India's Water Revolution #6: Urban Mega-Drought Solutions - YouTube

The rooftop is where a lot of the water harvesting...

I mean, it's where all the rain water is collected and being piped down towards our underground sumps and our open well.

This is the upper watershed, the highest elevation.

In our last episode, we saw how Padma Koppula of Aranya Agricultural Alternatives is bringing water security and ending economic migration for farmers in the driest region of South India.

In this episode, we travel South from Andhra Pradesh into the State of Tamil Nadu, into the coastal mega city of Chennai.

Tamil Nadu is located on the Southeast tip of India on what is called the Coromandel Coast

This coast has a different rainfall pattern than the other places we’ve visited in this series.

The majority of India gets its rainfall from the Southwest Monsoons that takes place between June through September.

That rainfall reaches India, but is blocked by the Western Ghats Mountains, creating a rain shadow on the Coromandel Coast.

Later on in the season, the winds change direction and bring the Northeast Monsoon in October and November, raining moisture from the Bay of Bengal over the Coromandel Coast.

This is when Chennai receives heavy rainfall, totalling an average of 1400mm (55 inches) per year.

Chennai is an urban mega region of over 11 million people.

It’s primary water supply is from a series of rain-fed lakes located within and adjacent to the city

Looking at Chennai’s water in economic terms, Chennai basically lives pay-check to pay-check without a lot of savings.

Meaning, these lakes fill up with the monsoon rains and supply water to the city and help recharge local bore wells.

But there is no big water supply buffer for when the Northeast Monsoon fails.

Meaning that every year, the city is only one poor monsoon season away from scarcity.

And for three years between 2017-2019, the rains did fail!

And these lakes dried up as the seasons progressed, until in the summer of 2019, the city hit a breaking point.

India's sixth biggest city is within an inch of zero day: no water. Running completely dry

Chennai is fighting for water. Restaurants have shut down! Schools cut working hours!

"We have plastic pots but where is the drinking water?" Water is not available for the last 3-4 days, not for cooking, not for bathing...

The government is bringing in a train full of water, from 100s of kms away

What he's telling us is that because there have been no rains, the groundwater levels have gone so low that there is no water coming through the bore wells right now.

And they are getting water tankers to come give them water at 3 AM. And what do they get? They get 3 small pots.

Now a family of 6 cannot survive with three small pots, and this is everyone's situation.

But this is not everyone's situation!

I wove my way through the busy streets to visit a very special house on a small plot in the heart of the city

that never ran out of water during the drought, due to their smart planning and water management strategies. 

Hi! I am Gayathri and this is my home in Chennai. I live with my parents, and we live in the central part of Chennai.

You are in my rooftop garden which is slowly grown and grown

We've had this garden now for close to 30 years. And I have a lot of plants here.

So definitely the other aspect is to create a nice microclimate because summers can be intense

It's a microclimate not just for the humans, it's also for the insects and the birds.

The rooftop is where a lot of the water harvesting...I mean all the rain water is collected and is being piped down towards our underground sump and our open well

This is the upper watershed, the highest elevation.

We has these massive rains, kind of like floods, that happened in 2015 December, and then we had the cyclone that happened in 2016

And after that, three years, I don't think our monsoons have been good.

Chennai has been a water-scarce city for many years. We've had water issues because we've mismanaged our water resources for very many years.

But this year (2019), it did get far more acute in the summer

The city water supply started dwindling. We didn't have much of it.

And it was quite stressful because we had to depend just on our own bore well and our open well supply

In terms of the drought - so that's happened. We've been rainfall-deficit. This year (2019), we've actually got some North East rains, but they've still been lower than what it should be

But it was kind of relentless, those 3 years of not having enough rains. For example, my lemon tree died

A lot of the trees we are growing are native, drought-resilient trees and cyclone-resistant trees, because the Coromandel coast is very much a cyclone-prone area

So that's another thing that has to be built into this ecosystem

The trees and plants we grow have to be something that is adapted locally, to the weather conditions

And they were always true historically, but they've gotten worse in recent times, because of climate change effects.

This entire site is 400 sq m, with a roof area of 150 sq m

Chennai’s average rainfall totals 1400mm per year.

Imagine that one square meter receives this 1.4 meters of yearly rainfall.

And since one cubic meter holds 1,000 litres, then each square meter in Chennai has 1,400 litres of rain falling on it in an average year.

When we do the math on Gayathri’s roof, we find that 200,000 litres of rain falls on it each year.

That is the equivalent of twenty water tanker trucks!

This goes the same for every rooftop in Chennai.

But the vast majority of rainwater is wasted down roads and drainage ditches without being harvested.

But not at this house. 

So all of the rainwater harvesting, all of these pipes come down here and go into this pit where they are filtered through

The water can actually go into two sumps, or underground water tanks, and then the excess goes to the well.

So this is one of the underground sumps and this is the second one.

This one is around 12,000 l and the old one is around 4000 l

We are getting water supply from the city also. It only comes at certain times. There's a timed supply, the city supplies on alternate days.

That is what this is pumping, the water line that comes from up there. There's a water meter up front.

And one of the reasons we built this, and this just got built in October this year was because when we had good rains, even a decent shower, this would fill up very quickly -- the 4000 l sump, and all the water would then go to the open well

And then the water level would come up, but then because everyone else is basically pumping water from deep bore wells, it would go down very quickly as compared to previous years.

So we would not be able to access the open well water for more than maybe 5 days

So it made more sense to be able to store more of our rain water in an actual tank, than to put it all in the open well.

Both our neighbours also have wells. Every house in Chennai used to have a well, but those have run dry.

And ours has never run dry in the 30 years

Even in the worst times, when we've had periods of extended water crises, there was always water you could see.

Just the fact that our open well has never run dry is connected to the fact that we've always had trees.

We have at least 20 trees in this very small space

Everything goes back into the soil and I think that that's maintained this water table

We've always had this number of trees. We've always reduced the amount of concrete surface

So we've had more soil and mulch that's drawing all the water

So what Gayathri is saying is that the presence of trees and soil that is rich in organic matter does a lot of work to hold moisture, like a giant sponge, so water slowly percolates through the ground to recharge the well.

This is our open well and it's easily 30 years old because it got dug when the house was built.

It's never gone dry

When we've had good monsoon rains, the water comes all the way such that I can touch it

So it's at the ground level. Like my mother says, the water is level there. Because we have clayey soil, the water takes time to percolate so we often have standing water in the garden

And the water level in the garden and the water level in the well, will be, kind of, level!

That's how much it gets filled.

I think the last time I saw that happen was when the floods happened in December 2015.

So it hasn't come up to that level in the past 3 years.

One of the ways, we...like we'll hear the sound of rain and then maybe 20 minutes later, we'll hear the water flowing into the well because it's quite a drop, right?

That's how we know...I mean that's an additional sound always in our ears, when it's raining

And we get quite excited about it. My mother is like, "Can you hear it? Can you hear it? It's raining. The well is filling!"

It's a good rain when we start hearing that.

So far we’ve seen how the water from the roof is being harvested, and how the water falling on the soil is being soaked up.

But there are even more surfaces that water is being harvested from, and those are the paved concrete walkways around the house.

This water is not being wasted either.

And there is an important structure they are using to collect every drop of water falling on the site to recharge the groundwater. 

We also made three more recharge wells.

And we just wanted to make it close to the open well.

And there's another one up-front, that is closer to our bore well, because we have a bore well in front.

We made sure that all the slopes are directed as much as possible with concrete, towards that particular recharge point

It's basically a 20 feet deep cavity that's been filled with gravel, and it's a pipe with slits.

They just went till they hit the sand so the water is going to percolate really quickly when it comes into this area

And because it's quite close to the open well, the idea is that it's going to recharge it, much quicker than, say clayey soil would, with all that mulch, because it does percolate more slowly through clay.

Does the laundry stone, does that also go into that?

So anything I wash there by hand, I make sure to use natural detergents and I just toss it into the garden, or I pour it in

I know that for you, it's obvious, but people like in the US would not understand the concept of a laundry stone.

Ok. Do you want me to show how a laundry stone works? I can do this. This is what I did this morning

The problems of water scarcity in a city like Chennai, and the many other water-scarce cities of the world, are not insurmountable, and are literally solvable at the home scale.

As a great man once said “Though the problems of the world are increasingly complex, the solutions remain embarrassingly simple.”

So whether you’re in Chennai or Cape Town or Cairo, mega-city mega-droughts are within our power to fix.

Like, subscribe, and join us for our next episode as we journey to the eco-city of Auroville

to see how they turned a degraded savanna into a thriving and diverse forest, all while purifying wastewater and replenishing groundwater tables.