Effects of Biases in NEXRAD Precipitation estimates and Effects of Biases in NEXRAD Precipitation estimates and Sub-Basin Resolution in the Hydrologic Modeling of Blue Sub-Basin Resolution in the Hydrologic Modeling of Blue River Basin Using a Semi-distributed Hydrologic Model River Basin Using a Semi-distributed Hydrologic Model Zahidul Islam and Thian Y. Gan [email protected][email protected]Department of Civil and Environmental Engineering Department of Civil and Environmental Engineering University of Alberta, Edmonton, Canada University of Alberta, Edmonton, Canada
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Effects of Biases in NEXRAD Precipitation estimates and Sub-Basin Resolution in the Hydrologic Modeling of Blue River Basin Using a Semi-distributed Hydrologic.
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Effects of Biases in NEXRAD Precipitation estimates and Sub-Basin Effects of Biases in NEXRAD Precipitation estimates and Sub-Basin
Resolution in the Hydrologic Modeling of Blue River Basin Using a Resolution in the Hydrologic Modeling of Blue River Basin Using a
Semi-distributed Hydrologic ModelSemi-distributed Hydrologic Model
Department of Civil and Environmental EngineeringDepartment of Civil and Environmental EngineeringUniversity of Alberta, Edmonton, CanadaUniversity of Alberta, Edmonton, Canada
Fig.2 : Rutter interception model(source: Biftu and Gan,2004)
Interception
•The Rutter interception model ( Rutter et al.,1971) is used to estimate the rainfall interception
Model Components of DPHM-RS
Fig.3 :Two source model of Shuttleworth and Gurney (1990)
(source: Biftu and Gan,2004)
Evapotranspiration(ET)
•Two source model of Shuttleworth and Gurney (1990)is used to compute ET
•Actual Evaporation from land surface and transpiration from vegetation canopy are computed separately.
•This model calculate the sensible heat flux and latent heat flux and then apply the energy balance for three layer :
•Above canopy
•Within canopy
•Soil
Model Components of DPHM-RS
Fig.3 :Two source model of Shuttleworth and Gurney (1990)
(source: Biftu and Gan,2004)
Evapotranspiration(ET) (..continued)
•Energy balance
secee
sc
ncnsn
ssens
ccenc
en
ELELEL
HHH
RRR
GHELR
HLR
HLR
Where,
0
0
0
Model Components of DPHM-RS
Fig.4 Conceptual representation of soil infiltration (source: Biftu and Gan,2004)
Soil Moisture
•Soil Profile of three homogeneous layer is used to model the soil moisture:
•Active layer:
• unsaturated, 15-30 cm
• Simulates rapid changes of soil moisture content.
• Transmission layer:
• unsaturated
•layer between base of the active layer and top of capillary fringe
•Simulates seasonal changes of soil moisture
•Groundwater Zone:
•Saturated
Model Components of DPHM-RS
Fig.4 Conceptual representation of soil infiltration (source: Biftu and Gan,2004)
Soil Moisture (..continued)
•Apply soil water balance in two layers:
•Case I: Z2 >0
•Case II: Z2 =0
Model Components of DPHM-RS
Saturated Subsurface Flow
•The water table equation from Sivapalan et al. (1987) is modified to simulate the average water table for each sub-basin.
Local Topographic Soil Index: From DEM of DTED
Catchments Average value of
Exponential Decay of Saturated Hydraulic Conductivity Ks
Most Important Calibration parameter for Soil Moisture
Model Components of DPHM-RS
Surface Runoff
•The surface runoff from bare soil:
•The surface runoff from vegetated soil:
•In DPHM-RS the resulting runoff becomes a lateral inflow to the stream channel within the sub-basin
•The surface runoff transferred into stream flow using and average response function for each sub basin.
Kinemsatic Response Function for Sub-basin 1
0
2
4
6
8
10
12
0 50 100 150 200 250
Time (hr)
Dis
ch
arg
e (
m3
/s)
Model Components of DPHM-RS
Surface Runoff
•Finding response function:
• A reference runoff (e.g. 1 cm ) is made available for one time step for all grid cells within the sub-basin.
•Kinematic wave equation is applied for each grid cell and flow is routed from cell to cell based on 8 possible flow direction until the total volume of water corresponding to reference runoff for a sub-basin is completely evacuated.
•Finding resultant runoff:
•The actual surface runoff for each sub-basin is then computed based on that average response function.
Kinemsatic Response Function for Sub-basin 1
0
2
4
6
8
10
12
0 50 100 150 200 250
Time (hr)
Dis
ch
arg
e (
m3
/s)
Model Components of DPHM-RS
Channel Routing
•Muskingum-Cunge Flow routing method is used to route the flow through the drainage network.
x
t
i Δx i+1
j
Δ
t
j+
1
+ C4
(Included Lateral Inflow )
Blue River BasinSouth Central Oklahoma, USA
Blue River BasinSouth Central Oklahoma, USA
•Catchment Type : Non regulated
•Terrain:
• Flat• elevation ranging from 150 m to 350 m (msl)