Sutlej

(called the Panjnad in the final section of the lower course), a river in Pakistan, India, and China; the largest tributary of the Indus River, which it joins from the left.

The Sutlej is approximately 1,500 km long and drains an area of 395,000 sq km. It rises in the Kailas Range and receives part of the runoff from Lakes Manasarowar and Langak. The upper course flows through a broad valley, which separates the Great Himalayas from the Kailas and Ladakh ranges. Then, flowing in a narrow gorge, the river cuts through the Great Himalayas and their southern spurs; here, the current is strong, and there are many rapids. At the city of Rupar, the Sutlej flows onto the plain of Punjab and continues across the plain to its mouth. The main tributaries, the Beas and Chenab rivers, flow in from the right.

The upper course is fed chiefly by snow and glaciers; elsewhere the river is fed predominantly by rain, chiefly the summer monsoons, and reaches maximum volume in July and August. The mean flow rate at Rupar is approximately 500 cu m per sec, and the maximum is about 20,000 cu m per sec. Below Rupar the flow rate decreases, since the river and its tributaries are used extensively for irrigation on the plain of Punjab.

Major irrigation canals from the Sutlej include the Dipalpur, Pakpattan, Panjnad, Sirhind, and Bikaner canals. During floods, the canals carry 100 to 300 cu m of water per sec. During high water, the Sutlej is navigable in some parts. The large Bhakra-Nangal hydraulic engineering complex has been built in India at the point where the river emerges from the mountains. The major cities on the Sutlej are Nangal and Phillaur in India and Bahawalpur in Pakistan.