Decentralized Nature Based Solutions – A Pathway to SDG 6.4 Acute water stress in Urban India

Krishna Swaroop Konidena, Aditi Pandey & Bijoy Jose (CDD India)

By the year 2050, half of India’s population will be urban. If current trends with respect to water supply and usage continue, India could experience a drop of 6% in its GDP due to water scarcity alone. A WWF scenario analysis carried out in 2020 concluded that 30 Indian cities fall into the category of “grave water risk” by the year 2050¹. Going by the Composite Water Management Report, by Niti Aayog, 2019², most of urban India might face a similar predicament. This report estimated that, as of 2019, 600 million people in India faced high to extreme water stress, with demand likely to outstrip supply 2 times over by the year 2030. As most of us are aware, India has only 4% of global water resources³ for a population that accounts for 17% of the global population. And these water resources are rapidly shrinking. In the upcoming 20 years, an estimated 50% of all India’s aquifers will be at critical or over-exploited levels.

The Government is rapidly working towards a water secure future for the country – through the Jal Jeevan Mission, Smart City Mission and AMRUT Mission. An important policy measure among them is the direction for all AMRUT cities to reuse/recycle 20% of used water by the year 2026. Given that urban India only treats 28% of its sewage and the remaining is disposed unsafely into the environment, the target to reuse 20% of used water may appear a tall ask.

However, this is transformative in its potential – only if we learn from a decade’s experience of small-scale, decentralized wastewater treatment units in urban centers like Mumbai, Bengaluru, Delhi and the like.

Reuse of treated water and SDG 6.4

Reuse of treated wastewater directly impacts SDG 6.4. By reusing treated wastewater, sustainable withdrawals can be ensured thereby helping conserve freshwater resources. It is pertinent to note that in urban India, the physical losses related to water transmission and distribution are at least 20%⁴. By reusing 20% of wastewater by treating it, directly lessens the burden on the supply infrastructure which is already overstressed. This reduces long term investments in the supply and distribution of freshwater disproportionately. More importantly, 20% of treated wastewater can be easily reused, close to the point of generation, for two major purposes:

1) Flushing
2) Urban Greening/Landscaping

Flushing and Urban Greening requirements can account for anywhere between 20-40% of the water use requirements in residential areas depending on the population, income levels, climatic conditions etc.

Decentralisation lessons from the last decade

Wastewater reuse for urban greening or flushing is not a new idea. Recognising wastewater as a valuable resource, most of the metropolitan cities have adopted guidelines and helped implementation of decentralized small scale STPs in their respective cities. However, a majority of the treated wastewater is not being reused. Moreover, it is found that in most cases the STPs are performing inefficiently, unable to meet the mandated standards⁵. This happens due to two key:

1) Preferring systems which are low on capital expenditure to begin with but are eventually high on life cycle costs. Once developed these are handed over to residential associations for operation and maintenance. Owing to high maintenance costs of the same, the associations are usually not able to afford continuous upkeep and maintenance.

2) STPs are complicated to operate and maintain, especially by unskilled operators who are often at the helm of STP upkeep and maintenance.

Role of nature-based solutions & the way forward

The challenges are thus myriad and complex. The time is ripe to relook at solutions that utilize natural processes extensively and effectively, consider life cycle costs of infrastructural solutions and the circular nature of designs implemented. Today’s solutions must take into consideration not just accessibility of clean water for all but also design solutions that ensure clean air for all.

Nature-based solutions utilise different natural elements like microbes; gravity; sun light while being easy to operate and maintain. At the same time, they can be aesthetically pleasing – which helps create a sense of ownership among the community. These solutions consume less energy and are less resource intensive compared to traditional methods. Nature Based Solutions can enable life cycle cost savings to the tune of 70% when compared to conventional STP systems, as in the case of Aravind Eye Hospital, Pondicherry.⁶ Also, with limited but focused hybridization, aimed at tertiary treatment, Nature Based Solutions can also be deployed in space constrained, densely populated settings – like a public toilet in a Mumbai Slum.⁷ Thus, our inability to reuse treated wastewater effectively is not due to lack of technological solutions but due to a lack of awareness and accessible resources that can ease decision making for the communities. The following first principles can help enable various communities to choose the right solution for their decentralized wastewater treatment system:

Also Read | Localizing Joint Accountability Mechanism to Achieve SDG 6.4

  • Adopting life cycle approach to ensure long term cost recovery.
  • Choosing systems that are easier to operate and maintain with optimal automation, considering that it is difficult to find and train skilled operators on a continuous basis
  • Choosing modular designs that provide the users with flexibility, scalability and eventually cost effectiveness.
  • Making Nature-Based Solutions the preferred choice, given that they also help mitigate climate change.
  • Incentivising the owners for adopting, implementing and maintaining sustainable decentralised systems through reduced water tariffs, property taxes.
  • Making design and development of decentralized wastewater treatment systems and reuse planning fundamental to city planning departments of each city. A classic example is the Slum Rehabilitation Authority (SRA), Mumbai having undertaken the same approach. This ensures that the poor and vulnerable can also aspire to water security, improving their quality of life.

Views expressed by Krishna Swaroop Konidena, Aditi Pandey & Bijoy Jose (CDD India)


1. https://www.wwfindia.org/?19602/Cities-across-the-globe-face-an-alarming-rise-in-water-risks
2. https://www.niti.gov.in/sites/default/files/2019 06/Final%20Report%20of%20the%20Research%20Study%20on%20%20Composite%20 Water%20Resources%20Management%20Index%20for%20Indian%20States%20conducted%20by%20Dalberg%20Global%20 Development%20Advisors%20Pvt.%20Ltd_New%20Delhi.pdf
3. Water security must be enhanced in India, The Statesman,25th October 2022
4. “The Challenge of Reducing Non-Revenue Water in Developing Countries,” The World Bank, dated December 2006
5. https://bengaluru.citizenmatters.in/bengaluru-apartments-stp-sewage-treatment-8888
6. https://www.researchgate.net/publication/344326092_Decentralized_Wastewater_and_Fecal_Sludge_Management_Case_Studies_from_ India_Decentralized_Wastewater_and_Fecal_Sludge_Management_Case_Studies_from_India
7. https://www.adgully.com/hul-launches-its-6th-suvidha-centre-in-partnership-with-bmc-hsbc-india-109082.html