The Oderteich dam

At the wooden bridge you will have reached the Oder valley. This stream flows into the Oderteich dam a few hundred metres further down. This dam was Germany's largest water reservoir until the end of the 19th century. Miners from Sankt Andreasberg erected the dam between 1715 and 1722. Along with other structures of the Upper Harz Water Management System, this has been a UNESCO World Heritage site since July 2010. The Oderteich dam was once erected to serve as a reliable water source even in times of drought that would provide water via the Rehberg ditch for the water-wheels of the mines of Sankt Andreasberg. Already at that time, it seems to have been customary that the costs of such major projects rose during construction. The final costs for the Oderteich dam amounted to about 11,700 imperial thalers, which was almost four times the expenditure initially envisaged. However, the king did not object to the repeated applications for and approvals of the amendments. The three responsible mining masters were rather awarded bonuses of between 12 and 100 thalers. Mining activities in Sankt Andreasberg were brought to a standstill in 1913. Since then, the facilities of the Upper Harz Water Management System have been used for electricity generation. The waters of the Oderteich dam are still flowing to Sankt Andreasberg to be used in several power stations and particularly in the Samson Pit. This has ensured the efficient operation of the Oderteich dam and Rehberg ditch until the present day. It is interesting to note that until the 1920s, the Oderteich dam was used to grow fish. Until into the Second World War, trout were still caught from the dam. Only since the 1950s, stocking attempts have failed. This had been caused by the decrease in pH value of the water since then, which probably was about 5 around 1900, but had dropped to about 4, due to the acidification of the soils and waters by air pollutants. The River trout could not survive under such acidic conditions. Thanks to the Europe-wide measures to improve air quality as well as the planting of deciduous trees along the stream banks of the Harz, the situation has improved markedly over recent years. A major achievement in environmental and nature conservation: according to recent investigations the River trout is slowly returning to its natural environment and is able to migrate upstream to 800 meters altitude.