It should have become commonplace now that what are described as natural calamities — floods, droughts, cyclones and quakes — are really part of a natural cycle, and that human beings have to learn to deal with the way bamboo trees respond to winds: bend to the force and get back to the normal position later. It is understandable that Bihar Chief Minister Nitish Kumar feels that the only way to deal with the Ganga in flood is to desilt the river. He has hinted that the Farakka dam, built near the Bangladesh border, which helps in diverting water into the Hooghly to make it navigable, is the problem, and, therefore, it has to be done away with because the dam is contributing to the siltation.

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While Kumar might have identified the problem rightly, the solution he is suggesting might be the least helpful. As a matter of fact it could turn out to be a wrong solution. But politicians are so pressed to find instant solutions to immediate problems that they do not have the time to pause and ponder over the problem as well as the solution. Prime Minister Narendra Modi has apparently agreed with Kumar and he seems to have suggested that a national de-silting policy will be formulated. It appears that the politicians, including Modi and Kumar, should take some lessons in natural hydrology, and not allow engineers to offer short-term solutions.

It has to be understood that rivers in general carry silt as they flow from their starting-point in the mountains and meander through the plains before they end up in the sea. When the rivers flood the plains, they leave behind rich soil, and silt is part of the enriching sediment they leave behind. When dams are built across rivers, the flow of the silt is impeded, and the reservoirs that hold back the river water also hold back the silt. It becomes necessary to desilt reservoirs from time to time. This is part of the solution. It is not the whole solution. 

The bigger problem to be addressed is that of understanding the silt that flows with the river, and which gets left behind along the course, enriching the agricultural fields in the process. There is a need to understand the phenomenon of the gradual silting that takes place all along the river. It would indeed be foolhardy to implement a mindless and blinkered desilting method across the board.

Silting is not the sole reason for the floods though it has been identified as the main cause for the calamity in Bihar. The siltation that occurs in the drainage canals, streams and rivers in Mumbai is of a different kind. Here the siltation is due to industrial effluents and human waste that clog the water ways. The floods are also caused by excess rains, which is not an uncommon phenomenon. What is then required is a large network of water-harvesting systems. 

There is also the need to study natural phenomena like river flows and the monsoon. What makes an overflowing river a calamity is that dense human habitations crowd the banks of rivers. If human habitations are constructed factoring in the possibility of rivers changing course over the years, then it should be possible to benefit from rivers in spate that enrich the soil that they flood. There could be greater benefits if enough leeway is given to the rivers instead of taming and damming them.