Step-by-step procedure to comply with the GRIHA criteria 17: Rainwater harvesting
To comply with GRIHA Criteria 17, which focuses on rainwater recharge and use, the following steps can be taken:
Step 1: Assess Rainwater Harvesting Potential
- Identify the total catchment area available for rainwater harvesting
- Calculate the potential amount of rainwater that can be harvested from the catchment area using the following formula: Harvested Water (kl) = Catchment Area (m2) x Annual Rainfall (mm) x Runoff Coefficient / 1000
- Runoff coefficient can be assumed as 0.75 for an average roof surface
Example Calculation: If the catchment area available for rainwater harvesting is 500 m2 and the annual rainfall in the region is 1000 mm, the potential amount of rainwater that can be harvested would be: Harvested Water (kl) = 500 x 1000 x 0.75 / 1000 = 375 kl/annum
Step 2: Implement Rainwater Harvesting Measures
- Install rainwater harvesting systems such as rooftop rainwater harvesting, surface runoff harvesting, or groundwater recharge structures
- Ensure that the harvested rainwater is properly filtered and stored in a separate tank for later use
- Consider using the harvested rainwater for non-potable applications such as toilet flushing, irrigation, and cooling tower makeup
Example Calculation: If a rooftop rainwater harvesting system is installed on a building with a catchment area of 500 m2, and the system is designed to harvest 80% of the rainfall, the total amount of rainwater that can be harvested would be: Harvested Water (kl) = 500 x 1000 x 0.75 x 0.8 / 1000 = 300 kl/annum
Step 3: Monitor and Report Rainwater Reuse
- Regularly monitor the amount of rainwater being harvested and used on-site
- Report the amount of rainwater being reused as a percentage of the total water demand of the building
Example Calculation: If the annual water demand of the building is 281852.11 kl and the total annual water recycle and reuse on site is 132486.53 kl, the percentage of on-site water reuse would be: On site water reused (%) = (Total annual water recycle and reuse / Annual Water Demand) x 100 = (132486.53 / 281852.11) x 100 = 47.01%
By implementing these steps, the building can comply with GRIHA Criterion 17 and promote sustainable water management practices.