Raj Bhagat P #Mapper4Life Profile picture
Feb 25, 2024 15 tweets 6 min read Read on X
Here's a compilation of my #maps which can help you in understanding the #Bengaluru #Water situation a bit better.

Bengaluru is unofficially a hill station which is located nearly a kilometre above sea level. Image
Being in the top of a ridge line, the city is partly within Kaveri watershed and partly in Ponnaiyar (Dakshina Pinakini watershed).
Being on top, water from elsewhere dont flow through Bengaluru but flow outward from the city
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Bengaluru right now depends on Kaveri river for water supply. Because of its height, Water is pumped for a height of 1000 feet from the river 100km away from the city Image
But, The Kaveri watershed is one of the most over exploited river system in India. Thousands of water diverting and storage structures make it possible to exploit in both Karnataka and Tamil Nadu which share the river
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Most of the water in Kaveri watershed is used for Agricultural purposes.

Basically, the expenditure is pretty high and the income however oscillates.

Which means, except few years of excessive rainfall/flooding in upstream, most of the years the region faces water shortage


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And remember, Bengaluru can't demand a lot of water from Kaveri also as only a part of the city is in watershed though the entire city is dependent on it (along with ground water & tankers)
In map, we can notice significant part of BBMP(marked in black) is not in Kaveri watershed Image
But most of the bigger development in Bengaluru is happening outside Kaveri watershed in the South East(ECity), East (Whitefield), and North (Airport)
This unbridled and unbalanced growth has put immense pressure on Bengaluru. Bengaluru is 10x larger than the next city in Karnataka. Increasingly the population and economy is skewed towards Bengaluru with people migrating from all the states & from other districts of Karnataka

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In short:
1. Kaveri is over exploited, requires conservation in all sectors (primarily agriculture) by both Karnataka & Tamil Nadu. Any year with average or less than average rainfall would result in drought /watercrisis not just for Bengaluru. This requires research & investment
2. Bengaluru is over grown considering it's geography and it is imperative that the growth across the country and within the state to be diversified to next tier cities and this would require investments in the same directiom
3. Bengaluru can't depend on Kaveri river alone coz of the risk involved. Failure of rainfall upstream last season is leading to the crisis this year. The city hence has to judiciously use the water it has (conserve), utilise the rainfall within city (harvest), & reuse wastewater
Before grilling Bengaluru on social media, please note that these issues of environment (flood, water crisis etc.) arising from poor planning and lack of geographical understanding, exist in most major metros across the country. Bengaluru is just reported better!
It is hence important for us as citizens (of not just Bengaluru), to focus on the processes that govern our planning, the methods through which we execute them, our pattern of growth, awareness etc.
Forgot to add this:
~97% of Indians live at an elevation lower than that of Bengaluru

And if you're at it, here's is my take on the geography of the city and the urban flooding issues it faces as presented in an event hosted by the Bangalore Room

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More from @rajbhagatt

Feb 24
#Thread

What geographical features can we observe from the sky while on a flight from Thiruvananthapuram to Chennai? (approx path in map) Image
Equip yourselves with apps for more information from GPS.. Also notice the weaker signals from the satellites on the right side because I am sitting on the left side windows. Also preload maps in google maps so that you can identify features Image
Image
In Thiruvananthapuram, we can notice a large sediment plume on the coast. This is largely around the Trivandrum Titanium Ltd
Read 27 tweets
Jan 11
#Thread on #Tiruchendur erosion

Of recently, we might have come across the news that a lot of erosion has happened right next to the famous Murugan temple in Tiruchendur. In this thread of maps, I would discuss the causes and possible solutions Image
Image
To provide context, this photo shows the area near the next to the temple which has eroded significantly and the beach used to extend further Image
#Satellite image shows the Tiruchendur coastline from last year in the month of January. The beach marked to the south of Murugan temple is the one facing erosion. Image
Read 20 tweets
Oct 15, 2024
#Thread without Maps on #floods
If physical problems and solutions are known theoretically, then why are we not able to solve flooding situations in our cities whether it is Chennai or Bengaluru or Delhi?

There are 4 layers to the prob - Technical, Planning, Finance, Governance
Technical:
Our cities are not designed to take the rainfall that they face. The storm water drains are inadequate and the network is disconnected. Most of the drains are built in adhoc manner (if they are built). But why does this happen?
Cities don't have a storm water management plan. A plan that can comprehensively provide the technical details on the storm water network based on run off calculations, land etc is absent in most cases or poorly prepared in the remaining.
Why hasnt been it prepared?
Read 16 tweets
Oct 2, 2024
#Thread on Vijaywada floods
In September this year, after a spell of heavy rain, Vijayawada was affected by severe floods. This thread would explore the geographical reasons behind it and what can be done from here.
(1/n) Image
2. #Map shows the profile of four major rivers in India. Vijayawada is in the lower section of Krishna river and close to where the river exits the plateau and enters the deltaic flat plains. Image
3. There are 3 basins in the region whose histories are intertwined. Vijayawada city is sitting on the Krishna and Kolleru systems. Though the Krishna river was also flooding, the city was actually flooded by Budameru Vagu, a seasonal river which is part of the Kolleru system Image
Read 26 tweets
Aug 24, 2024
Google maps shows my GPS position to be well inside the sea in #Chennai Marina beach. But I was away from it. Why?

#Thread continuation of my previous one on Chennai #Marina beach
1/n
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In the previous thread, I had explained how Marina beach is growing (sea becoming more and more land). Because of the longshore drift, lots of sand hence gets settled in the mouths of Cooum River. Image
To prevent further siltation in the mouth of the river, the government had built Groynes so that the capacity of the river doesn't get reduced. Image
Read 15 tweets
Aug 16, 2024
#Thread
#Marina beach is one of the most iconic destinations in Chennai and one of the most visited beaches in the world. However the beach as we see today didn't exist a century ago.

This thread explains the formation of #Chennai's Marina beach
1/n Image
This map below shows the approximate original coastline of Chennai during British era. It was much closer to the Kamarajar road. A promenade was developed during the british era and that is when it got the name, "Marina". However the big sandy expanse itself didnt exist
2/n Image
Seas are very dynamic in nature. Whenever the waves hit the beach which is called as "swash", they bring in sand and when the water goes back ("backwash"), it removes the sand. This balance is critical for beach existence.
Read 24 tweets

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