Rainwater harvesting system to be introduced in building-bylaws

Islamabad : The Capital Development Authority (CDA) is pondering over a proposal to introduce a rainwater harvesting system in building bye-laws that would make it necessary to have a storage tank on the rooftop of every household in the capital city.

According to the proposal, the capacity of the water storage tank would be 200 gallons for 5-marla house; 400 gallons for 10-marla house; 600 gallons for 1-kanal house; and 800 gallons for 2-kanal house.

The proposal has been given in an interim report and it is likely to be discussed at the appropriate level with an aim to resolve the water shortage problem that hits the city especially in the summer season.

According to the draft proposal, the collected rainwater would be used for the purposes of showering, gardening, laundry and car washing. The size of storage tank has been proposed according to size of the rooftop and residential unit as well.

The proposal stated that the average monsoon rainfall In Islamabad is 780mm (0.78m) and average daily consumption of water per unit inclusive of everything is 80 gallons per day, which is 300 to 380 litres per day globally.

The proposal also underlined the need for four Cs strategy -- capturing run-off from rooftops; capturing run-off from local catchments, capturing seasonal floodwaters from local streams and conserving water through watershed management.

The groundwater level has been falling every year by one or two meters. The CDA installed first ever rain harvesting system at Faisal Mosque in 2010 that was aimed at recharging the local water table for the city’s over one million residents.

The rainwater harvesting system is being used as an alternative and supplementary source of water in many regions of the world and it holds considerable potential in Pakistan, especially in areas like Islamabad.

According to the experts, the rainwater can be stored in any commonly used water storage container such as RCC masonry, plastic or polyethylene and it can also be charged into the ground water aquifer through any suitable structure like dug well, percolation well, boreholes, recharge trenches and water ponds.