Jökull - 01.12.1986, Blaðsíða 27

Fig. 17. Water basins in the western
Reykjanes peninsula. The ground-
water body can be divided in basins
and subbasins (Sigurðsson 1985).
Mynd 17. Vatnasvœði og grunn-
vatnsstraumar á utanverðum
Reykjanesskaga. Hcegt er að skilja
að vatnasvœði og undirvatnasvœði á
utanverðum skaganum (Freysteinn
Sigurðsson 1985).
sodic climatic changes, showing greater variations in
temperature and chemistry than the water deeper
down. Layering also follows to some degree the strati-
fication of the lava pile, the massive interiors of the
S1ngle lava flows acting sometimes as aquitards or
even aquicludes. The result is a very strong horizon-
tal-vertical anisotropy that reduces very effectively the
danger of upconing by overdraught. This means that
niore water can safely be extracted from a single well,
than would be the case under isotropic conditions.
The distribution of temperature and chemical para-
metres indicates that the freshwater body in the west-
ern part of the peninsula can be divided in basins and
subbasins with different water quality (fig. 17).
Mean values for the various basins are shown in
table 1.
FRESHWATER EXPLOITATION
The heaviest extraction of freshwater for communal
uses from the groundwater in the Reykjanes peninsula
is for Reykjavík and its suburbs from the spring areas
in Heiðmörk and Kaldársel (see fig. 2). The capacity
of the waterworks considerably exceeds 1 m3/s, but
the average extraction is somewhat less, probably near
1.2 m3/s for the total. This is near to 800 1 per day
and capita, which is a rather high consumption rate
(compared with the near by countries) but low on the
Icelandic scale, where lavish waste of water is a
Table 1
Chemical content (ppm)
t
Northern coastal area °C co2 sío2 Na+ K+ Mg++ Ca~ cr so4- pH/20°C
(3 boreholes) Lágasvæði, NW-part 37 12 7 16 1,0 2,9 3,0 25 6 7,1
(3 boreholes) Lágasvæði, SE-part 4,6 10 12 20 1,1 4,2 5,2 40 6,5 7,4
(5 boreholes) Off-flow from Svartsengi 5,0 15 14 33 1,6 6,6 7,2 70 11 7,7
(1 borehole) Southem coastal area 11,9 20 21 150 9 16 18 290 39 7,7
(3 open fissures) 7,2 18 15 100 4,6 15 16 225 32 7,5 25