The Brahmaputra in its Tibetan part has less silt despite a longer course primarily because the region is cold and dry, leading to smaller volumes of water and limited soil erosion. Tibet's cold and dry climate results in less rainfall and less soil erosion, hence less silt is carried by the river. Additionally, the Brahmaputra flows through rocky terrain with limited vegetation in Tibet, which also reduces soil erosion and silt production. In contrast, when the river enters India, it passes through regions with heavy rainfall and many tributaries from the Himalayas, which bring large amounts of silt into the river. In summary:
- Cold and dry climate in Tibet results in less rainfall and less soil erosion.
- River volume is smaller in Tibet with less sediment-laden water.
- Rocky terrain and limited vegetation reduce soil erosion.
- More silt is added downstream in India due to heavy rainfall and tributary contributions.
These factors combined explain why the Brahmaputra carries less silt in its Tibetan part despite having a longer river course there.
