Jökull - 01.10.1998, Page 40

Vatnajökull which flows from an elevation of 1990 m
of Bárðarbunga to 730 m; an outlet with an exception-
al area distribution as 410 km2 or 40% of the total area
is located between 1500 m and 1700 m elevation.
Second, Brúarjökull, the largest of the northern out-
lets of Vatnajökull flowing with a low slope from an
elevation of 1930 m to 580 m over a distance of 55
km. The Grímsvötn drainage basin is located in the
central area of the ice cap where ice drains into a de-
pression created by a subglacial geothermal area con-
tinuously melting ice (Björnsson, 1988). All the
drainage basins except Brúarjökull are located within
the active volcanic zone and abundant ash cover en-
hances melting in the ablation areas.
Point measurements were done on Örœfajökull at
an elevation of 1800 m a. s. 1. in last the two last years
considered in this report.
Meltwater from these glaciers drains to some of the
main river systems of Iceland (Fig. 1, Table 2). Hveifis-
fljót drains Síðujökull, Tungnaá Tungnaárjökull,
Kaldakvísl Köldukvíslarjökull, and Jökulsá á Fjöllum
drains Dyngjujökull. Two major river systems: Kreppal
Kverká and Jökulsá á Brú drain Brúarjökull. The dis-
charge of the glacial rivers is monitored by the Nation-
al Energy Authority at streamflow gauges some dis-
tance from the glacier (Fig. 1). The location of the sta-
tions and the total area of the river basins, including the
glaciers, is given in Table 1. At the discharge gauges
the percentage of the drainage basins covered by
glaciers is 12 for Tungnaá, 43 for Kaldakvísl, 57 for
Jökulsá á Fjöllum and 67 for Jökulsá á Brú.
The rivers Tungnaá, Kaldakvísl and Jökulsá á
area (km )
20 40
area (km )
20 40
area (km )
20 40
area (km )
20 40
2000
1600
0 200 400
cumulative area (km2)
0 200 400
cumulative area (km2)
area (km2)
0 200 400
cumulative area (km2)
0 200 400
cumulative area (km2)
area (km2)
Fig. 3. Area distribution with
elevation of several glacier
drainage basins of Vatna-
jökull.
- Flatarmálsdreifing nokkurra
skriðjökla með hœð.
0 40 80 120 0 40 80 120 160
cumulative area (km2) cumulative area (km2)
38
JOKULL, No. 45, 1998