Four years ago, the IITM campus decided to extend their 2 month summer vacation to 4 months. Why? Not enough drinking water for the hostels. There are 12 hostels with an average of 250+ students in each hostel for a period of 9 months of the calendar year. At a minimum of 45 litres per day per student, that works out to 135,000 litres per day. This demand was met by each hostel buying 2 water tankers everyday at about Rs 1,000 per tanker.
The monsoon and non-monsoon rain in Chennai during 2001 and 2004 was close to the average of 51" per year. But the rains of 2002 and 2003 failed completely.
The technique of rain water harvesting is now installed in each hostel. The collected roof rain water is piped into a nearby well. There are 4 large agricultural type wells (about 40 feet in diameter and 40 feet deep). These wells allow water to be collected as well as recharge the underground.
I wish to thank Prof. R. Dhamodharan, Prof. M. P. Maiya and Dr. Sekhar Raghavan (of Rain Centre)for their initial guidance and continued committment. The first pilot projects for Narmada and Tapti hostels were partially funded by IITM alumni. On successful completion of these 2 projects, IITM extended the RWH techniques to the remaining 10 hostels. The leadership and support provided by our Director and the Institute was vital in extending the program to all the hostels.
I visited the campus and the hostel sector on Jan 2, 2005. As of January 2005, 2 months after the monsoon rain in October, the 4 wells are still full of water. The well water (collected Rainwater) is filtered through a 4 stage filter and the resulting water is purer than 'aqua fina' by Pepsi immediately after the rain upto about few days. But after the contact with the well surface consisting of inorganic substances, it slowly turns salty due to dissolution of inorganic salts from the rocks.
[Note: Hostels in IIT Madras campus are named after India's rivers]
"At present the rain water is used to augment the corporation water supply in Alakananda, Jamuna, Ganga and Mandakini - all from Alakananda well; The water from Saraswathi well is used for Krishna, Cauvery and for all of the drinking water supply to the hostels using the modified RO plant located near Tapti. The Brahmaputra well is full and this water is the reserve water that will help us to produce drinking water during summer".
"It cannot be denied that RWH has gone a long way in enriching the ground water reserves in the hostel sector and is readily available for us to draw on demand." ..Prof Dhamodharan.
By the month of May, the hostels may be forced to purchase outside water from tankers. If this takes place, rain water harvesting would have supplied 6 MONTHS of water demand in the hostel sector. We can work further to make the supplies last a whole year.
The Cost of the RWH installation
The pilot project at the first hostel (Tapti) cost about Rs 80,000. There were 3 key elements to this cost.
1. There were drain pipes bringing the water from the roof and
letting it run off. Now we closed these pipes at the ground level
and connected them to a common collection point.
2. From the common collection point, we installed a 6" dia
pipe underground to the large well.
3. We cleaned the inside of the well.
Background on the campus
IIT Madras is located on Sardar Patel Road and is flanked by Adyar, and the Taramani and Velachery villages. The campus is close to the Rajbhavan. The 640 acres of land which form the campus were once part of the Rajbhavan and were later donated to the Institute.
The hostel zone
Way in the south section of the campus, about 2 miles from the main road, the hostel zone consists of about 12 hostels, all named after rivers, starting with Kaveri and Krishna. Each hostel when first built had about 250 rooms and 1 student per room. In order to accommodate more IIT graduates, additional rooms have been built. In some cases, each room may also accommodate two students each. The total number of students per hostel is around 300 and over. If you extend this level of occupancy over 12 hostels, the total population in this hostel zone is around 3,600, making the hostel sector the single largest population within the campus.
Rainfall in Chennai
Chennai gets most of its annual rain from the North East monsoon in the months of October, November and December. The annual average rainfall in Chennai is around 51". Of this total, October gets 11.1", November gets 14.8" and December gets 5.5" for a 3 month total of 31.4". But these are averages. The monsoon rain in 2001 and 2004 were almost around the average figures. In 2003, it rained heavily for 2 days in October as part of the monsoon and it failed.
Often, we are surprised by heavy down pours in the month of May with an average of 1.5" of rain. Besides the NE monsoon, every time there is a severe depression in the Bay of Bengal, Chennai gets ready to receive some rain. Even catastrophic cyclones are welcomed in Chennai since they bring rain. Often these cyclones come via Chennai and land in Andhra Pradesh. See picture 6 on the right panel.
Typical Urban RWH technique
The most common and easy means of capturing rainwater in a crowded
city like Chennai is Roof water harvesting. The picture above shows
how it is done in a residential home. At the IITM project, the water
falling on the roof of the hostel building was collected. Instead of the
sump (item 5 in the drawing), a large agricultural well - 40 feet in diameter
and about 40 feet deep was used. See pictures 2 and 3 on the right panel.
RWH installation for a single dwelling house in Chennai costs around Rs 5,000 (mostly the cost of the PVC pipe). For a flat complex with about 25 tenants, the cost will be around Rs 50,000 to Rs 70,000.
More information links
Indian Institute of Technology, Madras
Adyar, Chennai 600 036
Prof. Dhamodharan [damo@iitm.ac.in]
Rain Centre in Chennai
No 4, Third Trust Link Street,
Mandavallipakkam, Chennai 600 028.
Tel: (011) 2461-6134
Sekar Raghavan [sekar1479@yahoo.co.in]
Center for Science and Environment
41, Tughlakabad Institutional Area,
New Delhi. India - 110062
Tel: +91-11 29955124; 29956110; 29956394
Fax: +91-11 29955879
Sumita Dasgupta [sumita@cseindia.org]
State Government of Tamil Nadu - TWAD Board
Tamilnadu Water Supply and Drainage Board
31, Kamarajar Salai,
Chennai - 600 005
Phone : 8530420-30, Ext. : 406
