Incremental distributed modelling investigation in a small agricultural catchment: 2. Erosion and phosphorus transport

Abstract

Abstract:Distributed physically based erosion and phosphorus (P) transport models, run by the overland flow model described in Taskinen and Bruen (2006. Hydrological Processes 21(1)), are described. In the erosion model, the additional components to the basic model were the outflow of the particles by infiltration and a new model component, i.e. deposition when rainfall stops. Two ways of calculating the shielding factor due to the flow depth were compared. The P transport model had both dissolved P (DP) and particulate P (PP) components. The processes included in the DP model were desorption from the soil surface, advection, storage in the overland flow and infiltration. The PP model accounted for advection, storage in the flow, infiltration, detachment from the soil surface by flow and rainfall and deposition both when transport capacity of suspended solids (SS) is exceeded and when rainfall ceases. When the models were developed and validated in small agricultural fields of cohesive soil types in southern Finland, comparisons were made between corresponding processes and the significance of added components were estimated in order to find out whether increased model complexity improves the model performance. The sedigraphs were found to follow the dynamics of rainfall, emphasizing the importance of the rainfall splash component. The basic model was too slow to react to changes in rainfall and flow rates, but infiltration and deposition that acts during the cessation in rainfall improved the model significantly by enabling the modelled SS to fall sharply enough. The shielding effect of flow depth from the splash detachment was found to play a significant role. Transport capacity should also be included in erosion models when they are applied to cohesive soils. In this study, the Yalin method worked well. A strong correlation was obvious between the measured SS and total P concentrations, indicating that the main form of P in runoff is PP. This emphasizes the importance of a good sediment transport model in P transport modelling. The submodel used for DP desorption from the soil surface produced plausible results without any calibration.

Incremental distributed modelling investigation in a small agricultural catchment: 1. Overland flow with comparison with the unit hydrograph model

“…The same models that were best in the calibration also worked best in the verification. The fully distributed model provides a potential method for running water-quality models and testing their different processes in similar catchments and conditions, since, for example, taking into account spatial variation of slope, flow depth and velocity and different flow routes is enabled (see Nasr et al (2005) and Taskinen and Bruen (2006)). …”

Study on the Fabrication and Characterization of Piezoelectric Paper Made With Cellulose

“…However, detachment by rainfall impact often occurs when there is little or no flow available for transport. Major factors that affect raindrop detachment are rainfall characteristics, soil characteristics, ground and canopy cover, and surface water depth (Taskinen and Bruen 2007).…”

Uncertainties in Data and Models to Describe Event Dynamics of Agricultural Sediment and Phosphorus Transfer

“…Where sediment is a carrier, P transfer from land to water involves three connected processes: hydrology, sediment dynamics, and P dynamics (Hutchins et al, 2002). Mathematical models describing event dynamics of P transfer usually conceptualize these compartments with a high degree of complexity, ranging from spatially semi‐distributed models with a process‐based conceptualization of each compartment (e.g., Hutchins et al, 2002) to spatially distributed models where processes are derived from small‐scale physical principles (e.g., Taskinen and Bruen, 2007). However, the compartments of these models have rarely been tested individually and usually do not include estimates of uncertainties in data and models.…”