Formula & Calculation Methodology
Harvestable Water (Litres) = Area (sq m) * Rainfall (mm) * Runoff Coefficient (0.80 - 0.90).
Step-by-Step Worked Example
Terrace: 1,200 sq ft (~111.5 sq m), Rainfall: 950 mm, Concrete Roof (0.80)
- Total Harvest: 111.5 * 950 * 0.80 = 84,740 Litres / year
- Recommended Storage Sump (20%): ~16,948 Litres
Result: Annual Yield: 84,740 Litres (~85 Water Tankers Saved)
Frequently Asked Questions
Is rainwater harvesting mandatory in Indian cities?
Yes, most municipal corporations mandate RWH for plot sizes above 100 to 300 sq metres.
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