MODELING HILLSLOPE WATER J. J. van Tol, S.A. Lorentz & P. A. L. Le Roux Hydropedology dialogue...
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Transcript of MODELING HILLSLOPE WATER J. J. van Tol, S.A. Lorentz & P. A. L. Le Roux Hydropedology dialogue...
MODELING HILLSLOPE
WATER
J. J. van Tol, S.A. Lorentz & P. A. L. Le Roux
Hydropedology dialogue Pretoria 2014
INTRODUCTION Catchments are ideal management units Hillslope determine hydrological response Fundamental landscape unit Common form of organization and symmetry
Interaction between: Topography Climate Vegetation Geology Soils
Ideal scale for understanding and simulating hydrological process
Basic building block for some hydrological models
Progress in hillslope hydrology declined modellers
experimentalists
Modellers: Small scale physical descriptors Don’t incorporate the experimentalist’s knowledge
into model structure
HILLSLOPE HYDROLOGY
Hydrological modeling problem
Dominant paradigm in hydrological modelling a priori set of small scale theories and
process descriptions splitting the catchment into small enough
uniform elements for these theories to work Models require mapping of
heterogeneities and process complexities
Impossible!!
Hydrological modeling problem
Models rely on calibration Models ‘work’ but for wrong process
reasons Overparameterized Equifinality
Large degree of modeling uncertainty Unsuitable for PUB’s!!
Progress in hillslope hydrology declined modellers experimentalists
Modellers: Small scale physical descriptors Don’t incorporate the experimentalist’s knowledge into model
structure
Experimentalists Unconventional behaviour of new hillslopes No intercomparison Extrapolation value is low No minimum set of measurements to characterize a single
hillslope!!
HILLSLOPE HYDROLOGY
Hydrological modeling problem
Paradigm shift required Accept landscape heterogeneity and
process complexity
Find common threads, patterns, concepts and laws
Identify, classify and quantify
Hydrological soil type Symbol
Recharge
Interflow (A/B)
Interflow (soil/bedrock)
Responsive (shallow)
Responsive (saturated)
Weatherley: 5 hillslopes
Bedford: 2 hillslopes
Two Streams: 3 hillslopes
Cathedral Peak:
2 hillslopes
Baviaans: 2 hillslopes
Letaba: 4 hillslopes
Skukuza: 4 hillslopes
Bozrah: 2 hillslopes
Bloemfontein: 5 hillslopes
Riversdale: 1 hillslope
Mokolo: 5 hillslopes
Craigieburn: 3 hillslopes
PAP: 1 hillslope
Thaba Nchu: 2 hillslopes
Taylors Halt: 1 hillslope
Hogsback: 2 hillslopes
Noord Kaap: 2 hillslopes
Loeriesfontein: 2 hillslopes
Schmitsdrift: 2 hillslopes
Newcastle: 3 hillslopes
Observations and measurements
Catchment Hillslope Pedology Soil physics Hydrometrics Geology AICraigieburn 3 √ √ √ Granite 0.28
Letaba 4 √ √ √ Granite 0.2
Skukuza 4 √ √ √ Granite 0.25
Mokolo 5 √ x x Aeolian 0.2
New Castle 3 √ x x Sandstone/dolerite 0.35
Two Streams 3 √ √ √ Sandstone 0.4
Taylor’s Halt 1 √ √ x Sandstone 0.45
Noord Kaap 2 √ √ x Aeolian <0.1
Taba Nchu 2 √ x x Sandstone/mudstone 0.28
Schmitsdrift 2 √ x x Alluvium 0.15
Bloemfontein 5 √ x x Shales/dolerite 0.25
Cathedral Peak 2 √ √ √ Basalt >0.6
Weatherley 5 √ √ √ Mudstone/dolerite 0.5
Loeriesfontein 2 √ x x Shales 0.2
Hogsback 2 √ x x Shales/dolerite >0.6
Fort Hare 2 √ √ x Shales 0.26
Bedford 2 √ √ √ Shales 0.2Riversdale 1 √ x x Sandstone 0.5
Baviaans kloof 2 √ x x Conglomerate 0.2
PAP 1 √ x x Granite 0.3
Framework of hillslope classification
Van Tol JJ, Le Roux PAL, Hensley M & Lorentz
SA. Hydropedological classification of South
African hillslopes. Vadose Zone Journal, 2013
Application – distributed modelling
Application – wetlands (Hogsback)
Class 1
Class 4
Conclusions
We can: Indentify Classify
Dominant hydrological responses We need to:
Quantify!
THANK YOU!!
WRC