Ganga basin faces unprecedented floods in Aug 2017

Ganga Basin, particularly Bihar is facing unprecedented floods, starting on Aug 12, 2017. Water levels of Major tributaries of Ganga, including Kosi, Mahananda, Rapti, Ghagra, Bagmati, Gandak and Kamlabalan are close to or above the historically highest flood levels almost simultaneously. This has rarely happened in the past. The water level of Ghagra is close to HFL at Elgine Bridge in Barabanki district in Uttar Pradesh. Most other flood forecasting sites in North Bihar and East UP were shown as pink dots on CWC flood forecasting map on Aug 13-15, signifying that water level at these sites was above the danger level. This is possibly the beginning, this wave is expected to rise as it travels down towards Bihar and then W Bengal and Bangladesh.

As I wrote on the unprecedented Brahmaputra flood wave on Aug 12, from Aug 11 morning, the purple patch (signifying rainfall in access of 175 mm rainfall in previous 24 hours) on NASA daily Rainfall accumulation map[i] on Brahmaputra basin travelled west to Ganga basin in next two days. Such purple patches generally disappear in 24 hours, since the rains do not last to long. However, in the case of current phase, the purple patch lasted for about 48 hours over large parts of Ganga basin, all along India Nepal border region along the southern boundary of Nepal.

This provided sufficient warning for Centre and states of Bihar and UP to wake up and take all possible preparatory and disaster minimizing steps. One does not see any reflection of this on CWC (Central Water Commission) flood forecasting site[ii], their forecasts continue to come a few hours in advance at best, and even those proved substantiously erroneous or inaccessible.

Nasa Rainfall map of Aug 13, 2017 evening (India Time)

Let us take stock of how the floods arrived, based on CWC flood forecasting sites, as they still provide good picture, in absence of better alternative. The Patna based Ganga Flood Control Commission, as usual had nothing to show on its website.

Both the flood forecasting sites of the Mahananda river, namely Dhengraghat and Jhawa, crossed their respective HFLs of 1968 and 1987. This means that the Mahananda River water level broke almost 50 year old record at Dhengraghat and 30 year old record at Jhawa. At Jhawa, the HFL is at least 53 cm higher than the previous HFL, such jump in HFL is very rare indeed. The Dhengraghat HFL rise of 11 cm is nearer to usual. The water level rise at Jhawa was also unusually rapid.

The Kosi river water level was in fact the first one in Bihar this season to breach the HFL at night on Aug 12. This led to breach in embankments, as well known Flood expert of Bihar, Dr Dinesh Mishra reported. This possibly has delayed the arrival of this water to downstream flood forecasting sites along Kosi River. However, on 15th Aug, Baltara on Kosi River also entered the site where water level was within 0.5 m of HFL.

The Gandak River crossed HFL at Dumariaghat in Gopalganj district, while Rapti river in Ghagra basin crossed HFL at Balrampur, and both remain above HFL and show rising trend as I write this. Bagmati River at Benibad and the Kamlabalan River at Jhanjharpur remained shown as orange dot on CWC flood forecasting site (signifying that River water level was within 0.5 m of the HFL for respective sites), but did not cross HFL, partly because of the breach of embankments on these rivers. The full impact of breach of these embankments is not know, and possibly will never be know, but anecdotal news shows that the impact is huge and devastating.

Upstream dams like the Bansagar in Sone basin in Madhya Pradesh (which triggered the Aug 2016 flood disaster in Bihar by suddenly releasing huge quantity of water while downstream river was in floods due to heavy rains) and Tehri in Uttarakhand are almost full and could add to the crisis if they decide to release large quantities of water.

The cumulative impact of all these floods is bound to travel to Ganga, even though rains have decreased in catchments of Ganga tributaries. The role of Farakka barrage on Ganga River, in creating siltation, drainage congestion and backwater flood is once again likely to come in sharp focus in days to come, like the way it happened in Aug 2016. Bihar Chief Minister Nitish Kumar, heading a Mahagathbandhan govt last year blamed Farakka for the flood crisis in Bihar. Let us see how he responds this year, now that he heads a NDA govt, which is also in power at centre.

The floods also created extensive damage in Nepal, the full details are not yet known. Media earlier reported at least 36 deaths in Nepal[iii], among other damages.

In the table below I have given an overview of these sites where water level has already come within half a meter of highest ever recorded flood levels, including information about the water level attained, water level forecast and HFL recorded on CWC’s flood forecasting site.

Flood forecasting sites in Ganga Basin where river water level is

within 0.5 m of HFL or has crossed HFL

Site name River Dist/ state HFL attained / Date RWLevel attained / Time – Date RWLevel forecast / Time – Date
Dhengraghat Mahananda Purnia/ Bihar 38.09 / 15.08/1968 37.6R / 12-1308[iv] 37.85 / 06-1408
38R / 22-1308 38.3R / 06-1408
38.14S / 06-1408
38.2R / 08-1408
38.02F / 16-1408 37.55F / 06-1508
37.54F / 08-1508
Jhawa Mahananda Katihar/ Bihar 33.51 / 14.08.1987 33.08R / 22-1308 33.55R / 06-1408
33.9R / 06-1408 32.95F / 06-1508
34.04R / 08-1408
33.83F / 16-1408
Basua Kosi Supaul/ Bhiar 49.17 / 25.08.2010 48.73R / 14-1208 49.23R / 07-1308
49.23R / 08-1308
49.23F / 12-1308 49.14F / 22-1308
49.2F / 16-1308
49.15 / 22-1308
48.92F / 08-1508 48.9F / 07-1508
Baltara Kosi Khagaria/ Bihar 36.4 / 15.8.1987 35.94S / 22-1508 35.94S / 6-1608
Benibad Bagmati Muzzafarpur/ Bihar 50.01 / 20.07.2004 49.56R / 06-1408 49.6S / 06-1508
49.55S / 10-1508 49.55S / 06-1608
Jhanjharpur Kamlabalan Madhubani / Bihar 53.01 / 10.07.2004 52.5R / 16-1308 52.65F / 23-1308
52.67R/22-1308
52.69S / 06-1408 52.5F / 23-1408
52.56F / 20-1408
Dumariaghat Gandak Goaplganj/ Bihar 63.6 / 18.8.2004 63.12R / 08-1408 63.7R / 06-1508
63.31R / 20-1408
63.7S / 10-1508 63.45F / 06-1608
Balrampur Rapti Balrampur/ UP 105.51 / 16-08-2014 105.02R / 17-1308 105.35R / 08-1408
105.29R / 18-1408 105.55R / 08-1508
105.5R / 08-1508
105.52R / 11-1508 105.6R / 08-1608
Elgine Bridge Ghagra Barabanki / UP 107.616 / 16.08.2014 107.2R / 11-1508 107.35R / 08-1608

(unit: Meters)

Brahmaputra At Goalpara (Assam) site in Goalpara district on main stem of Brahmaputra (HFL of 37.43 m reached on 31.07.1954, possibly the oldest standing HFL record), the river water reached the level of 37.02 m (Steady trend) at 1200 hrs on Aug 15, 2017 and is forecast to remain at this level till 0600 hrs on Aug 16, 2017.

At Dhubri (Assam) site in Dhubri district on main stem of Brahmaputra (HFL of 30.36 / 28.8.1988), the river water reached 29.87 m (steady trend) at 2100 hrs on Aug 15, 2017 and is forecast to remain at this level till 0600 hrs on Aug 16, 2017.

These are the 8th & 9th sites in Brahmaputra basin, where river water level has reached within 0.5 m of HFL for that site, the list of seven earlier sites is given in our report[v] dated Aug 12, 2017. Large parts of Assam, North Bengal and other parts of Brahmaputra basin continues to remain flood impacted. 

Bangladesh flood forecasting website (http://www.ffwc.gov.bd/), however, provides, for each of its flood forecasting location, a graph that shows the actual water observation for the past week and also the forecast for the next five days. Its amazing, that CWC, with much better resources than Bangaldesh, cannot provide this.

Example of a graph from Bangladesh flood forecasting website

Damage in Bihar As per some media reports[vi], 41 people have already died, 25 districts are affected, 1.79 lakh ha cropped land is damaged, 3200 villages are inundated and 31 lakh people have been affected. These figures are likely to rapidly go up.

In Conclusion It is indeed sad that most of Bihar, large parts of North East and North Bengal are flooded as India celebrates 71st Independence day. The best message on this day would be to learn from our experience to minimize the damage, accept that floods will come and fix accountability for the lack of maintenance of embankments, rivers and wrong operation of dams. As we have not been doing that, we are inviting more and more disasters.

It remains to be seen how Nitish Kumar led Bihar govt deals with this crisis of unprecedented floods in Bihar in days to come.

SANDRP (ht.sandrp@gmail.com)

END NOTES:

[i] https://trmm.gsfc.nasa.gov/publications_dir/instant_2.html

[ii] http://www.india-water.gov.in/ffs/current-flood-forecast/

[iii] http://www.firstpost.com/world/nepal-floods-36-killed-12-missing-hundreds-displaced-due-to-landslides-torrential-rain-3924719.html

[iv] Explanation: 37.6R / 12-1308: 37.6 is in meters, as all levels are. R stands for Rising, similarly S stands for steady and F stands for Falling. This shows that trend of this site at this location, both in terms of actual level and forecast level. 12 means 12 hours, 1308 means the date is 13 Aug.

[v] https://sandrp.wordpress.com/2017/08/12/brahmaputra-basin-faces-unprecedented-flood-wave-in-aug-2017/

[vi] http://www.hindustantimes.com/india-news/floods-in-bihar-assam-bengal-train-services-hit/story-2ONGYWWBXp5ErnCwAvWnzO.html

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