The Upper Harz Ditches (German: Oberharzer Gräben, pronounced as /de/) are hillside ditches, running roughly parallel to the contour lines, that were laid out in the Upper Harz in Germany from the 16th to the 19th centuries to supply water power to the silver mines there. They are an important component of the Upper Harz Water Regale, a historical water system that is now a cultural monument.
The ditches consist of a trench and an embankment (Grabenbrust) next to it, made of spoil piled up when the ditch was excavated. The embankments are frequently protected from erosion by a dry stone wall. In most cases, they also act as inspection paths for the ditch keepers (Grabenwärter) and, today, as public footpaths. The ditches are only inclined at about 1–2 ‰ (i.e. about 1 to 2 millimetres per metre). As a result, they run almost parallel to the contour lines of the terrain.
As protection against seepage the embankment and bed of the ditch are usually sealed with grass sods or clay. At inlets, where the ditch crosses forest streams, there are so-called Fehlschläge, small weirs, by which the water flow in the ditch can be regulated. When water levels are high these have to be opened, i.e. the boards controlling the flow must be removed.
The hydraulic capacity of most ditches is between 100 and 200 litres per second; on the Rehberg Ditch it is up to 600 L/s and on the Dyke Ditch up to 1000 L/s.
The ditches are listed in an order which is based on the system by Preussag, who named the ditches in an order based on the power stations that could be supplied by them. At present only those working ditches still operated by the Harzwasserwerke are shown.
| English Name | German Name | Built | Length | Route | |
|---|---|---|---|---|---|
| Abbe Ditch | Abbegraben | 1827 | 1667 m | Drain from the Abbe east of Torfhaus to the Dyke Ditch | |
| Flörichshai Ditch | Flörichshaier Graben | 1827 | 1311 m | Part of the Oder west of Torfhaus to the Dyke Ditch | |
| Clausthal Flood Ditch | Clausthaler Flutgraben | 1827 | 4116 m | Drain from the source area of the Sieber and the Sonnenkappe to the Dyke Ditch | |
| Dyke Ditch | Dammgraben | 1732–1827 | 15.409 m | From the Brocken-Bruchberg area to the Upper Hausherzberg Pond | |
| Morgenbrodstal Ditch | Morgenbrodstaler Graben | 4111 m | Drain from the upper course of the Söse to the Dyke Ditch | ||
| Huttal Ditch | Huttaler Graben | 1763 | 1168 m | Link from Huttal Pond (†) to the Huttaler Widerwaage | |
| Jägersbleek Ditch | Jägersbleeker Graben | 726 m | From Jägersbleek Pond to the Fortune watercourse | ||
| Dorothea Water Wheel Ditch | Dorotheer Kehrradsgraben | 903 m | Stag Pond to the reciprocal water wheel (diameter 8.6 m) at the Dorothea Pit | ||
| Field Ditch | Feldgraben | 2112 m | From the southern part of the town of Clausthal to the Middle Pfauenteich | ||
| Kellerhals Ditch | Kellerhalser Graben | 508 m | Bypass for the Upper Kellerhals Pond | ||
| Upper Schalke Ditch | Oberer Schalker Graben | 2721 m | From the southern part of the Schalke to Hahnenklee, original length almost 9 km | ||
| Lower Schalke Ditch | Unterer Schalker Graben | 2721 m | From the southern part of the Schalke into Kiefholz Pond | ||
| Zankwiese Bottom Ditch (also Kahleberg Fault Ditch) | Zankwieser Grundgraben (also Kahleberger Bruchgraben) | 329 m | From Widerwaage Zankwiese Pond into Kiefholz Pond | ||
| Zellerfeld Ditch | Zellerfelder Kunstgraben | 4839 m | Originally 6.19 km long from the Middle Kellerhals Pond to Zellerfeld | ||
| Ringer Ditch | Ringer Graben | 383 m | From the bottom outlet of the Middle Zechen Pond to the Ringe Zechenhaus | ||
| Upper Einersberg Ditch | Oberer Einersberger Graben | 1250 m | From the bottom outlet of the Middle Zechen Pond towards Einersberg | ||
| 4th Stamp Mill Ditch | 4. Pochgraben | 991 m | In the Zellerfeld valley, parallel to the Zellbach | ||
| Eschenbach Flood Ditch | Eschenbacher Flutgraben | 874 m | From the Zellweg (Zellerfeld) into Lower Eschenbach Pond | ||
| Upper Eschenbach Chute | Oberer Eschenbacher Fallgraben | 350 m | From Lower Eschenb. Pond (upper drain) to the Schinderloch | ||
| Lower Eschenbach Chute | Unterer Eschenbacher Fallgraben | 291 m | From the Lower Eschenb. Pond (lower drain) to the Zellbach | ||
| Bremerhöhe Ditch | Bremerhöher Graben | 1287 m | From the Schinderloch (Zellbach) to the Rosenhof mines | ||
| Schmidt's Ditch | Schmidtsgraben | 453 m | Diversion of the Flambach around the two Flambach Ponds | ||
| Taubefrau Ditch | Taubefrauer Graben | 574 m | Eastern inlet ditch for the Sumpfteich | ||
| Wäsche Ditch | Wäschegraben | 420 m | From the bottom outlet of the Middle Grumbach Pond | ||
| Hedge Ditch | Heckegraben | 326 m | Part of the Lower Rosenhof Ditches in the area of Pixhai Mill | ||
| Stadtweg Bottom Ditch | Stadtweger Grundgraben | 193 m | From the bottom outlet of the Stadtweg Pond drain around the Mill Pond below | ||
| Jungfrau Ditch | Jungfrau Graben | 300 m | From the Winterwiese tunnel into the Middle Zechen Pond | ||
| Elisabeth Ditch | Elisabether Graben | 300 m | Diversion around the Lower Peacock Pond, formerly also intended to be part of the Dyke Ditch | ||
| Upper Rosenhof Chute | Oberer Rosenhöfer Fall | 1299 m | Consists of four link ditches between the tunnels of the ORF | ||
| Lower Rosenhof Chute | Unterer Rosenhöfer Fall | 637 m | four link ditches between the tunnels of the Lower Rosenhof Chute | ||
| Hühnerbrühe Ditch | Hühnerbrüher Graben | to 1725 | 775 m | Diversion of the Hühnerbrühe into the Oderteich (western Oderteich) | |
| Königskopf Ditch | Königsköpfer Graben | to 1725 | 1467 m | Bypass for several streams of the Königskopf into the Oderteich (from the east) | |
| Rehberg Ditch | Rehberger Graben | 1699 | 7211 m | From the bottom outlet of the Oderteich to Sankt Andreasberg | |
| Sonnenberg Ditch | Sonnenberger Graben | before 1600 | 3619 m | From parts of the Sonnenberg into the Rehberg Ditch |