Defence of dissertation in the field of water and environmental engineering, Mika Turunen, M.Sc. (Tech.)
Novel computational methods reveal subsurface flow and load pathways in agricultural fields.
The public examination of the doctoral dissertation of Mika Turunen, M.Sc. (Eng.), will be held on 28 April 2017 at 12.00 at the Aalto University School of Engineering. The title of the dissertation is Assessing water and sediment balances in clayey agricultural fields in high-latitude conditions. Field of the dissertation is water and environmental engineering.
Opponent: Professor Emeritus Per-Erik Jansson, KTH Royal Institute of Technology, Sweden
Supervisor: Professor Harri Koivusalo, Aalto University School of Engineering, Department of Built Environment
Electronic dissertation: http://urn.fi/URN:ISBN:978-952-60-7378-1
Contact information: Mika Turunen, +358 50 353 2938, firstname.lastname@example.org
Agricultural fields form complex hydrological systems, where water flow and load processes are interlinked. Dominating water balance components, erosion processes and sediment transport pathways are not comprehensively known. Mathematical models are often applied to study the hydrological processes, but process-based 3D models have been rarely applied in high-latitude conditions. In this thesis, water and sediment balances were assessed with a novel 3D model and empirical data.
According to the long-term observations and simulations in two clayey experimental sites, groundwater outflow can form a dominant water balance component due to lateral preferential flow paths. Field topography was found to control the magnitude of the groundwater outflow and preferential flow paths dominated water flow. The results demonstrate that due to the secondary drainage impact of groundwater outflow, steep fields require less efficient drainage procedures than flat fields. The field areas were also shown to share a hydrological connection with the adjacent regions via groundwater flow processes.
Preferential flow paths also induced the transport of sediment in the structured soils. The majority of eroded fine-textured topsoil was transported to the adjacent surface waters via subsurface drain discharge and groundwater outflow. When the subsurface load pathways dominate, widely applied buffer strips can only have a limited impact on the total loads. The 3D dual-permeability model was found to be a useful tool for the analysis of empirical data and for the comprehensive description of the field hydrology.