The river originates from Gunniang Mountain (姑娘山) near
Jiangna Town,
Yanshan County,
Wenshan Prefecture, Yunnan Province, China, at an elevation of about 1,500 meters. It flows southwards蜿蜒南流 and near Wengda Village, Panlong Yi Ethnic Township, it goes underground for approximately 3 km as a subterranean river. Resurfacing, it is known as the
Baga River (八嘎河) as it passes through
Baga Township in Yanshan County. Turning southeast and then east near Sanxing Village in Baga Township, it enters
Xichou County, where it is called the
Jijie River (鸡街河) along
Jijie Township. It then flows along the border of
Guangnan County and
Malipo County under the name "Dahe" (大河, "Big River"). Turning south, it forms the border between Malipo County and
Funing County, and from this point onwards it is consistently called the
Nanli River (南利河). For a 16.4 km stretch along the border of Funing County's
Muyang Town and
Tianpeng Town, the Nanli River serves as the international boundary between China and Vietnam. It exits China northwest of Tianpeng Town in Funing County. Upon entering Vietnam in
Lũng Cú Commune,
Tuyên Quang province, the river is known as the
Sông Nho Quế (儒桂河). It flows through the communes of
Đồng Văn and
Mèo Vạc in
Hà Giang province before converging with the Gam River at Nà Phòng in
Lý Bôn Commune,
Cao Bằng province. The total length of the river is approximately 192 km. The section within China is 185.7 km long, while the section within Vietnam is about 46 km long. The total drainage basin area is 6,052 km², with 3,716.6 km² (excluding separately exiting tributaries) lying within China and 2,010 km² within Vietnam. The average elevation of the basin is 1,255 m, with an average gradient of 18.7%. The karst landscape along its course features numerous peaks, basins, and underground rivers. == Hydrology ==