subsoil-trigger (circle) models.
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Copyright © 2003 by the Soil Science Society of America.