Sarasvati River and the decline of Indus Valley civilization are related with each other in Indian topography and history. The gradual progress of the decline of Indus valley civilization shows the union between the Indus valley civilization and Vedic culture. The discovery of Indus valley civilization points a new question about its decline. Formerly, the occidental archeologists inferred that the demise of the Indus valley civilization was made by the foreign invaders. This was made by the British archeologist Mortimer Wheeler. Later it was denied by another anthropologist Kenneth Kennedy. He was the first to prove that the Harappan civilization was diminished by the ecological and the natural imbalance and not by any foreign invasion. It was thought that the foreign invasion was made by the Aryans who were migrated from Central Asia. After that the progression was made by the Out of India theory. According to this hypothesis, Aryan culture was actually an outgrowth of the Indus Valley Civilization that was based in India. The crux of this theory is that the foundations of the Hindu traditions are wholly the product of Indian culture with no influences from outside sources.

Cause of Decline of Harappan Civilization by Saravati River
The Sarasvati River, one major river of the Sapta Sindhu that is the Seven Rivers is mentioned in ancient Sanskrit texts. It is mentioned in the Nadistuti hymn in the Rig Veda (10.75), the Sarasvati river flows between the Yamuna in the east and the Sutlej in the west. It is also encrypted in the Vedic texts like Tandya and Jaiminiya Brahmanas. In the Mahabharata as well mentions the existence of Sarasvati river and later it was dried up in a desert.

It was proved by an international team of geologist, archeologist and botanist that the Sarawasti River was the main villain behind the decline of Indus Valley civilization. However, in India the river is considered to have mythical roots. Some even consider that it is an invisible river or that it still flows underground. Another normally held perception is that the Sarasvati once flowed through the north Indian city of Allahabad, meeting there with two other rivers, the Ganges and the Yamuna. The confluence of these 3 rivers is known as "Prayag". It is now considered as a holy place of worship. But once upon a time, this river existed. The team proved through the satellite images and also the excavation from the Indus Valley Civilisation, the Harappans were an enterprising people taking the advantages of a window of opportunity. This is a kind of "Goldilocks civilization". It was coined by Liviu Giosan, a geologist associated with Woods Hole Oceanographic Institution. They reconstructed the dynamic landscape of the Indus plain where the Indus valley civilization developed 5200 years ago. It is also proved that the entire city was disintegrated between 3900 and 3000 years ago. In details as monsoon drying the subdued devastating floods, the land nearby the rivers, these rivers were still fed with waters and rich silt. This was favourable for agriculture.

This lasted for almost 2000 years but became arid. The major climatic changes like weakening of monsoon over the sub continent ended the Sarawasti River and also the Harappan civilization. Some 5000 years ago, the monsoon started weakening and the marshy land become wet across the Punjab region. The rivers of Indus valley fed by snow melt from the Himalayas and underwent a drastic change. As the silt from the monsoon declined they started incising the river valleys. There they made the fine balance between deposition and erosion along the rivers. The Indus Himalayan tributaries are perennial and water is provided by melting. All these rivers were incised and the valley became wide enough. It was within these flood valleys along the Indus and its tributaries that most of the Harappan settlements on this river belt are found. These valleys acted as a flood plain rich in alluvial soil. This soil was favourable for the agriculture. But the rapid flood ended the settlement areas.

The story was different on the other major river system called the Gaggar-Harkka river valley. Often identified with the mystic Sarasvati of Rig Vedic and the Puranic literature, Giosan and his team the river system has no communication with the Gangetic areas 10000 years ago. According to some scholars the Sarawasti River is mentioned in the Rig Veda. The Rig Veda describes Sarawasti as a mighty river cutting its bank as it emerged from the Himalayan Mountain in the Siwalik regions. Irrerespective of that wheather Yamuna or Sutlej joined it further along the course; this description cannot apply to the upper course of the Ghaggar. The description that is found from the Rig Vedas, better fits the river system of Afghanistan, and the people of later Harappa that is the Vedic people migrated down to Punjab roughly by 3700 years ago that is the after the collapse of the urbanization of Harappan civilization. That`s why in the later Vedic literature Sarawasti is not mentioned. The Ghaggar river system began to collapse from 3900 years ago. That is same implies to the disintegration of Harappan civilization. There the contact between the people of Indus Valley civilization and the Vedic civilization, which one calls the advent of Vedic civilization.