July 25: The Guwahati Metropolitan Development Authority (GMDA) is trying to make rainwater harvesting mandatory in its new building bylaws for the city, a source said.

“The new building bylaws are in process and will take at least a couple of months to draft. In general, there will be some tough provisions “ the source said.

Rainwater harvesting is a technique for collection and storage of rainwater before it is lost as surface runoff. The idea is to cope with the problem of diminishing groundwater levels and promoting conservation of water.

GMDA CEO M. Angamuthu said awareness drives would be conducted to educate people on the importance of rainwater harvesting.

“Some cities have already made it mandatory to incorporate rainwater harvesting in the building bylaws,” he said.

In fact, the Planning Commission constituted working group on Environmental Sustainability of Indian Cities for the formulation of the Twelfth Five Year Plan has recommended making rainwater harvesting mandatory.

“Cities should be encouraged (or it should be mandatory) to get a part of the water supply from rainwater harvesting systems. Low-lying areas, river flood plains and lakes may be identified and reserved for storing rainwater for better environmental conditions. A system of ground water table monitoring wells may be developed at the ward-level to be used for assessing efficiency of rainwater harvesting measures and also warning against excessive exploitation of ground water,” the report said.

The Centre of Excellence for Integrated Land use Planning and Water Resource Management at the civil engineering department of IIT Guwahati in its report on roof-top rainwater harvesting systems said stress on land and water resources is gradually increasing because of rapid urbanisation and consequently, many of its adverse effects have been surfacing in recent times.

“Frequent occurrence of floods is one of the major problems in urban centres endowed with heavy rainfall such as Guwahati and the nuisance it creates has been very much evident. However, in winters, these urban centres face acute shortage of water. In such a scenario, implementing roof-top rainwater harvesting systems in urban households can be a smart option,” it said.

It said the advantage of adopting a rainwater harvesting system is manifold because it reduces the runoff volume and the peak flow, and, hence, mitigates floods and recharges the ground water, which is a solution to water shortage problem in winters.

The centre had conducted a study on a pilot watershed in the Hatigarh Chariali area in order to design a rainwater-harvesting system.

A socio-economic survey of the pilot watershed indicated that most of the households were interested in implementing the rainwater-harvesting scheme, though their response regarding investment patterns was varied.

Sources said the Chennai Municipal Corporation had made rainwater-harvesting structures mandatory for issue of building permissions for all new buildings irrespective of size.