Geoscience Reference
In-Depth Information
Table 1 Summary of basin-scale data and flux results for the Mahanadi river basin (MRB) (from Asokan
et al. (
2010
) for 1901-1955, and new simulations with the same distributed hydrological model of the basin
for 1956-2000) and the Aral region (from Shibuo et al. (
2007
)—average results from two different
evapotranspiration models in that study; and Destouni et al. (
2010
), who extended the analysis and results
from the previous study to also include the Aral Sea itself and the evaporation from it)
Pre-reservoir
Climate-irrigation
Climate: hypothetical
scenario of only
climate change
Mahanadi River Basin
1901-1955
1956-2000
1956-2000
Data-given average temperature (C)
25.19
25.45
25.45
Data-given annual average precipitation
(mm yr
-1
)
1,334
1,274
1,274
Total modeled ET (mm yr
-1
)
668
706
656
Data-given irrigation water-use within the
basin (mm yr
-1
)
-
81
-
Modeled runoff at basin outlet (mm yr
-1
)
666
568
618
Observed runoff at basin outlet (mm yr
-1
)
515
a
-
-
Aral region
1901-1950
1983-2002
1983-2002
Data-given average temperature (C)
7.5
8.6
8.6
Data-given annual average precipitation
(mm yr
-1
)
249
260
260
Total modeled ET from whole region—
Aral Sea and its drainage basin (mm yr
-1
)
250
265
260
Modeled irrigation water-use within the
basin (mm yr
-1
)
-
23
-
Modeled runoff from drainage basin into
Aral Sea (mm yr
-1
)
35
7
36
Observed runoff from drainage basin into the
Aral Sea (mm yr
-1
)
38
6
-
a
Average runoff from available observations for the period 1990-2000 (Asokan
2005
)
Rabi, the Dry Season. The Wet Season extends from June to November, and the Dry
Season extends from December to May. Out of the total annual irrigation water of 11 km
3
(81 mm if normalized with drainage basin area) that is used for agriculture in the MRB,
7km
3
(52 mm) is available and utilized in the Wet Season and 4 km
3
(29 mm) in the Dry
Season (Asokan
2005
). For the Aral region, the growing season is from March to October,
while the remaining months of the year constitute the non-growing season. Figure
2
illustrates basin-average time series of annual average T (Fig.
2
a) and P (Fig.
2
b), and
Table
2
further shows the average seasonal T and P at the beginning and the end of
twentieth century for both regions.
The change (increase) in annual average T from the beginning to the end of the century
is 0.26 C in the MRB and 1.1 C in the Aral region. With regard to annual average P, its
change is a decrease of 60 mm per year in the MRB and an increase of 11 mm per year in
the Aral region. In the MRB, about 93 % of the total P occurs during the Wet Season. The
Dry Season crops hence depend mainly on irrigated agriculture even though less irrigation
water is available and used in this season (4 km
3
or 29 mm) than in the Wet Season (7 km
3
or 52 mm) (Asokan
2005
). In the Aral region, P is much more evenly distributed between
the growing and the non-growing season, the temporal extents of which are primarily
determined by T rather than by P (Table
2
).
