Effects of terrain slope on long-term and seasonal water balances in clayey, subsurface drained agricultural fields in high latitude conditions

摘要: Abstract Water outflow pathways affect environmental loads from agricultural fields, but the and effects of terrain topography on their proportions drainage design are not known in detail. In this study, a long-term hydrological dataset 3D FLUSH model were applied to field-scale assessment multi-yearly seasonal water balance two adjacent clayey subsurface drained fields with different slopes (1% 5%). The was calibrated then run an hourly time step input data throughout five studied years, it able reproduce measured components. results suggested that macropore flow had essential role processes fields. provided quantification how slope increased amount groundwater correspondingly decreased drain discharge. implication is field surrounding areas should be taken into account when optimizing intensities. Though most occurred outside growing periods, sustained all seasons. A correspondence observed between near-saturated surface soil conditions tillage layer runoff (TLR) events, which suggests TLR events high-latitude mainly triggered by saturation excess mechanism. During springs (once both section) clearly higher than during other seasons, likely induced frost. However, without computational schemes for frost-induced changes hydraulic properties satisfactorily reproduced discharge spring low springs, indicates typically generation may small. inaccuracies snowmelt formed uncertainty estimate components snowmelt.