Hörsteler Aa

de.wikipedia.org/wiki/Dreierwalder_Aa
"... The Dreierwalder Aa (section names: Ledder Mühlenbach - Ibbenbürener Aa - Hörsteler Aa) is a 36.1 km long, orographically left tributary of the Speller Aa in the Westphalian region of Tecklenburger Land.
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 114 m above sea level. NN. After passing Wöstemeier on the north-eastern outskirts, the Ledder Mühlenbach reaches Ledde. The river passes the village on the northern outskirts. However, the Mühlenbach flows around the Ledder Mühlenteich. From Ledde the river flows west for a short distance. It changes its name and is now called Ibbenbürener Aa (from stationing kilometer 29.7).As the Ibbenbürener Aa, the river continues to flow in north-westerly directions. Before the river reaches Ibbenbüren, it passes under the federal autobahn 30. About a kilometer further downstream, on the southern outskirts of Ibbenbüren, the river flows through Lake Aasee after about 10 km. This was created as a rainwater retention pond during the construction of the autobahn and is now used as a local recreation area. While the river flows around Ibbenbüren on the southern outskirts, the river passes the village of Schierloh on the northern outskirts. Further, flowing in north-westerly directions, the river changes 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 flow into the river behind Püsselbüren. The river crosses under the Mittelland Canal with a culvert. The culvert of the old journey was repeatedly bombed during the Second World War in order to bring the canal to drain, which was successful. Around 1990, the Mittelland Canal was relocated to defuse the numerous duds.About a kilometer after crossing the Mittelland Canal, the river reaches Hörstel. Here the course of the river turns to the north. The Bärenortsgraben and the Bodelschwingh tunnels flow into the Aa near Ostenwalde. Here the river turns west again. Around the mouth of the Poggenortgraben, the river changes its name again and is now called the Dreierwalder Aa (from stationing kilometer 7.5).
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Flowing again in a northwesterly direction, the Aa flows through Dreierwalde. A little later it passes the border with Lower Saxony and flows out at 32 m above sea level. NN on the left into the Speller Aa.On its 36.1 km long path, the Dreierwalder Aa overcomes a height difference of 82 m, which corresponds to an average bottom gradient of 2.3 ‰. It drains a 138.946 km² catchment area via Speller Aa and Ems to the North Sea. ..."
de.wikipedia.org/wiki/Dreierwalder_Aa