This standard provides guidelines for the planning, design, and implementation of water harvesting systems. It outlines methods for both rooftop and surface runoff harvesting, criteria for assessing water availability, and technical considerations for storage structures, filtration, and water quality maintenance.
Provides guidelines for planning, design, and implementation of rainwater harvesting systems for various applications.
Quick Reference Values
Runoff coefficient for concrete/asphalt roof0.8 - 0.95
Runoff coefficient for paved areas0.7 - 0.85
Recommended first flush diversion for initial rainfall0.5 - 2 mm
Typical depth of sand filter bed0.6 m - 1.0 m
Minimum cleaning frequency for catchment areaPrior to each rainfall season
Key Formulas
V = A * R * C — Formula for calculating potential harvested water volume, where V is volume, A is catchment area, R is rainfall, and C is runoff coefficient.
Practical Notes
Always incorporate a 'first flush' diverter to prevent initial, more contaminated rainwater from entering the storage system.
The runoff coefficient is the most critical variable; select it carefully based on the actual surface material and slope as per Table 1 to avoid over- or under-sizing the system.
Ensure storage tanks are opaque or placed underground to prevent algae growth, and are fully sealed with mosquito-proof vents and overflows.