Case Study - Ganges/Brahmaputra River Basin
Flooding is a significant problem in the Ganges/Brahmaputra river basin. They cause large scale problems in the low lying country of Bangladesh. There are both human and natural causes of flooding in this area.
Deforestation - Population increase in Nepal means there is a greater demand for food, fuel and building materials. As a result deforestation has increased significantly. This reduces interception and increases run-off. This leads to soil erosion. River channels fill with soil, the capacity of the River Ganges and Brahmaputra is reduced and flooding occurs.
Tectonic Activity - The Indian Plate is moving towards the Eurasian Plate. The land where they meet (Himalayas) is getting higher and steeper every year (fold mountains). As a result soil is becoming loose and is susceptible to erosion. This causes more soil and silt in rivers. This leads to flooding in Bangladesh.
The Ganga (Ganges) basin extends over more than 1 million km2 and encompasses parts of India (about 80% of the total basin area), Nepal, China and Bangladesh.
The length of the main channel is some 2,525km, while altitude ranges from 8,848m in the high Himalayas, to sea level in the coastal deltas of India and Bangladesh. The basin occupies a quarter of India’s land mass.
Although the river’s annual flow regime is subject to local variations, the predominant pattern is for a low-flow dry season from January to May and a wet season from July to November, with peak flows usually occurring in August.
The waters of the Ganga carry one of the highest sediment loads anywhere in the world, with a mean annual total of 1.6 billion tonnes, compared to 0.4 billion tonnes for the Amazon.
The Ganga basin is one of the most populous regions on Earth, home to 450 million people at an average density of over 550 individuals per square kilometre. In the delta zone this rises to over 900 per km2.
As a result, there is strong demand and competition for natural resources, especially water for domestic use and irrigation, and most of the basin tributaries are regulated by barrages. Fisheries along the river are of considerable economic value and their output makes a major contribution to regional nutritional needs.
There are some 30 cities, 70 towns, and thousands of villages along the banks of the Ganga. Nearly all of the sewage from these population centres – over 1.3 billion litres per day – passes directly into the river, along with thousands of animal carcasses, mainly cattle. Another 260 million litres of industrial wastewater, also largely untreated, are discharged by hundreds of factories, while other major
pollution inputs include runoff from the more than 6 million tonnes of chemical fertilizers and 9,000 tonnes of pesticides applied annually within the basin.
According to Hindu mythology, the Ganga River came down to Earth from the heavens. Today, the river symbolizes purification to millions of Hindus who believe that drinking or bathing in its waters will lead to moksha, or salvation. Many Hindus keep water from the Ganga in glass bottles as a sacred relic, or for use in religious ceremonies. The river becomes the final resting place for thousands of Hindus, whose cremated ashes or partially burnt corpses are placed in the river for spiritual rebirth.