[short_answer] Explain how the traditional 'tanka' system of rooftop rainwater harvesting works in the arid regions of Rajasthan. Why was it considered an effective solution to drinking water scarcity in that region?
Generated by claude-sonnet-4-6 · 2026-06-26 13:31 · grounding rag
Model Answer
In the arid regions of Rajasthan (Bikaner, Phalodi, Barmer), almost every house had an underground tank called a tanka built inside the main house or courtyard. The sloping rooftops were connected to the tanka through a pipe. Rainwater falling on the roof travelled down the pipe and was stored underground. The first spell of rain was not collected, as it cleaned the roofs and pipes; only subsequent showers were stored.
It was an effective solution because:
- Rainwater (palar pani) is considered the purest form of natural water.
- Water could be stored till the next rainfall, providing a reliable drinking water source when all other sources dried up in summer.
- The underground location kept the water cool and prevented evaporation.
Source: Water Resources, Chapter 3
---
Explanation
- The question is worth 3 marks, so examiners expect: (1) how the system works mechanically, (2) at least two reasons for its effectiveness.
- Key terms to use: tanka, palar pani, underground storage, sloping rooftop, pipe connection, first-spell discarding.
- Do not confuse tanka with khadins or johads — those are for agriculture, not drinking water.
- Mentioning the first spell of rain being discarded shows precise textbook knowledge and often fetches the extra mark.