Besides being one of the largest lakes of the Caucasus
region, it is one of the greatest freshwater mountain lakes of Eurasia. On its
origin the lake consists of 2 parts- Major and Minor lake basin. Twenty eight
rivers and springs flow into the lake, but only one major lake flows out. The
lake’s watershed basin comprises one-sixth of the total area, and is the
primary water resource of the country. As far as the precipitation goes, it is
very cold in winter and the lake freezes over every year. Summers are very hot
and rains often in spring and fall.
This is the way the hydrologic cycle works for the lake. It
begins when water evaporates from the surface of the lake. Moist air cools and
water vapor condenses to form clouds. Then moisture is transported to
atmosphere which then returns to surface as rain or snow. The water reaches to
the ground; some of it either evaporates back to atmosphere or enters the
surface as groundwater, which passes through small pores back into the lake or
atmosphere. The water that remains on the earth’s surface empties into the
lake, where the cycle begins again.
It was thought that
about 90% of the lake’s water loss was through evaporation. Even though the
lake was the primary drinking water resource in the area, most of the water was
used for irrigation. So throughout the years water has been taken from the lake
for irrigation at rates substantially higher than the natural inflow,
decreasing volume by 41%. This created a drawdown, which is lowering of water
levels in a reservoir or other body of water as a result of withdrawal. In the
1930’s the lake dropped by 20 meters and it was
feared that the water would disappear entirely. Significant
oxygen depletion occurred, which increased the rate of eutrophication. Because
of this drinking water was seriously threatened. In the past thirty years,
however, water levels started to rise and some of the area's most important
bronze age and medieval sites were threatened by the rising shore line.
http://www.armeniapedia.org
http://www.fao.org/docrep/003/x2614e/x2614e13.htm
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