Tanks are silver bullet for India's water woes; why they're disappearing, leaving us more vulnerable to a warming climate

A warming climate, bringing fewer rain days and more intense rainfall events in its wake, makes the role played by tanks even more critical.

Mridula Ramesh October 19, 2020 10:35:02 IST
Tanks are silver bullet for India's water woes; why they're disappearing, leaving us more vulnerable to a warming climate

A tank in Tamil Nadu. Image via Wikimedia Commons

Editor's note: This is the first in a two-part series on the critical role of tanks in India's water management system. It draws from Mridula Ramesh's upcoming book on water, to be published in 2021.


Imagine if you received all your annual income in a few days, but still had to make monthly payments — rent, EMIs, school fees, medical bills etc. You would need a place to store your money, wouldn’t you?

For much of India, a large chunk of its rain falls in just 15 days, often in about only 100 hours. This makes water storage and management critical, especially for the somewhat drier regions like Rajasthan, Tamil Nadu or Telangana. The erstwhile rulers of those regions built tanks — essentially lakes — thousands of them. For example, the Kakatiya dynasty, who ruled Telangana 12th to 14tn centuries focussed on tanks, realising the special key water storage held for prosperity. Somehow, in our rapid urbanisation in the past few decades, as house overtook field, we appear to have forgotten this defining facet of India’s rainfall management.

As I have said before, tanks are brilliant. They work in two ways: one, they store rainwater from whichever area they directly drain, and allow the rainwater a chance to percolate into the ground, rather than ‘runoff’.  Second, a subset of tanks, called system, or cascading tanks, are connected to a network of other tanks and to the river through canals. These system tanks are the beneficiaries of surplus non-local rainfall. During the southwest monsoon, many peninsular rivers swell with the rain from the Western Ghats, the mountains girding the western coast of India. This surplus water flows from the river through a set of channels to tanks, and as each tank overflows, downstream tanks and smaller satellite ponds, sometimes connected by channels, get filled.

Tanks are an elegant way to spread seasonal rainfall over the year.

To use a financial analogy, system tanks are like (sticky) Foreign Direct Investment that transfer non-local savings into the local economy. Tanks capturing local rainwater are like local savings being channelled into the local economy. A warming climate, bringing fewer rain days (or days where it rains), and more intense rainfall events in its wake, makes the role played by tanks even more critical.

The case of Hyderabad

Take, for instance, what is tragically unfolding in Telangana over the past week. We have two patterns — one of extreme rainfall, and the second of unwise land-use changes. In the first two weeks of October, several districts in Telangana received well above their ‘normal’ rainfall. In the same period, the Hyderabad district received nearly 30 centimetres of rain, almost three times the ‘normal’ amount. Several parts of the city received between 10-20 centimetres of rain in a day. With a warmer climate, such incidences will likely recur.

To blame the hair-raising images of a man being swept away on a road-turned-roaring-river on the climate alone would be unfair, and, perhaps more importantly, unhelpful. Did the intense rainfall translate into the fury we witnessed, because the water was squeezed into a space too small to hold it? Because we had converted lake bed to plot and thence to building, thrown rubble into river and tank, and asked flood waters to share space with torrents of sewage in already encroached and silted stream or river?

To wit, compare the picture of Hyderabad from 1991 to 2016 on these Google Earth images: shrinking the space for water to occupy merely makes it spill, or flood over, during intense rainfall spells.

Tanks are silver bullet for Indias water woes why theyre disappearing leaving us more vulnerable to a warming climate

Why then are so many tanks and lakes disappearing or falling into disrepair?

To answer this, let me come back to Madurai, where I live, and where tanks — until a hundred years ago — held pride of place. If you take a flight over Madurai any time after August, you would not be wrong in thinking that someone had shattered a giant mirror and strewn the shards across the land, because that’s how the thousands of tanks or lakes appear from the sky.

Water management has such a pride of place, that we found over 40 words in Tamil just to speak of water, with several words for a tank or lake — Eri, Kanmai, Kulam, Kuttai, Oorani, to name just a few. Each referred to a particular type of tank, designed largely for a particular purpose. Eri or Kanmai both referred to irrigation tanks, while Oorani referred to a drinking water pond, typically located like planets around a larger Eri or Kanmai. There were names for tanks within temples, tanks meant for livestock — clearly this was an important subject in the days of yore. There were also several roles assigned for water management — Neeraanikar, Neerkatti, Karaiyar, Kuzhathu Kaapalar — for water rotation, operating sluices, for cleaning the tanks, for ensuring there were no encroachments.

At Sundaram Climate Institute, we differentiate tanks in terms of functionality. As in relationships, tank functionality spans a spectrum. Highly functional tanks tend to provide tremendous benefits — both in variety and amount — to their immediate community. In our study of 42 rural tanks, we found functional tanks provided more than irrigation access; they provided cash flow — so vital to the rural economy — by enabling fishing, furnishing water for livestock, and, in many tanks, lotuses, which retail between Rs 5-10 for a single bloom. While farmers with better situated land appeared to value water rights highly, landless workers and smaller farmers reported valuing fishing, access to water for cattle, temple and burial rights more. Perceived as equally important were the non-financial benefits: Indeed, some of the smallest tanks were highly functional because the surrounding community thought of them as sacred, and researchers from our team were asked to remove footwear before venturing near the tank. Almost every tank we studied had a temple associated with it, with temple rights seen as an important aspect of the tank benefit ecosystem.

Tanks are silver bullet for Indias water woes why theyre disappearing leaving us more vulnerable to a warming climate

When our team spoke to an old woman grazing goats next to a small pond, she spoke of the pond as a living thing. No form of refuse can be dumped into pond tank, she said, as it is considered as God’s living place and respected. The tank’s god was called “Pattakati Oodaiyan”, and one family, with hereditary rights, lived in a small hut by that pond and was responsible for the maintenance of the pond. The pond, small as it was, provided enough water for the livestock, and for the community. This story too turned melancholic, as stories do. “Earlier we had country fish like iyerameen, koravai meen, keluthi meen,” the woman said, although she could not quite remember when they caught fish last, “Perhaps a few years back.” This year too, they tried placing some fish in the tank, but they died.

Sometimes, the word ‘community’ conjures up a warm and fuzzy image. This, in our experience, is not often the case. There were strong caste dynamics at play in the tank maintenance and access. However, without glossing over the caste and gender equations, we observed that all castes were worse off when a tank became dysfunctional, and the economically vulnerable sections even more so. With that caveat, when a tank provided regular benefits, a community is vested in keeping a tank healthy, and free of encroachments. So what happened to upend this not-quite-idyllic equilibrium?

We found there were three key reasons why tanks tended to die: (a) Centralisation of maintenance, (b) Urbanisation/ Encroachment, and (c) the emergence of new sources of water.


Let us begin with centralisation. The centralisation of tank maintenance has not always been good for tanks, specifically for the fishing ecosystem. One exception appeared to be the MNREGA scheme, which we found played a significant role in desilting local tanks, and strengthening bunds. One farmer spoke of 11 varieties of fish in earlier times, with lifecycles in sync with the rising and falling water levels. This diversity suffered when quantity was prioritised over quality, with the Katla coming to dominate the catch. The problem with larger catches is that it better suits larger bidders, often not associated with the village community. Then, of course, someone may complain of irregularities in process, and a court case is opened. For the bureaucrat responsible for the auction, being asked to appear in court is an unwanted pain in the neck, in the midst of a crowded day, and overflowing inbox. Slowly, fishing auctions fail to take place, or take place surreptitiously, meaning one key benefit to the community falls.

In urban tanks, apart from this hassle, the responsibility for evicting encroachers also moves to a government department. Given that evicting encroachers is anything but an easy affair, one needs time, means, power and single-minded zealousness to ensure success. This is easier to command if one’s livelihood depends largely on the wellbeing of the tank. Less so, if it only one of your many duties, and one you will receive a lot of pain in doing, but little credit. Besides, the motivation to maintain tank ecosystems reduces when new sources of water and employment come up.

New sources

In the end of the 19th century, the Mullaiperiyar dam was built to divert the waters from the river Periyar to the river Vaigai. The Vaigai had always been a non-perennial stream, and the thinking behind the dam was: ‘Why not move some water from the water-rich Periyar to the water-poor Vaigai’ — a sort of redistributive socialism with river water. Even back then, the idea was not new — it had been around for nearly a hundred years, but the tragic famine of 1876 gave it the final push.

By most accounts, this diversion seemed like a good idea — farmers were able to grow more, at least those connected to the system tanks that now received the additional water largesse from the Periyar-fed-Vaigai. Indeed, some parts of Tamil Nadu dedicate their harvest festival to the officer who built the dam, John Pennycuick. But there was a side effect: tanks in the Vaigai basin became less dependable as sources of water, first when the Periyar dam was built, then later when the Vaigai dam was built. This appears to be a non-sequitur, until one realises that when farmers received more water from the Vaigai, they became less interested in maintaining the tanks to eke out water, which makes downstream tanks less dependable.

But what gave the body blow to tanks was the advent of the tube well and the free electricity to power pumps for agricultural use. Slowly and steadily, the importance of tanks in irrigation came down — see the thinning yellow sliver in the graph below:

Tanks are silver bullet for Indias water woes why theyre disappearing leaving us more vulnerable to a warming climate

Net Irrigated Area by source (Directorate of Economics & Statistics, Department of Agriculture and Cooperation, Ministry of Agriculture, Government of India), Statistics Handbook of India

Borewells are usually a rich farmer’s province, the same farmers whose lands lie close to the more important systemic tanks. If they slack on maintenance, because they now have access the free water, the tank ecosystem suffers. Having the borewell also makes them less inclined to guard against encroachments and garbage being dumped into channels feeding downstream tanks. This further reduces the flow of water to the downstream tanks. Lastly, sand mining deepened the river bed, meaning in times of low flow, water could not flow from river to canal, because the water level was lower than the outlet level. All of these translated to tanks becoming an unreliable source of water. Indeed, the percentage of years during which where all the tanks were filled, fell from about 71 percent in the pre-Periyar years to about 33 percent in the period between 1986 to 2001. Naturally, this made farmers less keen on maintenance: Why labour on something that will not allow you to grow another crop or increase your yield?

In cities too, the rise of the borewell heralded the collapse of a civic sense. Why protest about encroachments and tank disappearance, when there were mountains of water available at the flip of a switch under one’s very feet?

Urbanisation and Encroachment

The deadliest blow comes when house or factory overtakes field. When fields with an established right to the tank water transform into housing plots, the new owners of the land lose water rights, and the tank becomes an orphan, ripe for conquest. Typically, the channel is first to fall: we saw this several time in our studied tanks: “The Odai [channel] to the tank from the Periyar river is blocked, earlier it was broad now it has narrowed done because of *** factory,” said many we spoke to.

In cities, this problem was widespread. In the second half of the 20th century, the population of India’s cities exploded. This just meant more and more people were being squeezed into a smaller place.

Tanks are silver bullet for Indias water woes why theyre disappearing leaving us more vulnerable to a warming climate

Population Growth of Major Indian cities, 1901-2011

Indian cities tend to be smaller than other global peers, as a recent Economic Survey on India showed. One reason for this is insufficient infrastructure. Take the case of transport — job opportunities tend to be highest in the centre of cities, where land prices are nose-bleedingly high. To take advantage of the jobs while also living within their means, employees need access to low cost, convenient mass transport. This missing link in Indian cities leaves roads crowded, and the poor living in slums close to their place of work. As a result, India cities are amongst the most land scarce regions in the world — especially within corporation limits.

With the masses pouring into the cities, municipal governments must provide infrastructure — bus depots, schools and such — to cater to their needs. But where would the land come from? Governments like announcements: “XYZ bus terminal will be built this year”. But the legendary, exquisite tortuousness of land acquisition in India makes quick infrastructure building impossible. And that’s where the tanks — once filled with water, the centre of community life, now neglected, choked with waste, and dry — become interesting. This is compounded by the water diversion policy of the irrigation department, which tends to preferentially supply water to those tanks which still have an ayacut (irrigation area) attached to them, above urban tanks. As the urban tanks go dry, they offer inviting, quickly-acquirable, new land in the heart of the city. Tanks are classified as ‘poramboke’ land, which allows the government to divert them for other purposes. Typically, when the tank bed wants to be diverted for other purposes, the concerned officer or Tahsildar makes an announcement that the tank has fallen into disrepair; it is an eyesore choked with waste and a breeding ground for mosquitoes etc.

Why don’t communities in urban environments care about what happens to tanks?

Again, there are several possible explanations. While the groundwater flowed freely, why care? Second is that we are conditioned to think of groundwater and surface water as separate. After all, they are governed separately, so why not think of them the same way. This ‘hydro-schizophrenia’, as Dr Mihir Shah terms it, is one reason we discount the value of tanks — because we don’t realise how tanks, or urban lakes as they have become, recharge the groundwater on which so many of us depend.

The hidden power of tanks

To test if indeed tanks influenced local groundwater levels we studied 36 urban and periurban tanks in Madurai, wherein we estimated groundwater levels at set distances using crowdsourced data from over 3000 persons. Our data gave us this graph that showed tanks did indeed appear to recharge groundwater in their vicinity:

Tanks are silver bullet for Indias water woes why theyre disappearing leaving us more vulnerable to a warming climate

Source: Sundaram Climate Institute Tank Study 2019-20

Then we asked, are all tanks equally effective? Turned out, not quite.

Tanks are silver bullet for Indias water woes why theyre disappearing leaving us more vulnerable to a warming climate

On the left hand side, was a stunning, large rural tank about a 10-minute drive from Madurai — you can see that the groundwater was available at quite shallow depths around the tank. On the right hand side, we see a tank in bad shape, a critical care patient if you will, with both inlet channels and the tank itself encroached upon. Unsurprisingly, it has a marginal impact on local groundwater levels. Clearly all tanks are not the same. But, what, we asked, makes a tank functional? Again, we checked the effect of several factors including size, land use patterns around a tank, urbanisation etc., on groundwater levels to see which were most impactful.

What mattered a great deal for system tanks was the condition of the inlet canal — if it was clogged or upset in any way, that was the end of the tank. For instance, there was a giant tank in our study that was almost always dry despite not being encroached in any way. Desilting that tank, which MNREGA focusses on, would not have helped rejuvenate the tank. The problem lay in the inlet, which, because of a road construction, now lay below the tank bed, with a road traversing between. For standalone tanks, we found an important predictor of functionality was the number of months a tank held water — any water. We also found land use patterns to have a strong impact, with more open and green spaces better helping recharge groundwater more. Importantly, the community was important: when the community spoke of a tank with pride, and protected, the tank tended to be highly functional. Our study helped us come up with a functionality index for a tank, and tank report card, serving the same purpose as a student report card.

This functionality is important, because we found functional tanks kept groundwater levels about 200 feet shallower.

Tanks are silver bullet for Indias water woes why theyre disappearing leaving us more vulnerable to a warming climate

This effect has economic consequences: we found that the average monthly spend on buying water of studied households who lived around a functional Oorani was Rs 100 lower than the average monthly spend on buying water of studied households living around a dysfunctional Oorani. That’s comparable to a free kilogram of rice per month per household.

Sadly, but unsurprisingly, the communities were not making the connection between having a functional tank in their backyard and paying less for water each month. Communities, also, until recently, were not making the connection between a functional tank, and some form of insurance against a changing climate. One way to do this would be to include the many functions of tank ecosystems in our curriculum. What else can we do to strengthen the bond between tank and community in an urban environment? We will see what that is in the next column.

Part 2 — Tank tourism can help build water resilience in Indian cities; being local, outdoors and socially-distanced make it timely


The writer is the founder of the Sundaram Climate Institute, cleantech angel investor and author of The Climate Solution — India's Climate Crisis and What We Can Do About It published by Hachette. Follow her work on her website; on Twitter; or write to her at cc@climaction.net.

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