River Ribe Å has a catchment area of 975 km² - the sixth largest Danish river. The main watercourses River Gelså (43 km) and River Fladså (46 km) runs westward, and the confluence of these two rivers begins the River Ribe proper 17 km before the outfall in the Wadden Sea.
The mean water discharge of River Ribe Å at the outfall is 14,000 l/s (min. 5,500 l/s; max. 60,000 l/s).The mean water discharges in the main tributaries are: Gelså 5,000 l/s, Fladså 5,000 l/s, Hjortvad Å 2,250 l/s. The River Ribe Å are controlled by a sluice at the outfall to the Wadden Sea .
The main parts of the watercourses in the Ribe Å system are regulated - although significant parts of the main stretches are unregulated, especially in Fladså and the lower parts of Gelså and some shorter stretches of River Ribe Å east and west of Ribe town.
85 % of the catchment area is utilised for arable agriculture. However, land use in the catchment is very varied, comprising intensive arable agriculture and forestry/plantation on the moraine islands and moorland plains, while the lower laying parts typically is used for extensive pastoral agriculture and haymaking.
Blocked in Ribe town
River Ribe Å passes through the city of Ribe by four runs. Three of them are blocked by milldams and one by a weir built for hydroelectricity production purposes.
The dams and weir in Ribe town cannot under any circumstance be negotiated by houting. The houting are thus prevented from getting access to potentially good spawning areas upstream Ribetown.
The hydroelectric turbine, the Stamp Mill, is still in function and supplies seven households with electricity. None of the three milldams can be removed, as groundwater levels below the city has to be maintained to prevent deterioration of the city’s foundation.
Upstream meadows
The dams and weir in Ribe town constitutes the basis for approx. 300 ha temporarily flooded meadows in the landscape east of Ribe.
The water levels on the meadows has always been regulated through management of the dams and weir in Ribe.
Levels are high during winter and considerably lower from April to October whereby significant areas of shallow water are dried out during spring.
Habitat area
The River Ribe Å is included in the 134.730 ha habitat area no. 78 ‘River Ribe Å, River Tved Å and River Varde Å west of Varde’.The major parts of the habitat area are within the Wadden Sea (see map).
International importance
The major watercourses in the River Ribe Å system are of international importance for their populations of houting, salmon, sea-, river- and brook lampreys, twaite shad and otter - all listed under Annex II of Habitats Directive.
The Houting-project will:
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(1) The Stamp Mill will be dismantled and most of the river discharge led through the new course. By historic reasons a certain discharge will be maintained at the other mill dams in Ribe.
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(2) The period where the meadows east of Ribe City are flooded will be prolonged, thereby creating a nursery area for houting fry.
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(3) In River Gelså the water intake at Gelsbro Fish Farm will be altered creating free passage for houting and other fish.
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(4) In River Fladså the weir at Fole Fish Farm will be removed.
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(5) In the Hjortvad Stream, a tributary running to River Ribe downstream Ribe town, two spawning grounds will be laid out.
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(6) A still existing royal privilege of netting off the entire River Ribe Å will be purchase purchased.
River Ribe Å with tributaries.
p : River stretch open to
houting from project
start
p : River stretch open to
houting after Houting-
project
p : River stretch closed but
suited for houting – the
stretch are not included
in the Houting-project
p : River stretch of no
interest to houting