The Oderteich is an historic reservoir about seven kilometres northeast of Sankt Andreasberg in the Upper Harz in central Germany.

Its capacity of 1.7 million cubic metres was, far and away, the largest of all the Upper Harz reservoirs at that time and was enough to cope with periods of low precipitation of up to three months.

Their design, however, could not simply be copied, because there was nowhere in the vicinity of the Oderteich to cut grass sods like those used to seal the dams of the Upper Harz reservoirs.

In doing so it was realised that the sand resulting from the weathering of granite, so-called granitgrus, if it was thoroughly tramped down, produced a very good seal.

[4] Planning was carried out in 1714 and, on 14 September, King George Louis authorised the construction of the Oderteich dam in a most gracious special decree and made the available the sum estimated for the project: a total of 3048 thalers and 27 gl.

Because excess water could neither be drained through the relatively small bottom outlet during the construction period nor be impounded, a spillway had to be continuously available whilst the dam was being built.

This resulted in an increase in the dam volume of around 55 percent and a doubling of the reservoir capacity to 1.67 million cubic metres.

The three chief miners (Bergmeister) and excavation engineers (Grabensteiger) were rewarded in 1724 with bonuses ranging from 12 to 100 Talers.

The water is still used for this purpose today and guarantees the economic operation and maintenance of the Oderteich and Rehberg Ditch.

The structure is clearly higher and the reservoir capacity just under three times the volume of the largest ponds around Clausthal-Zellerfeld and Hahnenklee.

The up- and downstream sides were given cyclopean stonework walls made of large blocks of granite with a slope of 1:0.5.

The dam wall has proved to be a very durable structure and, like the entire reservoir, is still virtually in its original condition.

These chutes, made of oak, have a right-angled cross-section of about 25 × 25 cm and feature a valve on the bottom of the shaft that operates in a similar way to the type of bathplug that is closed from below.

This valve can be pushed up or pulled shut using a rod operated from the control hut or Striegelhaus positioned above the shaft.

Originally the spillway ran for almost a 100 metres in a straight line southwards before the water dropped into the valley.

This was built in 1898 when the Oderteich Reservoir was empty in order to reduce the water flow whilst repairs were carried out to the bottom outlet.

This results in unusually high fluctuations in the water level of the reservoir, which can even change from being largely empty to overflowing within a few hours.

In addition, it reduces surface tension, something which causes conspicuous white horses such as occur in the turbulence at the intakes and outlets of the reservoir.

[2][9] This accolade is disputed, however, because in the early 18th century in the area of Clausthal-Zellerfeld, Buntenbock and Hahnenklee there was already a large number of 'reservoirs' (Talsperren) as defined by the German industrial norm, DIN 19700-11.

In the middle of the 1990s, the operators of the Oderteich, the Harzwasserwerke, laid out a waterside footpath (the WasserWanderWeg) as an educational trail.

The northern area is barred to swimmers in the summer by a chain and is meant to be exclusively reserved as a biotope.

In addition there is the former MTV Goslar ski lodge, built at the end of the 1940s and now partly hidden and which can also be booked today as accommodation for self-catering groups.