Jökull - 01.12.1982, Page 87

Chemistry and stable Isotope Composition of Geothermal
Waters in the Eyjafjördur Region, northern Iceland
HREFNA KRISTMANNSDÓTTIR
National Energy Authority, Grensásvegur 9, 108 Reykjavík, Iceland
SIGFÚS J. JOHNSEN
Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavík, Iceland
abstract
Geothermal water has been sampled in all existing springs
and drillholes in the Eyjajjördur region and analysedfor
dissolved solids and stable isotope ratios. The study is based
on analyses of40-85 samples.
The springs and drillholes are found to befed by at leasl
three separale reservoirs.
The main recharge areas of the reservoirs are traced by
stable isotope ratios to the North westem part of the glacier
Vatnajökull. Water in at least one of the reservoirs is believed
to be older than ten thousandyears.
INTRODUCTION
This study is a part of the geothermal prospect-
>ng, which has been going on in the Eyjafjördur area
during the last seven years. The sampling of water
for the geochemical studies was performed in two
main eíforts: the first in 1977 (Björnsson el al. 1978)
and this second one in 1979 — 1981. This study is
based on some 70 selected samples. The ö D had
been measured in a few samples ofgeothermal wat-
cr in the area by Amason (1976) but was in thisstudy
measured in additional samples. The ó 18 was
measured in samples from all natural springs and
drillholes in the area, a total of 85 samples. The
stable isotope ratios were also measured in samples
collected at depth in drillholes giving evidence of a
single inflow zone.
The aim of the isotope studies was to get a more
detailed pictureoftheorigin ofthe water and to split
the area into dilferent reservoirs. The study of the
dissolved solids in the water samplcs is used to
separate and connect aquifers, estimate under-
ground temperatures and as basis for the study of
scaling and corrosion risks during production.
Fig. 1. A topographic map of the Eyjafjördur
region showing the places sampled for geothermal
water.
Mynd 1. Kort af Eyjqfjarðarsvieðinu, sem sýnir pá
jarðhitastaði sem vatnssýni voru tekin á.
JÖKULL 32. ÁR 83