** The Monsoon and the fury of river Ganga : **
In India, the Ganga basin covers states of HimachalPradesh ,Uttarakhand , Uttar Pradesh, Haryana, Union Territory of Delhi , Rajasthan ,Madhya Pradesh, Chhattisgarh, Jharkhand, Bihar, West Bengal, and draining an area of 8,61,452 Sq.km which is nearly 26% of the total geographical area of the country.
The total length of river Ganga (measured along the Bhagirathi and the Hooghly) up to its outfall into Bay of Bengal is 2,525 km. The principal tributaries joining the river from right are the Yamuna and the Sone. The Ramganga, the Ghaghra, the Gandak, the Kosi and the Mahananda join the river from left. The Chambal and the Betwa are the two other important sub- tributaries. The major part of basin in Indian territory is covered with agricultural land accounting to 65.57% of the total area and 3.47% of the basin is covered by water bodies.
In order to utilize the vast water resources of river Ganga , no of storages / reservoirs were constructed on different tributaries for irrigation and flood control measures. These include Matatial, Sarda Sagar, Ramganga, Bansagar dam (Interstate MP-Madhya Pradesh, UP-Uttar Pradesh, Bihar), Rajghat Dam (Interstate MP, UP), Chambal Valley dam (Gandhisagar, Ranapratap Sagar, Jawahar Sagar), Tehri, Rihand and Mayurakshi , Kangsabati, DVC Damodar Valley Corporation reservoirs.
Thus, the entire water resources management mainly deals with the issues, related to both high and low flows in the river system, on different sub-basin.
We usually see that while India’s monsoon season matures, the rivers keep rising, causing flooding in many parts of the country.
Uttar Pradesh , Bihar and West Bengal are the major states, affected by floods. Many of the flood problems are resulted by the northern tributaries of Ganga such as Ghaghra, Gandak, Kosi and Mahananda from its northern side , though there are also flood problems , caused by Southern tributaries i.e. Like Yamuna and the Sone etc.
In the recent past, due to widespread rainfall throughout entire basin, the Ganga crossed the danger mark in Uttar Pradesh,Bihar, West Bengal, and neighbouring districts of . Moreover, along with, other important tributaries also rose with the effect of incessant rains and even some of them became in spate.
This resulted sharp rise in the water level of Ganga and also experienced the flood like situation in all the districts situated along the banks of the river. The 12 districts are affected in Bihar , where 28 districts are flood hit in UP along with several districts of Madhya Pradesh .
Earlier, it was seen that in Uttar Pradesh, with heavy rainfall in this monsoon season, the River Ganges (Ganga) rose above the danger mark, while the river Yamuna at Allahabad and the city had suffered flooding of this confluence for weeks.
Apart that, Bihar too, was under the threat of flooding looms over Patna, the capital of the eastern Bihar state. Actually, the Bihar became victim of floods in this monsoon followed by upland discharges in the successive manner, i) due to passing of high discharge from Kosi river region in Nepal, ii) the wide spread precipitations in Jharkand ,MP, and UP adding water to Sone river , with the result of high release of storage water from Bansagar Dam, usually takes 36 hours to reach Patna .
The water resources department also said that the discharge through the Sone was increased from 4.83 lakh cusec (18th Aug’16 , afternoon ) to 11.2 lakh cusec by 19th August’16 , morning , which later came down to 3.22 cusecs in the afternoon.
The previous record states that the discharge through river Sone was 14.48 lakh cusec in the last week of 1975, when one of the worst floods hit Patna. It was learnt that after the floods in 1975, when the waters of the Ganges and the Sone rivers caused extensive damage, a town protection work for of 8.5 km long Patna town was taken up .
The Central Water Commission (CWC) said the Ganga’s water level in the state capital at Gandhi Ghat in Patna at 8pm on 20th August 2016 was 50.52 meter mark, dangerously up from even the 1994 mark of 50.27m.
The report also said that on 23rd Aug morning the river’s water level rose up overnight by nearly 4.5ft. which inundated a stretch along the Ganga from Danapur to Patna City with flood water overflowing within residential apartments, houses and business .
It was stated that the Ganga and six other rivers were flowing above the danger mark in Patna, Bhagalpur, Khagaria, Katihar, Siwan, Bhojpur, Buxar and Hajipur districts, a disaster management department statement said.
When wide spread rainfall occurs throughout the basin area of river Ganga , it carries not only its direct discharge , but also collects the discharges from other associated tributaries. But, the situation becomes grave, when the peak discharge from individual sub basin, coincides with the main Ganga flow line.
Every river flow course has its sustainability to carry particular discharge. When the river crosses the extreme danger level, there is either spilling of river flow or breaches along the embankment at certain week point to drain out water towards country side.
It is pertinent to mention here that most of the river has little flow during the lean period. On the contrary , in each occasion of the incessant rains in the monsoon period , when high storm water runoff is generated from the respective catchment area , it starts draining through valleys to meet with the respective tributary and finally to flow out into major rivers. Now, according to pattern of synchronization of peak flows from the either side, the major river at the particular moment, started swelling and becomes vulnerable and in spate.
Every river has safe flood water passage. When it fails to accommodate, the damages start in various degrees•
The flood water initially passes through the main course, gradually it covers the entire stretch of flood plain or diara land and finally overwhelmed the adjoining lands with water spilling over the banks, when the river fails to accommodate the upland discharge within its flood plain. The depth of flooding however varies considerably at different locations according to classification of diara lands , Actually, the Upper diara lands are those lands which during the course of continuous depositions get elevated and are less frequently flooded, in comparison to the middle diara lands. The fury of river and its damages, at the particular location will depend how it can accommodate flood water in the river system.
Probably, to combat such incident of severe storm, efficient administrative action, shall be the most important tool to deal with. Timely responding & dissemination of warning effectively amongst the people, residing in the basin area may definitely help to minimize the huge losses in terms of human lives and other physical damages.
After all, we cannot stop the passage of flood water down the river, generated from the upper catchment or storage reservoir during such intensive rainfall. But, in that circumstance, the administrative authority , may come forward with the proper facts for the appraisal of the mass people in time by applying latest communication technology , intimating about the behaviour of flood inundation and its extent of severity at each stages of discharges vis- a- vis with its level of water and more so about the consequences and also , if the river fails to sustain to accommodate the flood discharge at the particular water level (WL) , then “what will be the probable areas likely to be inundated with the duration and depth of inundation”. Mapping of flooding zones are essential to educate people living along the banks on the vulnerability of their area during such deluges.
One thing is very pertinent to decide and identify the safe discharge of flood water to be allowed for the river ways”- the passage of which should not be encroached upon by human interference in any way.
Therefore, application of better planning & improved flood and disaster response in time may be our major thrust to tackle such great eventualities, particularly, aftermath of any such incessant rainfall.
More than a million people across Uttar Pradesh , Bihar , West Bengal have been adversely affected by floods. Bihar pointed out that that this has happened despite the fact monsoon has been shortfall to some extent . Actually, Bihar had to face flood havoc due to high upland discharges. This implies that it is entirely within the ambit of Governments to mitigate the impact of these events. While the states and central government have deployed the resources to deal with the situation, probably, a lot more can be done to minimise the large scale physical / financial damages and also losses to human lives and animals.
Major rivers in spate have been the primary cause of the current problem. The tragic fall out of this phenomenon can be averted if states begin to look on rivers as a organic whole. Any action, upstream or downstream, can spill over into other states along the river’s course. In addition , it need to enhance funding for water resources management which will help states take more preventive measures to combat flooding. Floods on this occasion have submerged rural areas as well as parts of urban areas located on riverbanks.
Urban flooding is usually a consequence of poor functioning of municipal corporations. Actually, in some cities, the adjoining outfall river takes a key role to accelerate the gravity of flood inundation / water logging in the city’s basin area. The overflowing water enters in to the city either damaging / overflowing banks or by ingressing via outlet drainage line when the outfall ruling water level exceeds the country side hydrological water parameters.
The floods also point to the need for closer coordination with neighbours too. An overflow in Nepal has repercussions in Bihar. While India and Nepal need to have a mechanism to find solutions to this problem and these need, probably greater interaction at the highest level on both sides. It may not be possible to prevent floods entirely, but it is possible to mitigate their impact. Our policies may work towards ensuring both.
However, the recent floods in Bihar, Uttar Pradesh and Madhaya Pradesh have brought the problem of silt and congestion into focus. One report said that the Water resources ministry had set up a committee on erosion and siltation in rivers to study the problems of erosion, siltation and requirement of desiltation /dredging of major rivers and suggest remedial measures. The main intention is to formulate a national silt management policy for ensuring uninterrupted flow of water within the sustainable capacity commensurate with the hydrological & physical parameters of the river system , not only in Ganga , but all other rivers, facing with the similar problem of silt deposition at different intensities.
It may be stated here , one opinion was expressed that the Farakka barrage may be one of the causes , that accelerating silts deposition at the upstream side of the barrage. The Farakka barrage is of 2.62 km long , constructed about 460 km downstream of Patna city. The design discharge is 27 lakhs cusec, with No. of Bays: 109, Lowest Bed Level: 10.30 m. above m.s.l. Pond Level: 21.9 m. above m.s.l.
The barrage does not store any water and allow entire flood water to the downstream side without any restriction, it appears that the Farakka barrage may not have direct impact to accelerate the flood discharge at the Patna city, remaining far away from the Farakka barrage. However, the problem of annual addition of high sediment in the upstream of the barrage is there . Now, the question arises that how much it influences for the sit deposition towards further upstream side and also the cause of slow receding of flood water along the river system . All such related issues would be examined during the study , by the newly formed river expert committee.
In the perspective of above , it appears, probably, that any de-silting work along the major rivers to the affected stretches, in order to have appreciable impact, may be a herculean job as it needs to be removed huge sediment and negotiate with the link projects for proper utilization of earth materials .