Jökull - 01.12.1992, Page 28

Figure 1. Map of Höskulds-
vatn and the surrounding
area. The Húsavík fault
traces are shaded and the
Höskuldsvatn catchment
area is encircled by a dotted
line. Contour interval is
100 m (redrawn from Land-
mælingar íslands, 1980).
- Kort afnágrenni Höskulds-
vatns. Misgengissprungan
um Húsavík er skyggð og
vatnasvœði Höskuldsvatns
er merkt með punktalínu.
PRECIPITATION
Meteorological observations have been made in
the vicinity of lake Höskuldsvatn for more than 60
years, including measurements of the precipitation.
However, it should be emphasized that measurements
of precipitation during the winter are very inaccurate,
because it falls mostly as snow, usually in moderate to
strong wind. No simple devices to measure snowfall
in strong wind do exist, and the measured precipitation
is probably smaller, possibly much smaller, than the
actual precipitation. This uncertainty of the measured
amount is present mainly if the precipitation falls as
snow, while during the summer, when the precipitation
falls as rain, the measurements are more reliable.
The published precipitation data for stations in
the vicinity of Höskuldsvatn reach back to 1929 at
Húsavík, the nearest station, and back to 1936 to
1938 at the stations Grímsstaðir, Sandur, and Reyk-
jahlíð (Veðurstofa íslands, 1924-1990). The station at
Húsavík has an almost continuous record, while the
other stations have less continuous observations, and
no annual precipitation is given for several years. How-
ever, the station at Húsavík has been moved several
times within the community. This makes any compar-
ison between precipitation of different periods very
uncertain, as the measured precipitation, especially if
it falls as snow, depends very much on the location of
Table 1. Average annual precipitation in mm for each
decade as measured at meteorological stations near
Höskuldsvatn (From Veðurstofa íslands, Veðráttan
1924-1990) — Meðalársúrkoma í mm á veður-
athugunarstöðvum í kringum Höskuldsvatn.
Years Húsavík Reykja- hlíð Sandur Mánár- bakki
1931-1940 545
1941-1950 472 402 455
1951-1960 615 405 526
1961-1970 782 412 548 544
1971-1980 799 414 602 539
1981-1990 888 473 574 610
the meter, relative to houses and other features of the
surroundings.
Table 1 indicates steadily increasing precipitation
during the last 5 decades at Húsavík and some in-
crease is indicated at other stations in the area. If
the catchment area of lake Höskuldsvatn has expe-
rienced similar increase in precipitation as observed
at Húsavík, then the rise in Höskuldsvatn lake level
may be entirely caused by the precipitation. It may
be noted that the observed precipitation at Húsavík
during the year of 1990, the last year of published
26 JÖKULL, No. 42, 1992