It is the youngest of the six Ruhr reservoirs and was only opened in 1980. The Kemnader See is primarily a recreational area for the population and students of the nearby Ruhr University, but is also a sedimentation basin for suspended matter carried in the river water to improve the drinking water quality of the Ruhr. In addition, a power plant has been producing hydroelectric power for the equivalent of 1,200 households since 2011. The lake stretches over three kilometers between the dam southeast of Bochum-Stiepel and the motorway bridge to the east near Witten-Herbede and is fed by the Ruhr, the Oelbach and Harpener Bach, and smaller tributaries. The shape of the lake is characterized by the Heveney harbor at the mouth of the Oelbach, which is separated from the lake by a long dam with a striking small lighthouse.
Until the reservoir was built, the Ruhr meandered slightly with banks secured by groynes through the flat valley. Since it formed the border between the cities of Bochum and Witten then and now, the original course of the river before it was dammed to form a lake can still be traced using political maps or OpenStreetMap, as the border still runs through the lake in the old curves. For example, the Ruhr ran close to the current Bochum shore at the Gibraltar mine.
The entire lake can be walked around as a pedestrian, cyclist or inline skater. There are partly separate paths for the different types of transport. The highlight is the Ruhr-In-Line, a route built with particularly smooth asphalt around the entire lake for inline skaters. Another special feature is the pedestrian bridge under the motorway bridge near Herbede. The lake is accessible to cyclists via the Ruhr Valley Cycle Route and the Ruhr Area Circuit. Regional hiking trails include the Ruhr University mining trail and the Bochum-South mining trail, which introduce the mining history in the south of the city and each run along the shore of the lake for a while. There are also various water sports, from surfing, boating, fishing to sailing. However, swimming is not allowed and is not recommended for health reasons.