The Upper Harz Ponds () are found mainly around the mining town of

Clausthal-Zellerfeld Clausthal-Zellerfeld () is a town in Lower Saxony, Germany. It is located in the southwestern part of the Harz mountains. Its population is approximately 15,000. The town hosts the Clausthal University of Technology. The health resort is locate ...

and the nearby villages of

Buntenbock The small village of Buntenbock lies on the plateau of the Harz mountains in Germany and is part of the mining and university town of Clausthal-Zellerfeld. It is a state-recognised climatic health resort and has accommodation for 200 visitors as ...

and

Hahnenklee Hahnenklee is a borough of the city of Goslar, in the German state of the Lower Saxony. It is located within the Harz mountain range between Goslar and Osterode. The population is about 1200 inhabitants. History Hahnenklee became a state-rec ...

in the

Upper Harz The Upper Harz (, ) is the northwestern and higher part of the Harz mountain range in Germany. The exact boundaries of this geographical region may be defined differently depending on the context. In its traditional sense, the term Upper Harz cover ...

mountains of central Germany. There are around 70

ponds A pond is a small, still, land-based body of water formed by pooling inside a depression, either naturally or artificially. A pond is smaller than a lake and there are no official criteria distinguishing the two, although defining a pond t ...

in total, both large and small. They were built by the

miners A miner is a person who extracts ore, coal, chalk, clay, or other minerals from the earth through mining. There are two senses in which the term is used. In its narrowest sense, a miner is someone who works at the rock face (mining), face; cutt ...

of the Upper Harz, mostly between the 16th and 18th centuries, and are important components of the

cultural monument A national heritage site is a heritage site having a value that has been registered by a governmental agency as being of national importance to the cultural heritage or history of that country. Usually such sites are listed in a heritage registe ...

known as the

Upper Harz Water Regale The Upper Harz Water Regale (, ) is a system of dams, reservoirs, ditches and other structures, much of which was built from the 16th to 19th centuries to divert and store the water that drove the water wheels of the mines in the Upper Harz region ...

- 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 The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...

World Heritage Site World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...

. About half the dammed ponds are classified today as

reservoirs A reservoir (; ) is an enlarged lake behind a dam, usually built to store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of water, interrup ...

, 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.

Purpose

The ponds were originally built for storing the water needed to drive the

water wheel A water wheel is a machine for converting the kinetic energy of flowing or falling water into useful forms of power, often in a watermill. A water wheel consists of a large wheel (usually constructed from wood or metal), with numerous b ...

s providing energy to the Upper Harz

silver mines Silver mining is the extraction of silver by mining. Silver is a precious metal and holds high economic value. Because silver is often found in intimate combination with other metals, its extraction requires the use of complex technologies. In ...

. These water wheels drove the

pump A pump is a device that moves fluids (liquids or gases), or sometimes Slurry, slurries, by mechanical action, typically converted from electrical energy into hydraulic or pneumatic energy. Mechanical pumps serve in a wide range of application ...

s, the hoisting equipment, the

stamp mills Stamp or Stamps or Stamping may refer to: Official documents and related impressions * Postage stamp, used to indicate prepayment of fees for public mail * Ration stamp, indicating the right to rationed goods * Revenue stamp, used on documents to ...

and, from 1820, the

man engine A man engine is a mechanism of reciprocating ladders and stationary platforms installed in Mining, mines to assist the miners' journeys to and from the working levels. It was invented in Germany in the 19th century and was a prominent feature o ...

s as well. To begin with, the ponds merely impounded water from their natural

catchment area A catchment area in human geography, is the area from which a location, such as a city, service or institution, attracts a population that uses its services and economic opportunities. Catchment areas may be defined based on from where people are ...

s. 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 monument A monument is a type of structure that was explicitly created to commemorate a person or event, or which has become relevant to a social group as a part of their remembrance of historic times or cultural heritage, due to its artistic, historical ...

s, rural conservation,

nature conservation Nature conservation is the ethic/moral philosophy and conservation movement focused on protecting species from extinction, maintaining and restoring habitats, enhancing ecosystem services, and protecting biological diversity. A range of values ...

and

recreation Recreation is an activity of leisure, leisure being discretionary time. The "need to do something for recreation" is an essential element of human biology and psychology. Recreational activities are often done for happiness, enjoyment, amusement, ...

. Several ponds also provide

flood protection Flood management or flood control are methods used to reduce or prevent the detrimental effects of flood waters. Flooding can be caused by a mix of both natural processes, such as extreme weather upstream, and human changes to waterbodies and ru ...

; others are used to supply

drinking water Drinking water or potable water is water that is safe for ingestion, either when drunk directly in liquid form or consumed indirectly through food preparation. It is often (but not always) supplied through taps, in which case it is also calle ...

. The operator of the ponds today is the ''

Harzwasserwerke The Harzwasserwerke GmbH (; English: Harz Water Works Limited) is a major German water company and dam operator based in Hildesheim, located within the German federal state of Lower Saxony. History Founded in 1928, the Harzwasserwerke were task ...

'', who also manage six modern

dams A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, ...

in the Lower Saxon part of the Harz.

Design

The barriers were built as

earth-fill dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface ...

s, the fill being usually excavated on site. Usually small

quarries A quarry is a type of open-pit mine in which dimension stone, rock, construction aggregate, riprap, sand, gravel, or slate is excavated from the ground. The operation of quarries is regulated in some jurisdictions to manage their safet ...

were established in the terrain earmarked as the future reservoir; this had the added advantage that it increased its eventual capacity. Neither

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

nor

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually ...

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 An oak is a hardwood tree or shrub in the genus ''Quercus'' of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisp ...

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 The Oderteich is an historic reservoir about seven kilometres northeast of Sankt Andreasberg in the Upper Harz in central Germany (geography), central Germany. It was built by miners from St. Andreasberg in the years 1715 to 1722 and, today, is a ...

northeast of

Sankt Andreasberg Sankt Andreasberg () is a former independent city in the Goslar (district), district of Goslar, in Lower Saxony, Germany. Since 1 November 2011, it has formed part of the town Braunlage. It is situated in the Harz, approximately west of Braunlage ...

, which is the only pond not grouted with grass turves, but with

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

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.

Flora and fauna

Although these water features have been artificially created, rare

flora Flora (: floras or florae) is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. The corresponding term for animals is ''fauna'', and for f ...

and

fauna Fauna (: faunae or faunas) is all of the animal life present in a particular region or time. The corresponding terms for plants and fungi are ''flora'' and '' funga'', respectively. Flora, fauna, funga and other forms of life are collectively ...

have evolved in and around many of the Upper Harz ponds. The water is low in

nutrients A nutrient is a substance used by an organism to survive, grow and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

and rather cool. The

crayfish Crayfish are freshwater crustaceans belonging to the infraorder Astacidea, which also contains lobsters. Taxonomically, they are members of the superfamilies Astacoidea and Parastacoidea. They breathe through feather-like gills. Some spe ...

, which has died out in most European waterbodies due to

crayfish plague Crayfish plague (''Aphanomyces astaci'') is a water mold that infects crayfish, most notably the European ''Astacus'' which dies within a few weeks of being infected. When experimentally tested, species from Australia, New Guinea and Japan were a ...

, 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 In ecology, habitat refers to the array of resources, biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species' habitat can be seen as the physical manifestation of its ...

for some extremely rare plant communities. On the soils of many ponds coral necklace (''Ilecebrum verticillatum''), strapwort (''Corrigiola litoralis'') or

shoreweed ''Littorella uniflora'' (vernacular name: (American) shoreweed) is a species of aquatic flowering plant native to the Azores, Morocco, most of Europe excluding the dry southeast, Iceland, and the Faroes. It prefers to live mostly submerged in nut ...

(''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 A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main Wetland#Types, types of wetlands. Other names for bogs include mire, mosses, quagm ...

(''Kleinseggenried''), which are rich in

sedges The Cyperaceae () are a family of graminoid (grass-like), monocotyledonous flowering plants known as sedges. The family is large; botanists have described some 5,500 known species in about 90 generathe largest being the "true sedges" (genu ...

, rushes and

cottongrass ''Eriophorum'' (cottongrass, cotton-grass or cottonsedge) is a genus of flowering plants in the family Cyperaceae, the sedge family. They are found in the cool temperate, alpine, and Arctic regions of the Northern Hemisphere, primarily in the mi ...

and

moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...

communities. The

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

population is primarily influenced by the

angling Angling (from Old English ''angol'', meaning "hook") is a fishing technique that uses a fish hook attached to a fishing line to tether individual fish in the mouth. The fishing line is usually manipulated with a fishing rod, although rodless te ...

clubs that lease fishing rights and stock the ponds with fish. Only native species of fish are desired, although

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 20 families, 164 genera, and about 1000 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

and

catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...

are excluded due to their incompatibility with the crayfish populations.

Table of Upper Harz Ponds

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 pond A mill pond (or millpond) is a body of water used as a reservoir for a water-powered mill. Description Mill ponds were often created through the construction of a mill dam or weir (and mill stream) across a waterway. In many places, the co ...

s are not included. A total of 143 dams and former dams have been documented. (†) means: pond out of service, largely dry. Dam remains exist. 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.

Sources

* Friedrich, Ernst Andreas (1982): ''Gestaltete Naturdenkmale Niedersachsens'', Landbuch-Verlag, Hannover 1982. {{ISBN, 3-7842-0256-X

External links

Ponds around Clausthal-Zellerfeld, Buntenbock and Hahnenklee