SoCoCA workshop
19-20/3-2013
Current-state vs. future-state
Chong-Yu Xu
Department of Geosciences, UiO

•
Change of Climate
–
Climate Variability
–
Climate Change (human influence)
•
Change in catchment characteristics
–
Natural variation
–
Human induced changes
•
Land use/land cover changes
• urbanization
•
Dams, reservoirs
To distinguish natural variation and climate change needs very long data

Hydrological impact of climate change
•
Nonstationarity of first moment
–
Trend
–
Changing point
•
Nonstationarity of higher moments
– CV 、 Cs 、 r, r
, etc
–
Change in frequency and return period,
– Change in probability distribution
•
Nonstationarity of relationships
–
Rainfall-runoff relationship
–
Relations among other variables

Hydrological impact of climate change
•
Nonstationarity of first moment
–
Trend
–
Changing point
•
Nonstationarity of higher moments
– CV 、 Cs 、 r, r
, etc
–
Change in frequency and return period,
– Change in probability distribution
•
Nonstationarity of relationships
–
Rainfall-runoff relationship
–
Relations among other variables
• Water resources assessment
• Hydrological design
• Extremes
• Hydrological modeling

Example: Nonstationary rainfall-runoff relationship
Double-mass curves 1956-2005. Unit: 10 3 mm Zhang et al., 2011

• Improving the theoretical/physical understanding of the causes by internal force and external force
– Natural variability? Global warming? Human activity?
– …
• Understanding of the behaviour of Non-stationarity
– Non-stationarity in the mean? CV? CS?
– Non-stationarity in the individual processes ?
– Non-stationary relationship between hydrological processes can tell more story about what is happening
• Methodological advancing for identification and quantification
– Non-stationarity is more than Mann-Kendall method can handle
– …

Hydrological modeling – past, present and future

Theory (physics) Hydrological models Groundwater models
1800
1900
1950
1960
1970
1980
1990
Chezy formula, 1749
Dalton equation, 1802
Darcy, 1856
Saint-Venant, 1871
Manning,1891
Green-Ampt,1911
Richards, 1931
Horton, 1933
Philip, 1954
Rational model, 1850
Sherman, 1932
Unit hydrograph
Nash ， Dooge linear& cascade reservoir
Lumped conceptual
Time-series modeling
Phyiscally-based, distributed
Large scale WBM ，
Land-surface model
Darcy equation, 1856
Dupuit equation ， 1863
Boussinesq equ.
， 1877
Slichter （ Laplace),1889
Meizner equation ， 1923
Theis equation ， 1935
Jacob equation ， 1940
Hubbert equation ， 1956
Neuman finite-diff ， 1969
Jacob Bear Dynamics of fluids in porous media ，
1972
MODFLOW ， 1975
Interaction of S-W model

General structure of large scale distributed models
Q
Translation
Attenuation Excess rainfall
Transfer function runoff
Unit hydrograph
Input
P
Runoff generation
Excess rainfall
Unit hydrograph
Grid
Runoff
Flow routing
Stream
T

The global and regional-scale WASMOD
Catchment hydrological model:
WASMOD
Large-scale hydrological model:
WASMOD-M
(Xu, 1992)
(Li et al., 2013; Gong et al., 2009,
2011; Widen-Nilsson et al., 2007,
2009)
(from Gong et al, 2009)
(from: Xu et al., 2002)

Applications of Hydrological modeling Method
• Gauged, stationary
–
Gap filling, record extension, forecasting
Split-sample test

Applications of Hydrological modeling Method
• Gauged, stationary
–
Gap filling, record extension, forecasting
• Impact of climate change and land use change
–
Non-stationary in time
•
Regional and global modeling
–
Ungauged region
–
Heterogeneity in space
•
Coupling with climate model
–
Spatial-time scale mismatch
Split-sample test

Applications of Hydrological modeling Method
• Gauged, stationary
–
Gap filling, record extension, forecasting
• Impact of climate change and land use change
–
Non-stationary in time
•
Regional and global modeling
–
Ungauged region
–
Heterogeneity in space
•
Coupling with climate model
–
Spatial-time scale mismatch
Split-sample test
?
?
?

Up to two decades ago, single models were used to predict hydrological impact of climate change scenarios

Xu, 1991. Water resources Management

Xu, 1991. Water resources Management

During the last two decades, hydrologists realized that there are large uncertainties in using hydrological models to predict climate change impact due to 3 reasons:
1.
Transferability of model parameters and structure across time ?
2.
Transferability of model parameters and structure across space ?
3.
Transferability of model parameters and structure across scale ?

Example:
Parameter values change with time period!
Which parameter set shall we use?
Merz, Parajka, Blöschl, 2011, Water Resources Research

Future water resources depend on model or climate?
Jiang, Chen, Xu, 2007 Journal of Hydrology

Example:
Future water resources depend on model or climate?
Jiang, Chen, Xu, 2007.
Journal of Hydrology

Climate
Catchment
Gauged
Stationary condition
Nonstationary conditions
Split-sample test Differential splitsample test
Un-gauged Proxy-basin test Proxy-basin differential splitsample test
Klemes, 1986

Ability of WASMOD in simulating climate change impact

Non-stationary climate conditions
Xu, 1999. Agricultural and Forest Meteorology

Stability of parameter values with time
Xu, 1999. Agricultural and Forest Meteorology

Results of proxy-basin differential split-sample test
Xu, 1999. Agricultural and Forest Meteorology

Mean annual Runoff and change
(2010-2029 vs 1990-2009)
10

E 20

WFD
E 30

E 40

E
10

S
10

RegCM4 R1
E 20
E 30 E 40

E
10

S
10

10

10

S

S
RegCM4 R2
E

E
30

30

E
E 40

E
40

E
20

S
30

S
20

S
30

S
20

S

S
30

S
30

S
0 100 200 300 400 >500 mm yr
-1
0 100 200 300 400 >500 mm yr
-1 mm yr
%
-1
Mean annual
(2010-2029)
10

E
10

S
Runoff RegCM4 R2
20

E 30

E
40

E
20

S
30

S
<-100-75 -50 -25 0 25 50 75 >100
% relative change
Li et al., SoCoCA
Case 1

Mean monthly change
2010-2029 vs 1990-2009
Runoff ET
Case 1
160
140
120
100
80
60
40
20
0
TRMM
WFD
1 2 3 4 5 6 7
Month
8 9 10 11 12
Li et al., SoCoCA

29

Water balance
Energy balance
Radiation budget

Example:
Parameter values change with time step (scale)!
How can we couple it with climate model that run in a time step of 15min?
Littlewood et al. 2008

1. More research is needed towards the transferability of hydrological models across time, scale, and space!
2. As above!
3.
…