Water scares city to Water Scarcity!

Title of this post is inspired from recent forward on social media about rain and water situation in Chennai. This forward also triggered the curiosity of data monks (a secret group) in Report Bee. Questions like?…

  • Where does Chennai get its water? What is its storage capacity?
  • How dependent is Chennai on Monsoons?
  • What will happen to water situation as Chennai’s population grows?
  • Is there a changing pattern in rains or weather?

We needed data to answer these questions. Luckily we had a good starting point for our data adventure – The website of Chennai Metro Water. This site has water levels of Chennai’s reservoirs (Lakes) for each day for the last 14 years (We wish it was 40 years of data!).

First step!

A Python script helped to retrieve the total volume of major reservoirs in Chennai. Once we had the data in the desired CSV format, it was play time 🙂

Where does Chennai get its water? What is its storage capacity?

We plotted various graphs to visualize the data and learn from it . The first graph, the total water levels from 2004 until today.


Observations from above graph, from 2004 up until 2012, the water levels have been fairly consistent across the year and these were years of water sufficiency. From 2013 onwards, there is a drastic fall in water levels across the 5 chief reservoirs which supply water to Chennai. This shortage of water did not stop even in 2015- December, the year infamous for Chennai floods.

Is there a changing pattern in rains or weather?

What we are seeing increasingly is a Monsoon that is holding itself back a little and then packs a punch too wet to handle in the months of Nov-Dec.

The truth is that when it rains so much in so little time, all water goes down the drain, literally. We need new ways to trap the monsoon efficiently.

Then, we visualized the 2004 to 2017 in an overlapping graph.

This visualization makes it is easy to compare the water levels across the years. In recent years, we run out of water faster and failed Monsoon threatens the city of drought. Validates the humour in the title of this post.

What will happen to water situation as Chennai’s population grows?

To understand this better, we calculated time taken for the water level to come to 3600 Mcft in a given year. Assuming that this level of water is a situation of concern. Listing the calculation for some of the years.

Jan 2006 – 8 months and 10 days to reach 3600 Mcft
Jan 2008 – 7 months and 20 days
Jan 2011 – 5 months to reach 5100 and then increases again
Dec 2015 – 8 months and 20 days to reach 3600 Mcft

In 2030, at full capacity in the 5 chief reservoirs, we’ll completely run of water in 9 months even if we get good rains. Chennai will face severe water scarcity in coming years.

  • Current Population of Chennai = 10,435,000, consumes 830 MLD/day
  • Predicted Population in 2030 = 13,921,000, will consume 1100 MLD/day
  • Reservoirs (Lakes) at Full Capacity = 300,000 MLD
  • Assuming no rainfall, No. of days the reservoirs will be sufficient for = 300,000/1,100 = 272 days (~9 months)

Do we need more desalination plants?  Do we need to build more reservoirs? Take a look at the table below.

Three were built in British era and other 2 much before! Are our catchment areas (reservoir locations) enough, do we need more?

How dependent is Chennai on Monsoons?

Monsoons are India’s lifeline. We used to be an agrarian economy dependent on rainfall for our survival in the global market. Today, years later, though the balance has shifted in favour of services more than manufacturing or agriculture, we are still dependent on these life-giving winds from the Indian Ocean. Even if not for agriculture in Chennai, it is to feed our rivers and put that glass of water on our dinner tables!