Net zero water: The why, what, and how | The Financial Express

Net zero water: The why, what, and how

While the Earth’s capability of recycling water is remarkable, the challenge is to maintain the quality of water that is being recycled.

net zero water, water level, water recycle, water scarcity, underground water, joshimath water crisis
The total amount of water on Earth has been constant for a fairly long time, at least since the time of dinosaurs – thanks to our planet’s incredible water cycle.

By Dr. Prashanth Suresh Kumar

Water scarcity is a rising concern globally; but wait, how is global water shortage even a possibility? Is our planet running out of water? Scientists are divided regarding the exact origin of Earth’s water. Did the Earth start as a dry planet and gain its water over millions of years through water-bearing asteroids and comets, or did Earth already have the water from the nebular gas that aided in the formation of the solar system? 

Regardless of which theory you choose, the total amount of water on Earth has been constant for a fairly long time, at least since the time of dinosaurs – thanks to our planet’s incredible water cycle. Every year, a significant amount of water evaporates from the earth’s surface, but the same amount returns in the form of precipitation like rain and snow. Therefore, the change in the mass of water on Earth is (Net) Zero! In other words, our current planet is self-sufficient with its water requirements.

Why is there a scarcity of water?

While the water recycling capacity of Earth is remarkable, the distribution of the quantity and quality of water across the planet is not the same. Growing population and urbanisation, leading to overexploitation and pollution of water sources, have amplified the scarcity of clean water. And if that was not putting enough stress on existing water supplies, the onset of climate change has complicated things even more. 

Global warming alters the water cycle by affecting the rate of evaporation as well as the moisture-holding capacity of the atmosphere. This in turn affects the frequency and intensity of rainfalls, potentially leading to draughts and floods in different regions. There have been calls for targeting net zero carbon emissions to mitigate the effects of climate change. But an equally important concept while addressing water scarcity is that of net zero water. 

In its simplest form, net zero water at a certain locality means that the locality is independent of external water supplies. The locality is able to self-sustain itself by either reusing the water consumed, or, by having sufficient rainwater harvesting, or a combination of both. This is similar to how our planet is self-sufficient through its water cycle, albeit on a much smaller scale. 

How to achieve net zero water?

However, achieving a net zero water locality comes with challenges. Firstly, the geography of the area determines the availability of rainfall. Secondly, while water reuse is being adopted across several sectors, the quality of water currently being reused is often compliable only for non-contact human applications, like horticulture, toilet flushes. But this would mean that contact applications like drinking, cooking, and showering, would still need a fresh supply of water. Finally, while it is easier to collect and treat wastewater/used-water from specific sources like sewage discharge points, the water used for activities like agriculture and horticulture is harder to recover after the water diffuses underground.

So, how close are we to making net zero water a common practice? We are making big strides in terms of technology; this includes advancements in weather prediction, surveillance of water sources, real-time monitoring of water quality, and wastewater treatment methods. It is currently possible to treat wastewater/used-water, to a quality even better than drinking water standards. 

The costs of such advanced treatments would become more viable as research goes into improving their energy efficiency. The bigger challenge would be inducing mindset shifts. Would people be willing to reuse treated water for applications like drinking and cooking? And what about the policies needed to implement best practices regarding recycling? With a concerted effort, we can replicate the water self-sufficiency of our planet; but will we?

(The author is an assistant professor at Plaksha University. Views expressed are personal.) 

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First published on: 16-01-2023 at 14:35 IST