Pancharevo Lake is a reservoir built along Pancharevo Gorge on the Iskar River (Danube River basin), between the mountains Vitosha and Lozenska Planina. It is located in western Bulgaria, nearby Sofia City, at an altitude of 600 m a.s.l. It has a length of 3 km, width up to 700 m, and depth of 20 m. The reservoir is used for drinking and industrial water supply, for sport and recreation activities. The region is characterised with high species richness and habitat diversity. The eastern lake shore is occupied by fragments of native oak forests and pine plantations, the slopes descending steeply to the water, somewhere ending with screes. Some rare plants as orchid species are found in this area. The lake ecosystem supports a great variety of aquatic plants, invertebrates, fish and birds. The Iskar River flowing into the lake is inhabited by fauna typical to the downstream part of the upper reaches as trout, barbel, chub, schneider, gudgeon, and minnow. Specific feature of the region are its thermal springs. The beautiful nature of the lake and its proximity to the capital make it a favorite place for vacation and recreation of Sofia citizens and tourists. The western shores of the lake are urbanised and densely populated (Pancharevo and Kokalyane villages). There are several recreation areas and facilities at the shores, including spa, sports, aquaculture and tourist facilities, providing possibilities for amateur and professional swimming, surfing, water skiing, rowing, angling, hiking and other activities. One of the consequences of this growing pressure of human activities is the introduction and spread of alien and invasive alien species in the region.