The 1,330 km² Vidå-catchment runs across the entire southern Jutland and originates as far east as less than 5 km from the eastern coast. The catchment is the fifth-largest in Denmark .
The mean water flow at the outflow into the Wadden Sea is approx. 15,000 l/sec. (min. 4,000 l/sec., max. 95,000 l/sec.). Water exchange with the Wadden Sea is regulated by the sluice at Højer town.
A modified river
90% of the catchment area is arable agriculture – the main parts of the watercourses in the system are heavily modified through drainage, dredging and physical alterations.
However, during the last decade the County of Southern has completed a number of nature restoration projects in the Vidå system including reconstructing of 27 smaller weirs making them passable for migrating fish and 12 projects bringing 37 km of straightened, modified water stretches back to original meandering
The houting in River Vidå
In spite of the heavily influence by man, the River Vidå has the largest natural population of houting in the entire Wadden Sea area - and thereby in the world! It is therefore of especial importance to preserve and help this population.
However, the population is vulnerable, as by far the majority of the spawning grounds are in a single branch of the Vidå system. Creating access for the houting to the entire water system will give a greater security that population will survive and increase.
Today, the houting and many other species are effectively kept from migrating further up into the River Vidå proper and its two tributaries Arnå and Hvirlå at the Bachmann’s Water Mill in Tønder town.
Important shallow-watered lakes
The River Vidå differs from other Danish watercourses running to the Wadden Sea , because of the occurrence of larger areas of open, shallow and stagnant waters. The open water surfaces of Lake Rudbøl and Magisterkog totals an area of approx. 87 ha with a mean water depth of 0.8 m .
Research on the biology of houting fry in the Vidå-system shows, that the Magisterkog and Lake Rudbøl are very important nursery areas for the houting fry – and may in fact be one of the key reasons that a population of houting has survived at all.
A river rich in species
The River Vidå system is inhabited by 24 different fish species - that is considered high in Danish terms. However, the sizes of a number of the populations are quite small and they only occur in limited parts of the river system.
The River Vidå is the single only water system in Denmark with the occurrence of the loach (Misgurnus fossilis ). Brook and River lampreys are also found the river system.
Habitat area
The River Vidå is included in the 494 ha habitat area no. 90 ‘Vidå with tributaries, Lake Rudbøl and the Magisterkog’ (see map ).
The Houting-project
In the Vidå system there are presently three major obstacles for the houting - the weir at Bachmann’s Water Mill in downtown Tønder City (1) , the weir in Sønderå at the Rens Fish farm (3) and the mill weir in Sønderå at St. Jyndevad (4). Fish ladders are present at the weirs and may be used by e.g. salmon and trout, but they are, however, not passable for houting.
With the Houting-project the obstacles in Tønder City (1) and at Rens Fish Farm (3) will be dismantled thereby enabeling free migration for the houting – and also for all other fish and invertebrates.
Furthermore, the Houting-project will restore approx. 80 ha of shallow-watered lakes (2) thereby creating new nursing areas for the houting fry.
The Houting-projects in the River Vidå - Bachmanns Mill (1); Lake Nørre Sø (2) and Rens Fish Farm (3).
p : River stretch open
to houting from
project start
p : River stretch open
to houting after
Houting-project
p : River stretch of
no interest to
houting