Mandichosee, Reservoir in Merching, Germany.

Mandichosee is a reservoir near Augsburg that stores fresh water for surrounding communities. The water body covers a large area and provides various access points around its shoreline for visitors.

The Mandichosee is the reservoir of Lechstaustufe 23 – Merching, a barrage on the Lech between Landsberg am Lech and Augsburg. Its structure combines a gravity dam with a weir and an earth embankment. In 2003 the lake was named after Mandicho, a 6th-century Bavarian prince. In 2016 a two-kilometre bypass channel with a fish ladder was added.

The lake's name, adopted in 2003, recalls Mandicho, a 6th-century Bavarian prince. Today the east shore hosts a VDWS surf school offering windsurfing and stand-up paddling courses and rentals from May to September, and regattas are held on the water. Local sailing and surfing clubs, including the Surf Club Augsburg and the Merching sailing association, are based here.

The reservoir lies west of Merching and east of Königsbrunn, with the Lochbach flowing to its west and the Verlorene Bach to its east. A two-kilometre bypass channel with a fish ladder, built in 2016, runs past the dam. The east shore holds a VDWS surf school open from May to September, offering windsurfing and stand-up paddle courses plus rentals; the neighbouring Kuhsee, Auensee, Weitmannsee and Ilsesee are easily reached by bike.

The reservoir is the largest body of water in the Aichach-Friedberg district. In 2016 a two-kilometre bypass channel with a fish ladder was built so fish can pass the weir; the Kuhsee, Auensee, Weitmannsee and Ilsesee lakes lie north along the Lech and are reachable by bike.