Hafnersee

The Hafnersee (Slovenian Habnarško Jezero ) is one of several lakes in the south of the Wörthersee lake valley Keutschacher (Carinthia ).

Geography

The lake is located in Keutschacher Seental in the Sattnitz, which owes its origin to a side branch of the Draugletschers. This has reshaped the tectonically preformed Talfurche. The Hafnersee is located 800 meters west of the Keutschacher lake. The subsoil consists of altkristallinen rock series together ( phyllite, mica schist, Kalkmarmor ). Above are clayey deposits from the Tertiary, which are 40 to 50 m thick. These in turn is the 400 m thick Sattnitzkonglomerat ( latest Pleistocene ).

The Hafnersee has two tributaries, the Rodabach, the Schiefling Techelweg drained, and the drainage of the southern Penkensees. Quantitatively, significantly, the proportion of groundwater.

To the west of Lake Hafner are extensive fens, by the results of the main tributary of the lake. Due to the coming of the humic acids from the bog lake has a natural brown color. The eastern shore is also flat, here arises the Rakouza or Rodabach, which flows into the lake Keutschacher. At the north and south banks are only small aggradation surfaces.

The influence area of ​​the lake is 12.7 km ² and consists of the western part of the Keutschacher Seentals, the northern slope of Turiawaldes and the southern slopes of the Wörthersee mountains.

The Hafnersee is oblong - rectangular. In the middle of the lake basin is separated by a 1.8 m deep shoal in two sub-basins. The western basin is 10 m deep, the eastern 9.1 m.

History

1974, a Neolithic pile dwelling was discovered on the central shoal of the lake. It is dated in the temporal context of the culture Mondsee in the Salzkammergut. This wetland soil settlement Hafnersee 6843! Stands under monument protection.

Hydrology and Ecology

The average discharge is 210 l / s The water renewal time is 1.2 months.

The water temperatures of the lake resemble the Hafner Keutschacher lake. The temperatures regularly reach 25 ° C. The temperature peaks are achieved in the second half of July. From late November to March, the lake is often frozen over, the ice thickness can reach 40 to 50 cm. From May to October, the lake on a strict stratification, due to its small depth can, however, do not form a typical hypolimnion. The temperature on the bottom of the lake in summer is about 10 ° C. The mixing of the lake water (circulation) will be held in the spring in March / April, in the fall in November.

The lake water is medium hard, with around 10 ° dH. This is due to the lime-rich catchment. The electrical conductivity at 330-420 ĩS / cm.

Currently, the lake is classified as low mesotrophic. The average total phosphorus content is 12 to 14 mg / m³. In phytoplankton Dinobryon divergens and Cyclotella prevail. In the summer of Pediastrum duplex is strongly represented. On animals, 21 species are planktonic rotifers, copepods 6 species (especially Eudiaptomus gracilis ) and 7 species of water fleas ( Bosmina longirostris, Daphnia hyalina, Daphnia cucullata and Ceriodaphnia pulchella ) represented.

The dense population and intensive agricultural and tourist use of its catchment area in the early 1970s led to a strong nutrient load of the lake ( eutrophication). With the growth of algae, there was a strong turbidity of the water. 1974 and 1975 nutrient-rich and oxygen-poor deep water was verprüht by pumps on the surrounding surfaces. The installation of a deep drainage was not possible because of the associated stress of the brook downstream Keutschacher lake. In the years 1974, 1975 and 1977, the water was free of oxygen at the end of summer stagnation below 5 m depth. The algal biomass was 1971-1976 extremely high with up to 20.5 g per cubic meter in the epilimnion. The biomass was formed mainly of Asterionella formosa ( diatom ). As of 1974, the sewer system was built in Keutschacher Seental, which was completed by the mid-80s mainly. Since then, the process is cleaned in the treatment plant Klagenfurt. Since 1985, the situation of the lake improved. Total phosphorus concentration in the epilimnion dropped from up to 62 g / l to less than 20 g / l, the average algal biomass to 2 g / m³ ( values ​​1990/1992 ). The oxygen levels rose, the Secchi depth increased.

Especially the southern shore is natural. Here you will find a variety of small animals have good living conditions. In the underwater plants holdings water snails, clams and many insects live.

The Hafnersee has a wealth of fish: pike, catfish, perch, carp, eel and 14 other species. A neozoon is the North American largemouth bass. The original main fish that Guster is greatly diminished in recent years. In the Waterside area and the outflow there stocks of crayfish (Astacus astacus ).

The lake is part of the 2,532 -acre nature sanctuary Keutschacher Lake Valley ( LSG.032, 1970).

Use

The lake is used for bathing. On the north shore there are lawns and swimming areas. On the northeastern shore there is a camp.

On Hafnersee only recreational fishing is operated.