Wied Musa is a valley system located off Ix-Xaghra tal-Marfa at Cirkewwa, Mellieha incised in the Upper Coralline Limestone formation. The most important component of the vegetation community of Wied Musa is the Long-Bracted Sedge (Carex extensa) a species listed in the Red Data Book for the Maltese Islands as Endangered. This plant grows along the valley bottom where pools of water accumulate during the wet season.
Part of the watercourse has been blocked by the construction of dams across the valley floor. Wied Musa used to support a saline marshland at the mouth of the valley but this was practically obliterated when a temporary road, which is now disused and blocked, was built over it during construction works on the coast road leading to the Gozo ferry terminal.
In an effort to protect the remnant habitats and the endangered species within this locality MEPA issued an Emergency Conservation Order, followed by the scheduling of part of Wied Musa as a Level 1 Site of Scientific Importance, with a Level 3 buffer zone as per Government Notice No. 661/94 in the Government Gazette dated 11 October 1994.