Fate of herbicides in cropped lysimeters: 1. Influence of different processes and model structure on vadose zone flow

Abstract Understanding transport and fate processes in the subsurface is of fundamental importance to identify leaching potentials herbicides or other compounds groundwater resources. HYDRUS‐1D was used simulate water flow solute arable land lysimeters. Simulations were compared observed drainage rates stable isotopes (δ 18 O) drainage. Four different model setups investigated statistically evaluated for their performance dominant characterization vadose zone under similar cultivation management climatic conditions. The studied lysimeters contain soil cores dominated by sandy gravel (Ly1) clayey silt (Ly2), both cropped with maize located Wielenbach, Germany. First, a single‐porosity setup chosen. For Ly1, modeling results satisfactory, but Ly2, damping isotope signature could not be fully covered. By considering immobile dual‐porosity improved. This due higher fraction fine pores Ly2 available storage, leading mixing isotopically enriched summer precipitation lighter winter water. Accounting isotopic evaporation fractionation did lead improved performance. Consequentially, difference hydraulic properties between two seems impact processes. Knowledge such differences crucial prevent contamination mitigate potential risks groundwater.