The availability of water varies significantly throughout the region. The area between Rijeka and Vinodol contains numerous freshwater springs that are largely tapped for water supply systems. Water significantly contributed to the geomorphology of the area, especially in the Bay of Bakar, a ria located between Rijeka and Kraljevica. At the seaward slopes of Velebit, in areas near Senj and Karlobag, surface watercourses are sparse. They form losing streams flowing to the sea, while springs of lower yield dry up during summer. The most significant watercourse in the region is the long Rječina River, flowing into the Adriatic Sea in the city of Rijeka. The islands of Cres, Krk, and Lošinj have significant surface water that is used as the primary water supply source on those islands. The most significant among them is Lake Vrana on the island of Cres, containing of water. The surface of the freshwater lake is at above sea level, while its maximum depth is . The Gulf of Kvarner is an especially significant area for the preservation of biodiversity.