Aa (Nethe)

The Aa at Herste

In a dry summer, the weak current below Reelsen dried up in the gravel of the stream bed. Looking upstream. (August 5, 2011)

The Aa is a 20.6 km long, orographic left tributary of the Nethe in North Rhine -Westphalia, Germany. As a tributary of the Nethe Aa part of the river system in the Weser.


The Aa rises on the eastern slope of belonging to Eggegebirge Rehberges ( 427.4 m) at an altitude of 350 m above sea level. NN, about 2 kilometers east of Altenbeken and above the east portal of the tunnel Rehberg in Bad Driburg - Langeland. First identified in the German base map as Big Water (this name is taken there for a parcel above Herstes as Large water again), first flows of the creek to the east and passes under approximately 2 km stretch of river, the railway Herford Altenbeken. From here it is also referred to in the DGK as Aa. A little later, the Aa used in a predominantly south-easterly direction and passes through the village on its eastern outskirts Reelsen. In Alhausen left side opens the current flowing through the town Rautenbach, the Aa few hundred meters to the southwest at the site flows past.

To the east of Bad Driburg opens on the right side of coming from there Schwallenbach in the Aa. After passing under the railway line Altenbeken - Kreiensen also opens the right hand side of Hilgen Bach. In Herste opens again on the right side of the Katzbach in the now again flowing in an easterly direction Aa. The Katzbach is 8.2 km in length, the longest tributary of the River Aa. West of Istrup then abuts the left side add the Escher Bach to Aa. After the river has flowed through the town of Riesel, it flows south-west of Brakel as a left tributary to 133 m above sea level. NN in the Nethe.

On its 20.6 km long road Aa overcomes a difference in altitude of 217 m, corresponding to an average bed slope of 10.5 ‰. The Aa drains a catchment area of 80.153 km ². The Aa results in heavy rainfall in Eggegebirge quickly in major water masses through the Aa Valley.


  • Rautenbach - 2.6 km long left tributary to 193 m above sea level. NN
  • Schwallenbach - 5,0 km long right tributary 181 m above sea level. NN
  • Hilgen Bach - a 5.5 km long right tributary 172 m above sea level. NN
  • Katzbach - 8.2 km long right tributary 155 m above sea level. NN
  • Escher Bach - 4.9 km long left tributary 149 m above sea level. NN

A specialty of a few hundred meters long, unnamed, right side stream at the southernmost point of St. John's Gelhaus pathway in Reelsen, where you can see it well. As Kalktuffquelle it forms with the participation of mosses small sinter terraces. In the summer he falls completely dry.

Mill trenches

Reelsen, Alhausen, Istrup Riesel and still own an old mill stream.

Plant stone bridges

At the Aa there are still some bridges obtained from cut stones:

  • At the Josef mill. Round Bridge with a bow ( by a simple concrete bridge replaced)
  • Herste. Arch bridge over the Katzbach with a bow at the Heristiestraße, access
  • Istrup. Arch bridge with four arches on the road Istruper


Fallen dry sinter terraces

South of Reelsen performs a wooden bridge over the St. John Gelhaus - way over the Aa. Looking upstream. (August 5, 2011)

Bridge the road in the stairs of Alhausen to Bad Driburg. Although the Aa had dried up at this time below Reelsens superficial and was also Rautenbach dry, flowing water again. Look downstream. (August 5, 2011)


See also: List of waters with Aa