Judarn is a small lake in

Bromma Bromma () is a borough (''stadsdelsområde'') in the western part of Stockholm, Sweden, forming part of the Stockholm Municipality. Bromma is primarily made up of Bromma Parish and Västerled Parish. The fourth largest airport in Sweden and the ...

, a western suburb of Stockholm, Sweden. Surrounded by forest and the Judarskogen nature reserve, it stretches between Åkeshov and

Södra Ängby Södra Ängby is a residential area blending functionalism with garden city ideals, located in western Stockholm, Sweden, forming part of the Bromma borough. Encompassing more than 500 buildings, it remains the largest coherent functionalist ...

. Three other lakes are found nearby: Kyrksjön, Lillsjön, and Råcksta Träsk. The name is

etymologically Etymology () The New Oxford Dictionary of English (1998) – p. 633 "Etymology /ˌɛtɪˈmɒlədʒi/ the study of the class in words and the way their meanings have changed throughout time". is the study of the history of the form of words ...

associated to ''ljuda'', the verb "to sound".

Characteristics

With an area of 74,000 square metres and an average depth of 2.7 metres (maximum 3.7 m), the lake contains 180,000 cubic metres of water and is supplied by a drainage area of 0.8 km². Originally supplying lake Lillsjön, Judarn today discharges into lake Mälaren. Regarded as one of the least contaminated lakes in Stockholm, Judarn receives

storm water Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed land ...

from a nearby traffic route which gives it considerable levels of

lead Lead is a chemical element with the Symbol (chemistry), symbol Pb (from the Latin ) and atomic number 82. It is a heavy metals, heavy metal that is density, denser than most common materials. Lead is Mohs scale of mineral hardness#Intermediate ...

resulting in a bathing ban, metal content otherwise being low and

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...

levels moderate. The lake, considered as being of great recreational and natural value, is part of the nature reserve Judarskogen and has a rich flora and fauna with many

aquatic plant Aquatic plants are plants that have adapted to living in aquatic environments ( saltwater or freshwater). They are also referred to as hydrophytes or macrophytes to distinguish them from algae and other microphytes. A macrophyte is a plant that ...

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, and

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" '' Triadobatrachus'' is ...

s. Its isolated location combined with low levels of

chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words , ("pale green") and , ("leaf"). Chlorophyll allow plants to ...

makes Judarn one of the clearest lakes in Stockholm, and notwithstanding low levels of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

nutrient content is low even during winters, with raised levels of PAH and

PCB PCB may refer to: Science and technology * Polychlorinated biphenyl, an organic chlorine compound, now recognized as an environmental toxin and classified as a persistent organic pollutant * Printed circuit board, a board used in electronics * ...

in deep sediments.

Geology

Geological traces of the inland ice which withdrew from the area some 11,000 years ago are found in the

moraine A moraine is any accumulation of unconsolidated debris ( regolith and rock), sometimes referred to as glacial till, that occurs in both currently and formerly glaciated regions, and that has been previously carried along by a glacier or ice sh ...

s around the lake. The huge square blocks of stone scattered in the area are the result of the earthquakes produced by the tension caused by the retiring ice. The geologist Gerhard de Geer studied the surrounding moraine ridges, which were eventually given his name, and geological excursions are still common in the area.

Flora

The flora in the lake itself is reduced to a few species, including White Waterlily, Common Bladderwort, and

Whorled Water-Milfoil ''Myriophyllum verticillatum'', the whorl-leaf watermilfoil or whorled water-milfoil, is a native to much of North America, North Africa, and Eurasia. It closely resembles another native milfoil, called northern water milfoil (''M. sibiricum'') ...

; while others plants are found along the beaches, including Narrow Leaf Cattail, Slender Tufted-sedge, Greater Pond-sedge, Marsh Cinquefoil,

Gypsywort ''Lycopus europaeus'', common names gypsywort, gipsywort, bugleweed, European bugleweed and water horehound, is a perennial plant in the genus '' Lycopus'', native to Europe and Asia, and naturalized elsewhere. Another species, ''Lycopus america ...

Yellow loosestrife Yellow loosestrife is a common name for several plants in the genus '' Lysimachia'' and may refer to: * ''Lysimachia'' × ''commixta'', native to eastern North America *''Lysimachia punctata ''Lysimachia punctata'', the dotted loosestrife, larg ...

Purple Loosestrife ''Lythrum salicaria'' or purple loosestrifeFlora of NW Europe''Lythrum salicaria'' is a flowering plant belonging to the family Lythraceae. It should not be confused with other plants sharing the name loosestrife that are members of the family Pr ...

, and Corn Mint. An isolated biotope of Greater Spearwort is found on the southern end of the lake. Among surrounding trees and bushes can be found Black Alder,

Buckthorn ''Rhamnus'' is a genus of about 110 accepted species of shrubs or small trees, commonly known as buckthorns, in the family Rhamnaceae. Its species range from tall (rarely to ) and are native mainly in east Asia and North America, but found t ...

Grey Willow Grey willow or gray willow may refer to: *''Salix atrocinerea'', a species of willow native to Europe commonly called grey willow *''Salix cinerea ''Salix cinerea'' (common sallow, grey sallow, grey willow, grey-leaved sallow, large grey willo ...

, and Bay Willow.

Fauna

The fauna is dominated by Gastropods,

Caddisflies The caddisflies, or order Trichoptera, are a group of insects with aquatic larvae and terrestrial adults. There are approximately 14,500 described species, most of which can be divided into the suborders Integripalpia and Annulipalpia on the ...

and

dragonflies A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threaten ...

. Fishes present in the lake include

Perch Perch is a common name for fish of the genus ''Perca'', freshwater gamefish belonging to the family Percidae. The perch, of which three species occur in different geographical areas, lend their name to a large order of vertebrates: the Per ...

, Roach, and

Crucian carp The crucian carp (''Carassius carassius'') is a medium-sized member of the common carp family Cyprinidae. It occurs widely in northern European regions. Its name derives from the Low German ''karusse'' or ''karutze'', possibly from Medieval Lati ...

Mirror Carp Mirror carp, regionally known as Israeli carp, are a type of domesticated fish commonly found in Europe but widely introduced or cultivated elsewhere. They are a variety of the common carp (''Cyprinus carpio'') developed through selective breedin ...

and

Signal crayfish The signal crayfish (''Pacifastacus leniusculus'') is a North American species of crayfish. It was introduced to Europe in the 1960s to supplement the North European '' Astacus astacus'' fisheries, which were being damaged by crayfish plague, b ...

have been introduced in the lake, the crayfish forming a population allowing fishing. A population of

Great Crested Newt The northern crested newt, great crested newt or warty newt (''Triturus cristatus'') is a newt species native to Great Britain, northern and central continental Europe and parts of Western Siberia. It is a large newt, with females growing up t ...

has now vanished, but the City of Stockholm is planning to reintroduce them by constructing dams and ponds to recreate their natural habitat.

Visiting

Walks around the lake are organized regularly by

Bromma borough Bromma () is a borough (''stadsdelsområde'') in the western part of Stockholm, Sweden, forming part of the Stockholm Municipality. Bromma is primarily made up of Bromma Parish and Västerled Parish. The fourth largest airport in Sweden and the ...

and the Society for Nature Conservation (''Svenska Naturskyddsföreningen''). Nearest metro station is Åkeshov.

References

{{reflist

External links

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Geography of Stockholm Norrström basin Lakes of Stockholm County