The country's many rivers flow from the highlands of the west to the Mozambique Channel in the east. Chief among these is the Zambezi River; its upper reaches form a lake behind Cabora Bassa Dam. Other major rivers include the Ruvuma, which forms part of the Tanzania border, and the Save and Limpopo rivers. Lake Nyasa forms part of the Malawi border and drains south through the Shire River into the Zambezi River.