Da River (Song Da)

Da River, also known as the Black River or Song Da, is the largest tributary of the Red River (Hong River) in northern Vietnam. The river originates in Yunnan Province, China, flows southeast through the mountainous provinces of Lai Chau, Dien Bien, Son La, Hoa Binh, and Phu Tho, and joins the Red River near Viet Tri. With a length of approximately 910 km (570 mi), it is the longest tributary of the Red River and one of the most important rivers in northern Vietnam.

The Da River drains a vast mountainous watershed characterized by deep valleys, rugged limestone mountains, and dense forests. Its strong flow and steep gradient have made it one of Vietnam's most important rivers for hydroelectric power generation. Major dams, including the Hoa Binh, Son La, and Lai Chau hydropower plants, have transformed the river into a key source of renewable energy while also providing flood control and water storage.

The river supports a rich freshwater fish fauna adapted to fast-flowing mountain waters. Common species include Bagarius yarrelli, Hemibagrus guttatus, Spinibarbus denticulatus, Onychostoma gerlachi, Acrossocheilus spp., Schistura spp., Silurus asotus, and numerous cyprinids, loaches, and catfishes. Reservoirs created by the hydropower dams have also become important fisheries supporting a variety of native fish species.

The Da River has played a significant role in the history, economy, and culture of northern Vietnam for centuries. Today, it remains one of the country's most important waterways, contributing to hydroelectric power production, freshwater fisheries, agriculture, and the ecological health of the Red River basin.