To facilitate periodic cleaning of the drains
Explanation
The Indus Valley Civilization is characterized by its advanced urban planning, particularly its underground drainage system. This system connected individual households to main street drains, which were constructed with burnt bricks and covered with stone slabs.Analysis of the Function:
- To allow rainwater to enter the drains is incorrect: While the drainage system managed rainwater, the inspection holes were covered and not designed as open intake points. Water entered the system through specific chutes or pipes from houses and street gullies.
- To facilitate periodic cleaning of the drains is correct: The drains were provided with inspection holes (manholes) at regular intervals. These holes were covered with stone slabs that could be removed. Their primary function was to allow workers to access the drains for periodic cleaning and the removal of accumulated silt or debris to prevent blockages.
- To separate solid waste from liquid waste is incorrect: The separation of solid waste from liquid waste was achieved through cesspits or sumps located at the outlet of individual houses before the water entered the main street drain. The inspection holes were located on the main lines for maintenance purposes.
- To ensure proper air circulation in the drains is incorrect: While air circulation occurs in drainage systems, the structural design of removable stone slabs at intervals specifically points to physical access for maintenance rather than ventilation as the primary function.
Key Takeaway: The provision of inspection holes in the Harappan drainage system demonstrates the civilization's emphasis on hygiene and the existence of a municipal mechanism for regular maintenance.