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Effect of spatial variability and seasonality in soil moisture on drainage thresholds and fluxes in a conceptual hydrological model
Author(s) -
McMillan H.K.
Publication year - 2012
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.9396
Subject(s) - drainage basin , drainage , environmental science , hydrology (agriculture) , spatial variability , water content , catchment hydrology , seasonality , smoothing , soil science , geology , geography , ecology , mathematics , geotechnical engineering , statistics , cartography , biology
This paper uses soil moisture data from 17 recording sensors within the 50 km 2 Mahurangi catchment in New Zealand to determine how measured variability in soil moisture affects simulations of drainage in a typical lumped conceptual model. The data show that variability smoothes the simulated field capacity threshold such that a proportion of the catchment contributes to drainage even when mean soil moisture content is well below field capacity. Spatial variability in soil moisture controls by extension the catchment drainage behaviour: the resulting smoothed shape of the catchment‐scale drainage function is demonstrated and is also determined theoretically under simplifying assumptions. The smoothing effect increases the total simulated discharge by 130%. The analysis explains previous findings that different drainage equations are required at point scale versus catchment scale in the Mahurangi. The spatial variability and hence the emergent drainage behaviour are found to vary with season, suggesting that time‐varying parameters would be warranted to simulate drainage. Copyright © 2012 John Wiley & Sons, Ltd.