Sätraån
Encyclopedia
Sätraån is a stream
in southern Stockholm
, Sweden
.
Previously stretching 6 km from Västertorp
and Segeltorp, Sätraån is today confined to the Sätra Open-air Area and approximately a kilometre long. The limited current discharge causes the stream to be reduced to minor temporary pools of water except during spring. Nevertheless, the stream is considered a valuable natural environment because of the ravine it has cut though the landscape and because of its location in a forest of recreational importance to the suburb Sätra
.
, nitrogen
, and metals; a situation explained by the inflow of groundwater
from an area larger than suggested by the extent of the watershed. Samples taken in 2000 showed levels of lead
, zinc
, and copper
were exceptional in the upper course.
and Pisidium
. An inventory in late 1999 / early 2000 also documented larvae of Chironomidae
flies and Asellus aquaticus crustacean
s; A few species of beetle
s and caddisflies
, including species more typical for moist environments such as wetlands and marshes. Also species sensitive to acidification, such as Gammarus pulex
and Baera pullata, were recorded. Near the mouth of the stream various species of mayflies
common to exposed lake shores and running waters were documented.
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
in southern Stockholm
Stockholm
Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...
, Sweden
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
.
Previously stretching 6 km from Västertorp
Västertorp
Västertorp is a suburb southwest of Stockholm.The suburb was constructed in the late 1940s. The Västertorp outdoor metro station was opened in 1964. Västertorp is recognized for the many sculptures decorating the area. The sculptures were placed on the initiative of Fritz H. Eriksson....
and Segeltorp, Sätraån is today confined to the Sätra Open-air Area and approximately a kilometre long. The limited current discharge causes the stream to be reduced to minor temporary pools of water except during spring. Nevertheless, the stream is considered a valuable natural environment because of the ravine it has cut though the landscape and because of its location in a forest of recreational importance to the suburb Sätra
Sätra
Sätra is a suburb of Stockholm, Sweden. It has its own Metro station.-See also:*Sätra metro station...
.
Catchment area
The catchment area, once encompassing a major portion of south-west Stockholm (roughly 11–12 km²), is today insignificant and the stream is drained during most of the year. The inflow was slightly increased in 2002 when a stormwater pipe was modified and a damm was built to treat the water. The mouth of the stream is located near a public bathe. Most of the surrounding area is covered by grass and forests with no settlements within the current catchment area.Environmental influence
Notwithstanding the limited extent of the catchment area, the few samples taken in the area showed significant levels of phosphorusPhosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
, nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
, and metals; a situation explained by the inflow of groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
from an area larger than suggested by the extent of the watershed. Samples taken in 2000 showed levels of lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
, zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
, and copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
were exceptional in the upper course.
Flora and fauna
Bottom fauna includes some 53 species, typically endurable to nutrient-rich aquatic environments offering stagnant waters and low levels of oxygen - most commonly various species of OligochaetaOligochaeta
Oligochaeta is a subclass of animals in the biological phylum Annelida, which is made up of many types of aquatic and terrestrial worms, and this includes all of the various earthworms...
and Pisidium
Pisidium
Pisidium is a genus of very small or minute freshwater clams known as pill clams or pea clams, aquatic bivalve molluscs in the family Sphaeriidae.-Subgenera and species:Subgenera and species within the genus Pisidium include:...
. An inventory in late 1999 / early 2000 also documented larvae of Chironomidae
Chironomidae
Chironomidae are a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae...
flies and Asellus aquaticus crustacean
Crustacean
Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at , to the Japanese spider crab with a leg span...
s; A few species of beetle
Beetle
Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...
s and caddisflies
Trichoptera
The caddisflies are an order, Trichoptera, of insects with approximately 12,000 described species. Also called sedge-flies or rail-flies, they are small moth-like insects having two pairs of hairy membranous wings...
, including species more typical for moist environments such as wetlands and marshes. Also species sensitive to acidification, such as Gammarus pulex
Gammarus pulex
Gammarus pulex is a species of amphipod crustacean found in fresh water across Eurasia. It is a greyish animal, growing to long.-Description:...
and Baera pullata, were recorded. Near the mouth of the stream various species of mayflies
Mayfly
Mayflies are insects which belong to the Order Ephemeroptera . They have been placed into an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies...
common to exposed lake shores and running waters were documented.