After Ice Age lake. The Hafnersee which is situated in the Keutschacher Seental is part of an after Ice Age lake. It owes its origin to a side- arm of the Drautal glacier. The geological underground of the catchment area consists of old- crystalline stones series like phyllites, mica schist and lime marble. On this older underground you find young- tertiary clay sedimentations of 40 to 50 meters height. These young tertiary layers are covered by the so called “Sattnitz-conglomerate” out of the youngest "Pleiozän" with a height of about 400 m. The catchment area includes the western part of the Keutschacher-See-Valley-Canyon as well as the northern slopes of the Turiawald and the soft southern slopes of the Pyramidenkogel.
The main inflow of the Hafnersee drains the flat moor in the west of the lake. Another inflow flows in on the southern shore. Its origin is the Penkensee, situated on the northern slope of the mountain chain Sattnitzzug. Besides these surface tributaries the Hafnersee is also fed by groundwater in a considerable amount. The runoff leaves the lake in the east, has a water amount of about 210l/s and drains through the Keutschacher See and the Reifnitzbach, into the Wörthersee.
Mostly natural shore zones. The lake is situated in a flat depression in 508 m above sea level. The lake basin has a longish, rectangular shape. It is parted into two basins by a shallow in the middle of the lake, where the ground climbs up to 1,8m under water surface. The greatest depth of the western basin is 10 m, in the eastern basin it is 9, 1 m. The shores are mostly natural. On the western bank there is a large flat moor, in the north and south there are smaller, reed covered silted up areas. Large parts of the northern bank are used as rest-care meadows and bathing areas, in the north- east a campsite was erected.
Usage for tourism. In the widened catchment area you can find numerous institutions for tourism. The largest settlement in the catchment area is Schiefling in the west of the lake. The areas outside the settlements are used in forestry and agriculturally.
The water of the Hafnersee is of a characteristic brown color that is caused by a high portion of Humane Acid. The Hafnersee is a very warm bathing lake. It has its warmest temperatures towards the end of July. The lake is strictly piled up from May to October, but because of the rather little depth of 10 m there cannot develop a typical hypolimnion. On the ground the lake has more than 10 °C in summer. The spring circulation takes place in March and April, the autumn circulation in November. Usually the lake is ice- covered from the end of November until March. The ice-sheets can reach 40 to 50 cm.
Landscape protection area. Because of the beauty of the landscape large areas have been included into the landscape protection area of the Keutschacher Seen-Tal, with 2.532 ha (LGBl.74/70, 86/71).
19 species of fish:
Pike (Esox lucius)
Bass (Perca fluviatilis)
Eel (Anguilla anguilla)
Lake trout (Salmo trutta f. lacustris)
Catfish (Silurus glanis)
Chub (Leuciscus cephalus)
Grass carp (Ctenopharyngodon idella)
Bitterling (Rhodeus sericeus amarus)
Bream (Abramis brama)
White bream (Abramis björkna)
Carp (Cyprinus carpio)
Bleak (Alburnus alburnus)
Roach (Rutilus rutilus)
Common rudd (Scardinius erythrophthalmus)
Tench (Tinca tinca)
Silver carp (Hypophthalmichthys molitrix)
Pike-perch (Sander lucioperca)
Trout bass (Micropterus salmoides)
Crucian carp (Carassius carassius)
The originally main species of the Hafnersee, the bream, has gone back during the last few years. On the other hand the number of red fins has increased. Like in the Wörthersee and the Keutschacher See the Micropterus salmoides has come into the Hafnersee at about the turn of the last century. You can find single lake trout in the lake, but they can reach weight up to 4 kg. Some of the stocked silver carps can reach weights up to 20 kg.
Crayfish population to be found in the lake. It houses a population of
Astacus astacus. You can find them in the shore zones as well as in the runoff, the Rachunzabach.
Valuation of the ecological status. The catchment area of the lake is the region, out of which the surface- and the underground waters flow into the lake. The borders of this area are formed by the watershed. The cartographic description of these catchment areas referring to the usage is the base for the valuation of the ecological status in regard to the general water instructions (WFD). All the fundamental data are registered in a data bank. With the help of the software Arc View GIS, version 3.2, the analysis of the geographic information took place. The topographic state, the natural vegetation and the antrophogen usage of the catchment area deliver important information about nutrient- and pollutant burdens.
40 different forms of vegetation. The descriptions are out of HARTL, STERN u. SEGER, 2001, “The Map of Carinthia`s Current Vegetation”. The geo-referenced data out of this work were blended with the catchment area and transferred into the data bank.
They differentiate 40 forms of vegetation. To have a better view on the results they are comprehended in the following tabulation in these main groups:
intensively used agricultural areas, farming green land, forests, surface- waters, built up areas, Alps and others.
34 forms of utilization in the catchment area. They were geo-referenced and blended with the digital register (DKM) out of 2003.The granted data were transmitted into a data bank and now afford information about the dimensional distribution of the different forms of utilization. The 34 forms of utilization have also been comprehended in the main groups like it has been done for the vegetation groups.
