Rainwater harvesting

Harnessing Rainwater for a resilient future

By: Staff Reporter
Rainwater harvesting is a scientific and controlled collection of rain for future use – identified as the most effective way to recharge groundwater. Despite its potential rainwater harvesting systems are still not thoroughly implemented in Indian cities.
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Overuse and exploitation of groundwater have played a major role in the dwindling water availability in urban India. According to the United Nations, India is utilising its groundwater faster than any other nation. The annual per capita water availability dropped from 1,816 cu m in 2001 to 1,545 cu m in 2011, a 15 per cent drop. It is further expected to drop to 1,341 cu m and 1,140 cu m by 2025 and 2050 respectively (MoWR, 2014). On the bright side, India is blessed with copious rain, receiving close to 1,083 mm of rainfall each monsoon season (IMD,  2016).

India’s Rainwater Potential

Collecting and conserving rainwater has been identified as the most effective method to harness freshwater. The process is quite simple. Rainwater is collected from roofs, roads, pathways and lawns before it is lost as surface runoff. Groundwater is also artificially recharged through this rainwater. The cost of installing a simple rainwater harvesting system is around INR 5,000 – 15,000 depending upon the roof area. It can however, increase up to INR 70,000 if a filtration sump is involved. For commercial structures, the cost can even go up to INR 5,00,000 (Singh, 2018)

It is but obvious, considering the spatial variability of the monsoon that the amount of rainfall will determine the amount of rain one can harness. For example, Delhi’s average rainfall stands at 550 mm (IMD, 2016). Considering a catchment area of 100 sq m, each building in Delhi can collect about 55,000 litres of water, out of which close to 49,500 litres can be used. The remaining 8,000 litres is lost as catchment run-off, through gutter drains. As per one estimate, close to 468 billion litres of rainwater can be conserved during the monsoon, in Delhi alone (Lalchandani, 2010). Similarly, Mumbai receives 2,186 mm of annual rainfall – so a 100 sq m catchment area can collect 218, 600 litres of water from which 196,700 litres can be harvested (Hasse, 1989). To reiterate how enormous the potential of rainwater harvesting (RWH) is, another study by the Government college of Engineering, Aurangabad, may be cited. Dividing the campus into two catchment areas through GIS mapping, each catchment was further segregated in to rooftop and open catchments. Interestingly, the potential of harvesting rainwater was close to a whopping 5.4 million litres each year over its 22,400 sq m area at a nominal investment of INR 5, 08, 700 (Keskar et al, 2016).

Rainwater Harvesting and Policies

Delhi was one of the earliest cities to propose RWH systems in gated neighbourhoods. In 2001, the erstwhile Ministry of Urban Affairs made RWH mandatory in all buildings having a roof area of more than 100 sq m and plot area of more than 1,000 sq m. Few colonies consequently strove to set up RWH systems. In January 2004, Nizamuddin East became the pioneering colony to install a RWH system, with a project conceptualised by the residents. Funds to the tune of INR 1.74 lakh was collected and 11 RWH pits were created in the parks of the colony. It presently collects close to 49 million litres each monsoon. Over the years, the colony has not only maintained the structures, but also ensured that the municipal corporation cooperate in helping to keep the three systems in good working condition. Other colonies and areas such as Panchsheel Enclave, Defence Colony and New Friend’s colony have also created effective RWH systems (CSE, 2016)

The Delhi Jal Board (DJB) has, to its credit, taken various steps to set up new RWH systems in different parts of the city. In 2016, the Indian Meteorological Department (IMD) predicted an ‘above normal’ monsoon, leading to proactive actions by the DJB with a view to tap the rainwater. It opened three ‘rain centres’ in RK Puram, Lajpat Nagar and Dwarka to provide information about simple, economic and efficient methods of rainwater harvesting (The Hindu, 2016).

However, the RWH systems in Delhi are beset with various problems. In 2015, for example, it was found that RWH pits in different parts of Delhi had been covered with concrete due to inter-departmental indifference (Sharma, 2016). Further, while the Ministry of Urban Development and Poverty Alleviation (MoUPA), had made rainwater harvesting mandatory in buildings with a roof area of more than 100 sq m mandatory as early as 2010 (CSE, 2010), the lack of penalty on defaulters prevented any effective implementation (Sharma, 2016). In November 2017, the National Green Tribunal (NGT) directed all private and government schools and colleges in Delhi to install RWH units within two months failing which a penalty of INR 5,00,000 was to be imposed (Ghosh, 2017). The institutions, however, failed to put RWH systems in place during the allotted time period, following which the NGT sent notices to the Public Works Department, Directorate of Education, Central Groundwater Authority and Delhi Jal Board, seeking their replies by March 20. No update on the status of RWH is in the public domain at present (PTI, 2018).

Rooftop rainwater harvesting system

On the other hand Chennai has had considerable success with its RWH laws, the reason being the willingness of the authorities to implement the 2002 law mandating RWH structure for every building. Following the enactment, the government in 2003 pursued a tight time line, imposing penalties on residents in order to ensure compliance. Failure to comply led to disconnection of water supply and even forceful installation, where charges were levied as property tax. The obligation compliance was limited not only to building owners, but was also extended to anyone who occupied the building, making it easier for building inspectors to find a responsible user as long as the building was in use (Vivek, 2016).

In a further development in 2005, the Jawaharlal Nehru National Urban Renewal Mission (JNNURM) was launched with a view to improve conditions of housing, sanitation and drinking water in over 60 Indian cities. JNNURM made amendments in building by-laws, making RWH mandatory in all mission cities. As of 2014, cities from 14 states and UTs – Chandigarh, Uttarakhand, Chhattisgarh, West Bengal, Maharashtra, Madhya Pradesh, Andhra Pradesh, Puducherry, Punjab, Karnataka, Odisha, Gujarat, Delhi and Mizoram, had amended their building bylaws to mandate RWH installation.

Consequently in 2012, the National Water Policy (NWP) recommended RWH systems as essential for access to a minimum quantity of potable water. The policy suggested that RWH systems should include scientific monitoring of parameters like hydrogeology, groundwater contamination, pollution and spring discharges. The importance of RWH systems was reiterated in the Draft National Water Framework Bill, 2016.

Endnote

Noting the significant divergence in the methods of implementation of RWH laws it becomes clear that its mere existence cannot ensure the much needed development of RWH systems.  Various cities, such as Ahmedabad, Bangalore, Kanpur, Indore, Mumbai etc. have bylaws or regulations mandating setup of RWH systems. The results, however, have been lackluster. Technology should be made easily accessible and citizens should cooperate with government agencies to build water resiliency in cities.

References

Center for Science and Environment (CSE), 2010. Legislation on Rainwater harvesting, April 5. Available at:  https://bit.ly/2yjsqzF

_________, 2016. Rainwater Harvesting at Nizamuddin (East), June 8.

Ghosh S., 2017. Install rainwater harvesting systems in two months, NGT tells Delhi schools, colleges, The Hindu, November 16.

Hasse R., 1989. Rainwater Reservoirs: Above ground structures for roof catchment. Most common rainwater tanks in comparison and construction manual,  GTZ. Available at https://bit.ly/2lgoaRb

Keskar A., Taji S, Ambhore R, Potdar S, Ikhar P, Regulwar D, 2016,  Rain water harvesting – A campus study, 3rd National Conference on Sustainable Water Resources Development and Management.(SWARDAM), 3, Available at: https://bit.ly/2lhJZX6

Lalchandani N., 2010, 468 billion litres rainwater wasted, Times of India, August 27.

Ministry of Water Resources (MoWR, 2017), Unstarred Question No. 103 answered on 02.02.2017, Available at: https://bit.ly/2lmKnE1

Press Trust of India (PTI), 2018. NGT issues notice to Delhi over rainwater harvesting, The Hindu, January 19.

Indian Meterological Department (IMD), 2016. Rainfall statistics of India 2016, Customized Rainfall Information System (CRIS), Available at  https://bit.ly/2t73cyh

Singh V, 2018, Water harvesting: The best way to end water shortages, Housing.com, April 16,  Available at: https://bit.ly/2ndq388

Sharma, 2016. Rainwater conservation takes priority in South Delhi, Hindustan Times, May 18.

The Hindu, 2016.  DJB opens three rains centers,  The Hindu, July 13.

Vivek, 2016.  Rainwater harvesting in Chennai: What made it work? IIM Kozhikode Society & Management Review, 5 (1): 91-106.

 

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