India is famous (and oftentimes infamous) for its monsoons. Given the scarcity of water resources in the country, harvesting rainwater gains great importance in increasing the water resources in the country. Rainwater Harvesting (or RWH) refers to collecting rainwater from rooftops and surfaces and directing them to either a reservoir (from where the water is used for domestic/agricultural/industrial purposes) or to a deep non-cemented pit that allows for groundwater to be recharged. In some parts, dew and fog are also collected using nets and other tools to collect water. In the Indian subcontinent, different forms of rainwater harvesting have existed across millennia. When contrasted, vernacular and modern forms of rainwater harvesting are best adopted collaboratively, based on the more suitable approach according to the geosocial features of the area.
Traditional/Vernacular Rainwater Harvesting Methods:
Found in the cities of Rajasthan, Bawaris essentially stepwells and created for community usage. They formed ancient networks of wells connected by surface and underground level canals. Since Rajasthan is mostly a desert region, these systems collect the sparse rain in the region and collect them in these human-made reservoirs. Bawaris are used both as reservoirs and recharge wells, which help regain water levels in the groundwater table and rejuvenate aquifers. The layered stone steps make the opening to the reservoir narrow and thus reduce loss of water through evaporation.
Also found in areas in and around Rajasthan, a Taanka is a cylindrical paved underground pit that collects rainwater from rooftops, courtyards and other catchment areas. These are used for individual families and can hold water for a whole season of summer.
Indeginious to southern parts of Bihar, Ahar Pynes are reservoirs with embankments on three sides built at corners of diversion channels of rivers in the areas. Pynes refer to artificial rivulets that are created to facilitate irrigation (most often paddy cultivation) and domestic usage during dry months of late winter and summer.
Small earthen check dams built on rivers and streams across the country are called Johads, or madakas (Kannada) and pemphara (Odia). With naturally high elevation on three sides, they conserve and recharge ground water and are usually interconnected with other johads through deep channels.
Khadins originated in 15th century Jaisalmer. These are embankments built across hillslopes in gravelly regions to collect rainwater from surface runoffs and are mainly used for agricultural purposes and water-saturated crop production.
A kund often looks like a Bawari and is also indegenous to desert regions of Rajasthan and Gujarat. Their differentiating characteristic is that they are more modern constructions, that use either lime and ash or, more recently, concrete to build the well-pits. The catchment areas provide water for communities and also work towards recharging the groundwater table.
In urban India, houses and housing development colonies are encouraged to build rooftop rainwater harvesting systems as either reservoirs for domestic water usage or to recharge the rapidly depleting ground water resources in metropolitan areas. This is becoming more important in urban spaces that are concretised without any provision for surface absorption of rainwater, which leads to portable water running off into drainage systems. In many Indian states, policy changes are mandating the use of rainwater harvesting systems; some of these are as follows:
The first Indian state to make RWH compulsory for every building in 2001, the scheme has been enforced in all rural areas as of 2020. The state has also created resources for awareness about harvesting rainwater and conserving water resources. Most significantly, the urban metropolis of Chennai has seen a 50% in the level of underground water reserves in 5 years and a positive change in the quality of groundwater.
In the state’s capital city, Bengaluru, building a RWH system is mandatory for all houses with over 60*40ft site area and all new constructions. To promote RWH and create awareness about water conservation, the Bangalore Water Supply and Sewerage Board has created the Sir MVisvesvaraya Rain Water Harvesting Theme Park showcasing 26 different types of RWH and conservation models.
In Pune city, rainwater harvesting is compulsory for any new housing society to be registered. On the other hand, rainwater harvesting is not mandated in the capital city of Mumbai, policy changes suited to the city’s dense population are being formulated