Explain why the Harappans used a sophisticated drainage system in their cities?

To prevent flooding

As the Indus Valley was often subject to sudden and unpredictable floods, the Harappans built a well-thought-out drainage system. They devised a network of sloped canals and ditches to quickly drain excess rainwater and prevent their streets from turning into puddles. They even considered underground pipes made of fired bricks to better channel wastewater or rainwater away from residential areas. This sophisticated drainage effectively protected homes and infrastructure from damage and the flooding that was common in the region. In the end, thanks to these efforts, the Harappans could live peacefully without having to worry that each monsoon season would become a problem.

To ensure the hygiene and sanitation of cities

The Harappans had hygiene all figured out: they were already thinking about efficiently disposing of their waste to avoid diseases. Their drainage systems kept the streets clean by directing wastewater away from homes. Since their population was dense, stagnant waste could lead to epidemics. So, they created well-designed enclosed drains distributed throughout the city to prevent dirty water from accumulating. It worked even without modern technology: quite an achievement. Thanks to all this, their urban spaces were much more healthy, particularly because bad odors and insect proliferation were kept to a minimum. It was a smart way to maintain public health in large cities.

To promote the supply of drinking water

The Harappans understood well that to live comfortably in the city, it was essential to manage drinking water intelligently. They built a system of separate pipes, with those reserved for wastewater being distinctly separate from those carrying clean water. Their goal? To avoid any contamination, of course. These clay pipes transported clear water to wells that were accessible and convenient for daily use. By maintaining this effective separation, they could ensure their inhabitants had fresh water, abundant and always ready for use. Not bad for a civilization thousands of years old, right?

To facilitate organized urban expansion.

The sophisticated network of sewers and drains allowed Harappan cities to expand without becoming chaotic. By creating a pre-organized infrastructure, architects could plan entire neighborhoods where everything was standardized: the size of the streets, the placement of houses, and even the depth of the channels. This helped to avoid typical issues of rapid urban expansion, such as congestion or poor waste management. As a result, cities like Mohenjo-Daro often display a regular layout where everything seems well thought out, evidence of a clear and deliberate intention to control urban growth from the outset.

To meet cultural and religious requirements.

The Harappans had a very strong relationship with water, linked to religious beliefs centered on purity and purification rituals. Having a well-designed drainage system meant ensuring that water flowed properly, that the city remained clean, and symbolically "pure." Moreover, it is known that they built public baths, probably intended for specific religious rituals or cultural practices. This drainage system thus helped maintain the water in an appropriate state to fulfill these symbolic, cultural, and religious roles.