'Råcksta Träsk' (
Swedish: "
Råcksta Swamp") is a small
lake in the western suburbs of
Stockholm,
Sweden. Notwithstanding its location in the vicinity of the Swedish capital and high levels of
lead and
copper, the lake is considered as an important breeding ground for
frogs, of moderate interest to pleasure fishing, and of minor interest for birds.
[2] There are three other small lakes located nearby:
Judarn,
Kyrksjön, and
Lillsjön.
Catchment area
The catchment area is mostly composed of forest and open terrain part of the
Grimsta nature reserve, with several minor wetlands. 20 percent of the catchment area is composed of residential buildings and 10 per cent of roads. 300 metres downstream is a historical mill administrated by a society devoted to local culture and history (''Vällingby hembygdsförening'') with limited means to regulate the water level. West of the lake is a grass-grown peak composed of excavated material from the construction of the suburbs
Vällingby and
Hässelby. Several heavily trafficked roads and a metro track passes above ground through the catchment area. 7 hectares of the area is occupied by the
Råcksta Crematorium and its cemetery.
[3]
The lake and the surrounding area is regarded as of great recreational value. Pathways were arranged around the lake in the 1970s, angling is popular, and, occasionally, a skating-rink is ploughed on the lake during winters.
[4]
Environmental influence
Local
storm water pipes, occasionally fouled with
oil of unknown origin, produces most of the affluent, with remaining contributions coming from local roads and run-off from residential areas, the latter bringing mostly
nutrients to the lake with minor contributions of
zinc and
copper (from roofs). High levels of
phosphorus have been recorded during late winters and summer. Reports in 1991-1997 of metal content in lake sediments noted moderate levels of
copper, the highest levels of
lead in any lake in Stockholm, and raised levels of
organic compounds such as
PAHs and
PCB in lower sediments. Levels of copper in the
water table were reported as 50 times national median value.
3
Flora and fauna
Phytoplankton content in August is mostly composed of
green algae, with minor populations of
diatom and
golden algae, and no presence of
cyanobacteria. Among
Zooplankton the most common is various species of
rotifers, with occurrence of
copepods,
bosminidae, and
ciliates.
4
The number of
aquatic plants is relatively small, with the lake floor dominated by
Rigid Hornwort, and free-floating plants including
Lemna Minor,
Yellow Water-lily,
White Waterlily,
Broad-leaved Pondweed, and
Amphibious Bistort. Along the shores are
Alisma,
Slender Tufted-sedge,
Cyperus Sedge,
Reed Sweet-grass,
Yellow Iris,
Purple Loosestrife,
Phragmites,
Rorippa amphibia, and many others. Commons trees found around the lake include
Black Alder and
Grey Sallow.
4
An examination in 1996 showed the
fish stock is dominated by
Crucian Carp accompanied by populations of
Perch,
Roach,
Tench, and
Common Carp. Introduction of
Trout and
Rainbow Trout was made in 1992.
Signal Crayfish is known to exist in the lake.
4
Bird life at the lake was abundant before the lake was dredged in 1973. Since it has been reduced the a population common to reed-rich lakes with a stable population of
Mute Swan,
Mallard,
Reed Bunting, and
common Moorhen.
4
The area is an important breeding locale for
Common Frog and
Common Toad, both species being protected and classified as of local and regional interest.
4
Visiting
Guided tours in the area by foot or bike are frequently arranged by the city and the
Society for Nature Conservation.
[5][6] Nearest metro station is
Råcksta.
See also
★
Geography of Stockholm
★
List of lakes in Sweden
Notes
1. Vattenprogram, p 5,1
2. Råcksta träsk
3. Vattenprogram, p 5.3-5.5
4. Vattenprogram, p 5.5-5.7
5. Västerortturen
6. SNF
References
★
Råcksta träsk
★
Vattenprogram för Stockholm 2000 - Råcksta träsk
★
B139 Råcksta träsk-reningsanläggning för dagvatten
★
Västerortsturen
★
SNF - Program 3 mars-2 maj 2007
External links
★
Aerial photo and map of the area
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