Dwangwa River, river in Malaŵi that is a tributary of Lake Nyasa. It rises in the western watershed of Malaŵi’s central plateau and flows in a northeasterly direction for about 100 miles (160 km) until it enters the lake. The river’s upper reaches exhibit ancient broad valleys and meanders, while the gorge cut for the river’s descent to the lake is narrow and recent. Dwangwa’s drainage into Lake Nyasa occupies a flat swampy area 25 miles (40 km) north of Nkhotakota.