Publication Name

Climate trends in the Ganges river basin

The Ganges river basin

Source: Gangotri Glacier, Uttarakhand, India

Mouth: Bay of Bengal

Length: 2,525 km

Area: 1,087,300 km 2 80

Countries: India (79%), Nepal (14%), Bangladesh (4%) and China (3%) 81

Main tributaries: Yamuna, Rama Ganges, Gomti, Ghagra, Sone, Gandak, Burhi Gandak, Koshi, Mahananda

The Ganges is one of the three main river basins in the Hindu Kush Himalayas. Its source is high in the Himalayan mountains where the Bhagirathi river flows out of the Gangotri Glacier in India’s Uttarakhand state. It takes the name Ganges farther downstream where the Bhagirathi and Alaknanda rivers join. As the Ganges flows out of the Himalayas it creates a narrow, rugged canyon. It then flows through the Indo-Gangetic plain, a vast fertile area that makes up most of the northern and eastern parts of India as well as parts of Pakistan, Nepal and Bangladesh. Part of the Ganges river is also diverted toward the Ganges Canal for irrigation in the state of Uttar Pradesh. In Bangladesh, the river’s main branch is known as the Padma, then downstream as the Meghna, before flowing into the Bay of Bengal and creating the world’s largest delta – the Ganges Delta – a vast and highly-fertile sediment-laden area.

Today, the Ganges river basin is the most populated river basin in the world with 400 million people. It has a population density of about 390 people per km 2 . Many Hindus visit the Ganges river in Varanasi, which is considered the holiest of cities. The city’s culture is also closely tied to the river, as the Ganges is the most sacred river in Hinduism. Climate trends Precipitation The Ganges basin receives nearly 1,000 mm of precipitation annually. The greatest amount of rain – 84% of the annual total – falls during the monsoon season. Of the remainder, 7% falls during the pre- monsoon season, 5% in the post-monsoon season, and 4% in winter. There are some differences in precipitation between the upper and lower Ganges basins. Although there is not much difference between the annual amount of precipitation in the lower and

upper parts of the basin, the number of rainy days varies considerably. In the upper basin, there are 179 rainy days, whereas in the lower basin there are 152 rainy days. The monsoon season accounts for 75% of the rain in the upper basin and 85% of the rain in the lower basin. For both the upper and lower basins, the number of rainy days is increasing, but the occurrence of rainfall greater than 10 mm/day is decreasing. The monsoon season shows a slight decreasing trend across the basin (although the trend is statistically insignificant, the amount may be significant). There is also an increasing trend in the duration of the monsoon season, with more dry spells within each season. During the winter season, there is an increasing trend in rainfall over most parts of the basin, and a decreasing trend in the central, southwest and extreme north of the basin.

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