How dams can control floods


  • There should be space for greater storage of water in reservoirs before the onset of monsoon.

In the aftermath of any Kerala tragedy, people are struggling to comprehend what happened and how to cope. A number of experts and politicians have stated various possible reasons for the tragedy.

  • Some have cited ill-thought-out development plans that have affected the sustainability of the Western Ghats, arguing that without thoughtful conservation, this was a tragedy waiting to happen.
  • Some have said that the rainfall was unprecedented.
  • Some others have said that Kochi airport was bound to flood given that it has been built on fields and wetlands adjacent to the Periyar river which swelled to dangerous levels during the floods.
  • Some have blamed dams, which were all opened when they were nearly full, causing heavy floods downstream and greatly affecting the lives of the people there.
  • While criticism and suggestions are natural after a tragedy of this magnitude, we should learn lessons from the experience. The question is, how do we avoid or minimise destruction after such an event?

The purpose of dams

  • The world over, dams are constructed mainly for the purposes of irrigation, power generation, and flood control.
  • While the first two roles are acknowledged, the role of dams in flood control has always been underestimated.
  • It is unfortunate that in both irrigation and hydel projects, flood control is completely ignored.
  • Authorities always look to store the maximum amount of water in reservoirs during the monsoon season, which is then used for irrigation and generation of electricity during the summer months.
  • It is an internationally accepted practice that the water level of a reservoir should be kept below a certain level before the onset of the monsoon season. This is so that when the monsoon rains come, there is space to store the excess rainwater and also so that water can be released in a regulated manner, thus preventing floods downstream when there is heavy inflow to the dams.
  • For instance, in May, Thailand wisely brought down the water level in the dams in the country to below 60% of the storing capacity before the rainy season.

Space in reservoirs:

  • In view of all these problems and to ensure that the flood control purpose of dams is met, it is important that at least 30% of the storage capacity of dams be kept free before the monsoon.
  • While simultaneously allowing discharge of water, it is possible to increase storage slowly as the monsoon progresses.
  • If the monsoons fail and dams fall short of water and there is a shortfall in electricity generation, this is not a loss compared to the possible loss of lives in the event of a flood of this magnitude.

Kerala’s situation:

  • In Kerala too, the dams were not managed well.
  • While earlier too there was no practice of keeping space for greater storage of water, rainfall has never been as torrential as it was this year. Hence, there were no floods.
  • It is difficult to predict what will happen during the ensuing northeast monsoon in Kerala in case of heavy inflow.
  • Whatever is the extra quantity of electricity produced and area of land irrigated because of the risky storage of water the dams, that cannot compensate for the loss of human lives, infrastructure and agricultural land.
  • The estimated loss to the State runs into thousands of crores. It will take years to rebuild Kerala.
  • Kerala receives rainfall mainly during the southwest monsoon and northeast monsoon.
  • These rains are controlled by winds that carry clouds from the Arabian Sea and the Bay of Bengal. Atmospheric depression that controls wind movement cannot be predicted months in advance.
  • The meteorological department can predict rains or cyclones only a few days in advance. Therefore, keeping space in reservoirs before the monsoon begins must be done whether or not there are heavy rains, as no State can afford to take risks in the manner that Kerala did.

Ensuring thoughtful policies:

  • It is time for the government and the public to formulate water management policies for reservoirs in such a manner that dams are used to control floods, not cause them.
  • There should be space for greater storage of water in reservoirs before the onset of monsoon.
  • There is over-dependence on hydel projects to produce electricity. It is time to think of non-conventional sources for electricity generation such as solar, wind and tidal power.
  • The practice of solar power generation in Kochi airport can be copied in similar large-scale projects by other government agencies.
  • The public too should be encouraged to adopt the practice of solar power generation. This will greatly reduce our dependence on dams for power generation.
  • The State Dam Security Authority, if competent, should be entrusted with the task of water management in reservoirs and with taking decisions in emergency situations.
  • The State government, the State Dam Security Authority and the National Water Commission should all be prepared to take bold decisions together on water management so that there are no such devastating floods in the future.


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