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Hydrologic simulations of the Upstream of Major Rivers in the Tibetan Plateau
Fengge
1
Su ,
Leilei
1,2
Zhang ,
Kai
1,2
Tong ,
Zhenchun
2
Hao ,
and Cuo
1
Lan
1Institute
of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing 100085, China. E-mail: [email protected]
2State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing , China
Abstract
3 Glaciated area within each basin
Glaciated area (%):
Yellow:
0.11
Yangtze:
0.93
Mekong:
0.43
Salween:
1.61
Brahmaputra:
2.17
Indus:
2.2
The Tibetan plateau (TP) is considered to be the water tower of Asia being the source
of many major Asian rivers such as the Yellow, Yangtze, Mekong, Salween, and
Brahmaputra river basins. The TP is characterized by a variety of elevations (with the
average of above 4000m), large area of snow mountains, glaciers, permafrost, and
mountain lakes. Studies have suggested that the surface temperature on the TP is
warming over the past 50 years, and major climate-induced changes have occurred,
World Data Center For Glaciology and Geocryology,
Lanzhou (http://wdcdgg.westgis.ac.cn/)
The contribution of snow and glacial melt to the total river runoff is not yet properly
quantified. Earlier studies suggest that the glacier-melting water is extremely important
in the Indus and Brahmaputra basins, but plays only a modest role for the other basins.
Hydrological models provide a useful approach for understanding and evaluating the
application of the Variable Infiltration Capacity (VIC) macroscale hydrology model to
Degree-Day glacier-melt-runoff module was incorporated into the VIC model to
represent the contribution of glacier-melting water to the total runoff. The modeled
water balance were evaluated with streamflow records with available observed
121972
173.65
137704
53800
173.01
0.8034
-0.37
92.39
100.54
0.6505
8.81
295.91
251.76
0.7997
-15.23
Model results with incorporating Degree-Day glaciermelt-runoff module
1
Source Region of Yangtze River
Area : 137 704 km2 Time :1961-2005
1
2
3
4
5
6
7
8
9
10
11
12
2500
1
0
Simulated
2000
(m3/s)
50
R2=0.9161
meteorological
gauge stations
150
1
2
3
4
5
6
7
8
9
10
11
6
7
8
9
4
5
6
7
8
10 11 12
R2=0.9389
10
11
12
50.00
6000.00
100.00
150.00
4000.00
200.00
2000.00
100
250.00
Month
150
0.00
Precipitation
1
2
3
simulated(glacier)
1000
200
500
0
1
2
3
4
5
6
7
8
9
4
5
Without glacier
250
stream stations
12 Month
9
0.00
50
0
The VIC model(Liang et al.,
1994;1996) was designed both for
inclusion in the GCMs (General
Circulation Models), and for use as a
stand-alone macro-scale hydrologic
model.
5
3
1500
1000
0
4
0
(m3/s)
100
3
2500
2000
Observed
1500
2
2
8000.00
Source Region of Yellow River
Area : 121 972 km2 Time : 1961-1999
0
2
Er
(%)
Streamflow simulations for the rainfall-dominated basins
4
200
The VIC model and Datasets
Yellow River at
Tangnaihai
Immerzeel et al. 2010; Liu et al. 2007; Yang et al. 2000; Xie et al. 2003; Liu 1999; Yang and Hu 1990
500
streamflow data.
NSE
Salween basin at Daojieba for 19612000 (Area: 110 224km2)
Precipitation(mm)
simulate the land surface water process over the upstream of major rivers in the TP. A
Drainage
area(km2)
Precipitation (mm)
impact of climate and cryosphere changes on river runoff. In this work, we describe an
Mean yearly run off(mm)
Observed
Simulated
Basin
Yangtze River at
Zhimenda
Mekong River at
Changdu
5
Observed (m3/s)
Nash–Sutcliffe coefficient of efficiency: NSE
Relative error: Er
Contribution of glacier-melting
water to total runoff (%):
Yellow:
0.6-0.8
Yangtze:
8.8-9.2
Mekong:
4.0-6.6
Brahmaputra:
38
Indus:
40.4-44.8
such as glacier melting and permafrost degradation. However, how the climate and the
induced changes affect the hydrology and water resources in the TP is still not clear.
Simulated (m3/s)
Streamflow(m3/s)
1
6
7
8
Observed streamflow300.00
9
10
11
12
simulated(no
glacier)
With glacier
300
10 11 12Month
Source Region of Mekong River
Area : 53 800 km2 Time : 1961-2000
1
2
3
4
5
6
7
8
9
10 11 12
2000
0
50
1500
R2=0.9581
Model features:
100
1000
1. Multiple vegetation classes in
each cell;
2. Energy and water budget closure
at each time step;
3. Subgrid infiltration and runoff
variability;
4. Non-linear baseflow generation
Datasets
Forcing: Daily Precipitation, Tmax, Tmin, and Wind Speed
Data source: 158 meteorological gauge stations; Data length :1961.1.1—2009.12.31
Vegetation: from UMD global 1km ×1km Land Cover
Soil: from IGBP-DIS[2000] (International Geosphere—Biosphere Programme Data
and Information System ) , Resolution: 1/12° ×1/12°
All forcing data were interpolated to 1/12° ×1/12° grid.
Observed streamflow data:
Basin
station
longitude
latitude
time
Drainage area(km2)
Yellow River
Tangnaihai
100.09
35.30
1961-1999
121 972
Yangtze
Zhimenda
97.13
33.02
1961-2005
137 704
Mekong
Changdu
97.11
31.11
1961-2000
53 800
Salween
Daojieba
98.53
24.59
1961-2000
110 224
150
200
500
250
0
0
Yellow River at Tangnaihai
Mekong River at Changdu
1
2
3
4
5
6
7
8
9
300
10 11 12 Month
Yangtze at Zhimenda
6
Summary and Further work
1. Runoff over the source regions of the Yellow, Yangtze, and Mekong rivers are mostly from
summer rainfall; the contribution of snow and glacier melting is minor.
2.The model simulations (around 40 years) over the Yellow, Yangtze, and Mekong river basins
suggest that the VIC model was able to reproduce the observed streamflow reasonably well
for the basins with little glacier distribution.
3. However, the VIC model considerably underestimated the baseflow in winter. When there is
frozen soil exists within a grid, the VIC model considers the grid as a whole impermeable
surface and does not take into account the heterogeneity of the infiltration capacity within the
grid , leading to very low baseflow.
4. The glacier has to be considered in streamflow simulations for basins of Salween,
Brahmaputra, and Indus basins where there are larger distributions of glacier. We will further
test the Degree-Day glacier module in the VIC model over these basins. Future work will
focus on improving the parameterizations of frozen soil, and incorporating an energy-based
glacier module in the VIC model to improve steamflow simulations for the river basins in
the TP.