Namma Metro - the biggest clean roof of Bangalore to Harvest Rainwater

Namma Metro - the biggest clean roof of Bangalore to Harvest Rainwater

Namma Metro has a potential to harvest around 300 Million Liter RAINWATER every year

Metro rail infrastructure in Bangalore has created rapid mass transport and also created one of the largest roofs in public space.

 As the metro rail viaducts are elevated and are not in reach of public or other animals, the surface is relatively clean. Also the trains are electric and will have no diesel or oil spills. The passenger cars are air-conditioned with fixed windows, which will prevent littering. This logically bring in the idea of harvesting rainwater from the largest roof of Bangalore - around 4,60, 000 sq. m.

Bangalore Metro Rail Corporation (BMRC) is one of the urban utilities to have adopted rainwater harvesting in a massive and practical way. The Metro has made simple arrangements to catch all the rainwater that falls on its station areas and use the same for non-potable uses.

 The metro Reach 1 to Reach 4 has 44 stations and 33 of them are over ground. The roof are available in these infrastructures can be of two types.

1.  Viaduct with 8.8 meter and

2.  Roof of the station above ground

The stations form a roof area at high density traffic flow and commercial activities.

The Viaduct run all along the motor roads and is elevated.

Every raindrop that falls on Bangalore roads will only go down the drain. But every drop that falls on the Metro corridor can be harvested. Each of the six stations on the Metro's operational stretch between MG Road and Byappanahalli have water tanks of one lakh liter capacity each, to store rainwater.

The rainwater from the viaduct flows in the direction of the natural gradient as of the ground / road below. The flow of this water on the top of the viaduct is directed to the centre and finally reaches the grating at the centre of the pillar.

It is proposed to harvest roof top rainwater from Stations and Viaduct. The roof top rainwater from stations is a high volume flow at a busy junction and it is proposed to channelize this water through underground pipes either under the road / foot path on inside storm water drain sidewalk. The rainwater pipes through this underground system is discharged into a system of first flush lock and filtration system underground at a nearest open space / park / playground / parking area. The filtered rainwater is temporarily stored in an underground sump. The stored water will be pumped up and taken for final processing. Similarly the water collected from the stockyards and rising range of the station is also tapped / harvested.

The stored rainwater can be treated at storing or treated on line while pumping. The rainwater being pure form of water does not have salt and minerals or chemicals which are undesirable. Treating filtered rainwater is only by chlorination to remove bacterial contamination.

The rainwater flowing on the viaduct can be handled in two ways:

1.      Collecting the discharge from pillars at ground level and laying a trunk line along the viaduct next to the pillar under the road following the centre of the gradient. This trunk line leads water to a central location at a park.

2.      Collect rainwater directly below the grading at the top of the pillars and run a trunk line in the hollow portion of the viaduct. The pipe will follow the contour and gradient of the viaduct.

The trunk line at a suitable point can be drawn out at an intersection at the top of the pillar and below the Viaduct separate intersections.

Highlights of Rainwater Harvesting @ Namma Metro:

	Metro Rail
	Total length	42300	m.
	E-W Corridor (Phase-1)	18100	m.
	N-S Corridor (Phase-2)	24200	m.
	Width of segments	12	m.
	Below ground length	8822	m.
	Above ground length	33478	m.
	Number of Stations	41	No.
	Stations above Ground	32	No.
	Each Station Roof Area	4925	Sq. m.
	Roof Area-Biyappanahalli Depot	48552	Sq. m.

The above proposal is only the suggestion from KSCST, IISc, Bangalore.