CWC - Central Water Commission

Rivers crossing HFLs in Oct-Nov 2021

Feature image probably shows flooded human habitation along Cheyyeru river after Annamayya project failure on Nov. 19. However, caption of image published in Deccan Herald report does not mention it.

India has been witnessing unusual monsoon rains in 2021. First the delay in South West Monsoon[i] withdrawal till third week of October 2021 brought heavy rainfalls in several states of North India in the first half of October 2021. Then the extreme rainfall spells during North East Monsoon[ii] have caused floods in several parts of south India in quick succession in November 2021.

In October 2021, the all India rainfall has been 33% above normal while November rainfall being record breaking 86% above normal. The formation and interactions between low depressions and western disturbances largely contributed in record breaking rainfall events during this period including the onset of La Nina phenomena.   

The unprecedented rainfall has also resulted in rivers breaching of Highest Flood Levels (HFL) at 30 sites including 7 sites in North India, 1 in East and 22 sites in South India, according to Central Water Commission (CWC) Flood Forecasting site[iii] in these two months. The analysis of all such incidents in 2018[iv], 2019[v], 2020[vi] and 2021[vii] can be seen on SANDRP website.

Ganga Basin  

Following unprecedented rainfall[viii] in third week of October 2021, several rivers in Ganga basin flooded dangerously in Uttarakhand and Uttar Pradesh. This heavy downpour also led to breach in HFLs at least at 7 sites of which 6 are in Uttarakhand and 1 in Uttar Pradesh.

All the 6 sites in Uttarakhand are Level Monitoring (LM) sites and the lone site in Uttar Pradesh is Level Forecast (LF) site. The highest rise of 3.97 metre (m) above previous HFL is recorded at Ramnagar Barrage on Kosi river in Nainital followed by 3 m rise above old HFL at Ghat site on Sarda river in Pithoragarh district.

Hydrographs of rivers beaching HFLs in Uttarakhand.

This event also exposed unpreparedness in CWC flood monitoring works as there were glitches at several sites where no progress in hydrographs was registered for a day while the rivers were in extreme flood situation. Moreover several sites in Sarda basin were out of work during the deluge.

So far, CWC has not updated the new HFL at any of the sites mentioned in the table below. On the contrary, in several cases, it has removed old HFL and dates for these sites. For Paliakalan site in Kheri, CWC has changed Warning Level (WL) from 152.32 m to 153.1 m and Danger Level (DL) from 153.32 m to 154.1 m.

Old HFLDateNew HFLDate/ Time of new HFLRise above old HFLLevel Above old HFL for hrsHFL Up-dated?
1Karanprayag (A) NAChamoli Uttarakhand 758.3 m18.08.2019759.92 m19.10.2021 15:00 hrs1.62 m22 hrsNo
2Devprayag (A) AlaknandaPauri Uttarakhand 466.9 m18.08.2019467.48 m19.10.2021 07:00 hrs0.58 m2 hrsNo
Pithoragarh Uttarakhand 472 m16.08.2011475 m19.10.2021 14:00 hrs3.0 m10 hrsNo
4Pancheshwar SardaChampawat Uttarakhand 432.5 m16.08.2011433.3 m19.10.2021 14:00 hrs1.9 m8 hrsNo
Nanital Uttarakhand 476.89 m18.08.2019478.79 m19.10.2021 22:00 hrs0.27 m23 hrsNo
6Ramnagar Barrage KosiNainital Uttarakhand 216.98 m01.06.2019220.95 m19.10.2021 14:00 hrs3.97 m41 hrsNo
7Paliakalan SardaKheri, UP152.32 m 153.32 m155.32 m21.07.2014155.82 m20.10.2021 18:00 hrs  0.5 m47 hrsNo

Brahmaputra Basin

It’s almost after 25 years that Teesta river at Mekhliganj LF site has breached the old HFL that too in later half of October. CWC website has not updated the new HFL readings.

District/ StateWL/
Old HFLDateNew HFLDate/
Rise above old HFLAbove old HFL for hrsHFL Up-dated?
1Mekhliganj TeestaKochbihar
W Bengal
65.45 m 65.95 m66.45 m13.07.199666.62 m20.10.2021 07:00 hrs0.17 m8 hrsNo

Cauvery Basin

In Cauvery basin HFL is breached at 4 sites of which 3 are LM and 1 LF site. Interestingly river Shimsa at Thoreshettahalli LM site has breached old HFL thrice within a month cumulatively gaining 0.69 m rise over HFL attained in October 2019. CWC lacks old HFL dates for Ayyar river at Thandalaiputhur LF site and Marudaiyar river at Varanavasi LM site. CWC has not updated new HFL recordings at its website as on December 12, 2021. 

Hydrographs of rivers breaching HFL in Cauvery basin in Karnataka.

WL/ DLOld HFLDateNew HFLDate/ TimeRise above old HFLAbove old HFL for hrsHFL Up-dated?
1Thoreshettahalli ShimsaMandya Karnataka 624.41 m17.11.2021 01:00 hrs624.59 m21.11.2021 11:00 hrs0.18 m23 hrsNo
1A   624.05 m23.10.2021 11:00 hrs624.41 m17.11.2021 01:00 hrs0.36 m14 hrs 
1B   623.9 m07.10.2019624.05 m23.10.2021 11:00 hrs0.15 m08 hrs 
2Pudunagara UduthorehallaChamaraja Nagar, Karnataka 587.71 m06.12.2017587.8 m15.11.2021 07:00 hrs0.09 m25 hrsNo
3Thandalaiputhur AyyarTiruchira-ppalli
Tamil Nadu
97.3 m 98.3 m98.5 mNA98.735 m26.11.2021 10:00 hrs0.235 m07 hrsNo
4Varanavasi MarudaiyarAriyular   Tamil Nadu 61.8 mNA62.02 m26.11.2021 10:00 hrs0.22 m06 hrsNo

Hydrographs of rivers breaching HFL in Cauvery basin in Tamil Nadu.

Pennar Basin

Old HFL is breached at 2 LM and 1 LF sites in Pennar river basin. All 3 sites have recorded new HFL on November 19-20, 2021. While at Singavaram LM site river Chitravathi has set new HFL after 33 years, the Pennar crossed old HFL at Nellore Anicut LF site after 39 years. This is the event when the record breaking rains and failure of Pincha and Annamayya projects[ix] have caused large scale flood destruction in four districts of Andhra Pradesh.

District/ StateWL /
Old HFLDateNew HFLDate/
Rise above old HFLAbove old HFL for hrsHFL Up-dated?
1Singavaram ChitravathiAnantpur Andhra Pradesh 260.355 m12.09.1988261.58 m20.11.2021 01:00 hrs1.225 m13 hrsYes
2Nandalur CheyyeruCuddapah Andhra Pradesh 137.2 m17.11.2015138.12 m19.11.2021 09:00 hrs0.92 m15 hrsYes
3Nellore Anicut PennarNellore Andhra Pradesh15.91 m 17.28 m18.7 m30.11.198219.57 m20.11.2021 06:00 hrs0.87 m~17 hrsNo

East flowing rivers (EFR) between Pennar & Kanyakumari

At least 17 HFL breach incidents has been witnessed in just 18 days of November 2021 (between 12 and 29, November). 7 of the breaches are recorded in single day of November 19. Interestingly all of these are LM sites.

Hydrographs of rivers breaching HFL in EFR between Pennar & Kanyakumari in Andhra Pradesh.

At 2 sites Buggaagraharam on Nagari river in Chittoor district of Andhra and at Monnavedu site on Kosasthalaiyar river in Tiruvallur district of Tamil Nadu HFLs are breached twice while Kallar river at Poyyapakkam site in Ranipet district of Tamil Nadu registered HFL breach thrice during these days.

Hydrographs of rivers breaching HFL more than once at Poyyapakkam & Monnavedu sites in EFR between Pennar & Kanyakumari under Tamil Nadu state.

Cumulatively, the HFLs have gone up by 2.52 m at Mannavedu and 0.72 m at Poyyapakkam sites. The highest single time rise over old HFL is seen at Kumarapalayam site on Varahanadhi river in Puducherry which is 2.135 m followed by 1.78 m rise at Puduvayal site on Aranair river, 1.15 m rise at Chengalpatu site on Palar river at Chengalpattu district and 1.03 m rise at Nariyampattu site on Palar river in Vellore district.

Hydrographs of other rivers breaching HFLs in EFR between Pennar & Kanyakumari under Tamil Nadu state.

CWC lacks old HFL dates for Panneswaram Madam site on Ponnaiyar river and Ayilambedu site on Kosasthalaiyar river. It has not updated new HFL records for Poyyapakkam and Venganur site on Periyaodai river. Thirunavalur is newly functioning site on Gadilam river in Vellipuram district which witnessed significant rise on November 19, 2021 and 36.27 m is its first HFL there.

WL/ DLOld HFLDateNew HFLDate/
Rise above old HFLAbove old HFL for hrsHFL Up-dated?
1Narasinga-rayanipet PoiniChittoor Andhra Pradesh 269.03 m27.11.2020269.59 m19.11.2021 09:00 hrs0.56 m17 hrsYes
2Buggaagra- haram
Chittoor Andhra Pradesh 95.45 m12.11.202196.25 m19.11.2021 01:00 hrs0.8 m11 hrsYes
2A   94.75 m27.11.202095.45 m12.11.2021 06:00 hrs0.7 m12 hrs 
3Panneswaram Madam PonnaiyarKrishnagiri Tamil Nadu 447 mNA447.52 m19.11.2021 14:00 hrs0.52 m16 hrsYes
Tamil Nadu
 197.92 m20.11.2020198.55 m19.11.2021 01:00 hrs0.63 m13 hrsYes
5Vazhavachanur PonnaiyarThiruvanna- malai
Tamil Nadu
 138.782 m17.11.1991139.4 m19.11.2021 06:00 hrs0.618 m17 hrsYes
6Poyyapakkam KallarRanipet
Tamil Nadu
 101.91 m19.11.2021 09:00 hrs102.38 m29.11.2021 04:00 hrs0.47 m24 hrsNo
6A   101.74 m12.11.2021 05:00 hrs101.91 m19.11.2021 09:00 hrs0.17 m17 hrs 
6B   100.94 m10.12.2020101.74 m12.11.2021 05:00 hrs0.8 m46 hrs 
7Monnavedu KosasthalaiyarTiruvallur
Tamil Nadu
 101.32 m12.11.2021 19:00 hrs102.82 m20.11.2021 05:00 hrs1.5 m20 hrsYes
7A   100.3 m05.12.2020101.32 m12.11.2021 19:00 hrs1.02 m47 hrs 
8Ayilambedu KosasthalaiyarVellore
Tamil Nadu
 97.85 mNA97.97 m21.11.2021 12:00 hrs0.12 m07 hrsYes
9Nariyampattu PalarVellore
Tamil Nadu
 99.75 m13.10.2021100.78 m19.11.2021 23:00 hrs1.03 m>110 hrsYes
Tamil Nadu
 97.47 m27.11.202099.25 m12.11.2021 08:00 hrs1.78 m18 hrsYes
11Venganur PeriyaodaiCuddalore Tamil Nadu 78.26 m04.12.202078.79 m26.11.2021 03:00 hrs0.53 m08 hrsNo
Chengalpattu Tamil Nadu 28.2 m02.12.201529.35 m19.11.2021 14:00 hrs1.15 m~84 hrsYes
13Kumarapalayam VarahanadhiPuducherry 13.12 m31.12.201115.255 m19.11.2021 12:00 hrs  2.135 m51 hrsYes
 Thirunavalur GadilamVellipuram Tamil Nadu   36.27 m19.11.2021 17:00 hrs   

Hydrographs of Varahanadhi river breaching HFL at Kumarapalayam site in Puducherry.

West flowing rivers (WFR) from Tapi to Tadri

The Manimala river at Pullakkayar site in Kottyam witnessed sudden rise of 3.425 m above old HFL on October 16, 2021.

District/ StateWL/ DLOld HFLDateNew HFLDate/
Rise above old HFLAbove
old HFL for hrs
HFL Up-dated?
1Pullakkayar ManimalaKottyam Kerala96.2 m 98.2 m98.315 m07.08.2020101.74 m16.10.2021 13:00 hrs3.425 m09 hrsYES

West flowing rivers (WFR) from Tadri to Kanyakumari

The Kodaiyar river breached the HFL at Thiruvarambhu LF site in Tamil Nadu thrice this year cumulatively rising 2.11 m higher than August 2018 HFL. CWC has not updated the new HFL so far.

WL/ DLOld HFLDateNew HFLDate/
Rise above old HFLAbove old HFL for hrsHFL Up-dated?
1Thiruvarambu KodaiyarKanyakumari Tamil Nadu11 m 12 m15.67 m17.10.2021 05:00 hrs15.7 m13.11.2021 21:00 hrs1.02 m10 hrsNo
1A   14.68 m26.05.2021 14:00 hrs15.67 m17.10.2021 05:00 hrs0.99 m20 hrs 
1B   14.58 m15.08.201814.68 m26.05.20210.1 m03 hr 

River Basin and State Wise Summary

In just two months of October and November 2021, rivers have breached old HFLs at least at 30 sites including 5 sites (Kodaiyar river at Thiruvarambu, Kosasthalaiyar river at Monnavedu,  Kallar river at Poyyapakkam in Tamil Nadu, Nagar river at Buggaagraharam in Andhra Pradesh and Shimsa river at Thoreshettahalli site in Karnataka) where HFLs is breached twice or thrice during this period.

Out of this 24 are LM sites and 6 are LF sites. Maximum HFL breach incidents (13) have taken place in EFR between Pennar and Kanyakumari.  The HFL breaching incidents were seen at 27 sites during South West monsoon 2021.

SNBasinStatesLevel MonitoringLevel ForecastTotal
  Uttar Pradesh000101
2BrahmaputraW Bengal000101
  Tamil Nadu010102
4PennarAndhra Pradesh020103
5EFR between Pennar & KanyakumariAndhra Pradesh020002
  Tamil Nadu100010
6WFR from Tapi to TadriKerala000101
7WFR from Tadri to KanyakumariTamil Nadu000101
 Sub Total 240630

Month wise summary

There were 9 HFL breach incidents in Oct 2021, while Nov 2021 has seen 21 such events.  

Month   RiverBasins  Total
 GangaBrahma-putraCauveryPennarEFR between Pennar & KanyakumariWFR from Tapi to TadriWFR from Tadri to Kanyakumari 

In addition this, there are at least 6 sites (2 LF and 4 LM) where old HFL has either been touched or missed by narrow margins, details of which is given in table below.  

Old HFL/
level date/ time in Oct/ Nov 2021
Missed HFL breach by
1Pipalkoti AlaknandaChamoli Uttarakhand 1051.86 m 27.07.2021
03:00 hrs
1051.8 m
14:00 hrs
0.06 m
    1051.78 m 19.08.2019  
2Kachhla-bridge GangaBudaun, Uttar Pradesh161 m 162 m162.79 24.09.2010162.79 m
01:00 hrs
3Bendrahalli SurvarnavathiChamaraja Nagar, Karnataka 634.7 m 13.09.2013634.65 m
10:00 hrs
0.05 m
4Venganur VellarCuddalore Tamil Nadu 78.26 m 04.12.202078.12 m
07:00 hrs
0.14 m
5Ashramam PazhayarKanyakumari Tamil Nadu45.5 m 6 m7.1 m NA7.1 m
17:00 hrs
6Kuzhithurai ThambraparniKanyakumari Tamil Nadu 8.83 m 08.12.20108.31 m
05:00 hrs
0.52 m

CWC’s flood monitoring work remains inconsistent, opaque as being highlighted regularly by SANDRP. It’s randomly updating new HFLs for some sites and skipping doing same for most of the sites. For example out of 30 HFL breach incidents as documented here, it has not updated new levels for 16 sites while 4 of these sites lack old HFL dates as on December 12, 2021.

Due to wrong data entry Doni river level is shown increased by 141.59 m suddenly at Talikot site in Bijapur district.

Cumulatively, HFL breach incidents have taken place at 57 sites (at 27 sites during South West Monsoon and 30 in the month of October and November) in 2021 (38 are LM & 19 LF sites).

Bhim Singh Rawat (











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