Unscientific dredging of rivers and tributaries

The dredging of river bed, dam reservoirs, etc may have adverse effect on availability and storage of water. In eighties, in Bundi city of Rajasthan a dam reservoir bed was dredged to have more storage. But dredging caused the depletion of the dam reservoir just after rains. The dredging actually removed the clay bed of the reservoir resulting in porous bed and ultimately all the water of the dam reservoir leaked and there was no water left in dam submergence after rainy season i.e. in the month of October. People even engineers without thinking and analyzing the problem, starts copying the things which may be dangerous. I have dealt with this problem of River Rejuvenation in detail in my paper titled Preservation of water resources and their proper utilization available at https://drive.google.com/open?id=0B7OEEuzHbopKUWRSQ3JCTUR6dWM  . Anybody can view and download. If you have any problem , please write to me at yagrawal@bsnl.in  . I wonder that without removing obstructions in free flow of water in rivers and their all the tributaries, how any river can be Rejuvenated. How only dredging can rejuvenate a river ? This practice of river rejuvenation by dredging is incorrect and needs to be stopped immediately. It is a pure wastage of resources without any benefits. It will cause a long term damage to the river flow.

The mismanagement of water resources in Maharashtra and other states is the real reason of present harsh scarcity of drinking water in Latur and other areas of India. I wonder why the Ministry of Water Resources, Govt. of India is sleeping and why it is not issuing proper guidelines to the states how to combat with such a harsh water scarcity? Or it looks that the Ministry of Water Resources, Govt of India do not have adequate knowledge to deal with such situations.

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• River Widening
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5 Answers

1. Please factor in that ECOLOGICAL BALANCE of the River Systems has been damaged by dumping of sewerage, untreated or partially treated sewerage and effluents, involuntary disposal of solid wastes with storm water flows during first few heavy rains...resulting into (a) Inceased BOD and highly reduced DO in River waters ; (b) Orbainic sludge created in the process makes the top layer of the river bottom a base for pollutants that also interfere with the natural percolation of river waters into the acquifers, (c) Planned or unplanned interventions in the River systems and its Flood plains have altered the flows --making natural flows less than the minimum flows during certain periods, thereby reducing the capacity of the river system to maintain its cross section, making silt pile up as flow velocities become less than 0.6 m/sec... and (c) desilting by the ageold practice of excavation/ removal of sand from the river beds has been drastically changed to prevent / regulate illegal mining of sand  -- So, objections to Dredging for removal of silt alongwith Slush and Pollutants along the bottom top cover is nacessary to improve the flows, reduce the pollutants, decrease the BOD .Same is much more relevant for Manmade water reservoirs/ lakes....as continuous dredging of top cover of bottom , of silt can also increase their storage capacity and increase their useful life while also improving the quality of water and acquatic life..Unscientific dredging at localised space beyond certain depths can create problems but it is avoidable.

   1 Comment

   1. You are right. I just wish to make it clear that I only mean that the dredging should be based on scientific / engineering diagnostic analysis of the river portions, not just to dig the river considering it will cause more inflow of water in river. It is totally undesirable. Other than the reasons mentioned by you, there may so may other reasons, differing river to river and place to place.

2. Dear Mr Shankar, What I mean by scientific dredging is that a scientific / technical assessment should be done whether we need the dredging of a river or not ? What is the purpose of dredging a river ? The rivers are natural drainage channels to carry water received from glaciers and/ or rainfall in catchment areas. The dredging of river is not going to add quantity of water in the river flow. But in Maharastra and Karnataka the dredging is being done / proposed for increasing the availability of water in rivers. This a incorrect. If there are obstructions in natural flow of water natural or man made, they need to be removed, in a way suggested by technical experts. But just deepening and widening of the river arbitrarily, is not going to help to increase the availability of water in the river. As regards dams, the soil strata in submergence area of a dam reservoir and dam section, needs to be impervious, so that the stored water does not percolate through the submergence area and the dam section. Otherwise the stored water in dam reservoir will percolate down and dam will be empty in a short time, making the dam reservoir useless. The silt/ sand collected in the submergence area should be removed in such a way that this process does not remove the impervious soil strata. However the best way to minimize the inflow of sand and silt in dam reservoirs , is to do afforestation in the catchment area. I hope I have replied your query. I shall welcome further questions if any.

3. The title of the posting mentions unscientific dredging. Does it mean there is a scientific dredging? To most of us who are not specialists in the line of river rejuvenation, common understanding is there is deposition of silt whic may be fraction of a meter in depth to several meters. With a huge water spread of a storage reservoir, reduction in water storage can be huge. For the benefit of participants of this forum, I would request mr. agarwal to clarify the points mentioned above.

4. Our Rastrapita Mahatma Gandhi raised his voice against the atrocities being forced upon Indian people by the British colonial rule. The people of India supported him in exchange and he could oust British rule without using arms. Now the people of India in many states and water deficit areas are dying without water. But the ministers of Modi Govt and the state chief ministers are not doing enough to arrange to provide drinking water for the poor backward people living in villages and urban areas. These ministers are provoking people to have anti administration sentiments in the public, which may be dangerous to the unity and integrity of India. Will the Modi Govt will like to to initiate its all out efforts to stop dis satisfaction among people ?

5. Sir I agree with you, I strongly feel that water conservation/harvesting is not rocket science, we just have to look back and take it from our ancestors. If you take example of any kingdom which ruled our country had constructed water harvesting structures based on the geological conditions and needs. With modern science and development we have tools to exploit natural resources at an alarming rate, deplete it very fast without any conservation efforts. Now, time has come to act for a sustainable development and I strongly feel that "Without POLITICAL WILL and PUBLIC Participation" achieving things is not possible.