"We direct the Delhi government, all public authorities and the Government of India to ensure that rainwater harvesting systems are installed in every project without default. Each department as well as the corporation would notify an officer who shall be responsible for ensuring that the already installed rainwater harvesting systems and/or that are installed in future, work efficiently and are maintained properly," the order stated. There are about 35 flyovers in Delhi with rain harvesting structures but many don't function, say activists.

NGT further directed that every government department and municipal corporations notify an officer who shall be responsible for ensuring that the already-installed rainwater harvesting systems and those that will be installed "work efficiently and are maintained properly". The bench also directed that the name and phone number of the officer be publicized on respective department websites.

"A quarterly report shall be submitted to a committee which will be constituted by the chief secretary and the ministry of environment, forest and climate change. The committee shall perform all supervisory functions," the order stated.

"We asked the tribunal to consider the fact that rainwater harvesting systems cannot be installed on every flyover," said Narender Pal Singh, a lawyer representing Delhi government.

Every project except those located in areas where the water table is relatively high will have to follow this order. The committee will have to "personally certify" wherever groundwater level is high and where a rainwater harvesting system may not be required. "The report on the construction of rainwater harvesting systems on flyovers would be submitted within one month from today," the order added.