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Browsing by Author van Dam, J.C.

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  • Determination of the relative macroporosity and the effective aggregate width for different macropore geometries with disk infiltrometers

    • Authors: Urbina, C.A.F.;  Advisor: -;  Participants: van Dam, J.C.; van den Berg, F.; Ritsema, C.J.; Tang, D.W.S. (2020)

  • The computation of ξ accounts for differences in the macropore area and macropore water flow between noncylindrical and cylindrical shapes. A total of 15 combinations of macropore width and effective aggregate width were used to construct the geometrical figures and compute both wf_nc and wf_c. For the cylindrical, ring, and rectangular slab shapes, the macropore water flow was solved using analytical solutions. For the hexagonal and brick shapes, the macropore water flow was solved numerically using COMSOL Multiphysics. Remarkably, the computed ξ was constant and equal to 1.5 for all four noncylindrical shapes under analysis. We show that the solution is exact for laminar flow under ...
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  • Parameter sensitivity of SWAP–PEARL models for pesticide leaching in macroporous soils

    • Authors: Urbina, C.A.F.;  Advisor: -;  Participants: van den Berg, F.; van Dam, J.C.; Tang, D.W.S.; Tang, D.W.S. (2020)

  • The outputs analyzed were the concentration in drainage water, the average concentration in groundwater between 1 and 2 m, and the concentration in the soil system at 100‐cm depth. Influential parameters found through the Morris method were analyzed using the Sobol–Jansen method. The results for bentazon indicate that the degradation half‐life (DT50), the bottom depth of the internal catchment (zic), and the proportion of the internal catchment at the soil surface (pic_0) are critical parameters in all the outputs analyzed. For imidacloprid and compound I, the most relevant parameters for drainage output are the Freundlich sorption exponent (Fexp) and zic; for groundwater, the relevan...
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  • Water Flow in Soils with Heterogeneous Macropore Geometries

    • Authors: Urbina, C.F.A.;  Advisor: -;  Participants: van Dam, J.C.; Hendriks, R.F.A.; van den Berg, F.; Gooren, H.P.A.; Ritsema, C.J. (2019)

  • We analyzed the measured pressure head and outflow in column experiments with a uniform matrix (Exp. I), one central macropore (main bypass) (Exp. II), and HMG (Exp. III) and evaluated the performance of the models HYDRUS‐1D and SWAP under these conditions. Two replicate soil columns were prepared with a 62‐cm silty loam layer above a 5‐cm sandy loam layer. Well‐defined infiltration and drainage conditions were applied to top and bottom boundaries, respectively. Pressure head and outflow were measured at short time intervals, and calibration was performed by PEST. Experiment I was conducted to calibrate the matrix parameters and Exp. II to calibrate macropore parameters. In Exp. III, ...