WORLD OF SCIENCE
Distributing water
DR. T. V. PADMA
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How did the people of the Indus manage to water their cities?
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In Indus cities, each house or group of houses had a private well, made with wedge-shaped bricks that slotted together in a cylindrical shape strong enough to withstand the weight of water when the well was full. This is not a simple matter, and required calculation — otherwise a well could collapse once it was full of water.
How did the Indus people keep wells and bathing facilities watertight? First, they used bricks that fitted together tightly. Second, they coated the outer layers of structures that needed to stay watertight with a substance called bitumen, which is nothing but natural tar.
Mohenjodaro's Great Bath is a pool 12 ft long and 23 ft wide. Its outer layers are made watertight with bitumen. Water from the bath emptied into a massive drain, which was engineered not to cave in when the pool was full.
Since smaller bathing facilities have been discovered nearby, archaeologists think the Great Bath was a special place with religious significance, not a public swimming pool. But they still aren't too sure how the Great Bath was filled with clean water.
Strategic location
Dholavira presented a special problem. Its dry climate was not ideal for agriculture, but its location, close to the sea, gave it a strategic trade advantage. So how did Dholavira's population get the water that they needed? Indus engineers came up with an interesting solution: they located the city on a slope between two storm water channels that accumulated water from the seasonal rains. They also constructed several cisterns, and carved reservoirs out of solid rock to store freshwater to support Dholavira's population.
At the coastal city of Lothal, archaeologists excavated a site that some think was an ancient dock. If so, it would mean that Indus people probably had a high level of knowledge about local tides and other aspects of near-shore geology.
Cities provide clues about the people who designed and lived in them.
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