TY - JOUR
T1 - On the implementation of the surface conductance approach using a block-centred surface-subsurface hydrology model
AU - Liggett, Jessica
AU - Knowling, Matthew
AU - Werner, Adrian
AU - Simmons, Craig
PY - 2013/7/4
Y1 - 2013/7/4
N2 - In physically based catchment hydrology models, dynamic surface-subsurface interactions are often represented using the surface conductance (SC) coupling approach. Guidance on SC parameterisation within block-centred codes is limited, and common practice is to express the SC coefficient as the quotient of the vertical saturated hydraulic conductivity and the half-cell thickness of the uppermost layer. This study evaluates the implementation of the SC approach utilising a popular block-centred, surface-subsurface hydrology model (MODHMS) to simulate one-dimensional infiltration experiments under Hortonian conditions. Results show that defining the SC coefficient based on a half-cell thickness of the uppermost subsurface cell inhibits accurate prediction of infiltration rates (qe) and the time to initiate surface runoff (tro) for the adopted rainfall-runoff scenario. Increasing the SC coefficient independently of the grid allows for accurate simulation of qe, but not tro. The addition of a thin layer at the surface is shown to improve model accuracy substantially, such that qe and tro approach those obtained using an equivalent mesh-centred model (i.e. where the surface and upper subsurface nodes are coincident). Whilst the addition of a single thin layer in block-centred codes allows improved prediction of surface-subsurface interaction, it does not provide a surrogate for fine discretisation throughout the subsurface that is necessary for accurate simulation of unsaturated zone flow. This study offers guidance on the implementation of the SC approach in a block-centred code and demonstrates the importance of systematic testing of parameters (that are otherwise calibrated) in physically based surface-subsurface hydrology models.
AB - In physically based catchment hydrology models, dynamic surface-subsurface interactions are often represented using the surface conductance (SC) coupling approach. Guidance on SC parameterisation within block-centred codes is limited, and common practice is to express the SC coefficient as the quotient of the vertical saturated hydraulic conductivity and the half-cell thickness of the uppermost layer. This study evaluates the implementation of the SC approach utilising a popular block-centred, surface-subsurface hydrology model (MODHMS) to simulate one-dimensional infiltration experiments under Hortonian conditions. Results show that defining the SC coefficient based on a half-cell thickness of the uppermost subsurface cell inhibits accurate prediction of infiltration rates (qe) and the time to initiate surface runoff (tro) for the adopted rainfall-runoff scenario. Increasing the SC coefficient independently of the grid allows for accurate simulation of qe, but not tro. The addition of a thin layer at the surface is shown to improve model accuracy substantially, such that qe and tro approach those obtained using an equivalent mesh-centred model (i.e. where the surface and upper subsurface nodes are coincident). Whilst the addition of a single thin layer in block-centred codes allows improved prediction of surface-subsurface interaction, it does not provide a surrogate for fine discretisation throughout the subsurface that is necessary for accurate simulation of unsaturated zone flow. This study offers guidance on the implementation of the SC approach in a block-centred code and demonstrates the importance of systematic testing of parameters (that are otherwise calibrated) in physically based surface-subsurface hydrology models.
KW - Catchment modelling
KW - Fully integrated model
KW - MODHMS
KW - Surface conductance approach
KW - Surface-subsurface interaction
UR - http://www.scopus.com/inward/record.url?scp=84878786748&partnerID=8YFLogxK
U2 - 10.1016/j.jhydrol.2013.05.008
DO - 10.1016/j.jhydrol.2013.05.008
M3 - Article
VL - 496
SP - 1
EP - 8
JO - Journal of Hydrology
JF - Journal of Hydrology
SN - 0022-1694
ER -