Rit (Vísindafélag Íslendinga) - 01.06.1976, Qupperneq 159

The isotope studies presented in this work are in good agree-
ment with the model of Einarsson.
The hot spring Húsafell (sample No. 122), located farthest to the
east in the area, has a much lower deuterium content than other
hot springs in Borgarfjörður, 8D = — 91.3%0. The Húsafell thermal
water is obviously derived from a groundwater system quite dif-
ferent from that which feeds the hot springs in Reykholtsdalur
farther west. A present-day precipitation with a ðD-value similar
to that of the thermal water at Húsafell is only found to the east
and nearest in the northern part of the glacier Langjökull.
West of Húsafell, in Reykholtsdalur and Bæjarsveit, there are
numerous hot springs (samples No. 123-125 and No. 127-135)
which all have about the same deuterium content, mean ðD being
— 74%0. All these hot springs are thus believed to belong to the same
deep groundwater system and a possible recharge area for this
groundwater system is the area just west of the glacier Langjökull.
The hot springs in the valley Lundarreykjadalur, Brautartunga
(sample No. 138), with öD = — 73%0, and Reykir and Englands-
hver (samples No. 136 and 137), with 8D = — 77%0, differ markedly
in deuterium content. Englandshver is likely to receive its water
from the southern part of Langjökull but Brautartunga from the
area just west of it.
The hot spring Efri-Hreppslaug (sample No. 126) has a 8D =
— 68.3%0. Since the temperature of the water is only 37°C, it is most
likely that the deep water has mixed with some local groundwater.
The wells Leirá (sample No. 139), with 8D = — 73.8%0, and
Akranes (sample No. 140), with 8D = — 71.3%0, have a similar
8D-value which is also similar to that at Brautartunga. All these
sources lie on a line which can be extended to an area west of the
southern part of Langjökull where the precipitation also has the
same 8D-value.
Consequently, it is logical to assume a south-west deep ground-
water flow which originates in the above-mentioned areas and ex-
tends at least to the coast and possibly somewhat farther under the
sea-bed. Since the wells Kollafjörður and Seltjarnarnes and K-1 in
the previously discussed Reykjavík and Mosfellssveit areas also have
a similar 8D-value, they most likely also belong to the same deep
groundwater flow.
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