The Upper Harz Ponds (German: Oberharzer Teiche) are found mainly around the mining town of Clausthal-Zellerfeld and the nearby villages of Buntenbock and Hahnenklee in the Upper Harz mountains of central Germany. There are around 70 ponds in total, both large and small. They were built by the miners of the Upper Harz, mostly between the 16th and 18th centuries, and are important components of the cultural monument known as the Upper Harz Water Regale - a network of dams, ditches, ponds and tunnels that was built to supply much-needed water power for the mining industry in the Harz mountains. Today the Water Regale is being proposed as a UNESCO World Heritage Site. About half the dammed ponds are classified today as reservoirs, but they have now become characteristic features of the Upper Harz and are home to some extremely rare plant and animal species.
The Upper Harz Ponds also have the oldest working dams in Germany.
The ponds were originally built for storing the water needed to drive the water wheels providing energy to the Upper Harz silver mines. These water wheels drove the pumps, the hoisting equipment, the stamp mills and, from 1820, the man engines as well.
To begin with, the ponds merely impounded water from their natural catchment areas. But in many cases, their inflow was later increased significantly through the use of additional collection ditches.
Today the ponds are operated for several reasons: the protection of historic monuments, rural conservation, nature conservation and recreation. Several ponds also provide flood protection; others are used to supply drinking water.
The operator of the ponds today is the Harzwasserwerke, who also manage six modern dams in the Lower Saxon part of the Harz.
The barriers were built as earth-fill dams, the fill being usually excavated on site. Usually small quarries were established in the terrain earmarked as the future reservoir; this had the added advantage that it increased its eventual capacity. Neither clay nor silt could be used as grouting material because they did not occur in sufficient quantities in the Upper Harz. The Upper Harz miners had, however, learned from experience that grass sods or turves made excellent grouting; by placing them one on top of another, in a similar fashion to building a wall, a layer of sods up to a metre thick would be built into the dam which ensured that it remained watertight.
A wooden conduit (Holzgerenne) acted as a bottom outlet. It was usually made of oak due to its great durability. The valve was a so-called Striegel, which acted like a plug and closed off the inlet to the wooden channels and was operated by rods. Both grass sod grouting and wooden bottom outlets are still in use in many of the ponds.
The dams themselves are between 4 and 15 m high and the impounded volumes varied between 10,000 and 600,000 m3. One notable exception is the Oderteich northeast of Sankt Andreasberg, which is the only pond not grouted with grass turves, but with granite sand known as granitgrus and with a dam height of 21 m and reservoir volume of 1.7 million m³ of water stands head and shoulders above the other ponds in terms of size.
Although these water features have been artificially created, rare flora and fauna have evolved in and around many of the Upper Harz ponds. The water is low in nutrients and rather cool. The crayfish, which has died out in most European waterbodies due to crayfish plague, has been able to survive in many Upper Harz Ponds thanks to their isolated locations. Pond operators and fishing leaseholders have worked successfully to increase their numbers.
The operation of the ponds over many centuries with constantly changing levels of water has also created a habitat for some extremely rare plant communities. On the soils of many ponds coral necklace (Ilecebrum verticillatum), strapwort (Corrigiola litoralis) or shoreweed (Littorella uniflora) may be found growing. They are dependent on this constant fluctuation of water levels in the reservoir and so the nature conservation authorities have agreed with the pond operators an operating regime that will secure the existence of these plants in the waterbodies concerned. By other ponds there are meadow bogs (Kleinseggenried), which are rich in sedges, rushes and cottongrass and moss communities.
The fish population is primarily influenced by the angling clubs that lease fishing rights and stock the ponds with fish. Only native species of fish are desired, although eel and catfish are excluded due to their incompatibility with the crayfish populations.
The following list includes the majority of the dammed ponds built by the Upper Harz miners, where they are still in operation or where the dam ruins are still clearly visible. Mill ponds are not included. A total of 143 dams and former dams have been documented.
| English Name | German Name | Built | Capacity in m³ | Height above base in m |
|---|---|---|---|---|
| Old Sandpiper Pond | Alter Wasserläufer Teich | before 1565 | 32,000 | 5.30 |
| Capercaillie Pond | Auerhahnteich | 1684 | 61,000 | 7.74 |
| Bärenbrucher Teich | before 1634 | 186,000 | 7.09 | |
| Carl Pond | Carler Teich | 1673 | 14,000 | 5.10 |
| Upper Einersberg Pond | Einersberger Teich, Oberer | before 1672 | 140,000 | 9.16 |
| Middle Einersberg Pond | Einersberger Teich, Mittlerer | before 1672 | 16,000 | 7.74 |
| Lower Einersberg Pond (†) | Einersberger Teich, Unterer (†) | |||
| Duck Marsh | Entensumpf | |||
| Highest Eschenbach Pond (†) | Eschenbacher Teich, Oberster (†) | |||
| Upper Eschenbach Pond | Eschenbacher Teich, Oberer | 1548 | 62,000 | 10.50 |
| Lower Eschenbach Pond | Eschenbacher Teich, Unterer | 1548 | 167,000 | 8.85 |
| Eulenspiegel Pond | Eulenspiegler Teich | around 1546 | 61,000 | 3.43 |
| Upper Flambach Pond | Flambacher Teich, Oberer | 1701 | 88,000 | 6.50 |
| Lower Flambach Pond | Flambacher Teich, Unterer | 1693 | 48,000 | 5.03 |
| Upper Raft Pond | Flößteich, Oberer | before 1680 | 11,000 | 5.00 |
| Lower Raft Pond | Flößteich, Unterer | before 1680 | 10,000 | 4.28 |
| Flöß Pond (Piß Valley) (†) | Flößteich, (Pißtal) | |||
| Fortune Pond | Fortuner Teich | 1721 | 296,000 | 14.33 |
| New Grumbach Pond | Grumbacher Teich, Neuer | after 1714 | 108,000 | 8.67 |
| Upper Grumbach Pond | Grumbacher Teich, Oberer | before 1680 | 180,000 | 10.50 |
| Middle Grumbach Pond | Grumbacher Teich, Mittlerer | after 1680 | 72,000 | 9.20 |
| Lower Grumbach Pond | Grumbacher Teich, Unterer | before 1680 | 82,000 | 7.52 |
| Haderbach Pond | Haderbacher Teich | before 1693 | 103,000 | 9.43 |
| Upper Hahnebalz Pond | Hahnebalzer Teich, Oberer | before 1695 | 66,000 | 8.11 |
| Lower Hahnebalz Pond | Hahnebalzer Teich, Unterer | 1676/86 | 52,000 | 6.50 |
| Hasenbach Pond | Hasenbacher Teich | 1660 | 140,000 | 9.12 |
| Hare Pond (†) | Hasenteich (†) | |||
| Upper Hausherzberg Pond | Hausherzberger Teich, Oberer | 1588 | 180,000 | 7.18 |
| Lower Hausherzberg Pond | Hausherzberger Teich, Oberer | before 1613 | 198,000 | 9.35 |
| Haus Sachsen Pond | Haus Sachsener Teich | |||
| Herzberg Pond (Goslar) | Herzberger Teich (Goslar) | around 1560 | 95,000 | 12.00 |
| God's Help Pond | Hilfe-Gottes-Teich | before 1763 | 12,300 | 8.30 |
| Stag Pond | Hirschler Teich | before 1671 | 599,000 | 11.40 |
| Smelter Pond, Zellerfeld | Hüttenteich, Zellerfeld | before 1673 | 13,000 | 6.42 |
| Smelter Pond, Altenau | Hüttenteich, Altenau | 1688 | 49,000 | 11.73 |
| Huttal Pond, Upper (†) | Huttaler Teich, Oberer (†) | |||
| Huttal Pond, Lower (†) | Huttaler Teich, Unterer (†) | |||
| Jägersbleeker Teich | around 1670 | 380,000 | 13.65 | |
| Johann Friedrich Pond | Johann-Friedricher Teich | 1674 | 96,000 | 6.79 |
| Carp Pond (Hahnenklee) (†) | Karpfenteich (Hahnenklee) (†) | before 1680 | ||
| Upper Kellerhals Pond | Kellerhalsteich, Oberer | before 1679 | 68,000 | 10.78 |
| Middle Kellerhals Pond | Kellerhalsteich, Mittlerer | 1724 | 436,000 | 14.90 |
| Lower Kellerhals Pond, | Kellerhalsteich, Unterer | before 1679 | 53,000 | 8.10 |
| Kiefhölz Pond | Kiefhölzer Teich | before 1671 | 248,000 | 9.72 |
| Klein-Clausthal Pond | Klein-Clausthaler Teich | around 1680 | 29,000 | 8.34 |
| Little Crane Pond, | Kranicher Teich, Kleiner | before 1675 | 11,000 | 2.47 |
| Great Crane Pond, | Kranicher Teich, Großer | before 1675 | 110,000 | 8.24 |
| Kreuzbach Pond | Kreuzbacher Teich | before 1680 | 9,000 | 5.58 |
| Kuttelbach Pond | Kuttelbacher Teich | 1674 | 163,000 | 12.75 |
| Lange Pond | Lange Teich | 1719 | 15,000 | 6.73 |
| Langer Pond | Langer Teich | before 1606 | 49,000 | 7.30 |
| Upper Nassenwiese Pond | Nassenwieser Teich, Oberer | around 1671 | 132,000 | 8.82 |
| Lower Nassenwiese Pond (†) | Nassenwieser Teich, Unterer (†) | before 1743 | 48,000 | 6.0 |
| New Pond (Lautenthal)(†) | Neue Teich (Lautenthal) (†) | after 1680 | 11,800 | 5.8 |
| Oder Pond | Oderteich | 1715-1721 | 1,670,000 | 18.00 |
| Little Oker Pond | Okerteich, Kleiner | 22,000 | ||
| Upper Peacock Pond | Pfauenteich, Oberer | before 1551 | 121.000 | 8.27 |
| Middle Peacock Pond | Pfauenteich, Mittlerer | before 1551 | 259.000 | 9.53 |
| Lower Peacock Pond | Pfauenteich, Mittlerer | before 1551 | 214,000 | 8.94 |
| Pixhai Pond | Pixhaier Teich | 1672 | 281,000 | 8.75 |
| Polster Valley Pond | Polstertaler Teich | 1728 | 46,000 | 6.48 |
| Prince's Pond | Prinzenteich | 1686 | 385,000 | 8.74 |
| Röhre Pond | Röhrenteich | |||
| Lower Schalke Pond | (Unterer) Schalker Teich | 1730 | 151,000 | 11.28 |
| Middle Schalke Pond (†) | Schalker Teich, Mittlerer | |||
| Upper Schalke Pond (†) | Schalker Teich, Oberer | |||
| Schlacke Valley Pond | Schlackentaler Teich | 3,200 | ||
| Schröterbach Pond | Schröterbacher Teich | 1652 | 73,000 | 9.06 |
| Schwarzenbach Pond | Schwarzenbacher Teich | before 1608 | 146,000 | 7.39 |
| Semmelwiese Pond | Semmelwieser Teich | 1691 | 53.000 | 7.24 |
| Silberteich | 1755 | 22,000 | 8.0 | |
| Upper Spiegelthal Pond | Spiegelthaler Teich, Oberer | before 1673 | 51,000 | 7.67 |
| Lower Spiegelthal Pond | Spiegelthaler Teich, Unterer | 1672 | 152,000 | 10.91 |
| Stadtweg Pond | Stadtweger Teich | 1727 | 294,000 | 10.12 |
| Stuffen Valley Pond (†) | Stuffentaler Teich (†) | |||
| Marsh Pond (Buntenbock) | Sumpfteich (Buntenbock) | before 1639 | 189,000 | 6.91 |
| Than Pond | Than-Teich | before 1684 | 12,000 | 6.45 |
| Sandpiper Pond | Wasserläufer Teich | before 1659 | 25,000 | 5.78 |
| Wiesenbeke Pond (Bad Lauterberg) | Wiesenbeker Teich (Bad Lauterberg) | 1715 | 480,000 | 14.50 |
| Zankwiese Pond | Zankwieser Teich | 1688 | 107,000 | 9.67 |
| Upper Mine Pond | Zechenteich, Oberer | before 1661 | 33,000 | 5.85 |
| Middle Mine Pond | Zechenteich, Mittlerer | before 1661 | 45,000 | 6.70 |
| Ziegenberg Pond | Ziegenberger Teich | around 1645 | 313,000 | 8.94 |
Where no data is given, this usually indicates that the pond ended up in other hands before the mines closed and has not been precisely documented.