The Bellacher Weiher (also spelled Bellacherweiher or Bellacher-Weiher; according to the official maps simply Weier without a qualifying word) is a pond in the municipality of Bellach in the Swiss canton of Solothurn. It is located directly at the southern foot of the Jura and has an area of approx. 3.35 hectares and a maximum depth of 2.20 m.
The pond was originally intended to supply the city of Solothurn with fish. According to Kurt Jäggi's account in the 1977 Bellacher calendar, a master Ulrich von Egliswil, a dam builder, was commissioned by the city council in 1456 to build the current pond. According to the Bellach village history of 1990, however, this was a different pond called the Oberer Bellacher Weiher, which later lay in the municipality of Selzach, while the pond that still exists today was not dammed until 1548 as the Seusetweiher or Unterer Bellacher Weiher. It soon became apparent that the cost of putting the fish in the ponds was not in a good ratio to the yield from the ponds. "The fishing out of the ponds was mainly a celebration for the councilors themselves, who attended in large numbers and were fed with plenty of fish and wine." These banquets for the Solothurn council reduced the proceeds considerably, as at least 101 council members and probably other guests attended each time. The council considered keeping the ponds or selling them several times, "but the desire for a banquet always won out."
Battle on March 2, 1798
The pond also went down in the annals in 1798, when the most important battle took place on its shores between Napoleon's troops under General Schauenburg, who were invading the country, and the Solothurn troops of General Josef Bernhard Altermatt, with the French quickly winning and then occupying Solothurn and the rest of the canton without a fight.
In 1861, the mechanical cotton weaving mill Schwarz & Co. took over the Bellach pond and used its water, which was piped to the weaving mill, to power its machines. Since then, the pond has been known locally as the "Black Sea" or "Black Sea". The weaving mill also leased the pond for fishing. In 1945, it was declared a cantonal nature reserve.
Until the beginning of the 20th century, the Bellach pond was also used to produce natural ice. It was also useful for farmers, as they were allowed to use the runoff to irrigate their fields.