Lo River (Song Lo)

Lo River is one of the largest tributaries of the Red River (Hong River) in northern Vietnam and southern China. The river originates in Yunnan Province, China, where its upper course is known as the Panlong River. After crossing into Vietnam, it flows through the provinces of Ha Giang, Tuyen Quang, and Phu Tho before joining the Red River at Viet Tri. With a total length of approximately 470 km (290 mi), the Lo River is one of the principal waterways of the Red River basin.

The river drains a mountainous watershed characterized by steep valleys, limestone formations, and dense forests. Numerous tributaries contribute to its flow, making the Lo River an important source of water for agriculture, hydropower generation, transportation, and fisheries. Its upper reaches are known for their scenic landscapes and high biodiversity, while the lower reaches flow through fertile agricultural plains.

The Lo River supports a diverse freshwater fish community. Common species include Hemibagrus guttatus, Bagarius yarrelli, Spinibarbus denticulatus, Onychostoma gerlachi, Chanodichthys erythropterus, Opsariichthys bidens, Silurus asotus, and numerous cyprinids, catfishes, and loaches native to northern Vietnam. The river is an important fishing ground for local communities throughout its course.

The Lo River plays a vital role in the ecology and economy of northern Vietnam. As one of the two largest tributaries of the Red River, it contributes significantly to the basin's water resources, sediment transport, and biodiversity while supporting agriculture, inland fisheries, and hydroelectric development.