Jökull - 01.12.1988, Blaðsíða 47

ppm, depending on the prevailing winds and the
exposure of the coast. Ascending the steep moun-
tains in northem and eastem Iceland the chloride
decreases rapidly to 2 - 3 ppm, while higher concen-
trations are found in the low valleys and fjords
penetrating far inland. The chloride content is
accompanied by other elements in somewhat vari-
ous ratios, dependent on meteorological and oro-
graphic conditions. Reactions with the rocks
increase the content of cations and notably that of
silica.
In the vicinity of high - temperature geothermal
fields an increase in chemical contents can be
observed in the groundwater, especially in silica and
sulphate, but also in chloride and the overall chem-
istry. When these relatively small and restricted
areas are excluded as well as the coastal stretches
with the strongest marine component, the chemical
content of the exploitable fresh water in Iceland is
usually within a rather narrow range and is low
compared to e.g. groundwater in Central and
Westem Europe. Local deviations occur in the low-
lands, where extensive peat bogs contribute a cer-
tain amount of organic compounds to the groundwa-
ter, as can be seen in the increase in carbon dioxide.
This leads to an increased dissolution of cations,
especially the earth-alkaline but also alkaline ions.
In the highlands the summer snowmelt reduces the
chemical concentrations, which is especially clear in
the low silica concentration. In general the ground-
water in Iceland, where accessible and exploitable,
is potable but perhaps somewhat too low in chemi-
cal contents for biologically optimal human con-
sumption.
Contamination and protection—The spring water
is throughout clean and free of turbidity, with the
exception of some springs, temporarily fed by
infiltration from glacial rivers. The same applies to
the groundwater from permeable bedrock and most
rockslides. Groundwater extracted from river grav-
els may show some turbidity when the rivers are in
flood and the aquifer is thin. Many rivers may dur-
ing floods carry such excessive loads of mud, that it
by far surpasses any filtrating capacities that the
communal water works might financially afford.
Despite the high infiltration rates and the thin
vegetation and soil cover the cold climate and the
long flow paths of the groundwater usually eliminate
any biological contamination. The oxygen content
in the precipitation and the reactive, volcanic glass,
which constitutes a high proportion of the bedrock,
reduce organic matter in the groundwater rather
easily. These circumstances combined with the fact,
that the drainage areas for most water works are
situated in uninhabited areas, have at large
prevented any serious pollution of the extracted
water. The expansion of the settlements and
increased and, literally speaking, widespread out-
door activitites are swiftly encroaching on the previ-
ously self-protected areas. In many cases the areas
lack the necessary protective soil cover. This creates
a real danger of contamination, especially in view of
the vulnerability of these areas.
PROBLEMS OF SUPPLY
INCREASEIN DEMANDS FOR
QUANTITY AND QUALITY
Use of groundwater for industrial and domestic
purposes is steadily increasing in Iceland (Fig. 6).
Some prime factors of influence can be discemed.
These factors are of varying age and different in
intensity. All of them, however, place demands on
an increase both in the quantity and quality of the
extracted groundwater. Some examples of the quan-
titative demands of different user groups are shown
in Fig. 7.
As seen from Fig. 7, the public water consump-
tion of a small fishing village is about one third of
that of its fish industry. But a fish farm hatching one
million smolts consumes water at a rate that is two
orders of magnitude larger than the public consump-
tion of a village.
The age-old rural society — In the raral society of
past centuries the need for water was limited to the
household, and the consumption can be estimated as
having been in the order of 20 1/inh.xday. The WC
was unknown, cleaning of earthen floors was by
sweeping, there were no water conduits and
JÖKULL, No. 38, 1988 45