Rit (Vísindafélag Íslendinga) - 01.06.1976, Page 78

enriched in the heavier isotopes relative to the precipitation. In
Iceland, hoth geological and climatic conditions suggest such an
enrichment to be of rather small importance. In Iceland there is a
relatively cold climate and high precipitation rate. Furthermore,
a great part of the country is covered by porous surface layers.
Therefore, at least in the warmer seasons, most of the rain pene-
trates rapidly into the ground and down to the groundwater table
where practically no evaporation can take place. The small amount
of water that is left on the surface then evaporates completely.
If we compare the results obtained from regular measurements
of the deuterium content of cold springs and surface streams (see
Figs. 15 and 16) with the data listed in Table 7, we arrive at the
following conclusion. The ðD-value of a single sample collected
from cold springs or surface streams, except those streams fed by
a considerable amount of glacial meltwater, appears to reveal the
mean 8D-value of the water source. In cases where a cold spring
or surface stream is of local or known origin, it reflects without
a great error the mean 8D-value of the precipitation at the place in
question. Consequently, a single sample of local cold spring or sur-
face stream of known origin can be used to give directly the mean
deuterium content of the precipitation at the respective place in
Iceland. This was first suggested by Friedman et al. (1963).
This is a much simpler way of obtaining information on the
mean deuterium content of the precipitation, than carrying out
regular deuterium measurements on the precipitation itself, pos-
sibly for a period of several years, and this is the method we use
in this work to show the distribution of deuterium in precipitation
throughout the country, except in regions covered by glaciers.
Since 1961 a systematic sampling of local groundwater and sur-
face streams of known origin has been carried out throughout the
country. A total of 768 samples havebeen collected from 657 points
and their deuterium content is listed in Table II in the Appendix.
Table II gives the name of the sampling place, the characteristics
of the water source, latitude and longitude, the date of sampling,
temperature and 8D- The temperature has only been measured in
some cases. The characteristics of the water source referred to in
the table are indicated by capital letters, where S = surface stream,
C = cold spring, and II = drill hole. The latitude and longitude
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