Originating in the Himalayan mountain complex, there are three distinct drainage systems of the Indian Subcontinent: the Indus River Basin, the Ganges River Basin, and the Brahmaputra River Basin.

Indus River Basin:
The Indus River is one of the longest rivers in Asia, originating in the Tibetan plateau and flowing through the Himalayas before entering Pakistan. The basin covers an area of around 1,165,000 square kilometers and includes parts of Tibet, India, Afghanistan, and Pakistan. The Indus River Basin is important for agriculture and supports the livelihoods of millions of people in the region.

Ganges River Basin:
The Ganges River is the most sacred river in India and is considered a goddess in Hinduism. The river originates in the Himalayas and flows through India and Bangladesh before emptying into the Bay of Bengal. The Ganges River Basin covers an area of around 1,080,000 square kilometers and is home to over 400 million people. The basin is important for agriculture, industry, and tourism.

Brahmaputra River Basin:
The Brahmaputra River is one of the major rivers of Asia, originating in Tibet and flowing through China, India, and Bangladesh before emptying into the Bay of Bengal. The Brahmaputra River Basin covers an area of around 580,000 square kilometers and is home to over 130 million people. The basin is important for agriculture, fisheries, and transportation.

In conclusion, the Himalayan mountain complex gives rise to three major river systems in the Indian Subcontinent: the Indus River Basin, the Ganges River Basin, and the Brahmaputra River Basin. These river basins play a vital role in the economy and livelihoods of millions of people in the region.