Kiesgrubensee Gremberghoven

The gravel pit was shut down in the 1980s and designated a nature reserve in 1989. The lake fills nearly the entire former excavation; a small island protrudes from the water in the north. The creation of shallow-water habitats is barely feasible here.

The narrow sandy-gravelly shoreline is largely free of vegetation. Behind it, tall, steep embankments rise with pioneer vegetation of mosses, fungi, and lichens alongside planted shrubs. The eastern slope in particular features numerous slope collapses and open bare-soil surfaces. Several near-vertical embankment tops provide ideal conditions for sand martin colonies; kingfishers and great crested grebes also breed at the lake.

The site is classified as an oligotrophic to mesotrophic calcareous water body with stoneworts. Habitat types include extraction lakes and sand and gravel workings. The flora ranges from silver birch, goat willow, and Scots pine to dog rose and privet, as well as aquatic plants such as various pondweeds.

Leisure activities, unsympathetic water management, pollution, and fly-tipping are identified as threats. Protective measures include fencing off sensitive areas, restricting fishing and other recreational uses, and litter removal. The site is otherwise left to natural succession, in part to preserve the lake as a resting habitat for migratory waterbirds.