Gravitational distribution systems – cities traditionally supplied by gravity In which of the following cities is water distribution historically carried out predominantly by a gravitational system (i.e., high-level storages feeding zones by gravity)?

Introduction / Context:
Topography strongly influences the selection of distribution schemes in urban water supply. Upland sources allow storages at elevations that can feed consumers by gravity, which improves energy efficiency and reliability.

Given Data / Assumptions:

• Traditional, widely cited examples in Indian water-supply texts.
• Gravity distribution implies primary reliance on head available from source and service reservoirs, with limited pumping within zones.

Concept / Approach:
Hilly or coastal-upland cities with high-level sources or service reservoirs often employ gravity systems. Dehradun, located in the foothills, and Mumbai (Bombay), supplied from upland reservoirs, are classic examples. In contrast, Delhi and Kolkata rely extensively on river intakes and pumping to convey and distribute water across flat terrain.

Step-by-Step Solution:
Identify cities with natural elevation advantage → Dehradun and Mumbai.Recognize Delhi and Kolkata as predominantly pump-fed due to flat topography.Choose the combined option reflecting the gravity tradition in Dehradun and Mumbai.

Verification / Alternative check:
Classic design examples cite gravity-fed supplies from high-elevation lakes/reservoirs to Mumbai and hill-fed sources to Dehradun.

Why Other Options Are Wrong:

• Single-city answers omit the other well-known case.
• Delhi and Kolkata are largely pump-operated networks.

Common Pitfalls:
Equating gravity conveyance from source with gravity distribution everywhere; many systems use a mix of both, but the question targets the predominant historical approach.

Final Answer:
Both Dehradun and Bombay (Mumbai)