“Water-Energy-Pollution” Nexus for the Energy and Pollution Footprints of Cities

The growing world population and global urbanisation trends have raised serious concerns over energy demand. These concerns have been exacerbated by the challenges of climate change and pollution, which fuel worry over availability of the basic necessities like clean water and food. Whilst several studies discuss the effects of pollution on these needs, adequate attention has not yet to be paid to the inter-linkages between the water, energy and pollution sectors.

This nearly unacknowledged relationship between water-energy-pollution was explored in our recent work at the University of Surrey (Kumar and Saroj, 2014). We explored the topic in relation to growing megacity Delhi in order to demonstrate the importance of this relationship, but the results could be applied to other growing cities elsewhere.


A simplified framework showing constituents of water–energy–pollution nexus.

Rapid urbanisation is and will be a hallmark of the 21st century, since a large part of world population is living in developing countries where urbanization is accelerating. This modern urbanisation leads to complex socio-economic and environmental issues, including a greater need for resources and services to satisfy increasing populations. While energy is one such need, its production and consumption is closely linked with key environmental challenges. These include water, which is a key material of thriving economic activities and good public health, and air pollution, which is important for a healthy life and can be affected by the burning of fossil fuels, for example.

Water is required in the operation of power plants and forms an important part of energy consumption activities. Therefore, the implications of energy consumption in modern society carry multidimensional facets. We argued in our work that there is a need for establishing a broader nexus, called “water–energy–pollution”, which takes into account the implications of energy production, related water consumption and environmental pollution (air and water) together. The notion of this integrated nexus can play an important role in systemic appraisal of energy production and consumption in growing urban environments.

We took Delhi to demonstrate the usefulness of this three-dimensional nexus. Delhi houses about 8% of the total population in the world’s megacities. The energy production and consumption activities have resulted in water resource depletion and contamination and high levels of air pollution.

In 2010, one of the main energy generation sources for New Delhi was a 735MW thermal power plant, which consumes nearly one and half million cubic meters of clean water every day; this is about 30% of New Delhi’s water supply capacity. Hence, clean water is crucial input to energy generation process, and the production of clean water from wastewater requires energy. Likewise, energy production by thermal power plants emits both health and climate emissions and so is the case of transport sector through combustion of a considerable amount of fuel (energy).

Our methodology of normalising emissions per unit energy and considering the energy implications of water consumption and treatment provides some interesting insights. For example, climate emissions per unit energy consumption from the transportation sector were found to be small in contrast to health emissions. On the other hand, the climate emissions dominate over health emissions when energy is generated by the power plants. As for water, energy consumption for water and wastewater treatment is small but seems to indicate that water consumption for energy production is much more critical. This means that controlling the energy consumption in the transportation sector or the water supply/replenishment is unlikely to bring notable benefits to climate emissions and total energy savings, respectively. However, energy savings by the transportation sector and power plants can bring substantial benefits by cutting health emissions and climate emissions by switching to cleaner fuels and better vehicle technology, and advanced technological measures for the carbon capture and storage, respectively. In summary, the energy required in cleaning the environment (air and water) is small in comparison to benefits it would bring in terms of sustainably running the urban system of energy production and consumption as a necessary component of social and economic development.

Use of an integrated approach make it possible to reach a balance so that we can keep producing or consuming required energy in urban systems, and also maintain the good air and water quality along by minimising emissions of air pollutants. This approach could allow the true impact assessment of energy production and consumption on environment and on the quality of life in future urban world.


Kumar, P., Saroj, D.P., 2014. Water-energy-pollution nexus for growing megacities. Urban Climate 10, 846-853. [Online link]

This post has been jointly written by written by Dr Prashant Kumar and Dr Devendra Saroj from the University of Surrey, UK.

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Prashant Kumar

About Prashant Kumar

Prashant is a Senior Lecturer at the University of Surrey. His team’s research is focused on atmospheric aerosol particles, urban air pollution and wind engineering. Till date, he has authored over 85 journal articles, and about the same number of conference papers, with in excess of 1100 citations. He is currently serving as an executive editor for the "Journal of Civil & Environmental Engineering", besides acting as an editorial board member of 7 International Journals including "Science of the Total Environment".

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