How did a stepwell store rainwater during the monsoon season?

During the monsoon season, a stepwell functioned as a large cistern to preserve water. The structure was designed with a wide, stone-lined, sloping excavation that allowed it to collect and store rainwater as it fell.

As the water level rose, the trench would fill to capacity, often submerging the stairs—which were used to access the water during dry periods—sometimes up to the surface of the land. This ingenious system allowed the structure to serve as a vital reservoir, ensuring a water supply in regions with a monsoonal climate where rainfall is concentrated into a few weeks of the year.1