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Hörzendorfer See

Hörzendorfer See is a man-made lake in the Hörzendorf district in the municipality of Sankt Veit an der Glan in Carinthia. It is eutrophic and each year various parameters measuring the eutrophication are taken.

Location
The lake is located in the hill country north of Ulrichsberg, about three kilometres south of the city. Tributaries are the Hörzendorfer stream (also called Draschelbach) from the south and the Projerner stream from the west; its outlet is the Hörzendorfer stream in the northeast.

History
The lake used to be managed as a drainable carp pond. The original name was Holzer Pond, and in the 19th century the Mayer Pond. In the 19th century, more water was drained from the pond for the operation of the powder mills on Hörzendorfer Bach.

Description
The lake is located in the 444-hectare nature reserve Hörzendorfer See - Tanzenberg (LGBl. No. 36/1970).

Today the lake is used for fishing and bathing. But one must pay to swim in the lake during the season. In winter, the lake freezes reliably and is ideal for ice skating.

Fauna of the Hörzendorfer See
The following 15 fish species can be found in the Hörzendorfer See:

Aitel (Leuciscus cephalus), perch (Perca fluviatilis), bream (Abramis brama), largemouth bass (Micropterus salmoides), Northern pike (Esox lucius), Crucian carp (Carassius carassius), common carp (Cyprinus carpio), common bleak (Alburnus alburnus), roach (Rutilus rutilus), rudd (Scardinius erythrophthalmus), tench (Tinca tinca), brown trout (Salmo trutta f. lacustris), pumpkinseed (Lepomis gibbosus), Wels catfish (Silurus glanis), and zander (Sander lucioperca).

The most common species are carp, pikeperch, and pike. Neozoa are largemouth bass and sun bass. Up until the 1980s there was a large population of European crayfish (Astacus astacus), which became extinct in the lake 1991 due to a subsidence of the lake during renovation of the outlet. This was followed by stocking with North American signal crabs (Pacifastacus leniusculus).

Direct translation of Report16
Warm bathing water. The Hörzendorfer See lies in a hilly country that extends from the Zollfeld to the west and is formed by the foothills of the Ulrichsberg. The bedrock consists essentially of volcanic rocks from the Magdalensberg series, over which quartz sandstone and quartz conglomerates (Gröden sandstone) lie. The area is glacial and covered with thick moraine deposits. During the glacier retreat, the Hörzendorfer See basin was filled with a body of dead ice. The lake basin was sealed in the east with a dam and the lake was dammed. The water once served as a drainable fish pond, mainly for fish farming; Today it is a popular bathing lake due to the high water temperatures in summer. In winter the ice rink is visited by numerous athletes.

As a result of severe eutrophication phenomena, a deep water drainage was installed in 1982, through which nutrient-rich, oxygen-poor deep water flows into the drain. The tributary flows into the lake in the west. The drain leaves the lake in the east via a monk.

Breeding ground for birds. On the south bank of the lake, natural bank vegetation consisting of reeds, rushes, bulrushes and various types of large sedge has been largely preserved. The extensive reed belt is one of the breeding grounds for the little bitterns, little grebes, coots and mallards. In addition, the rich food supply of fish and small animals attracts a number of migratory birds. Larger reed stands can also be found in the area of ​​the tributary.

Use of the surrounding area. A large lawn for sunbathing adjoins the north shore of the lake, which is frequented by numerous bathers in the summer months. The road leading past in the east of the lake is only separated from the lake shore by a narrow reed belt. In the wider area of ​​the lake there are extensive agricultural areas, on which mainly maize is grown, as well as some more or less large wooded parcels with mainly spruce or pine monocultures.

Landscape protection. Much of the original vegetation around the Hörzendorfer See was destroyed by human intervention and a diverse cultural landscape was created. The area was declared a landscape protection area Hörzendorfer See-Tanzenberg in 1970 (LGBl. No. 36/1970).

in 2020 the report states:"With an average chlorophyll-a content of 40 µg / l and an average biovolume of 5.2 mm³ / l, the water corresponded to a eutrophic nutrient level with high algae production. Dinophyceae were dominant on both dates, representatives were Peridinium willei, Peridinium aciculiferum and Peridinium sp ." Water surface temperatures varied between 24.2°C and 24.8°C, and pH between 8.1 and 8.5 (alkaline).