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A great range of climatic zones have been recorded within
Armenia. The country is located centrally in the sub-tropical
zone, and thus is prone to arid (desert and semi-desert) conditions.
However, the altitudinal variation within the country results
in further variation in climatic zones, in addition to existing
latitudinal clines.
In general, the country receives a high amount of sunshine;
ranging from 2600 hours per year (in Yerevan) to 2800 hours
per year (shore of Lake Sevan). The average temperature throughout
the year varies geographically from 2.70C (Mount Aragats)
to 140C (at Meghri). July and August are usually the warmest
months (Table 2), while average minimum temperatures recorded
in winter vary geographically (from -3.10C at Meghri in the
north-east, to -18.90C at Berdashen).
Table 1.2. Maximum average monthly temperatures in summer
and annual rainfall in different altitude zones
|
Altitude zone
|
Average monthly temperature in summer
|
Annual rainfall(mm)
|
|
Low-level
Mid-level
High-level
|
24-26 C
15-20 C
10-15 C
|
250-300
400-600
700-1000
|
Average annual precipitation is around 600 mm, but varies
in different altitudinal zones (Table 1.2) Most precipitation
occurs in the spring, while the second half of the summer
is dry. Relative humidity averages 60% (ranging from 44% in
summer to 80% in winter). Long-lasting snows exist on mountains
over 1300m. In these areas snowfall may reach 2m, whilst snowfall
reaches 0.5m on the lower steppes.
Armenia has extremely limited water resources. In total the
country receives a total of 18 km3 water throughout the year,
mainly from rainfall, however most of this is lost by evaporation.
Two major river systems are present in Armenia (Map 4; Annex
1), and these can be found in the Kur basin (7890 km2 of rivers)
and the Arax basin (21900 km2 of rivers). The average density
of river networks throughout the country is equivalent to
0.4 km/km2. These rivers are mainly fed by snowmelt, rain
and underground waters. Extensive flooding occurs in spring
as a result of runoff from snow melt and heavy rainfall. Overall,
the flow in rivers totals 7 km3, however this may fall to
5 km3 at some times. The rivers represent a potentially important
resource, not just for water supply and irrigation, but also
for hydroelectric power (estimated to be equivalent to 1.7
million kWt).
|
Name of lake
|
Location
|
Ltitude(m above sea level)`
|
Surfacce(sq.km)
|
Volume(1000m 3)
|
Max.Depth(m)
|
|
Kari
|
Near summit of Mount Aragats
|
3190
|
0.12
|
357
|
8
|
|
Akna
|
Near Mount Agzdahak
|
3030
|
0.8
|
2500
|
15
|
|
Arnot
|
Estern slopes of Mount Geghama
|
2350
|
0.04
|
206
|
12.6
|
|
Gazana
|
At the head of Geghi river
|
3590
|
0.06
|
360
|
10
|
|
Kaputan
|
At the head of Kajarants river
|
3300
|
0.1
|
1500
|
22
|
|
Ai
|
Mount Gharabagh
|
2990
|
0.6
|
180
|
4.5
|
|
Sev
|
Mount Ishkhanasar
|
2666
|
2
|
9000
|
7.5
|
|
Arpi
|
East of Ashotsk Basin
|
2025
|
22
|
100 000
|
8
|
|
Aighr
|
North of Ararat Valley
|
860
|
0.07
|
310
|
9.4
|
|
Parz
|
North of Areguni mountains
|
1400
|
0.27
|
84
|
8.0
|
Lake Sevan is the largest lake in Armenia, and one of the
largest alpine lakes in the world. It is located at 1916 m
above sea level, between a series of mountain ranges (Gegham,
Vardenis, Sevan and Areguni). Lake Sevan contains 80% of Armenian
water resources (1585 billion m3) which is over 35 times more
than the volume of water in reservoirs, and this plays an
important role in regulating the country's water balance.
Lake Sevan also supports the agricultural, industrial and
energy sectors in Armenia, with its waters having been used
for energy generation and irrigation since 1933.
The chemical composition of Lake Sevan is very distinctive,
with significantly high levels of phosphorus (0.32 g/m3) but
low nitrogen levels (0.003 g/m3). Biological production in
the lake is through macrophytes (with a biomass of 7000 g/m2),
while phytoplankton is of less importance (biomass of 0.3
g/m3). However, the chemical and ecological composition of
the lake has changed considerably as a result of substantial
declines in the water level over recent years.
During the period 1933 to 1981 the level of Lake Sevan dropped
dramatically.This was the result of a number of factors which
led to increased offtake of its waters, not the least the
devlopment of hydroelectric power stations downstream. The
lake system and its ecological balance were greatly disturbed
by this process, which reduced the volume of the lake by 42%,
with areas round the edges of the lake drying out. The consequences
included changes in the temperature of the lake (heat release
from its surface decreased by 2%), changes in circulation
within the lake and increased acidity and eutophication, given
favorable conditions for algal growth (Table 1.4). The first
signs of the lake's eutrophication were recorded in 1964,
when green and blue algae blossomed in the lake. The changes
in the conditions within the lake have led to degradation
of the whole ecosystem, and changes in various processes within
the area of the lake (including bio-degradation, sedimentation
and diffusion).
The drainage of the lake also had important effects for the
fauna. Drying of parts of the rocky bottom of the lake destroyed
the principal trout breeding sites. In addition, around 10,000
ha of wetland and semi-wetland areas also dried out. These
areas were previously used by up to 160 species of migratory
birds, and only 50 of these species are now recorded. The
populations of mammal and reptile species in the area have
also declined significantly, and there is evidence of changes
in species composition.
In response the problem of eutrophication, the decision was
made to increase inflow to Lake Sevan from neighbouring rivers
(including the River Arpa). Since 1982, between 250 and 270
million m3 of water has been carried from the Arpa River each
year, through the 48km long Arpa-Sevan tunnel. As a result,
the volume of water in the lake has risen, and between 1984
and 1990 the level of the lake increased by 1.2m. In addition,
a number of physio-chemical, biochemical and bio-production
processes have stabilized, and changes in the lakes biota
have been reversed, resulting in significant decreases in
the levels of eutrophication.
However, demand for water from Lake Sevan for energy production
rose dramatically during the period 1991 - 1995, and this
resulted in a 2.2m drop the level of the lake, and further
destabilization of physical, chemical and biotic processes,
leading to build up of organic residues in the water of the
lake. Analysis of the causes and effects of eutrophication
in Lake Sevan indicates that mitigation of the negative processes
associated with eutrophication will require an increase of
6m in the level of the lake. This will buffer the lake from
changes in the related watersheds and from accumulation of
organic matter from sediments. The problems associated with
Lake Sevan have been analysed and an action plan has been
developed for the lake by the World Bank (May 1998), which
includes detailed activities for the recovery of the lake.
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