The Upper Harz Water Tunnels (German: Oberharzer Wasserläufe, pronounced as /de/) are part of the Upper Harz Water Regale - a network of reservoirs, ditches, tunnels and other structures in the Harz mountains of central Germany. The German term Wasserlauf refers to the underground element (i.e. the tunnels) of the network of watercourses used in the historic silver mining industry of the Upper Harz. This network of ditches and tunnels was used to supply the mines with headrace waters for their water wheels from the 16th century onwards. In the system of the Upper Harz Water Regale there are over 35 such tunnels with a total length of about .
Although explosives were already in use in the 17th century in the mines of the Upper Harz, tunnels continued to be hewn out by hand, that is with hammer and chisel for much longer. The reason was that there were difficulties in determining the right amount of gunpowder and fears that tunnels running just under the surface would collapse or that the explosive would produce fissures in the rock causing water to leak away. Almost all water tunnels were driven by counter-heading. Until the 18th century the miners excavated tunnels by following the weakest rock; this sometimes created a zigzag route that deviated significantly from the direct line. Not until the 19th century were tunnels driven in a strictly direct line using explosives.
The incline necessary to create a flow of water often amounted to less than 1% (in other words less than drop for every of length). The profile of the older tunnels, that had been driven with hammer and chisel, was sometimes as small as high and wide. The newer tunnels, however, were generally high and wide.
Compared with ditches, tunnels had the important advantage that the water flowing through them underground could not freeze up. The tunnels were laid primarily to short cut the long ditch runs around mountains. Such cuts also produced a steeper incline (shorter distances descending the same height difference have a steeper slope). This raised the flow velocity and hence the hydraulic capacity of the watercourse. The disadvantage of tunnels was the high investment cost of building them.
The working tunnels shown in this table follow the order in the latest listing by Preussag, which is based on their use in the various power stations.
| English Name | German Name | Built | Length | Route | |
|---|---|---|---|---|---|
| Kellwasser Tunnel I | Kellwasser Wasserlauf I | 1821 | m | Dyke Ditch (Blochschleife) to the Nabe valley | |
| Kellwasser Tunnel II | Kellwasser Wasserlauf II | 1821 | m | Blochschleife to Wiege on the Dyke Ditch | |
| Rothenberg Tunnel | Rothenberger Wasserlauf | 1868 | m | Dyke Ditch: crosses the Rothenberg | |
| Coventhai Tunnel | Coventhaier Wasserlauf | 1852 | m | Dyke Ditch: crosses the Coventhai | |
| Dietrichsberg Tunnel | Dietrichsberger Wasserlauf | 1863 | m | Dyke Ditch from Fortune Pond to the "Fenster" | |
| Bielenwiese Tunnel | Bielenwieser Wasserlauf | 1864 | m | Dyke Ditch from "Fenster" to "Teilung" (Mönchstal) | |
| Mönchstal Tunnel | Mönchstaler Wasserlauf | 1677 | m | Dyke Ditch from Mönchstal into the Upper Hausherzberg Pond | |
| Franz August Tunnel | Franz Auguster Wasserlauf | 1832 | m | Dyke Ditch from the Teilung into the Lower Peacock Pond | |
| Jägersbleek Tunnel | Jägersbleeker Wasserlauf | 1771 | m | Träncke Ditch to the Jägersbleek Pond | |
| Huttal Tunnel | Huttaler Wasserlauf | 1763 | m | Hirschler Pond to the Huttaler Widerwaage | |
| Fortune Tunnel | Fortuner Wasserlauf | 1785 | m | Jägersbleek Ditch into the Middle Peacock Pond | |
| Prince Wallis Tunnel | Prinz-Walliser Wasserlauf | about 1740 | m | Nassenwiese Ditch into the Johann Friedrich Tunnel | |
| Johann Friedrich Tunnel | Johann-Friedricher Wasserlauf | 1673 | m | From the Johann Friedrich Pond to the Dorothea Water Wheel Ditch | |
| Kellerhals Tunnel | Kellerhalser Wasserlauf | 1842 | m | From the Middle Kellerhals Pond to the New Kellerhals Ditch, later used in the course of the Zellerfeld Ditch | |
| Winterwiese Tunnel | Winterwieser Wasserlauf | before 1690 | m | From the Zellerfeld Ditch into the Jungfrau Ditch / Middle Zechen Pond | |
| Bremerhöhe Tunnel | Bremerhöher Wasserlauf | 1704 | m | Bremerhöhe Ditch to the Rosenhof Mining Area | |
| Bärenbruch Tunnel | Bärenbrucher Wasserlauf | 1949 | m | From the Bärenbruch Pond into the "Upper Rosenhof Chute" | |
| Upper Schwarzenbach Tunnel | Oberer Schwarzenbacher Wasserlauf | 1808 | m | "Upper Rosenhof Chute" to the Hasenbacher Widerwaage | |
| Upper Hasenbach Tunnel | Oberer Hasenbacher Wasserlauf | 1811 | m | "Upper Rosenhof Chute" to Hasenbacher Widerwaage | |
| Upper Flambach Tunnel | Oberer Flambacher Wasserlauf | 1763 | m | "Upper Rosenhof Chute" from Flambach to the Johannis valley | |
| Upper Johannistal Tunnel | Oberer Johannistaler Wasserlauf | 1839 | m | "Upper Rosenhof Chute" Johannistal to the Klein Clausthal | |
| Upper Klein Clausthal Tunnel | Oberer Klein-Clausthaler Wasserlauf | 1776 | m | "Upper Rosenhof Chute" from Klein Clausthal to the Rosenhof Mines | |
| Ziegenberg Tunnel | Ziegenberger Wasserlauf | 1847 | m | "Lower Rosenhof Chute" from Ziegenberg Pond to the Schwarzenbach | |
| Lower Schwarzenbach Tunnel | Unterer Schwarzenbacher Wasserlauf | 1870 | m | "Lower Rosenhof Chute" from the Schwarzenbach to the Hasenbach | |
| Lower Hasenbach Tunnel | Unterer Hasenbacher Wasserlauf | 1845 | m | "Lower Rosenhof Chute" from the Hasenbach to the Flambach | |
| Lower Flambach Tunnel | Unterer Flambacher Wasserlauf | 1844 | m | "Lower Rosenhof Chute" from the Flambach to the Johannistal | |
| Lower Johannistal Tunnel I | Unterer Johannistaler Wasserlauf I | 1835 | m | "Lower Rosenhof Chute" from the Johannistal to the Klein Clausthal | |
| Lower Johannistal Tunnel II | Unterer Johannistaler Wasserlauf II | 1835 | m | "Lower Rosenhof Chute"(continuation of Johannistal Tunnel I) | |
| Lower Klein Clausthal Tunnel | Unterer Klein-Clausthaler Wasserlauf | 1792 | m | "Lower Rosenhof Chute" from the Kl. Clausthal to the Rosenhof Mines | |
| Dorothea Rösche | Dorotheer Rösche | before 1771 | m | Drainage for the water wheel (Radstube Kehrrad) at Dorothea Pit | |
| Gesehe Tunnel | Geseher Wasserlauf | 1698 | m | Rehberg Ditch to the Gesehr / St. Andreasberg | |
| Schulte Adit | Schulte Stollen | 1838 | m | From the Innerste river to the Wiemannsbucht (Bad Grund) | |
| Upper Eichelberg Tunnel | Oberer Eichelberger Wasserlauf | 1889 | m | From Wiemannsbucht to Schönhofsblick | |
| Lower Eichelberg Tunnel | Unterer Eichelberger Wasserlauf | 1855 | m | Drain from the Knesebeck Shaft |
"Disused" refers to all those tunnels that are no longer in service. Some of these are completely preserved; others, however, have largely fallen into ruin. The following list makes no claim to being complete.
| English Name | German Name | Built | Length | Route | |
|---|---|---|---|---|---|
| Old Dietrichsberg Tunnel | Alter Dietrichsberger Wasserlauf | 1662 | m | Dyke Ditch: Bypasses the Dietrichsberg; became superfluous on the construction of the New Dietrichsberg Tunnel in 1863. | |
| Old Upper Klein Clausthal Tunnel | Alter Oberer Klein-Clausthaler Wasserlauf | m | Upper Rosenhof Chute: Bypasses the Hüttenkopf | ||
| Old Lower Klein Clausthal Tunnel | Alter Unterer Klein-Clausthaler Wasserlauf | m | Lower Rosenhof Chute: Bypasses the Hüttenkopf | ||
| Benedict Tunnel | Benedikter Wasserlauf | m | Upper Kehrzug Ditch into the Hirschler Pond | ||
| Kalte Küche Tunnel | Kalte Küche Wasserlauf | 1821 | m | Dyke Ditch: crosses the Rothenberg; tunnel closed on the construction of the Rothenberg Tunnel in 1868. | |
| Crane Tunnel | Kranicher Wasserlauf | 1878 | m | from the bottom outlet of the Crane Pond (Hahnenklee) to the Lower Raft Pond (Bockswiese) | |
| Langer Tunnel | Langer Wasserlauf | before 1815 | m | Short channel from the Oker region to the Langer Pond | |
| Nassenwiese Tunnel | Nassenwieser Wasserlauf | m | from the Nassenwiese Ditch to the Johann Friedrich Tunnel | ||
| Piss Valley Tunnel | Pisstaler Wasserlauf | 1732 | m | Stadtweg Ditch (from the Stadtweg Pond) to Bockswiese | |
| Polsterberg Tunnel | Polsterberger Wasserlauf | 1767 | 1,23 km | Originally a gallery in the Eisenstein mine; between 1767 and 1813 tunnel from the Polsterberg Pumpworks (Polsterberger Hubhaus) to the Huttal Pond | |
| Schwarzenberg Tunnel | Schwarzenberger Wasserlauf | 1813 | m | Links the outlet area of the Söse with the Oker river | |
| Tannhai Tunnel | Tannhaier Wasserlauf | 1875 | m | Links the Kellerhals Pond, Kellerhals Tunnel to Bockswiese, Wäsche Ditch |