Ilm (Saale)

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Catchment and river basin map Ilm (Saale) .png
Water code EN : 5638
location Thuringia , Germany
River system Elbe
Drain over Saale  → Elbe  → North Sea
origin Confluence of Lengwitz and Freibach
50 ° 38 ′ 40 ″  N , 10 ° 51 ′ 16 ″  E
Source height 600  m above sea level NN (950 m (Freibach); 750 m (Lengwitz)) 
muzzle in the Saale near Großheringen Coordinates: 51 ° 6 ′ 17 "  N , 11 ° 40 ′ 7"  E 51 ° 6 ′ 17 "  N , 11 ° 40 ′ 7"  E
Mouth height 120  m above sea level NN
Height difference 480 m
Bottom slope 3.6 ‰
length 134.2 km
Catchment area 1,042.7 km²
Discharge at the gauge Gräfinau-Angstedt
A Eo : 154.8 km²
Location: 108 km above the mouth
NNQ (08/14/2003)
MNQ 1923–2014
MQ 1923–2014
Mq 1923–2014
MHQ 1923–2014
HHQ (08/10/1981)
129 l / s
380 l / s
2.46 m³ / s
15.9 l / (s km²)
22.7 m³ / s
79.6 m³ / s
Discharge at the Mellingen
A Eo gauge : 627 km².
Location: 53.9 km above the mouth
NNQ (09/10/1929)
MNQ 1923–2014
MQ 1923–2014
Mq 1923–2014
MHQ 1923–2014
HHQ (06/01/2013)
150 l / s
760 l / s
4.26 m³ / s
6.8 l / (s km²)
36.8 m³ / s
98.4 m³ / s
Discharge at the Niedertrebra
A Eo gauge: 894.3 km².
Location: 10 km above the mouth
NNQ (15.09.1929)
MNQ 1923–2014
MQ 1923–2014
Mq 1923–2014
MHQ 1923–2014
HHQ (01.06.2013)
570 l / s
1.61 m³ / s
5.91 m³ / s
6.6 l / (s km²)
41.8 m³ / s
112 m³ / s
Left tributaries Krummbach , Tonndorfbach , Hengstbach , Pfiffelbach , Emsenbach ; s. u.
Right tributaries Schorte , Wohlrose , Deube , Schwarza , Magdel , Lehnstedter Bach , Heressener Bach , Utenbach ; s. u.
Medium-sized cities Ilmenau , Weimar , Apolda
Small towns Stadtilm , Kranichfeld , Bad Berka , Bad Sulza
Residents in the catchment area approx. 185,000
Sternbrücke in Weimar

Sternbrücke in Weimar

The Ilm is a left tributary of the Saale in Thuringia . It is 134.2 km long over the Lengwitz source stream, nominally according to the TLUG , and 134.9 km over the Freibach , and drains a catchment area of 1043 km² in central Thuringia, with minimal shares in southern Saxony-Anhalt.

The Ilm rises in the Thuringian Forest southwest of Ilmenau , then flows through a strong karst region, seep into the parts of their water and Jump other tributaries of the Saale accrue over Weimar and Apolda to the border of Saxony-Anhalt, where it opens into the Saale . After the Saale, Werra and Unstrut, the Ilm is the fourth longest river in Thuringia and also the fourth longest tributary of the Saale.

There are no larger dams in the entire catchment area of ​​the Ilm ; the largest reservoir is the Hohenfelden reservoir, which is just 42 hectares in size, in the Tannrodaer Waldland north-west of Kranichfeld . In the lower reaches of Bad Sulza , Saale-Unstrut wines are grown on the slopes of the Ilm Valley . In terms of cultural history, the Ilm is significant as a river through Weimar, it inspired artists there such as Johann Wolfgang von Goethe and found its way into their work.


The Ilm has significantly shaped the landscape and runs along its entire length in a valley that is clearly carved into the relief. The river flows through the Ilm district and the Weimarer Land district as well as the independent city of Weimar . At Großheringen north of Bad Sulza it flows into the Saale . In its course, the Ilm crosses the most varied of landscapes from the Thuringian Forest to the Saale-Unstrut region . It cuts the Ilm-Saale-Platte in its middle course between Stadtilm and Weimar over a length of over 50 km .

Spring streams

The nominal Ilm begins its course on the northern slope of the Thuringian Forest north of Stützerbach in the Ilm district , to which it gave its name, at 575 m above sea level. Here is the confluence of the three rivers Lengwitz, Freibach and Taubach , commonly referred to as the source streams of the Ilm , which arise south of Stützerbach on the crest of the mountains not far from the Rennsteig . The longest source stream is the Freibach (6.5 km), which rises at the Schmücke , while the 5.8 km long Lengwitz with source at Allzunah shares the direction of flow with the Ilm and the 3.8 km long Taubach im Ilmbrunnen (also called Ilmquelle called) rises below the Great Finsterberg .

Upper course

In the Ilm floodplain forest near Langewiesen

The Ilm initially flows north through the Meyersgrund to Manebach , where it turns to the east and runs through the Manebacher Grund to Ilmenau . This first part of the river course is relatively unregulated, to the right and left of the Ilm there are areas that are flooded during floods. In Ilmenau, the Ilm forms a wider valley basin in which the city extends at the transition from the Thuringian Forest to its (Paulinzellaer) foreland . Here the Ilm has been straightened and laid in a deeply excavated bed. On Grenzhammer east of the city which opens Schorte a first major tributary. There the Ilm breaks through the basement of the Thuringian Forest for the last time between the Ehrenberg in the north and the Tragberg in the south and emerges through the Ilm-Auwald from the Ilmenau valley basin towards the southeast to Langewiesen . Shortly after Langewiesen, the wide valley is spanned by the 1681 meter long Ilm valley bridge on the high-speed line from Nuremberg to Erfurt . It is the longest bridge in Thuringia.

After a change of direction to the northeast, the Wohlrose increases from the right to 415.6  m above sea level with the confluence of the Wohlrose . NHN after 23.7 kilometers of flow (inc. Lengwitz) the catchment area of ​​the Ilm from 96.7 km² by a good 60% to 157.2 km². The uptake of water from the Thuringian Forest has been completed and the runoff will now rise significantly more slowly.

Upper middle course

In the now northeast-oriented course through the red sandstone of the Paulinzella foreland, the Ilm flows through Gräfinau-Angstedt with Gräfinau on the left and Angstedt on the right side of the river. Cottendorf follows on the left and Dörnfeld on the right of the Ilm and the Singer Berg (548 m) on the right side of the Ilm. The river enters the karstified and dry shell limestone formation of the Ilm-Saale-Platte , which is dominated by its Zeugenberg Singer Berg, but also in its southern core area to the right of the Ilm reaches heights of up to 548 m ( Großer Kalmberg ) and thus the Rivers overlooked by about 220 m.

Behind Griesheim , the confluence of the Deube from the right in the Oberilm district leads to Stadtilm , the fifth largest city in the Ilm Valley, with a large railway viaduct on the Arnstadt – Saalfeld line . In this area up to Kleinhettstedt , Großhettstedt and Dienstedt , open and wooded landscapes alternate. The river loses a lot of water to the karst subsoil, which reappears in the Oberwillinger Spring and in the Remdaer Spring . In dry summers, the Ilm can completely seep away in this area, for example around Kranichfeld in 2003 and 2016. There is also a karst cave in Dienstedt .

Tannroda forest and breakthrough valley between Bad Berka and Mellingen

Ilm in Bad Berka
Buchfart watermill

In Kranichfeld the Ilm experiences after 54.6 km of flowing distance (inc. Lengwitz) at an altitude of almost 300  m above sea level. NHN a change of direction from north-northeast to east-northeast. Here the shell limestone of the Ilm-Saale-Platte is interrupted by the red sandstone window of the Tannroda woodland . This window stretches upstream along the Krummbach , Tonndorfbach and Steingraben brooks on the left to the west and Schwarza , Dammbach and Klingelbach on the right to the east. Between the stream valleys, the wooded red sandstone ridges reach heights of up to 429 m (Vogelheerd in the east), but are clearly dominated by the shell limestone edge heights such as the Riechheimer Berg (513 m) in the west, to which the terrain rises steeply in one layer .

After the confluence of the Krummbach below Kranichfeld, the towns of Tannroda (Schwarza), Munich (Tonndorfbach) and Bad Berka (Klingelbach and Steingraben) are located at the confluences of the side valleys . From Tannroda the Ilm runs again in a north-northeast direction, in which it leaves the Tannrodaer woodland below Bad Berka.

With the return of the shell limestone, the character of the Ilm valley changes significantly. In a canyon-like , winding valley through limestone cliffs, the river runs in an east-northeast direction over Hetschburg (confluence of the Hengstbach from the left), Buchfart and Oettern .

Magdalaer Graben to Weimar

Ilm at the Taubach watermill

At Mellingen and immediately after crossing the federal motorway 4 , the Ilm meets the intersection of two major fault zones . The Apolda fault zone , which extends the course of the Ilm to the northeast as far as Apolda , meets at an obtuse angle with the Magdala fault zone coming from Magdala in the southeast . From the latter, the Ilm flows after 78.3 km (inc. Lengwitz) to about 215  m above sea level. NHN from the right towards the Magdel , whose direction of flow to the northwest it takes over in a now clearly widened valley; from the direction of the Apolda fault zone flows into the Lehnstedter Bach , also from the right .

From Mellingen to the Weimar City Palace , the Ilm Valley is almost completely undeveloped. The park on the Ilm begins below Taubach , Ehringsdorf and Oberweimar and is part of the Unesco World Heritage Classic Weimar . Here the course of the river is designed and integrated into the English landscape garden . Weimar's old town lies on the west bank of the Ilm, from which the Asbach flows from the left and, before it was relocated in the 1920s, the Lottenbach as well .

With the inflow of the Asbach after 88.3 km of flow (inc. Lengwitz) to about 215  m above sea level. NHN the river experiences its last change of main direction of flow towards the northeast.

Lower course

Ilm weir in Weimar
The Ilm in front of Tiefurt's houses

After the change of direction in Weimar, the Ilm, which now meanders through an open, barely forested landscape to the northeast, represents a marginal river of the Thuringian Basin . Right at the beginning of this last section, it is crossed by another large railway viaduct, the Weimar – Gera railway line .

In Tiefurt behind Weimar there is another castle on the Ilm, where it is also integrated into an English landscape garden. This is followed by Kromsdorf , consisting of Großkromsdorf on the left and Kleinkromsdorf on the right of the Ilm, and then Denstedt , Ulrichshalben , Oßmannstedt and Oberroßla , where the Ilm enters the urban area of Apolda . The city itself lies behind a hill in the eastern side valley of the Herressener Bach , which flows into the Apolda fault zone at an acute angle below the city. Nevertheless, the Ilm valley is also densely populated in this area. Shortly after each other, Niederroßla , Zottelstedt , Mattstedt , Nauendorf , where the Herressener Bach flows from Apolda, are followed by Wickerstedt , Flurstedt , Obertrebra , Niedertrebra , Eberstedt and Darnstedt .

The last town in the Ilm valley is Bad Sulza , a brine bath, behind which the Ilm valley narrows and digs deep into the relief. Due to this location with its local climate, viticulture is possible on the south-east facing slopes. Immediately below the city, the tributary draining by far the largest catchment area flows into the Emsenbach from the left . The Emsenbach is also the only flowing water in the otherwise entirely inner-Thuringian river system of the Ilm, which also drains parts of Saxony-Anhalt .

Below Großheringen the Ilm empties after 134 km at an altitude of almost 120  m above sea level. NHN from the left into the Saale , which curves here and follows the direction of the Ilm valley to the northeast. Because of its landscape and mild climate, the area at the mouth of the Ilm is also known as Thuringian Tuscany . The confluence of the Ilm into the Saale lies on the state border between Thuringia and Saxony-Anhalt , the Ilm being the longest river that runs exclusively in Thuringia.


The following table lists the tributaries of the Ilm, including all with a catchment area of ​​more than 10 km². Catchment area sizes without decimal places are estimates (see footnotes); the specified lengths correspond to measurements via corresponding geopaths.

Tributary Inflow
[m above sea level NN]
Lengwitz Quellbach 5.8 10 577 Stützerbach 5638-1?
Taubach Quellbach 3.8 580 Stützerbach 5638-1?
Freibach Quellbach 6.5 10 577 Stützerbach 5638-1?
Langebach right 2.8 Manebach 5638-1?
Moosbach Left 2.2 Manebach 5638-1?
Gabelbach right 3.4 480 Ilmenau 5638-1?
Rottenbach Left 4.2 Ilmenau 5638-1?
Schorte right 9.6 18th Ilmenau 5638-1?
Rittersbach right 2.9 Langewiesen 5638-1?
Burkersteich / Herrenteich brook Left 3.2 Langewiesen 5638-1?
Wages right 5.3 431 Langewiesen 5638-1?
Wohlrose right 17.7 57.2 416 Gräfinau-Angstedt 5638-2
Wumbach Left 3.5 409 Gräfinau-Angstedt 5638-3?
Sorger Bach right 5.2 10 Gräfinau-Angstedt 5638-3?
Singer Bach right 3.5 Dörnfeld on the Ilm 5638-3?
Humbach Left 5.9 382 Cottendorf 5638-3?
Main trench Left 2.6 Griesheim 5638-3?
Deube right 9.1 24 360 Stadtilm 5638-3?
Deeschbach right 4.0 Kleinhettstedt 5638-3?
Oesteröder trench right 3.7 Dienstedt 5638-3?
Mettbach Left 6.6 11 Dienstedt 5638-3?
Krummbach Left 7.7 19th Crane field 5638-3?
Schwarza right 13.4 51.9 285 Tannroda 5638-4
Tonndorfbach Left 11.6 28 280 Munich 5638-5?
Dammbach right 7.2 Bad Berka 5638-5?
Klingelbach right 4.6 Bad Berka 5638-5?
Stone trench Left 4.1 10 Bad Berka 5638-5?
Hengstbach / Hengstgraben Left 8.9 27 Hetschburg 5638-5?
Magdel right 13.1 62.4 230 Mellingen 5638-6
Lehnstedter Bach right 8.2 16 Mellingen 5638-7?
Possenbach Left 3.9 Taubach 5638-7?
Lottenbach Left 5.1 13 Weimar 5638-7?
Asbach Left 6.0 10 Weimar 5638-7?
Dry brook Left 3.7 Tiefurt 5638-7?
Erlgraben right 4.8 10 Denstedt 5638-7?
Aland trench right 3.0 Ulrichshalben 5638-7?
Pfiffelbach Left 8.1 19th Zottelstedt 5638-7?
Herressener Bach / Sulzbach right 14.0 61.6 148 Nauendorf 5638-8
Utenbach right 8.9 17th Flurstedt 5638-9?
Keligaben right 3.7 Niedertrebra 5438-9?
Weidenangerbach right 2.5 under. Niedertrebra 5638-9?
Bruehlbach right 2.4 above Bad Sulza 5638-9?
Emsenbach Left 15.5 96 under Bad Sulza 5638-9?



Ilm floods in April 1994
The Ilm level at 1.05 m at the Fischerhütte (Ilmenau) during the flood in spring 2006

The width of the Ilm is comparatively small. From less than 2 m in the upper reaches it grows to only 8-10 m, to reach 15 m shortly before the mouth. Their depth varies between 10 and 80 cm. Due to the geological subsoil, the water is rich in nutrients and is in the pH range around the value 7. The nature of the floodplains and shading by trees significantly impede the growth of aquatic plants. The river bed is made up of pebbles of different sizes, rock, and sometimes sand. The average flow rate of 6 m³ / s can be significantly exceeded in floods . The last devastating Ilm floods took place on April 14, 1994 and June 1, 2013, when, after prolonged rainfall, there was strong surface runoff. The Ilm overflowed its banks and flooded large areas of its floodplain and many of the structures in it.

Aquatic fauna

Grayling , brown trout and rainbow trout , minnows , gudgeons , loaches , cops , perch , roach , rudd , chub and occasionally eels can be found in the clear waters of the Ilm .

Origin of name

The river name is possibly derived from the Old High German ilme ( elm ). However, a pre-German origin is considered more likely. The name would be of Baltic-Celtic origin and would be traced back to the Lithuanian elmes (the liquid that comes out of the corpses' mouth).

Cultural history

Ilm at the Weimar cone bridge

In documents from 932 and 956 the area through which the upper and middle reaches of the Ilm flowed was called Longawici Gau , later also the Längwitzgau . It reached from the area around Arnstadt with the Käfernburg into the Schwarzatal. The memory of this area was preserved with the name Lengwitzer Mauer for the southeastern part of the Arnstadt city ​​wall. Due to the Germanization from 804, the name Lengwitz changed to Ilm . Only its upper reaches Ilm kept the old (Slavic) name Lengwitz.

The first place foundations in the Ilm valley are handed down from the 9th century by the Breviarium Sancti Lulli of the monastery Hersfeld . At that time, the lower Ilm valley around Apolda was first settled, occasionally places on the middle course have been handed down, such as Dienstedt from 842 and Weimar from 899. Settlement of the upper course began in the 11th century ( Griesheim 1089), in 1198 Langewiesen was first mentioned. The settlement of the Ilm valley was completed by the 13th century, with the exception of Manebach and Stützerbach in the Thuringian Forest.

It is noteworthy that the Ilm divided several villages as a border river until 1945.

place left the Ilm right of the Ilm
(until 1945)
Prussia Saxony-Weimar-Eisenach / Thuringia
(until 1920)
Saxe-Coburg and Gotha Saxe-Weimar-Eisenach
(until 1920)
Schwarzburg-Rudolstadt (Gräfinau) Schwarzburg-Sondershausen (Angstedt)
(until 1920)
Saxony-Meiningen Saxe-Weimar-Eisenach

In the past, the benefits that residents drew from the Ilm were varied. Besides fishing, they allowed numerous were they cutting mills , paper and flour mills , hammer , or stamp mills and mass mills operated. It also served the tanners and glassworks as a water dispenser.

Despite its lack of water, the Ilm was a long-used traffic and farm route, primarily for timber rafting . The ponds created for this purpose in the Schortetal (Knöpfelstaler pond) and the large pond in Stützerbach served as reservoirs. The latter was also used to protect against flooding and to supply impact water for the Ilmenau mining industry. Today it no longer exists. The damage when his dike broke , which ran across the village, was devastating .

For a long time there were only two bridges over the Ilm in Ilmenau ; the Tannenbrücke in the west (Handelsstrasse Erfurt – Nürnberg) and the Kienrußbrücke in the east ( Oehrenstöcker Strasse). Today there are several dozen bridges over the river in the city.

On May 29, 1613, the Ilm was one of the rivers that were affected by the Thuringian Flood . Severe thunderstorms in large parts of Thuringia caused the rivers to overflow within a few hours, causing great damage. In the village of Zottelstedt near Apolda, for example, the water level of the Ilm rose by six to eight meters and almost completely destroyed the village in the bank area. 44 houses in Weimar also fell victim to this flood. The last major flood occurred in the spring of 1994 and also affected neighboring rivers such as the Gera and the Saale.

In Ilmenau, the river bed was relocated during the mining period to lower the water table.

During the years of industrialization , a number of companies arose on the Ilm, which both obtained service water from it and discharged waste water into it. Including glassworks in Stützerbach and Ilmenau, an Ilmenau paint factory and agricultural facilities.

Ilm tourism

Logo of the Ilmtal cycle path
The Ilm in Tiefurt near Weimar

The Ilm Valley Cycle Path was laid out along the entire course of the river and offers good conditions for cycling with little or no traffic. The cycle path connects to the Rennsteig cycle path on the upper reaches and the Saale cycle path at the confluence .

The Ilm in poetry

My banks are poor, but hear the quieter wave
If the stream leads them by, many an immortal song.
  • Johann Wolfgang von Goethe:
Main and Ilm (1826)
I left the great river
To a little one to Christmas me;
If the but a source
To be some good, beautiful.
The Ilme
If the Ilme Bach is modest
Flows meandering quietly in the valley,
Covered by twig and willow
Half-hiding keeps pouring
Does he often hear the flute
Faithful and good of his poet
When the glow of the dawn
Rests on the gentle waves.
Much has sprung from me
Much was offered to you
And so I succeeded
That they make me a river.
A traveler wants to see me
Like the Danube, like the Rhine,
I hide, let him go
Because I'm too small.
Performance of the Ilm in the mask procession on December 18, 1818 in Weimar in honor of the mother of the Empress of Russia
Up at my source
Many a song was created
That I with deliberate speed
Infused into all lands.


Ilm Valley Viaduct in Stadtilm
Ilm valley bridge near Langewiesen

The Ilm Valley has been used as a traffic artery since the region was settled. The two most important traffic routes along the Ilm are the federal highway 87 from Ilmenau via Apolda to Naumburg and since 1846 the Thuringian Railway , which accompanies the Ilm valley from Weimar to the confluence with the Saale and represents an important connection in the German railway network.

Otherwise, only short sections of railway lines and federal roads run through the Ilm Valley. In the Ilmenau area, these are federal road 4 from Ilmenau to Stützerbach and federal road 88 from Ilmenau to Langewiesen and, parallel to it, the Rennsteigbahn and the Ilmenau – Großbreitenbach railway line . In the Weimar area, the Ilmbahn between Kranichfeld and Hetschburg and the Weimar – Gera railway between Weimar and Mellingen run in the valley of the river. In contrast to most of the other large river valleys in Thuringia, the construction of a continuous railway line along the Ilm never came about, as it was cut up by numerous national borders until Thuringia was founded in 1920 and, with the exception of Weimar, there was no major city in the valley. So the rail traffic shifted to the two neighboring valleys of the Gera in the west and the Saale in the east.

The valley is crossed by three large railway bridges. The first among them was the Weimar Viaduct (153 m long) opened in 1876 on the Weimar – Gera railway line . 1894 followed Ilmtalviadukt (201 m long) of railway Arnstadt-Saalfeld and between 2007 and 2010 the Ilmtalbrücke the Nuremberg-Erfurt high-speed railway in Langewiesen which m with 1681 the longest bridge of Thuringia is. Other well-known bridges over the Ilm are the Sternbrücke in Weimar (stone arches) and the covered wooden bridge in Buchfart from 1613. The federal motorway 4 crosses the Ilm near Mellingen with a 299 m long and 14 m high bridge.

Individual evidence

  1. a b c d e f g h River lengths according to geopaths (kmz, 88 kB)
  2. a b Thuringian State Agency for the Environment (ed.): Area and water code index and map. Jena 1998; 26 pp.
  3. a b c German Hydrological Yearbook Elbe Region, Part I 2014. (PDF) State Office for Flood Protection and Water Management Saxony-Anhalt, pp. 168–170 , accessed on November 3, 2018 (at:
  4. a b c Map of the rivers of Thuringia from 10 km² catchment area ( TLUG ; PDF; 1.23 MB)
  5. Values ​​with more than 10 km², but without decimal places, are estimated! This means that the EZG has been approximately measured using polygons. All rivers without information have less than 10 km² catchment area according to the TLUG, those with the information "10" have more than 10 according to the TLUG and 10 or less according to the measurement.
  6. also: Tiefborntal (see waterway map)
  7. The Lottenbach was a tributary of the Ilm until the 1920s, but has flowed into the Asbach since it was diverted.
  8. via Kirschbach 6.1 km
  9. Elfriede Ulbricht: The river basin of the Thuringian Saale . 1st edition. Max Niemeyer, Halle (Saale) 1957.

Web links

Commons : Ilm  - collection of images, videos and audio files