Roofs, rain and life: How to incentivize and implement rainwater harvesting

Co-author: Carmen Anthonj , Assistant Professor GeoHealth, Geo-Information Science and Earth Observation (ITC) of the University of Twente

While rainwater harvesting can result in numerous benefits for consumers and the water sector overall (read our previous blog here), it’s not always clear how to effectively promote and increase the prevalence of this practice. 

RWH systems can be built relatively easily with local skills and resources, using simple and easy-to-maintain technologies that are inexpensive once installed. RWH systems can be modular in nature by allowing expansion, reconfiguration or relocation, and can easily be retrofitted to an existing structure or built during new construction.  However, despite the many benefits, households often find it difficult to implement rainwater harvesting.  The initial installation cost of RWH systems on residential housing is relatively high and a common barrier to adoptionⁱ. Moreover, while there are legal, social and environmental barriers as well, recent experiences have documented means of overcoming those barriers and reinforcing water management practicesⁱⁱ.  

There are many ways to encourage rainwater harvesting and improve its implementation, within which governments can play a strong role. The use of government subsidies as incentives can encourage the installation of RWH systems and increase the number of users, particularly among poorer households. The regulatory frameworks are essential for the effective design of these incentives, like in Brazil. In Germany, the promotion (by grants and subsidies) of RWH at the local government level resulted in equipping almost one third of new buildings built with rainwater collection systems. The Government of Indiaⁱⁱⁱ, for example, provides financial assistance for the installation of RWH systems. The Surat Municipal Corporation has made RWH mandatory for new buildings with a plot size of >4,000 m² and provides up to a 50% (up to Rs. 2,000) subsidy to citizens to encourage rainwater recharging. In Gwalior and Jabalpur, a 6% rebate in property tax in the year of completion of RWH construction is provided to the building owner as an incentive (CSE, 2019).  

Promoting rainwater use through housing regulations that stipulate that all newly built buildings and structures must include rainwater roof catchments is common in Taiwan, Texas and Brazil. Although laws and other governmental policies are the key driver for the implementation of RWH, overall, robust policies to systematically promote the installation of RHW are often lacking or scattered. In Brazil for example, RWH is barely covered in legislation at the federal level, but more common at the local level. In absence of a national policy regulating RWH, some state laws and mainly municipal regulations have taken the task of covering this legislative gap, as local authorities may be more aware of specific problems for the region and thus implement specific legislation for the municipality. Large numbers of different laws and regulations at different scales complicate the process of implementation. Besides, the scattered legislation does not cover all aspects of RWH: the main goal of regulations is usually encouraging the installation of RWH systems, but incentives for the implementation are rare, and no legislation exists that addresses treatment to improve the quality of rainwater (da Costa Pacheco et al., 2017). Besides, coordination between state and non-state stakeholders in RWH, and residents lacking awareness or knowledge of policies, are common challenges (Bui Thi Thuy et al., 2019; Matto & Jainer, 2019). 

A Prospective Vision for RWH 

The strategic management of rainwater can reduce disaster risk for communities faced with water scarcity, droughts or flood risks. Access to clean water is essential during the pandemic for handwashing, hygiene and preventing the spread of COVID-19. The scalability of RWH must ensure that water is provided and available when needed free of contamination, and as a resilience option in remote rural areas that are hit hard by climate change and rainfall variability. All the efforts to bring these solutions to increase water availability must carefully consider cost-effectiveness and co-benefits for small-scale irrigation and other productive uses of water. Integrated research that involves geospatial analysis and remote sensing can provide the evidence to demonstrate a stronger case to expand RWH globally, and improve their operational, financial and environmental sustainability.    

ⁱ _{The payback time could take years, and such a cost-benefit trade-off makes the installation of RWH systems uneconomical for households in view of its low return of investment (Lee et al., 2016). Installing RWH systems is not attractive to marginalized households, or those who do not own the land they reside on such as leaseholders and occupants of ‘disputed land’ (Staddon et al., 2018).}

ⁱⁱ _{Another reason for low adoption of RWH is that water quality can be compromised if not properly managed. Rooftop catchments are usually contaminated with dust, dirt, leaves, bird droppings or dead animals, all of which can jeopardize the quality of rainwater. The material used for tanks can also affect microbial quality of the water. Storage tanks for rainwater can develop a sludge layer that attracts mosquitoes and insects. Bacteria and other contaminants can be removed with debris screens and filters, and with first-flush diversion, and stored was can be filtered and disinfected, but these measures are often not used (Bui Thi Thuy et al., 2019; Campisano et al., 2017). In order to properly design RWH systems, an understanding of rainfall patterns and other technical parameters is required, but these are often lacking. If any such parameters are overlooked, RWH systems may be ineffective, or insufficient to hold reliable supply (Bui Thi Thuy et al., 2019; Lee et al., 2016).}  

ⁱⁱⁱ _{In India, the Central Ground Water Authority has directed group housing societies (low-cost mass housing schemes for groups acquiring land together), institutions, schools, hotels, industrial establishments and farm houses outside of New Delhi, where ground water levels are more than 8 meters below the ground surface, to adopt RWH systems on their premises. The Ministry of Urban Development and Poverty Alleviation has made RWH in all new buildings on plots of 100 m² or larger in New Dehli mandatory. Building plans are not sanctioned unless such provision is provided. Moreover, buildings with plots of 200 m² or larger extracting groundwater through tube wells or boreholes need to implement RWH (CSE, 2019).} 

Related: 

• Roofs, rain and life: Rainwater harvesting for safe water supply and sustainable co-benefits
• Utilities of the Future: How to build universal and resilient water supply and sanitation systems