The mythical Stymphalia is one of the few natural mountain lakes of Greece with special features that hosts a big variety of animals and plants. The lake is well-known from the greek mythology and the Labours of Heracles. The legendary hero came here to slay the Stymphalian birds, the man-eating birds with bronze beaks and iron wings that destroyed the herds and the crops of the region. The lake, although relatively small in size compared to the large lakes of the mainland, is considered to be the most important natural lake in the Peloponnese and the most important mountain lake in Greece. It is located in the southwest of the prefecture of Korinthia and has been formed in the center of an elongated plateau at an altitude of 620 meters. To the north and west of the lake rises the big Ziria mount, to the south lay Olygirtos and Mavrovouni mountains and to the east is embraced by the smaller Gavria and Veseza mountains. It is a shallow lake with an average depth of 1.5 m and a maximum of 4 m, but usually its depth is between 0.5 m and 2.5 m. Its size changes seasonally and is directly related to rainfalls. The largest area of Stymphalia reaches 7,7 sq.km. and the lesser 3,5 sq.km. During droughts the lake becomes almost completely dry, something that happened at the years 1978, 1989 and 1993. The maximum length of the lake reaches 3,5 km, the maximum width is 1.5 km, while the water catchment area extends to 218 sq.km. Stymphalia is a typical example of a polje, something that is evidenced by the presence of dozens of karst formations in the surrounding area. The lake feeds by a system of streams (Kastaniotikos, Lykorema, Sofeneto, Koliou, Agia Sotira, Rapi), from the small river Stymphalos, from various springs (Kastania, Kefalovrysos, Kefalari, Drisa, Drosopigi, Velatsouri, Lafka) and from the basin of Pellini through the Lagovouni tunnel. Lake Stymphalia has an interesting drainage system. Most of the overflowing waters are directed to the Vochaikos Chandakas canal and then flow through the tunnel of the ancient aqueduct of Andrianus to the Asopos river and to the lowlands of Korinthia. Another part of the lake’s water flows through cave-sinks, such as Gidomandra and Fortsa, to the Argolic Gulf. It is interesting that the procedure was reported by Pausanias, who observed that “the waters of Stymphalia disappear into a land gap and appear again in Argolida, where they formed the river Erasinos". The lake is marshy and shallow, and along with the surrounding area it is characterised by a wide variety of habitats, such as reed beds, wet meadows, shrubs, dense fir forests, streams and cliffs. Stymphalia is threatened by the continuous pumping of its water for irrigation, the expansion of crops and the chemical fertilisers that has transformed it into an eutrophic lake that now resembles a huge reed bed. It is striking that the issue of the sustainable management of Stymphalia holds over 1,800 years since the time of Emperor Andrianus. Unfortunately, and despite the efforts of various conservancies, this famous lake of Greece is today at risk of total drying and extinction.
The stout grass (Phragmites australis) dominates the flora of the lake, having reached more than 65% of the surface. The flora is supplemented by lesser bulrush (Typha angustifolia), while on the northern banks are willows, maples and plane trees. The surrounding area is full of kermes oaks, lentiscs, heaths, strawberry trees, various oaks, ashtrees, almond-leaved pears and mock privets. A little bit higher begin the forests of the greek firs with a few spots of black pines. Inside the lake and its banks the flora consists of 24 aquatic plants, like Myriophyllum spicatum, Myriophyllum verticullatum, Persicaria amphibia, Ranunculus peltatus subsp. baudotii, Ceratophyllum demersum, Butomus umbellatus, Iris pseudacorus and Nasturtium officinale. Important plants around the lake are Convolvulus mairei, Asperula arcadiensis, Arenaria filicaulis subsp. graeca, Pimpinella rigidula, Onosma erecta subsp. erecta, Cerastium dubium, Inula verbascifolia subsp. parnassica and Astragalus suberosus subsp. haarbachii. Other plants in the area are Agrostemma githago subsp. githago, Onobrychis ebenoides, Seseli tortuosum, Crocus hadriaticus, Crocus laevigatus, Iris unguicularis, Ornithogalum collinum subsp. collinum, Anchusella cretica, Capsella grandiflora, Consolida ajacis, Convolvulus cantabrica, Legousia speculum-veneris, Helichrysum luteoalbum, Verbascum epixanthinum, Tordylium officinale, Lunaria annua subsp. pachyrhiza, Asperula arvensis and orchids Cephalanthera longifolia, Anacamptis laxiflora, Orchis italica, Orchis quadripunctata, Ophrys spruneri, Ophrys mammosa and Ophrys argolica.
Stymphalia is an important habitat for the avifauna with many bird species nesting in the area, while dozens visit it during migrations. In the area still arrive glossy ibises that were connected with the Stymphalian birds because of the metallic shades on their wings. The lake is an important habitat for the reproduction of the rare ferruginous duck. Other species of ducks are mallards, shovelers, widgeons, pochards, gadwall and garganeys. Among the herons here live purple herons, grey herons, great egrets, little egrets, squacco herons, little bitterns, bitterns and night herons. Significant predators of the area are the short-toed eagle, the marsh harrie, the hen harrier, the honey buzzard, the common buzzard, the sparrowhawk, the goshawk, the peregrine and the kestrel. Other birds of Stymphalia are turtle doves, woodpigeons, mute swans, coots, moorhens, water rails, little grebes, black-necked grebes, little ringed plovers, ruffs, snipes, woodcocks, black terns, eagle owls, long-eared owls, little owls, barn owls, scops owls, nightjars, middle spotted woodpeckers, kingfishers, skylarks, crested larks, woodlarks, meadow pipits, water pipits, grey wagtails, song thrushes, mistle thrushes, blue rock thrushes, nightingales, rufous bush robins, wrens, dunnocks, subalpine warblers, great reed warblers, sombre tits, blue tits, long-tailed tits, penduline tits, rock nuthatches, red-backed shrikes, woodchat shrikes, jays, hooded crows, starlings, reed buntings, black-headed buntings, cirl buntings and corn buntings.
Stymphalia hosts eight species of amphibians: fire salamander, greek newt, common toad, green toad, tree frog, balkan frog, greek frog and agile frog. The most important reptiles of the lake are the endemic of the Peloponnese lizards, the peloponnese slow worm, the greek algyroides and the peloponnese wall lizard. Other reptiles are pond turtles, balkan pond turtles, marginated tortoises, Hermann’s tortoises, glass lizards, snake-eyed skinks, limbless skinks, balkan green lizards, balkan wall lizards, worm snakes, smooth snakes, four-lined snakes, balkan whip snakes, levant montpellier snakes, grass snakes, Dahl’s whip snakes, cat snakes, leopard snakes and nose-horned vipers. The most important mammal of the are is the golden jackal, which had made an impressive return the last years. Other species of Stymphalia are otters, foxes, badgers, pine martens, weasels, eastern hedgehogs, hares and forest dormouses. It is interesting that the lake hosts the southernmost point of the presence of coypu (Myocastor coypus) in Europe. Stymphalia is also known for many species of bats such as the greater horseshoe bat (Rhinolophus ferrumequinum), the lesser horseshoe bat (Rhinolophus hipposideros), the Savi’s pipistrelle (Hypsugo savii), the common pipistrelle (Pipistrellus pipistrellus), the soprano pipistrelle (Pipistrellus pygmaeus), the Kuhl’s pipistrelle (Pipistrellus kuhlii), the serotine bat (Eptesicus serotinus), the common noctule (Nyctalus noctula), the common bent-wing bat (Miniopterus scheibersii), the free-tailed bat (Tadarida teniotis), the long-fingered bat (Myotis capaccinii) and the greater mouse-eared bat (Myotis myotis). The most important animal of the lake is the Stymphalia minnow (Pelasgus stymphalicus), a fish that is included in the “Red Book of Endangered Species” as it lives exclusively here and in a few rivers of the Peloponnese. Other fishes of the lake are the european carp (Cyprinus carpio), the peloponnese chub (Squalius peloponnensis) and the stymphalia chub (Squalius moreoticus).