Translating Soils Information for Hydrological Modelling Reflecting on the Big Picture from the 1970s to the Present Roland Schulze Professor Emeritus of Hydrology & Senior Research Associate Centre for Water Resources Research School of Agricultural, Earth & Environmental Sciences University of KwaZulu- Natal, Pietermaritzburg, RSA
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Translating Soils Information for Hydrological Modelling Reflecting on the Big Picture from the 1970s to the Present Roland Schulze Professor Emeritus.
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Translating Soils Information
for Hydrological Modelling Reflecting on the Big Picture from the 1970s
to the Present
Roland Schulze Professor Emeritus of Hydrology & Senior Research Associate
Centre for Water Resources Research School of Agricultural, Earth & Environmental Sciences
University of KwaZulu-Natal, Pietermaritzburg, RSA
Defining Moments …From Way Back !
1. “A vital role is played by soil, for it is the capacity of the soil to absorb, retain and release water that is the prime regulator of the evapotranspiration and runoff response of a catchment” (England & Stephenson, 1970)
2. A catchment is not a lumped system in regard to soils, and pronounced differences in magnitude and sequence of hydrological processes have been observed in soil units within a catchment (England, 1970)
3. “Soils of the Tugela Basin” (van der Eyk et al., 1969)
Falling in Love …With a Subject MatterDefining Years …1970 -1974
The Drakensberg
Cathedral Peak Research Catchments
Energy and Water Budgets on Slopes with Different Gradients & Aspects
‘TOP’ OF THE ATMOSPHERE
EXTRATERRESTRIAL RADIATION
Solar Constant (1361 W.m-2)
Earth’s Radius Vector (Time of Year)
Angle of Inclination
(Latitude; Time of Year; Time of Day)
Direct Radiation ATTENUATIONS
Atmosphere (Water Vapour; Aerosols; Altitude; Optical Air mass)
Terrain (Slope; Aspect; Albedo)
Cloud (Type; Time of Day)
N
E
S
W ASPE
DALT Normal to Slope N
S
AZIM
ALT
W
N
S
E
SLP
THET
Diffuse Radiation ATTENUATIONS
Solar Altitude
Slope
(b) HORIZON SHADING ALT < HOR
(a) SLOPE SHADING ALT < SLP
ALT
HOR
ALT
SLP
1000 -
750 -
500 -
250 -
0 - 17 16 15 14 13 12 11 10 9 8 7
Time of Day (h)
Glo
bal
Rad
iati
on
Flu
xes
(W.m
-2)
- - - 35o NNW (290o)
32o S (170o)
NOVEMBER 20, 1986
Mapping Energy
Budgets on Sloping Terrain
Considerations
Verification
Understanding Soils … Getting Hands
Dirty
Land Cover Class Land Treatment/Practice/Description
Stormflow Potential
Hydrological Soil Group A A/B B B/C C C/D D
Veld (range) and Pasture
1 = Veld/pasture in poor condition 2 = Veld/pasture in fair condition 3 = Veld/pasture in good condition 4 = Pasture planted on contour 5 = Pasture planted on contour 6 = Pasture planted on contour
And, the Advent of Soils LAND TYPES from the Binomial Soil Classification, and their Databases
# Based on relatively uniform climate, terrain, soil patterns # With detailed soils inventory on soil series, clay %, texture class, profile thickness… # With the Land Type made up of several soil series# Including information on Terrain Units making up a Land Type
“Translating” Land Type Information to Hydrological Model Needs
Rules for Partitioning Soil Horizon Thicknesses
Drilling Down to Terrain Unit Level
BASIC PREMISE
Operational hydrological models should be able to be “driven” by standard datasets which are freely available from national networks and by standard (usually non-hydrological) spatial digital information available at national level, suitably “translated” (I.e. converted) into model input variables, for the models then to operate over a range of desired spatial scales
Result … Detailed mapping of soil attributes which are critical to hydrological modelling from 16600+ Land Type Polygons
(Schulze and Horan, 2008)
Result … Detailed mapping of soil attributes which are critical to hydrological
modelling (Schulze and Horan, 2008)
Result … Detailed mapping of soil attributes which are critical to hydrological modelling (Schulze and Horan, 2008; Schulze,
2012)
Quo vadis? An operational hydrologist’s perspective
Operationalising terrain unit delineation Mapping soil fertility in detail Getting a better handle on hydraulic conductivity Towards a general model of interflow Ringfencing soils with high organic matter content More detailed delineation of wetlands soils Delineating unstable soils for hydrological
modelling Getting a better handle on drainage rates of soils