Indus River is one of the longest rivers in the world and has a length of around 2,000 miles (3,200 km). It’s interesting to know that its name is derived from the Tibetan and Sanskrit name Sindhu. Also, the total drainage area of this river is about 450,000 square miles (1,165,000 square km), of which 175,000 square miles (453,000 square km) is in the ranges and foothills of the Himalayas, the Hindu Kush, and the Karakoram Range. The remaining part lies in the semiarid plains of Pakistan.

Indus River System

Physical Features

The river starts from the southwestern Tibet Autonomous Region of China near Lake Mapam and is located at an elevation of about 18,000 feet (5,500 metres). It’s just a short distance beyond Leh, in Ladakh (in the Indian-administered state of Jammu and Kashmir), and it is also joined by its first major tributary, the Zaskar River on its left. In the same direction, the Indus is joined by its famous tributary the Shyok River on the right bank into the Pakistani-administered areas of the Kashmir region. The Indus has got all its well-known tributaries from the eastern Punjab Plain.

Once it has got water from the Punjab Rivers, the Indus valley becomes a lot larger, and especially during the flood season (July to September), it transforms into several miles wide. At an elevation of about 260 feet (80 metres), it passes through the plains in western and southern Punjab province in Pakistan. Since it moves so slowly across the plain, it lands up depositing the accumulated silt on its bed, which is, as a result, raised above the level of the sandy plain. In fact, a majority part of the plain in Sindh (Sind) province in Pakistan has been built up by alluvium that has been laid down by the Indus. There have been embankments constructed in order to prevent flooding, but a lot of times floods still destroy large areas. Such devastating floods happened in the years 1947, 1958, and 2010.

Hydrology System

All the major rivers of the Indus River system are snow-fed. Therefore, their flow is always different at times of the year. For instance, the flow is bare minimum during the winter months (December to February); there is a rise the level of water in spring and early summer (March to June), and floods are bound to happen during the rainy season (July to September).

The Indus and its tributaries get their waters from the hilly upper parts of their catchments. So, their flow remains the maximum when they come out of the foothills, and then a little surface flow gets added in the plains, where the evaporation and seepage process reduces the flow volume considerably. On the contrary, a lot of water gets added by seepage during the monsoon months. In the main stream of the Indus, the water level is at its lowest from mid-December to mid-February.

The upper Indus has around 26.5 cubic miles (110 cubic km)—somewhat less than half the total supply of water in the Indus River system annually. There is a lot of physiographic and historical proof to establish that at least since the days of the Indus civilization or the dawn of civilization— about 4,500 years ago—the Indus has been constantly shifting its course from the southern Punjab province to the sea. Currently, the river is held back by some higher ground from Sehwan to Thatta at the head of the delta, but there is a possibility that there will be more shifting in future. There is also a lot of proof that there has been shifting of the Chenab, Ravi, Sutlej and Beas rivers during the historical period.

Climate

Right from the source to its mouth, there is a precipitation between 5 and 20 inches (125 and 510 mm) annually in the Indus region. Excluding the mountainous sections of Pakistan, the Indus valley is between the driest parts of the subcontinent. The Northwestern winds are responsible for sweeping the upper Indus valley in winter and they are responsible for about 4 to 8 inches (100 to 200 mm) of rainfall—which is vital for the successful growing of wheat and barley. Note that the mountainous region from the upper Indus gets a precipitation largely in the form of snow. But a huge amount of the river water comes from the melting snows and glaciers of the Karakoram, Himalayan ranges and the Hindu Kush. The monsoon rains (July to September) offer the rest of the flow. When it comes to the climate of the Indus valley, January is always below freezing point in the mountainous north, while the daytime in July has high temperatures of about 100 °F (38 °C) in Sindh and Punjab provinces. Jacobabad, which is considered to be one of the hottest spots on Earth, is located west of the Indus River in northern Sindh and frequently records summer temperatures of 120 °F (49 °C).

Plant and Animal Life

In the Sindh province on the lower Indus, about 10 to 25 miles (15 to 40 km) area from the river has desert conditions and it is dominated by sand and poor grass cover. There is also irrigation by floods or canals that occurs, which helps cultivation, but intensive irrigation more often than not produces soil salinization. In the northern Sindh and Punjab province, the tendency of overgrazing and felling timber for the purpose of producing fuel has destroyed a lot of natural vegetation. Additionally, extended human interference along with natural drainage and deforestation in the Himalayan foothills has been responsible for a drop in groundwater levels and a further loss of vegetation.

Today, a lot of efforts have been taken for reforestation in some parts of the Thal area in the Punjab region east of the Indus and they have been largely successful. There are some cultivated areas next to the river that has many trees, and the narrow piece below the mountains looks somewhat like a parkland. There are plenty of coniferous trees in the mountainous region along the upper Indus.

The Indus is also quite rich in fish. The most popular variety is known as the hilsa, which is the most-important edible fish found in the river. Some of the important fishing centres are Tatta, Kotri, and Sukkur that are all located in the Sindh province.

People

The population living around the upper reaches of the Indus—e.g., Tibetans, Balti and Ladakhis—show resemblance with Central instead of South Asia. They all are fluent in the Tibetan languages and practice Buddhism, even though the Balti community has adopted Islam. Even the concept of Pastoralism is imperative in the local economy. In the main Himalayan ranges, there are areas drained by the headwaters of the major Indus tributaries, which have formed a transitional zone where the Tibetan cultural features blend with those of the Indian Pahari (hill) region.

In all other areas of the Indus valley, the inhabitants speak the Indo-European languages and are Muslims, which reflects the fact that there have been repeated incursions of peoples entering the Indian subcontinent from the west over several millennia. Additionally, the Dardic-speaking groups (Kafir, Kohistanis, Kashmiri Gujar and Shinas), of the Indo-European origin occupy the rough mountains of the western Kashmir region. The long-lived Burusho who speak a language called Burushaski, which has no known ties to any other language, live in the Hunza River valley.