HR: 14:00h
AN: H53I-02    [Abstracts]
TI: Understanding Flow Pathways, Mixing and Transit Times for Water Quality Modelling
AU: * Dunn, S M
EM: s.dunn@macaulay.ac.uk
AF: Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, United Kingdom
AU: Bacon, J R
EM: j.bacon@macaulay.ac.uk
AF: Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, United Kingdom
AU: Soulsby, C
EM: c.soulsby@abdn.ac.uk
AF: School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UF, United Kingdom
AU: Tetzlaff, D
EM: d.tetzlaff@abdn.ac.uk
AF: School of Geosciences, University of Aberdeen, Aberdeen, AB24 3UF, United Kingdom
AB: Water quality modelling requires representation of the physical processes controlling the movement of solutes and particulates at an appropriate level of detail to address the objective of the model simulations. To understand and develop mitigation strategies for diffuse pollution at catchment scales, it is necessary for models to be able to represent the sources and age of water reaching rivers at different times. Experimental and modelling studies undertaken on several catchments in the north east of Scotland have used natural hydrochemical and isotopic tracers as a means of obtaining spatially integrated information about mixing processes. Methods for obtaining and integrating appropriate data are considered together with the implications of neglecting it. The tracer data have been incorporated in a conceptual hydrological model to study the sensitivity of the modelled tracer response to factors that may not affect runoff simulations but do affect mixing and transit times of the water. Results from the studies have shown how model structural and parameter uncertainties can lead to errors in the representation of: the flow pathways of water; the degree to which these flow pathways have mixed and the length of time for which water has been stored within the soil / groundwater system. It has been found to be difficult to eliminate structural uncertainty regarding the mechanisms of mixing, and parameter uncertainty regarding the role of groundwater. Simulations of nitrate pollution, resulting from the application of agricultural fertilisers, have been undertaken to demonstrate the sensitivity of water quality simulations to the potential errors in physical transport mechanisms, inherent in models that fail to account correctly for flow pathways, mixing and transit times.
DE: 1804 Catchment
DE: 1846 Model calibration (3333)
DE: 1847 Modeling
DE: 1871 Surface water quality
DE: 1873 Uncertainty assessment (3275)
SC: Hydrology [H]
MN: 2007 Fall Meeting