Massa River (Morocco)The Massa River is a river in southern Morocco located in the Sous region. It originates in the Anti-Atlas and flows northwest ending in the Atlantic Ocean at Sidi R'bat after flowing through the Souss-Massa National Park.Yusuf Ibn Tashfin DamConstructed in 1972, the Yusuf Ibn Tashfin dam is the main dam on the Massa river.