The Harpen Ponds, also known as Werner Ponds, are two still waters on the border between the Harpen and Werne districts of Bochum near the Ruhr-Park shopping center. Originally designed as sewage ponds for mining, they are now a local recreation area.
The Harpener Bach feeds the two water surfaces. In addition, warm mineral-rich mine water from the former Robert Müser colliery is introduced into it, which leads to a milky, cloudy color and sometimes to unpleasant smells. The high chloride content (up to 40 grams per liter) and the constant 20 ° C temperature of the pit water favor a special fauna and flora at the point of discharge. According to the European Water Framework Directive, waters must be restored to their natural state by 2015; However, the RAG has a special permit from the Arnsberg district and may continue to do so until 2021.
The northern pond is 230 meters wide and 180 meters long, the southern one a maximum of 140 meters wide and 460 meters long. Between the two ponds, a hiking trail leads to the former mine dump of Robert Müser.
Mallards, pond and pale claws, great crested grebes and swans breed at the pond. Gray herons as well as meal and barn swallows can also be observed. The city of Bochum has set up benches along the way and created the wedding forest.
In 2009 the Bochum Botanical Association examined the biodiversity at the Harpen ponds and detected the red kite, the skylark and the ants' cricket as well as the sand sedge, the tufted carnation and the frog bulrush on the plants in rare and remarkable animals.