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Wednesday, November 25, 2020

Explained: Why the 2,800 lakes in Hyderabad could not prevent a flood this year

Hyderabad's lakes were created for drinking water and irrigation purposes. Over the years, due to the expansion of the city, their original purpose was forgotten but they continued to stay relevant for flood regulation. So, why didn't this prevent the city from flooding?

Written by Rahul V Pisharody , Edited by Explained Desk | Hyderabad | Updated: October 28, 2020 8:34:17 am
Hyderabad, Hyderabad floods, Hyderabad lakes, Hyderabad waterways, Why did Hyderabad flood, Indian ExpressIrrigation department officials reinstate the breached embankment of the Balapur Talab, anticipating heavy rains as predicted by the IMD, in Hyderabad, Monday, Oct 19, 2020. (PTI Photo)

The man-made Hussainsagar lake was Hyderabad’s main drinking water source till the early part of the last century. But even as the city, established by Muhammed Quli Qutb Shah of the Qutb Shahi dynasty in 1591, expanded beyond the fortified walls of the Golconda, the heart-shape lake built across a tributary of the river Musi, was only one of the several hundreds of lakes that dotted the region.

In less than a century, the city has expanded from 55 sq.km to 625 sq.km under the Greater Hyderabad Municipal Corporation (GHMC). The jurisdiction of the Hyderabad Metropolitan Development Authority (HMDA) spreads over 7,257 sq.km covering parts of a few neighbouring districts as well, and had 2,800 lakes as per as 2017 estimate.

The water bodies were created for drinking water and irrigation purposes at a time when water management was considered crucial in this otherwise arid region for centuries. This network of man-made water bodies, interconnected by several natural waterways, ultimately led to the River Musi in most cases. Along with these small lakes, in the aftermath of the 1908 floods in Hyderabad, the Nizam government commissioned two big reservoirs, Osman Sagar and Himayat Sagar, on the periphery of the city to regulate the water flow from Musi and its tributary Esa.

But the rivers have since vanished. Discharge of sewage and industrial effluents, encroachments by government and private individuals, and decades of neglect had everyone thinking the river would never flow again. Most of the former waterways are open sewers now. But, on October 13, the river was in spate once again after a record downpour. Low-lying localities and colonies that were built on the lake beds and nullahs were submerged in no time. Many days later, hundreds of these colonies were still under water.

Between the Krishna and the Godavari

Based on hydrology, present-day Hyderabad can be divided into Krishna and Godavari basins. Traditionally, all the rainwater falling in the catchment areas of Musi would discharge into Musi which is one of the 22 tributaries of the Krishna river. And newer localities to the west of Hyderabad, including Gachibowli and the IT corridor, are all in the catchment areas of the Godavari.

In both Krishna and Godavari basins, the city has a network of lakes and drains which carry the excess water from one to another and then finally into the Musi and Majeera rivers.

Senior Hydrogeologist BV Subba Rao says lakes were built in the past based on the natural topography and rainfall trends. “These were not created for flood control mitigation but as draught mitigation structures. Every 2 sq.km had a lake to ensure water for drinking and irrigation purposes to every habitation. Flood regulation was only one of the purposes,” he explains.📣 Follow Express Explained on Telegram

Hyderabad, Hyderabad floods, Hyderabad lakes, Hyderabad waterways, Why did Hyderabad flood, Indian Express People cross a bridge as the Musi river overflows after heavy rainfall in Hyderabad, India, Sunday, Oct. 18, 2020. (AP Photo: Mahesh Kumar A.)

The forgotten lakes

Over the years, owing to the expansion of the city, the lakes were not in demand for their primary purposes of irrigation and drinking water. But they continued to be relevant for flood regulation.

Despite this, in the last few decades, several colonies, as well as large real estate ventures, have come up in the full-tank levels — the buffer area — of lakes, large water bodies that existed for centuries have shrunk in size, encroachments have eaten into natural waterways, and stormwater drains get easily clogged.

Also read | Deluge of August 2000 was the warning Hyderabad chose to ignore

As per the GHMC data, parts of the Nadeem Colony abutting Shah Hatim Talab had water rise to 12 feet after the downpour on October 13. Devi Nagar and Chudi Bazaar colonies in Goshamahal saw the water rise to 10 feet. Similar were the scenes in several other colonies like Hafiz Baba Nagar, Al Jubail Colony, Ghazi-e-millat colony, Chandrayangutta, Ghouse Nagar, Moin Bagh, Edi Bazaar, Talab Katta and Riyasat Nagar in the old city area. All these localities witnessed water rise to 4 feet. Close to two dozen colonies around LB Nagar too faced a similar fate.

Hyderabad, Hyderabad floods, Hyderabad lakes, Hyderabad waterways, Why did Hyderabad flood, Indian Express Floodwater gushes through a street following heavy rains, at Falaknuma, in Hyderabad. (PTI Photo)

As many as 33 lives have been lost to heavy rains and floods in the city, with the GHMC estimating that at least 37,409 families have been affected. The Municipal Administration minister pegged the city’s losses at Rs 670 crore.

Don’t miss from Explained | Tracking the weather system that gave Hyderabad its rainiest ever day

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