a river in Rumania; left tributary of the Danube. Length, 348 km; basin area, 10,570 sq km. The river rises from two sources on the slopes of the Southern Carpathians. Along its upper course, it flows across the Petroseni basin and then cuts through the Surduc Pass, flowing onto the rolling Oltenian piedmont plain. In its lower reaches, it flows through a broad valley. There is high water during the spring; heavy flooding occurs at irregular intervals. The average rate of discharge on the lower reaches is about 80 cu m per sec. The Jiu is not navigable. The cities of Petrila, Petroseni, and Tirgu-Jiu are along its course; the city of Craiova is located in its valley.