engleski

The Vrana lake hydrology (Island of Cres-Croatia)

The Vrana Lake on the island of Cres in the Adriatic Sea represents a specific phenomenon of karst hydrology. The island of Cres covers an area of 404.3 km2 with an average volume of 220x106 m3 of fresh water in the lake. The island has an average rainfall of 1, 063 mm. with a Mediterranean climate. The lake has a bottom reaching a depth of 62 m below mean sea level. The average water level is 14 m above mean sea level. The most proable theory on the origin of the lake and its hydrologic-hydrogeologic functioning state that it is a flooded polje in karst. The water budget method was used to define the lake catchments area at approximately 25 km2. During the last six years, there has been drastic decrease of about 3 m in the lake’ s water level. This phenomenon was analyzed and it was calculated that 53 percent of the water-level decline was caused by water discharges from the lake to satisfy water supply demands, and 47 percent was due to a period of low precipitation during the analyzed period.

karst hydrology ; lake water budget ; catchment area in karst ; Lake Vrana ; Island Cres ; Croatia

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