What affects SiB2 runoff? TANG QIUHONG OKI/KANAE LAB. MEETING
Univ. of Tokyo 2006/01/30
Slide 2
Objective To make a better runoff and discharge simulation with
SiB2 in arid environment. Requires data on Forcing data for SiB2
Observed discharge to check the SiB2 output
What makes the Roff1? Yellow River basin, One Grid Left: Canopy
interception loss (j m 2 ) Right: Ground interception loss For the
running time from 94-1-1 to 94-7-3 : Precipitation = 228 mm ; NET E
cg = E c (32.6) + E g (0.96) = 33.5 mm Ec = 124.8 - 92.3;
condensation is 92.3 mm Eg = 2.82 - 1.85; condensation is 1.85 mm
Condensation ( 92.3+1.85= 94.1 mm ) is too large.
Slide 6
Revision of SiB2 condensation Limit condensation, and change SH
(Sensible heat) to balance energy.
Slide 7
After Revision (1) Roff1: 1%Roff2: 9% Roff3: 79%Roff4: 11%
Roff1: 57%Roff2: 3% Roff3: 34%Roff4: 6% OLD NEW Yellow River basin,
Averaged Yellow River basin, Huayuankou Station D obv = 1088 m 3 /s
D new = 747 (-31%) D old = 2225 (104%) D obv = 1088 m 3 /s D new =
747 (-31%) D old = 2225 (104%)
Slide 8
After Revision (2) Yellow River basin, Tangnaihai Station
Yellow River basin, Zhangjiashan Station D obv = 644 m 3 /s D new =
111 (-83%) D obv = 644 m 3 /s D new = 111 (-83%) D obv = 46 m 3 /s
D new = 43 (-8%) D obv = 46 m 3 /s D new = 43 (-8%) No baseflow No
surface runoff
Slide 9
Conclusion on SiB2 Runoff (1) SiB2 generates too large
condensation and get a error runoff. Limiting condensation can
improve much of the runoff and discharge simulation. But the model
gives little surface runoff. the model underestimates runoff. Base
flow can not be simulated. Still problems exist
Base flow Flow over a sloping bed Target: To get a steady base
flow Soil parameters: FAO soil components Cosby et al parameters
Slope : FAO soil map slope (S s ) = S s
Slide 13
Discharge at stations (1982-2000) Time resolution: daily
Discharge at stations (1982-2000) Time resolution: daily
Slide 14
Discharge at stations (1982-2000) Time resolution: monthly
Discharge at stations (1982-2000) Time resolution: monthly
Slide 15
Discharge at stations (1982-2000) Time resolution: monthly
1982-2000 averaged value Discharge at stations (1982-2000) Time
resolution: monthly 1982-2000 averaged value
Conclusions on Runoff Calculation The calculated runoff is much
decided on the runoff generating mechanism in the hydrological
model. Groundwater is required to simulate the base flow. Subgrid
heterogeneity is very important to runoff calculation.
Precipitation heterogeneity will affect the runoff
calculation.
Soil water depth in top 2cm soil (cm) Time resolution: daily
Soil water depth in top 2cm soil (cm) Time resolution: daily
Slide 20
Soil water depth in top 1m soil (cm) Time resolution: daily
Soil water depth in top 1m soil (cm) Time resolution: daily
Slide 21
Soil water depth in top 2cm soil (cm) Time resolution: monthly
Soil water depth in top 2cm soil (cm) Time resolution: monthly
Slide 22
Soil water depth in top 1m soil (cm) Time resolution: monthly
Soil water depth in top 1m soil (cm) Time resolution: monthly
Slide 23
Soil water depth in top 2cm soil (cm) Time resolution: monthly
1982-1993 averaged value Soil water depth in top 2cm soil (cm) Time
resolution: monthly 1982-1993 averaged value
Slide 24
Soil water depth in top 1m soil (cm) Time resolution: monthly
1982-1993 averaged value Soil water depth in top 1m soil (cm) Time
resolution: monthly 1982-1993 averaged value
Slide 25
Conclusions on soil moisture Top 2cm soil moisture is
relatively well reproduced. Simulated 1m soil moisture variation is
smaller than the observation. The simulated soil water content
(absolute water content) is much decided by the soil parameters.
The station observations may not represent the averaged states of
soil moisture. Subgrid heterogeneity of soil parameters should be
considered.
Slide 26
Future plan Subgrid heterogeneity of soil parameters (e.g. K s,
porosity, etc.) Irrigation water withdrawals prediction.
