Simulation of boundary condition effects on preferential tile drain outflow for a bromide field tracer experiment
Abstract
Preferential flow was hypothesized as possible cause for chemical leaching from tile-drained agricultural fields with structured soils originating from glacial till sediments at Bokhorst experimental site. Although tile water outflow peaks could somehow be reproduced, single-porosity models were unable to describe leaching patterns, characterized by highest Bromide concentrations for the first and decreasing concentrations for subsequent leaching events after application. 2D-dual-permeability model simulations for a vertical cross-section perpendicular to the tiles, require definition of initial and boundary conditions and spatially-resolved state variables separately for each of the two pore domains. The objective was to distinguish between effects of model approach and that of boundary conditions. The observed drain tile data are described comparing 2D single- with 2D dual-permeability approach. Simulations include differently evaluated soil hydraulic and transport parameter sets and boundary condition types to represent natural areal rainfall and partial-area irrigation. Depending on the soil parameters, the application of bromide in dissolved form with the irrigation water yielded initially larger preferential outflow concentrations than application as salt at the soil surface layer. Lateral flow effects during spatially switched and temporally intermittend irrigation may increase dispersion and reduce preferential leaching patterns. The spatial heterogeneity of the most sensitive mass transfer term parameters and the boundary conditions seem to be important for improving model predictions.
- Publication:
-
EGS - AGU - EUG Joint Assembly
- Pub Date:
- April 2003
- Bibcode:
- 2003EAEJA.....5127G