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Rogsån below the rapids section, Falu municipality, Sweden

Sponsored by

Sweden, Uvnäs, Falun

Rogsån is a small creek in central Sweden, that despite a long history of logging, mining, and being cut-off at both ends by dammed lakes, host a relatively rich ecosystem. The water runs from the clear and oligotrophic lake Rog in the north, down past several dams of varying sizes, into lake Varpan about 8km to the South. The stream changes character from a strong flow and a pool-and-riffles section below the outlet of lake Rog, to more of a lowland type with slower water and plenty of waterlilies in the lower sections.

Fish diversity is quite low; with perch (Perca fluviatilis), pike (Esox lucius), and roach (Rutilus rutilus) being the most common species, but with trout (Salmo trutta) and miller’s thumb (Cottus gobio) found occasionally. Plant diversity is a bit more impressive with Juncus bulbosus meadows, “forests” of waterlilies, and patches of Chara sp., Utricularia intermedia, Myriophyllum alterniflorum, Lobelia dortmanna, and more.

Submitted by
Emil Nordström
GPS
60.7102814, 15.6052961
Geographical region
Northern Europe
Drainage Basin
Mälaren Lake
River catchment
Dalälven River
Water body type
Creek
Water body name
Rogsån
Water body part
Outflow
Water body course
Upper course
Water body: tributary of
Tributary name

Videos above and below water

Water Chemistry

Water information

Water type
Fresh water
Water color
Clear water
Water transparency
High
Concentration of sediments
Low
Water temperature
4-22 °C
Water flow/curent
Slow

Chemical parameters

pH
6.9
Conductivity
56
GH
KH
Dissolved Oxygen

Substrate in nature

Sand
Grey
Pebble/Gravel
Mixed
Stone
Mixed
Stone form
Irregular
Silt/Mud
Brown
Leaves
Few
Driftwood
Many
Submerged terrestrial vegetation
no

Aquatic Biotope

Date of collecting
14 August, 2022
Collecting area
Open water
Water depth
2,0m
Air temperature
Sunlight
Full sun

Environment

Environment
Affected by human activity
Affected by human activity
Agriculture
Agriculture
Little
Surrounding area

The surrounding area is mainly pine plantations, with occasional spruce and deciduous trees. Large sections of the river banks consists of rubble brought over the centuries from a local mine, while more natural sections has a shoreline of either granite rocks of various sizes or thickets of reeds and sedges.

Underwater landscape

This part of the watercourse has a relatively rich plant community, with a mosaic of species depending on waterflow, light exposure, substrate and depth. The center is mainly Juncus bulbosus meadows, with Isoetes mixed in at the deeper sections and water lilies in calmer areas. Where the substrate is coarser and flow higher multiple plant species like Lobelia dortmanna, Myriophyllum, and Utricularia grow together, while in the strongest flow vegetation is sparser; with mainly patches of Juncus, Utricularia, or Chara.

Fish:

  • Lymnaea stagnalis (Lymnaeidae)
  • Perca fluviatilis (Percidae)
  • Rutilus rutilus (Cyprinidae)
  • Esox lucius (Esocidae)

Crustaceans:

  • Pacifastacus leniusculus (Astacidae)

Aquatic plants:

  • Lobelia dortmanna (Campanulaceae)
  • Utricularia intermedia (Lentibulariaceae)
  • Myriophyllum alterniflorum (Haloragaceae)
  • Isoëtes sp. (Isoëtaceae)
  • Potamogeton sp. (Potamogetonaceae)
  • Nuphar lutea (Nymphaeaceae)
  • Nymphaea alba (Nymphaeaceae)

Wetland plants:

  • Juncus bulbosus (Juncaceae)
  • Carex sp. (Cyperaceae)
  • Phragmites australis (Poaceae)
  • Menyanthes trifoliata (Menyanthaceae)
Threats to ecology

Currently the main threats are clear-cutting of the surrounding forest, leading to increased nutrient and light levels, and water regulation for hydropower, causing low or unnatural flows.

Historically the stream has suffered from clear-cuts, straightening and other hydro-morhpological changes, mining run-off, and more hydropower, but at the moment it’s slowly recovering from these.

Riparian zone

Trees near the aquatic habitat
Many - Pinus sylvestris (Pinaceae)
Trees near the aquatic habitat
Many - Picea abies (Pinaceae)
Trees near the aquatic habitat
Many - Alnus sp. (Betulaceae)