In social and economic terms, the Indo-Gangetic Plain is the most important region of India. The plain is a great alluvial crescent stretching from the Indus River system in Pakistan to the Punjab Plain (in both Pakistan and India) and the Haryana Plain to the delta of the Ganga (or Ganges) in Bangladesh (where it is called the Padma). Topographically the plain is homogeneous, with only floodplain bluffs and other related features of river erosion and changes in river channels forming important natural features.
Two narrow terrain belts, collectively known as the Terai, constitute the northern boundary of the Indo-Gangetic Plain. Where the foothills of the Himalayas encounter the plain, small hills known locally as ghar (meaning house in Hindi) have been formed by coarse sands and pebbles deposited by mountain streams. Groundwater from these areas flows on the surface where the plains begin and converts large areas along the rivers into swamps. The southern boundary of the plain begins along the edge of the Great Indian Desert in the state of Rajasthan and continues east along the base of the hills of the Central Highlands to the Bay of Bengal (see fig. 1). The hills, varying in elevation from 300 to 1,200 meters, lie on a general east-west axis. The Central Highlands are divided into northern and southern parts. The northern part is centered on the Aravalli Range of eastern Rajasthan. In the northern part of the state of Madhya Pradesh, the Malwa Plateau comprises the southern part of the Central Highlands and merges with the Vindhya Range to the south. The main rivers that flow through the southern part of the plain–the Narmada, the Tapti, and the Mahanadi–delineate North India from South India (see Rivers, this ch.).
Some geographers subdivide the Indo-Gangetic Plain into three parts: the Indus Valley (mostly in Pakistan), the Punjab (divided between India and Pakistan) and Haryana plains, and the middle and lower Ganga. These regional distinctions are based primarily on the availability of water. By another definition, the Indo-Gangetic Plain is divided into two drainage basins by the Delhi Ridge; the western part consists of the Punjab Plain and the Haryana Plain, and the eastern part consists of the Ganga-Brahmaputra drainage systems. This divide is only 300 meters above sea level, contributing to the perception that the Indo-Gangetic Plain appears to be continuous between the two drainage basins. The Punjab Plain is centered in the land between five rivers: the Jhelum, the Chenab, the Ravi, the Beas, and the Sutlej. (The name Punjab comes from the Sanskrit pancha ab , meaning five waters or rivers.)
Both the Punjab and Haryana plains are irrigated with water from the Ravi, Beas, and Sutlej rivers. The irrigation projects emanating from these rivers have led to a decrease in the flow of water reaching the lower drainage areas in the state of Punjab in India and the Indus Valley in Pakistan. The benefits that increased irrigation has brought to farmers in the state of Haryana are controversial in light of the effects that irrigation has had on agricultural life in the Punjab areas of both India and Pakistan.
The middle Ganga extends from the Yamuna River in the west to the state of West Bengal in the east. The lower Ganga and the Assam Valley are more lush and verdant than the middle Ganga. The lower Ganga is centered in West Bengal from which it flows into Bangladesh and, after joining the Jamuna (as the lower reaches of the Brahmaputra are known in Bangladesh), forms the delta of the Ganga. The Brahmaputra (meaning son of Brahma) rises in Tibet (China’s Xizang Autonomous Region) as the Yarlung Zangbo River, flows through Arunachal Pradesh and Assam, and then crosses into Bangladesh. Average annual rainfall increases moving west to east from approximately 600 millimeters in the Punjab Plain to 1,500 millimeters around the lower Ganga and Brahmaputra. Indo-Gangetic Plain Page. LOC data