The correct answer is (a) Tamil Nadu.
Tamil Nadu was the first state in India to make roof water harvesting compulsory for all houses. The Tamil Nadu Rainwater Harvesting Act, 2001, was passed in order to conserve water and improve groundwater recharge. The Act requires all new buildings to have a rainwater harvesting system installed, and existing buildings to have one installed within five years.
The Act has been successful in increasing the amount of rainwater that is harvested in Tamil Nadu. In 2002, the state harvested an estimated 1.2 billion cubic meters of rainwater. By 2012, this had increased to 2.5 billion cubic meters.
The Act has also had a positive impact on groundwater recharge. In 2002, the average groundwater level in Tamil Nadu was 12 meters below the surface. By 2012, this had improved to 8 meters below the surface.
The Tamil Nadu Rainwater Harvesting Act is an example of a successful policy that has helped to conserve water and improve groundwater recharge. The Act has been replicated in other states in India, and it is an example of how policy can be used to address the challenges of water scarcity.
The other options are incorrect because they are not the first state in India to make roof water harvesting compulsory to all the houses.