(section names : Ledder Mühlenbach - Ibbenbürener Aa - Hörsteler Aa )
Hörsteler Aa near Gravenhorst
|Water code||EN : 3448|
|location||North Rhine-Westphalia , Lower Saxony ; Germany|
|Drain over||Speller Aa → Große Aa → Ems → North Sea|
|source||Northwest of Leeden
|muzzle||Southeast of Spelle in the Speller Aa
|Height difference||82 m|
|Bottom slope||2.3 ‰|
|Catchment area||138.946 km²|
| Discharge at the Hoerstel
A Eo gauge: 88.66 km²
Location: 10.54 km above the mouth
|550 l / s
738 l / s
1.57 m³ / s
17.7 l / (s km²)
10.2 m³ / s
27.2 m³ / s
|Small towns||Tecklenburg, Hörstel|
The Dreierwalder Aa (section names : Ledder Mühlenbach - Ibbenbürener Aa - Hörsteler Aa ) is a 36.1 km long orographic left tributary of the Speller Aa in the Westphalian region of Tecklenburger Land , Germany .
The Dreierwalder Aa rises as Ledder Mühlenbach in the northwestern end of the Teutoburg Forest about 3 km northeast of Tecklenburg and about 2.3 km northwest of Leeden at an altitude of . After passing Wöstemeier on the northeastern edge of the village, the Ledder Mühlenbach reaches Ledde . The river passes the village on the northern outskirts. The Ledder Mühlenteich is surrounded by the Mühlenbach. From Ledde the river flows a short distance to the west. It changes its name and is now called Ibbenbürener Aa (from stationing kilometer 29.7).
As Ibbenbürener Aa, the river continues to flow in a north-westerly direction. Before the river reaches Ibbenbüren , it passes under the federal motorway 30 . About one kilometer further downstream, on the southern outskirts of Ibbenbüren, the river flows through the Aasee after about 10 km . This was created as rain retention water when the motorway was built and is now used as a local recreation area. While Ibbenbüren flows around on the southern edge of the village, the river passes the village of Schierloh on the northern edge of the village. Further on, flowing in a north-westerly direction, the river changes its name again at Püsselbüren and is called Hörsteler Aa (from stationing kilometer 16.6).
The Jordanbach coming from the Dickenberg and the Stollenbach of the former Westfeld join behind Püsselbüren . The river crosses under the Mittelland Canal with a culvert . The culvert of the old voyage was bombed repeatedly during World War II in order to cause the canal to run out, which was also successful. Around 1990 the Mittelland Canal was relocated a little to defuse the numerous duds .
About one kilometer after crossing under the Mittelland Canal, the river reaches Hörstel . Here the course of the river turns in a northerly direction. At Ostenwalde the Bärenortsgraben and the Bodelschwingh tunnel flow into the Aa. Here the river turns west again. At around the mouth of the Poggenortgraben , the river changes its name again and is now called Dreierwalder Aa (from station km 7.5).
On its 36.1 km long path, the Dreierwalder Aa overcomes a height difference of 82 m, which corresponds to a mean bed gradient of 2.3 ‰. It drains a 138.946 km² catchment area via Speller Aa and Ems to the North Sea .
Heavily salty pit water is discharged from the eastern field of the Ibbenbüren mine between Ibbenbüren and Püsselbüren . The water flow increases here by an average of 0.4 m³ / s to 1.78 m³ / s. The chloride load is around 600 tons per day. With a water quality class of III-IV, the Aa is considered "very heavily polluted". The salinity corresponds to that of the central Baltic Sea . Only a few specialized plant and animal species can survive in this environment.
- German basic map 1: 5000
- Topographical Information Management, Cologne District Government, Department GEObasis NRW ( Notes )
- Deutsches Gewässerkundliches Jahrbuch Weser-Ems 2008 Lower Saxony State Agency for Water Management, Coastal Protection and Nature Conservation, accessed on January 22, 2016 (PDF, German, 6184 kB).
- Water directory of the State Office for Nature, Environment and Consumer Protection NRW 2006 ( Memento from February 15, 2010 in the Internet Archive ) (PDF; 1.03 MB)
- Ibbenbürener Aa. (pdf; 94 kB) (No longer available online.) State Office for Nature, Environment and Consumer Protection North Rhine-Westphalia , archived from the original on June 26, 2013 ; Retrieved April 18, 2013 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.