The curse of Farakka: Purpose defeated
The Hooghly River used to get dry in the last century. We made the Farakka Barrage in the seventies to divert water of the Ganga to the Hooghly to keep her alive. Subsequently we made agreement with Bangladesh to share water of the Ganga equally
The Hooghly River used to get dry in the last century. We made the Farakka Barrage in the seventies to divert water of the Ganga to the Hooghly to keep her alive. Subsequently we made agreement with Bangladesh to share water of the Ganga equally.
We are now diverting one-half of the water to Hooghly and one-half is going to Bangladesh through the Padma River, by which name Ganga is known in Bangladesh. Farakka has been successful in making the Hooghly live again. However, three problems have arisen.
First problem is that the Sunderbans are getting eroded due to Farakka. The sediments brought by the Ganga are distributed unequally between Hooghly and Padma. The Farakka Barrage has gates to regulate the flow to Hooghly and Padma. A pond has been formed behind the barrage. The sediments settle in this pond.
The water coming out from below the gates of Farakka goes to Bangladesh. This water carries more sediments. Water from the upper levels of the pond goes to the Hooghly. This water carries less sediments. The result is that while water is shared equally, more sediments go to Bangladesh and less to Hooghly.
Both Bangladesh and India are suffering due to this imbalance. The more sediments going to Bangladesh are leading to the deposition of sediments in bed of the Padma, choking of the channel and increased flooding in Bangladesh.
A fortuitous result, however, is that part of these excessive sediments reaching the Bangladesh seacoast are leading to accretion of the land of Bangladesh. On the other hand, the water going to Hooghly has less sediments. This brings trouble of a different type. The sea has a natural hunger for the sediments just as we have hunger for bread.
Since the Hooghly is bringing less sediments, the hunger of the sea is not satisfied, and the sea has started to eat the Ganga Sagar Island. In this way, the Farakka Barrage is eating the sacred land of India.
The Tehri Dam and Haridwar and Narora Barrages have added to the problem. The sediments brought by Bhagirathi River is arrested in the reservoir of Tehri Dam. The sediments brought by Alaknanda are partly removed along with water at Haridwar and Narora Barrages even during the monsoons.
As a result, there is less water and less sediment in the Ganga below Narora. Of these, the less water is leading to a reduction in the velocity of the river and, even though the amount of sediments is also less, the Ganga is not able to carry these less sediments to the sea. The result is that these sediments are settling in the channel of the river and the riverbed is rising.
Such deposition of sediments took place before the making of Tehri and Narora as well. However, at that time we had massive floods once every five or 10 years and the sediments that had been deposited in the previous few years were pushed to the sea. The channel was cleaned-up and capacity of the river to carry floodwaters was restored.
Presently, however, the riverbed is not getting cleared of the deposited sediments, the channel is not getting cleared, the capacity of the Ganga to carry flood waters is getting reduced, she is not able to accept the floodwaters brought by Kosi and Gandak and entire Bihar is repeatedly being inundated by the floods.
The reduction of water in the Ganga and, consequently, in the Hooghly due to the abstraction of water at Haridwar and Narora is having another unexpected result. The sea brings in large amount of sand with it during the high tide which is stronger. It is, however, not able to carry this sand back with the low tide which is weaker.
Therefore, the sea has always deposited sediments in the mouths of the Ganga. Indeed, part of the land of Ganga Sagar being eaten by the sea today is being deposited in the mouths of the Ganga. This natural phenomenon has become adverse because these sediments were previously being pushed back into the sea during the major floods.
This is not happening now because water is less because of Tehri, Haridwar and Narora. The result of this deposition is that it is becoming progressively difficult for ships to come into Haldia and Kolkata ports. Often a dredger moves in front of a ship clearing the channel for the ship to move on. The purpose of Farakka to assist navigation has been utterly defeated.
The solution to these problems requires a comprehensive study. Some preliminary thoughts can however be shared. Firstly, we need to find alternative ways of diverting the water to the Hooghly such that the balance between water and sediments is not disturbed.
One possibility is to dredge the Bhairavi and the Jalangi Rivers downstream of Farakka. These rivers join the Hooghly. We divert the water-and-sediment of the Ganga to the Hooghly though these rivers if we do not make a barrage and a pond wherein the sediments settle.
Secondly, we must think of removing the Tehri Dam, and Haridwar and Narora Barrages to bring back the major floods so that two objectives can be attained, namely, (1) the channel can be cleared and floods can be reduced; and (2) the sediments can be pushed to Ganga Sagar and erosion can be contained.
This will certainly lead to a reduction in the availability of water for irrigation in Uttar Pradesh. However, water can be made available for irrigation by making recharge wells that recharge the groundwater aquifers.
The rainfall in Uttar Pradesh is, perhaps, 20 times more than the catchment of Tehri; and the holding capacity of the groundwater aquifers of Uttar Pradesh is also about 30 times more than the capacity of Tehri. We can get much more irrigation by groundwater recharge than we are getting from Tehri.
The third step to be taken is to make an agreement with Bangladesh to provide 80 percent water to Bangladesh during one month in the monsoons, and 80 percent to the Hooghly next month.
This will restore the major floods in the Padma and Hooghly, push the sediments coming from the upstream and the sand coming with the high tide back into the sea. That will clear the channel of the Hooghly and perhaps save the Haldia and Kolkata ports from incapacitation.
(The writer is formerly Professor of Economics at IIM, Bengaluru)