Why was the city's water system so important, and so remarkable?

In the Rann of Kutch, in Gujarat, lie the remains of one of the great cities of the Harappan civilisation. Dholavira was lived in for about 1,500 years, from around 3000 BCE, and it is one of the very few well-preserved towns in South Asia from that distant age. Of the more than 1,000 Harappan sites found so far, it is the sixth largest. In July 2021 it became India's 40th World Heritage Site.

The city was carefully planned. A walled city stood beside a cemetery to its west. Inside the walls were a fortified castle with a ceremonial ground beside it, a fortified middle town and a lower town, the areas perhaps set apart for people of different occupations. Unlike most Harappan towns, which were built near rivers, Dholavira stood on the island of Khadir, close to sources of copper, shell, semi-precious stones and other raw materials, and well placed for trade that reached as far as Oman and Mesopotamia.

Its most remarkable feature is the way it saved water in a dry land. The people collected water from seasonal streams, from the little rain that fell and from the ground, and stored it in large reservoirs cut into the stone along the city's eastern and southern walls. They also dug wells into the rock, among the oldest examples known; the most impressive is in the citadel. This system is counted among the most efficient of the ancient world, and it was built, like much of the city, of stone.