Dam Disaster · Dam Induced Flood Disaster

Andhra Pradesh: Pulichintala Dam Gate disaster shows improper maintenance and operation

In another dam related disaster in Andhra Pradesh, a flood gate of K L Rao multi-purpose irrigation project also known as Pulichintala  Dam was washed away on August 5, 2021 raising flood alarm in downstream areas along Krishna river. As per latest information the gate has been fixed and officials have started filling up the reservoir again. However, there is no official statement regarding exact causes, financial losses, damages to dam structure and downstream flood impact caused by the apparently avoidable dam disaster. The rule curve seems to be violated in operation of every dam and the gates do not seem to have been properly maintained. An independent enquiry needs to be immediately set up to find out what lessons we can learn and how we can fix accountability for the disaster.

The Incident

The incident occurred around 03:30 am when officials were lifting the two hydraulic-operated gates of the Pulichintala project to release surplus that the dam received overnight. They were to lift the gates to a height of two feet. Within 10 to 15 seconds, the welding holding the gate number 16 to the dam structure came apart and completely blew away the gate due to pressure of the floodwater.

There was heavy inflow[i] of water from upstream Nagarjuna Sagar Project (NSP) following which the engineers started lifting the crest gates of the Pulichintala dam one after another to release the water downstream. The dam has 24 gates and gate number 16 was washed away.

Visiting the area, P Anil Kumar Yadav, State Irrigation Minister said that the incident took place due to breaking of hydraulic girder[ii] under the tremendous pressure of water and an expert committee was set up to further look into the issue.

He also said that the a temporary gate ‘Stop Lock Gate’ would be installed by next day while Suryanarayana the Project Director said the gate could be repaired if the water level was brought down by 10 thousand million cubic feet (TMC). 

When the incident occurred the water level at dam[iii] was 175.21 ft against the full reservoir level of 175 feet with a storage of 44.54 TMC against gross capacity at FRL of 45.77 TMC. The inflows and outflows were 1,33,695 cusecs and 4,51,192 cusecs respectively.

Krishna District Collector J Nivas and Guntur District Collector Vivek Yadav issued flood alerts to all villages along the river upto Prakasam Barrage in Vijayawada as Pulichintala officials raised more gates[iv] to discharge flood waters to reduce pressure on the dam.

Revenue department officials in Krishna district started evacuating people from low-lying areas along the river as the flood discharge was expected to steadily increase to 6 lakh cusecs by August 5, 2021 night.

There was already heavy discharge taking place downstream the project and the incident caused release of additional[v] at least 40,000 cusecs flood discharge.

Flood impact estimation map by APSDMA.

According to Krishna district collector almost five lakh cusecs of water was expected to reach Prakasam barrage in 8-12 hours. At the time of incident Prakasam barrage was receiving[vi] an inflow of 58,939 cusecs of water. The reservoir was already filled to its storage capacity of 3.07 TMC and the authorities were releasing additional water by lifting the gates.

As per C. Narayana Reddy, engineer-in-chief, the Stop Lock gate installation replacing the radial crest gate number 16 was expected to be done by August 7. However the authorities continued draining[vii] water from the Pulichintala dam throughout August 6 and 7 as project was receiving inflow of 64,963 cusecs of water from upstream Nagarajuna Sagar project besides having inflows from other sources.

Finally, after 72 hours, the stop-lock gate was installed[viii] on August 8 morning as the water storage was brought down to 5 TMC. After this, all gates were closed again to fill up the dam. The project was receiving inflows of about 40,000 cusecs.

Incidentally, three rounds of tremors of 3.0, 2.7 and 2.3 magnitude were felt by villagers surrounding the Pulichintala project between 7.15 am- 8.20 am on August 8. Seismology experts said mild tremors took place in the region over the last seven days.

Pulichintala Project

According to Water Resources Department, Andhra Pradesh website[ix] Dr K.L. Rao Sagar Pulichintala Project is a balancing reservoir constructed across river Krishna near Pulichinta Village, Bellamkonda (M) in Guntur District for storing 45.77 TMC to stabilize irrigation 13.08 lakh acres in four districts of West Godavari, Krishna, Guntur and Prakasam.

This major ongoing irrigation project has 4X30 MW hydro power installed capacity with 20,37,656 cusecs maximum designed flood discharge and independent catchment (downstream of NSP) area of 20,028 sq km.

It was given administrative approval in Nov 2005 for project cost of Rs. 681.604 crores which was further revised to Rs. 1281 crores in Aug 2009 and Rs.1816.17 crores in Jan 2014. The website has no information on its present work status.

The project is also part of Modernization of Canals & Drainage system under Krishna Delta which was started in Nov 2007 with a cost of Rs. 4573 Cr. As per the website, about 49.36% of work is completed.

According to other reports, the project was inaugurated in 2013 and started[x] impounding Krishna river water in August 2014. The cost of the project has exceeded Rs.1850 crores. The YSR Congress Party government is having the burden of clearing[xi] dues worth of Rs 199 crore along with interest as the previous regime failed to pay for Pulichintala project.

Who are responsible for Pulichintala flood disaster?

Although the Andhra Pradesh Water Resources Information and Management System (APWRIMS) website[xii] has been publishing real time data of water levels in all the reservoirs in the state (SANDRP has written[xiii] in details on positive aspects and shortcomings of the website), however this incident shows APWRIMS has not helped the cause of efficient or safe dam operation.

The NSP, a major reservoir with 312.05 TMC storage capacity, located 115 km upstream, NSP was being filled up since July 28, 2021 and it already had 311.15 TMC water on Aug 4, 2021, a day before incident. The dam managers released significant amount of water downstream following heavy rainfall spell around that time. 

The Pulichintala project operators too had started filling up the dam since July 28, 2021. On Aug 4, 2021, the reservoir level had increased to 44.54 TMC just 1.23 TMC short of 45.77 TMC, the full reservoir capacity of the project and it did not have adequate flood cushion. Given upstream releases and heavy rainfall in dam catchment, the officials here suddenly started emptying the reservoir to manage flood threat.

It is at this time when the hydraulic gate number 16 of the reservoir developed ‘technical fault’ and could not stand the pressure created by water deluge. The reservoir level was brought down to 22.75 TMC on Aug 5, 2021 and further down to 5.75 TMC to fix the problem. But in the process, the officials had to release massive amount of water in downstream areas creating dam induced flood disaster.

Ironically, the Prakasam barrage located some 80 km downstream has been following the same dangerous trend of filling up reservoir to full capacity when south west monsoon season has full one and half months to go, ignoring the rule curve norms. The APWRIMS website shows that the barrage level is more or less 3.07 tmcft right since early August 2020.

Currently Prakasam or NSP (just 0.9 TMC short of full capacity) has no flood cushion. As the incident has led to emptying the Pulichintala project, it is having 20.29 TMC flood cushion with dam managers trying to fill it up again. While the damaged gate was not fixed for next 72 hours, there was continuous heavy flows in Krishna river for three days flooding the downstream areas.

The south west monsoon arrived in AP on right time on June 5. So far, the state has received 322.05 mm rainfall against the normal of 320.05 mm. As on August 11, 2021, out of 13 districts 4 are in large excess (rainfall more than 60% above normal) category, 1 in excess (rainfall 20-59% above normal), 8 in normal (rainfall within +/- 19% of normal) and just one in deficit (rainfall more than 20% below normal) category. With 24 and 14 percent surplus rains, the Krishna and Guntur districts are in excess and normal category respectively.

Moreover the upstream riparian state of Telangana has received 28 percent more rains (575.3 mm against the normal of 449.3 mm) and lower Krishna basin has got 46% more rains (529.2 mm against 363.2 mm normal) as on August 11, 2021.

Clearly, violating the rule curves, the dam operators were filling up the reservoirs to full capacity while at least 50 days of active monsoon season are remaining. Thus they had left no flood cushion for accommodating possible heavy rainfall and release all the incoming water into flooded downstream rivers, claiming TINA (There Is No Alternative) factor that they love.

The officials have operated the dam in similar manner, suddenly releasing water when faced heavy rainfall or inflows from NSP thus creating flood disaster in downstream areas in August 2020, August2019, September 2018.

Evidently, such incidents and resultant flooding are quite avoidable if the dams are maintained and operated properly, keeping rule curves in mind. The real time rainfall and flow data and advance weather forecast can help the dam managers only if they wish to use the information to improve their functioning and approach.

Such dam induced flood disasters are becoming routine as there is no credible, independent inquiry and critical analysis by outside experts. Even in this case, there is no update on two member committee set up to inquire reasons behind washing away of Pulichintala dam gate.

Compiled by Bhim Singh Rawat (bhim.sandrp@gmail.com)

POST SCRIPT

In another example of wrong operation of these dams on Krishna river; a gush of over 80,000 cusecs of water left more than 100 lorries, meant for sand transportation, stuck inside river Krishna at Chevitikallu in Krishna district on August 14. Over 75,000 cusecs of water came from upstream Dr K L Rao Sagar Project at Pulichintala while another 5,000 cusecs came from Munneru rivulet due to heavy rain in the catchment, revenue officials said.

Sand excavation was being carried out at a reach inside the river and the trucks were meant to carry it out. There had been no warning whatsoever about the impending flood flow and so we went about our work. But we could not return because of the water surge and our vehicles got stuck, some truck drivers said. Revenue officials said they too had no prior information about the flood flow. As the NSP upstream Pulichintala got filled to the brim, water was being discharged downstream. Since a crest gate got damaged at Pulichintala last week, there was no way to impound it there and hence the discharge, the local tehsildar said. Unless water is let out downstream from the Prakasam Barrage in Vijayawada, the flow at Chevitikallu can’t be curtailed.

You may also like to see:-

Krishna-Bhima basin floods in Oct 2020 breaks 56-year-old record

Dams Floods 2018: Filling up Dams well before Monsoon end, Invitation to Disaster

2019 Monsoon: Instances when Dam Safety Came into Question

Dam Floods & Embankment Breaches in South West Monsoon 2020

References:-

[i] https://www.deccanchronicle.com/nation/in-other-news/050821/flood-alert-issued-in-aps-krishna-district-after-pulichintala-dam-gat.html

[ii] https://www.thenewsminute.com/article/flash-flood-alert-two-andhra-districts-after-pulichintala-project-gate-breaks-153492

[iii] https://www.deccanchronicle.com/nation/in-other-news/050821/flood-alert-issued-in-aps-krishna-district-after-pulichintala-dam-gat.html

[iv] https://indianexpress.com/article/cities/hyderabad/andhra-pradesh-dam-gate-breaks-in-guntur-district-flood-alert-issued-7439888/lite/

[v] https://www.newindianexpress.com/states/andhra-pradesh/2021/aug/05/flood-alert-issued-in-andhras-guntur-krishna-districts-after-gate-of-pulichintala-dam-washes-away-2340511.amp

[vi] https://www.deccanchronicle.com/nation/in-other-news/050821/flood-alert-issued-in-aps-krishna-district-after-pulichintala-dam-gat.html

[vii] https://www.deccanchronicle.com/nation/in-other-news/070821/temporary-gate-to-be-erected-at-pulichintala-dam.html

[viii] https://timesofindia.indiatimes.com/city/vijayawada/gate-no-16-fixed-at-pulichintala-project-dam-filled-with-water/articleshow/85160103.cms

[ix] https://irrigationap.cgg.gov.in/wrd/getDistricts#klraosagar

[x] https://en.wikipedia.org/wiki/Pulichinthala_Project

[xi] https://www.deccanchronicle.com/nation/in-other-news/070821/temporary-gate-to-be-erected-at-pulichintala-dam.html  

[xii] https://apwrims.ap.gov.in/

[xiii] https://sandrp.in/2018/11/14/apwrims-impressive-water-information-system-of-andhra-pradesh/

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