India has both tropical as well as subtropical climate. So according to the climatic conditions, different types of houses are made in different states of India. In some states, due to lot of rainfall and snow fall , houses have sloping roofs and in arid regions , houses with thick walls are made to protect people from extreme heat.

Based on the type of roofs, houses are divided into sloped roofs or flat roofs. Different types of materials are used for slanting roof houses. This varies from dry leaves, palm leaves or grass as in huts or clay tiles as in cottages or reinforced concrete as in modern villas.

In the semi arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi, and Barmer, almost all the houses traditionally had underground tanks or tankas for storing drinking water . The tanks could be as large as a big room. The tankas were part of roof top rainwater harvesting system and were built inside the main house or the courtyard. They were connected to the sloping roofs of the houses through a pipe. Rain falling on the roof tops travels down the pipe and was stored in these underground tankas. The first spell of rain was usually not collected as this would clean the roofs and pipes.

The rain water could be stored in tankas till the next rainfall making it an extremely reliable source of drinking water when all the other sources would dry up, particularly in summers. Rainwater, or palar pani ,as commonly referred to in these parts is considered the purest form of natural water. Many houses have underground rooms adjoining the tank to beat the summer heat as it would keep the room cool.

Tamil Nadu is the first state in India which has made roof top rainwater harvesting structure compulsory to all the houses across the state. There are legal provisions to punish the defaulters.

Roof top rainwater harvesting is the most common practice in Shillong, Meghalaya. It is interesting because Chirapunjee and Mawsynram situated at a distance of 55km. from Shillong receive the highest rainfall in the world, yet the state capital Shillong faces acute shortage of water. Nearly 15-25 per cent of the total water requirement of the household comes from roof top water harvesting

Green roof technology text and image :Kartik SMSMB India
Source: Science text book published by NCERT