(i) Western Rajasthan is a desert because it lies ‘ in the rain shadow area of the Aravalli Hills in the Bay of Bengal branch of the southwest monsoons coming from the east. These winds when strike the Garo Khasi Hills, are diverted west and northwest along the Ganga plain. As these winds advances, imparting rain, they become less humid and are dry when they reach the Indus Basin in the extreme northwest. (ii) The two Himalayan drainage systems of India are: 1. The Indus drainage system. 2. The Ganga drainage system.