a river in southeastern Brazil, a left tributary of the Paraná. The Tietê is 1,120 km long and drains an area of 71,900 sq km. It rises in the northwestern Serra do Mar and flows through the Brazilian Highlands. The river has many rapids and a 22-m waterfall near the settlement of Itapura, which is near the mouth. Freshets occur in the summer. The average water discharge in the lower course is about 620 cu m per sec. The upper Tietê has hydroelectric power plants fed by reservoirs. The city of Säo Paulo is on the Tietê.