India, June 9 -- A depleted Yamuna, close to a record low, has pushed two of the capital's largest treatment plants to reduce capacity, and led to scarcity of water supply to parts of north, central and west Delhi this summer.

Levels at the Wazirabad pond-the reservoir serving the Wazirabad and Chandrawal water treatment plants-dropped to 668.6 feet (above sea level) last week, about five feet below the 674.5-feet operational threshold.

The latest shortfall is the result of the summer heat, but Delhi has for long reeled under a chronic mismatch between the city's water supply infrastructure and its burgeoning demand.

The Delhi Jal Board (DJB) operates nine water treatment plants that draw raw water from three sources: the Yamuna, suppl...