The city was built in a semi-arid region averaging 260 mm rainfall annually. There were no perennial water sources. Subterranean water was saline, potable water scarce. How did Dholavira manage?

Two storm water channels, Manhar (north) and Mansar (south) flanked the city. The city was laid out on a 13 m gradient (higher in the east to lower in the west), ideal for reservoirs. It seems the planners knew this. They made a series of 16 reservoirs between the inner and outer walls of the city to collect the monsoon runoff from the channels, which amounted to 250,000 cu.rr. of water.

Inside the citadel (inner city), there are large storm drains with apertures. These were not for wastewater, as archaeologists first thought, since they were not connected to housing or bathing platforms. These were for rainwater. The air-apertures ensured easy passage of rainwater.