The river that drains the Assam Valley is the Brahmaputra River. Let's delve into the details of this magnificent river and its significance in the region.

The Brahmaputra River:
The Brahmaputra River is one of the major rivers in Asia, flowing through China, India, and Bangladesh. In India, it traverses through the northeastern states of Arunachal Pradesh and Assam, draining the Assam Valley. The river is considered sacred by Hindus and is often referred to as the "Son of Brahma."

Origin:
The Brahmaputra River originates from the Chemayungdung Glacier in the Kailash Range of the Himalayas in Tibet. It is formed by the confluence of two rivers, the Siang and the Lohit, near the town of Sadiya in Arunachal Pradesh. From there, it enters the Indian state of Assam and flows through the Assam Valley.

Flow through the Assam Valley:
The Brahmaputra River meanders through the Assam Valley, which is a broad and fertile plain between the eastern Himalayas and the Patkai Range. It is considered one of the largest riverine plains in the world. The river flows in a southerly direction, passing through major cities like Guwahati, Tezpur, and Dibrugarh.

Importance:
1. Irrigation: The Brahmaputra River is vital for irrigation in the Assam Valley. Its floodplains are highly fertile, supporting extensive agriculture. The river's waters are used for irrigation, particularly for growing crops like rice and tea, which are essential to the region's economy.

2. Transportation: The Brahmaputra River serves as a major transportation route in the region. It is navigable for a significant stretch, facilitating the movement of goods and people. Ferries and boats are commonly used for transport, connecting various towns and villages along the river.

3. Hydroelectric Power: The river's flow and gradient make it suitable for the generation of hydroelectric power. Several dams and hydroelectric projects have been constructed along the Brahmaputra River, helping to meet the energy requirements of the region.

4. Biodiversity: The Assam Valley, through which the Brahmaputra River flows, is known for its rich biodiversity. The river supports a diverse range of flora and fauna, including the endangered Gangetic dolphin, various species of turtles, and numerous migratory birds.

Conclusion:
The Brahmaputra River is the principal drainage system of the Assam Valley. It plays a vital role in the region's agriculture, transportation, energy generation, and biodiversity. The river's majestic presence and its influence on the landscape have shaped the lives of the people living in the region for centuries.

The Brahmaputra of Assam is undoubtedly one of the largest rivers, not only of India but of the world, that traverses a distance of about 2900 Sms. through Tibet (China), India and Bangladesh, draining an area of nearly 580,000 Sq.