Geoscience Reference
In-Depth Information
Russia and the eastern Hudson Bay drainage in Quebec. Areas of low runoff include
the southwestern Ob Basin and the south-central part of the drainage in Canada.
The mean annual runoff as averaged across the Arctic drainage is calculated at
212 mm yr
−1
. There should be a correspondence between mean annual runoff and
mean annual P-ET as computed from atmospheric reanalyses. Annual P-ET fields
interpolated to the Arctic drainage do capture the general features of observed run-
off. There is also considerable disagreement, however, related to the different reso-
lutions of the data sets and to errors in the reanalysis fields.
The ungauged areas of the Arctic drainage can be assessed by comparing
Plate 7
and
Figure 6.12
. The ungauged areas include much of coastal Eurasia, the
Arctic islands, northern Alaska, and the Canadian Arctic Archipelago. It remains a
challenge to estimate runoff from these ungauged areas and assess their contribution
to the freshwater budget of the Arctic Ocean.
6.5.4
Annual Runoff for the Major Drainage Basins
Table 6.1
provides basin-averaged values for the four major river systems of precipi-
tation (P), P-ET, ET, and runoff (RU) along with estimates of the runoff ratio (RU/P)
and the fraction of precipitation lost through ET (ET/P). These are calculated over
the water year. The water years is often more convenient and physically meaningful
for hydrologic applications than the standard calendar year. Here, the water year is
defined as October (when snowfall starts to accumulate) through September (the
end of the summer). Precipitation is based on the analysis of Serreze et al. (
2003a
).
Runoff is based on updated records in R-ArcticNET. In contrast to previous results,
ET is estimated as the difference between P and RU. The means for the Eurasian
basins are based on the water years 1960/1961 through 1997/1998 (thirty-nine
years). For the Mackenzie, the shorter time series of precipitation and of discharge
(at Red River station) results in only seventeen years with shared records.
L. Bowling, D. Lettenmaier, and B. Matheussen (
2000
) summarize various esti-
mates of RU/P for the major Arctic-flowing rivers. R
U
/P can be thought of as the
efficiency in which precipitation is converted to runoff. Values for the Ob range
from 0.25 to 0.33. These are considerably lower than estimates for the Yenisey
Table 6.1.
Components of the water budget averaged for water years (October through
September) for the four major drainage basins
P (mm)
ET (mm)
RU (mm)
RU/P
ET/P
Basin Area (10
6
km
2
)
Ob
533
396
138
0.26
0.74
3.02
Yenisey
495
256
239
0.48
0.52
2.58
Lena
403
182
221
0.55
0.45
2.44
Mackenzie
411
241
171
0.41
0.59
1.69
Note
: Basin areas are also provided.
Source
: From Serreze et al. (
2003a
).
