Climate Change and India’s water

(A version of this appeared first in Firstpost on Sep 19, 2018)

MR - Rann

Undoubtedly, the water situation of India, which asks about a fifth of the world’s population to survive on less than 1/30th of the world’s water, is precarious.

This is now. What about the future? India’s population is growing, getting wealthier, and, oh yes, the climate happens to be changing. The water crisis will worsen, if we neglect the management of our water. Let us see how.

Climate Change will play havoc with India’s Water supply

Floods and Storms

As the climate warms, the water cycle changes. This begins with hotter air’s ability to hold more water vapour – that’s a law of physics. This results in more powerful storms – like the type we have witnessed in the past decade.

Moreover, scientists from the Indian Meteorological Department have shown that the number of days on which it rains has been coming down, which makes extreme rainfall events, such as the heavy downpours such as those that helped create the Chennai flood of 2015, more likely. This intense rainfall also translates to a greater fraction of the rainfall ‘running off’, rather than percolating into the ground, unless, of course, there is a water body (like the ones we delight in building over) to capture the runoff from an area, store it, and allow it to percolate into the ground.

The Niti Aayog’s Composite Water Management report has remained mum on the effects of climate change on India’s water, reasoning perhaps, we are in a bad enough situation as it is. But as we shall see in later piece, we may just need that extra motivation that a warming climate provides to manage our water.

Sea level rise and Salt water intrusion

Another aspect by which water and climate change intersect is by rising sea levels first. In the long run, land is lost to the sea. We make the sea level rise worse by making our land sink. Land sinks as we pump out groundwater, and Indian coastal cities are masters at doing this. To give some perspective, global sea level rise was about 1.7 mm per year between 1901–2010, while the land subsidence (or sinking) rate was about 13 mm per year in Kolkata! But more relevant to India’s coastal cities, some of who are reliant on groundwater for their drinking needs, is the salt-water intrusion into groundwater reserves. As we pump out groundwater, it makes it easier for the saltwater to push in. This makes the supply of potable, or drinkable, water for coastal cities go down.


Moreover, storm surges become more deadly as seas rise – one paper published in Nature Climate Change, puts global risks from coastal flooding at upwards of $1 trillion (yes, you read that right) per year if (expensive) adaptation measures are not taken. This water needs to be managed as well.

Changing Rainfall patterns – Geographical variability and temporal volatility

How climate change affects (and will affect) the Indian monsoon is a trillion-dollar question. There is no doubt that a warmer climate will change it – but how? There is robust research to show that since 1951, most of India has seen monsoon rainfall decrease. There are papers that use models to predict that, in future, while the overall monsoon rainfall will increase, it is likely that the variability between monsoon seasons is also likely to increase. This means, going forward, rather than having close to ‘normal’ monsoons, we will have more volatile rainfall, characterised by flooded cities and states, or parched fields both increasing both in severity and in frequency. The geographical variability is also set to increase: a vulnerability atlas compiled by the Central Research Institute of Dryland Agriculture shows, amongst other things, that  June rainfall will likely decrease in Northwest and Peninsular India in 2021-2050 relative to 1961-1990. This has direct implication for farmers on crop choice and planting practises, as well as on government food procurement practises. Many districts have reduced their resilience by overexploiting their groundwater.

Vulnerability Atlas - Fall in June rainfall

Some parts of Peninsular India, and a few districts in the dry Northwest are predicted to have lower annual rainfall by 2021-2050, which requires rethinking of water sources of major cities such as Chennai and Bengaluru. A point to note: Many of these predictions are based on models which are more reliable on a global scale, rather than on a district scale. More research is required to fine tune these models, because building resilience in such a diverse country works best on data at hyperlocal levels.

Moreover, rising temperatures mean a greater fraction of any water in reservoirs or lakes will be lost to evaporation leaving less to feed cities and farms.

Demand is going up

While supply is getting ‘kooky’ (to use the appropriate, technical word), demand is likely to only rise.

India is getting wealthier. Between 2013-2017, India’s GDP per capita grew by about 6% per year. This means, in about 12 years, the wealth of an average India will double (Aside: there are problems in using GDP per capita as a measure of wealth, but it will do for a first cut). Now, let us see if water use and wealth are correlated. For this, let us take water withdrawal per person and plot it against the GDP per person. Since agriculture use is qualitatively and significantly different from residential or industrial use, let us check whether these two measures correlate for lower middle-income countries who have a high share of agricultural use in their overall water use (i.e., above 85%).


Figure 1: Water withdrawal per capita vs GDP per capita for Lower Middle Income countries with high agricultural water use (data from the Food and Agriculture Organization Aquastat database, most recent values.

With this data, we can reasonably conclude that India’s water use per capita will rise as it develops economically. This intuitively makes sense – wealthier households often have access to more plentiful and convenient water sources and thus use more water (bathing using a shower rather than with a bucket) for personal and household hygiene. Wealth also often translates to a higher consumption of animal products, which tend to guzzle far more water than their plant-derived counterparts. Given India’s rising population, wealth and accordingly, water use per capita, by 2030, India’s overall water use could easily double.


Can this rising demand be managed?

In those parts of India where volatility and rainfall both increase, one way to cope is to build inventory or water storage. But as we saw last time, India ranks poorly in its storage availability and Indian cities have decimated their storage. Our data on water storage is outdated, and probably an overestimate, as well, given silt, encroachments etc. which will reduce the amount of functional storage we have.

In those areas that are projected to receive less rainfall going forward, for farmers, the obvious answer is by widening access to irrigation. But over half of India’s agricultural area is rainfed. States also vary widely in how well their farmers are irrigated:


Rainfed Area by states

Figure 2: Niti Aayog Composite Water Management Index, percentage area under rainfed irrigation.

For cities located in areas with falling water availability (higher evaporation, less rainfall), water management is key – pricing water, measuring it, adding new sources of supply etc. All well and good, but if it was so easy, why haven’t we done it until now. Lack of awareness is part of it, which is why we will go into specific solutions to coping with rising demand and volatile or falling supply (and there are plenty of success stories) in subsequent articles. But personally, I believe our real problem lies elsewhere. Which is where we go to next.


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