Typology and ecological classification of lakes and rivers (eds. Marja Ruoppa and Krister
Karttunen). TemaNord 2002:566: 86-88. 2002
ICELANDIC RUNNING WATERS; ANTHROPOLOGICAL IMPACT AND
THEIR ECOLOGICAL STATUS
Jón S. Ólafsson1, Gísli Már Gíslason1 & Hákon Aðalsteinsson2
1Institute
of Biology, University of Iceland, Grensásvegur 12, IS-108 Reykjavík,
Icaland.
2The National Energy Authority, Grensásvegur 9, IS-108 Reykjavík, Iceland.
Introduction
The classification of Icelandic running waters and their ecosystem has mainly been based on
the bedrock type and topography, which was proposed by Kjartansson (1945) and later
modified by Gardarsson (1979). This classification has been applied in the literature since it
was proposed more and less untested until recently (Gudjónsson 1990, Gíslason et al. 1998,
Malmquist et al. 2000, Olafsson et al. 2001, 2002). The two main types of Icelandic running
waters involve, glacial rivers on one hand and non-glacial rivers (spring-fed and direct run-off
rivers) on the other hand. The glacial rivers can be found in most parts of Iceland, though
being most common in the South and South East Iceland (Table 1).
The former classification has proven to be valid when tested by distribution and habitat
selection of the Atlantic Salmon (Salmo salar) (Gudjónsson 1990) and chironomids and
simuliids (Olafsson et al. 2001,2002). Amongst the main environmental variables explaining
the species composition of chironomids and simuliids are altitude, cathchment characteristics
such as vegetation cover and area of wetlands as well as the type of bedrock.
The isolation of the island, its young bedrock and recent deglaciation characterize the
fauna and flora of Icelandic freshwaters. In comparison to freshwater biota of other Nordic
countries it posesses low diversity (Petersen et al. 1995). The most prominent freshwater
macro-invertebrates are small crustaceans and dipterous insects.
Anthropological impact on rivers
Anthropological impact on catchments, rivers and lakes has probably started soon after the
first human settlement in Iceland in the 9th century. However, both prior to human settlement
as well as later, volcanic activity may have had some severe impact on the freshwater
ecosystems. The main impact by humans can be categorized as:
a) Changes in vegetation cover of catchments, deforestation and soil erosion due to
overgrazing,
b) Draining of wetlands, bogs, marches, ponds and lakes, mainly for providing hay fields,
c) Hydroelectric development, diversion of rivers between catchments as well as changing
the flow regimes,
d) Road works, bridges and mining
e) Changes of faunal diversity due to introduction of salmon to salmon free areas by
providing fish passways, alteration on native fish populations by introduction of farmed
populations.
Effect on ecological status
Human influence on ecological status of rivers has in some instances been considerable
because of a) deforestation and soil erosion the retention of water in the catchments has
reduced; b) deforestation and soil erosion has reduced the input of coarse and fine particulate
matter (cPOM and fPOM)), which has lead to decline in populations of shredders; c)
Typology and ecological classification of lakes and rivers (eds. Marja Ruoppa and Krister
Karttunen). TemaNord 2002:566: 86-88. 2002
reduction of nutrient input into the rivers and less productivity caused by less cover of soil in
the catchments; d) changes in flow regimes due to draining of lowland wetlands, mainly
reduced the retention time of the water in the catchments; e) less silt in glacial rivers that have
been dammed near their headwaters to make storage reservoirs, which can lead to increased
invertebrate diversity in the rivers; f) increased disturbance on animal life in rivers that are
used for gravel mining or in the vicinity of newly build bridges and roads; g) increased
mixing of farmed and native fish population is a threat that has gained an increased attention
recently, however, little data is available on the topic. Human impacts on rivers in Iceland are
considerable and has undoubtedly reduced the species diversity and decreased the
productivity of river ecosystems.
GLACIER FED RIVERS
NON GLACIER FED RIVERS
Glacier melt water. Great
annual and diurnal fluctuations
in discharge and temperature,
usually low in pH (6-8) and
conductivity (10-80μS/cm). Low
biodiversity. S, SE, E and
NE Iceland.
Precipitation and springs.
SPRING FED RIVERS
DIRECT RUN-OFF RIVERS
Sub terrain springs in
neo-volcanic areas on
permeable palagonite
bedrock formations.
Stable discharge and
temperature, high pH
(7.0-10.0) and conductivity
(80-200 μS/cm). High
biodiversity. SW, S and
NE Iceland.
Mainly surface water, on
impermeable tertiary basalt
bedrock. Great annual fluctuations
in discharge and temperature,
relatively low pH (7.0-7.5) and
conductivity (20-120 μS/cm).
(1) SPRING FED RIVERS
(1) RUN-OFF RIVERS
With lake influence, high
in fPOM and moderate
biodiversity.
Mainly short rivers with little
influence from lakes or wetlands. Great
fluctuations in discharge and temperature,
with low conductivity (10-70 μS/cm).
NV, N and E Iceland.
(2) SPRING FED RIVERS
(2) RUN-OFF RIVERS
Without lake influence (hot and
cold) usually lower in fPOM
than no. 1 (above) but moderate
biodiversity.
Mainly , buffered with deep valley
lakes. Considerable fluctuations
discharge and temperature,
Conductivity: 60-70μS/cm.
Fairly low biodiversity.
W Iceland.
(3) RUN-OFF RIVERS
Originated from well
vegetated wetland plateau (moor).
Buffered by wetlands (ponds and lakes),
medium fluctuations in discharge
and temperature, reduced by wetland
buffer effect, relatively high
conductivity (50-120 μS/cm). Fairly high
biodiversity. W, NW, NE
and E Iceland.
________________________________________________________________
Table 1. The main types of running waters in Iceland; their characteristics and
distribution (Based on Gardarsson 1979, Malmquist 1998, Adalsteinsson & Gíslason
1998, Olafsson 2001 and 2002).
Typology and ecological classification of lakes and rivers (eds. Marja Ruoppa and Krister
Karttunen). TemaNord 2002:566: 86-88. 2002
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