As the current floods to have hit Punjab and Azad Jammu and Kashmir for a fourth consecutive year leave behind harrowing tales of lives lost and massive destruction of infrastructure, livestock, properties and cash crops, the debate among academics has now veered towards a narrative that increasingly questions the utility and usefulness of dams and barrages. As Multi-Sector Initial Rapid Assessment (MIRA) gets underway in collaboration with the United Nations Office for Coordination of Humanitarian Affairs (UNOCHA) to ascertain the exact damage caused by floods, the loss to the national economy is likely to be between $ 10 billion and $ 15 billion, more than what was caused by the 2010 flooding.
Those who advocate an approach of non-structural measures to contain floods base their opposition to dams and barrages on the phenomenon of sedimentation, massive investments on building of water reservoirs, embankments and dykes, coupled with loss of natural sponges due to deforestation and drainage of wetlands. All projects involving water storage and change in the courses of rivers are inherently controversial because they entail displacement of people and destruction of habitat, adversely impacting the ecosystem. The fact of the matter is that dams have traditionally proved their usefulness by virtue of their multipurpose role in water storage so critical to the economy, populace and industry, inexpensive power generation and mitigation of flood hazards.
As far as sedimentation is concerned, it is a natural phenomenon that occurs in watercourses whether dams are built or not. Siltation in reservoirs reduces their capacity but in no way does it exacerbate floods due to a high level. Had there been no reservoirs, the riverbeds would have gone higher due to years of siltation and flooding would have increased because, in Sindh, the Indus flows at a higher level than the adjacent ground and is contained within bunds. So water courses/rivers are prone to accumulate silt that causes the floodwater to rise in riverbeds, thereby aggravating the severity of floods. Negating the importance of dams on the basis of this phenomenon does not make much sense as the world has explored ways and means to control the phenomenon of sedimentation.
As for as the argument of massive investment in the building of dams/barrages/dykes and embankments is concerned, it is a globally accepted fact that construction requires huge funding but they pay back their cost after a certain period of time. The decision to breech embankments/dykes during peak floods depends on the simple logic of minimising losses as efforts are made to protect populated areas from flooding. Most barrages have been built for 100-year floods and fuse plugs have been incorporated in the side embankments to be blown up in case the flood exceeds the safe design of the barrage. Normally, water is directed to less inhibited areas so that the damage is lessened.
It is not necessary that dams can mitigate floods. In the same way, there is no reason why dams cannot mitigate floods. Dams can only mitigate flood hazards if they have enough storage capacity. In the absence of dams and water reservoirs that trap a huge quantum of floodwater depending upon their storage capacity, flood losses are sure to grow manifold. Flood mitigation in the two mega dams of Pakistan is incidental, i.e. they can absorb the flood peak when they are not full. Even when they are full, they still dampen the flood peak by calculated discharge from the reservoir when all outlets are open. Pakistan’s storage is less than 11 percent of average annual flows against 40 percent of the world’s average.
The Chenab River enters the plain areas of Pakistan and does not have any storage along its route because the construction of reservoirs is subject to certain geological and technical conditions. Marala and Trimmu barrages have very small storages, which cannot absorb floods. During floods, the canals are also closed to save them from siltation and breaches. The proposed Chiniot dam project, if constructed on River Chenab, cannot play an effective role in flood mitigation as it has a storage capacity of merely one million acre feet. Besides, it will cause a huge displacement of people.
In the recent floods, the role played by a raised Mangla dam in taming peak floodwater, storing much of the water inflows from River Jhelum and releasing only a small quantity of water merits special mention. Had raised Mangla dam not been there to store peak inflows, the floodwater of the Jhelum and Chenab Rivers would have merged to cause greater havoc in Trimmu barrage and downstream than what has been witnessed now.
The role played by dams in flood mitigation can be measured from the example of China’s Three Gorges Dam that has played a role in saving the lives of 15 million people and protecting 1.5 million acres of farmland in the area around the Yangtze River. In the absence of the Three Gorges Dam, China experienced devastating floods after every 10 years. The last such flood in 1998 caused the deaths of 14,000 people, left 14 million people homeless and dented the Chinese economy with a loss of $ 24 billion. Besides flood control, the dam is also being used for the generation of hydroelectric power and navigation.
Unlike the devastating floods of 2010 flowing down from the Rivers Swat, Kabul and Indus, the recent flooding in the Chenab and Jhelum Rivers was caused by cloudbursts and heavy rains in their catchment areas. Even those areas of the country that normally record low rainfall experienced cloudbursts and thus recorded heavy rains. So the point being contended here is that floods can only be controlled and their consequent losses minimised if there are dams to trap their water. In case there is no dam in the way of floodwater, the magnitude of destruction can be too horrendous to imagine.
The building of water reservoirs and barrages does not mean that non-structural measures cannot be adopted. Non-structural measures like monitoring of precipitation, river and reservoir storages and flow measurements, forecasting, early warning, appropriate disaster warning and strategy, also are important in flood management. It is an internationally accepted norm to take structural measures such as construction of levees and embankments in addition to non-structural measures such as supplying timely information to people about the threats of flooding and getting them evacuated. In Pakistan, people dwell in the riverine areas in violation of laws. It is not the fault of the dams but the inability to strictly adhere to laws and orders of local authorities responsible for flood ravages.
In addition to flood mitigation, dams have played a key role in the sustainability of development by serving communities’ needs for fast-paced socio-economic growth. They have generated employment, decreased poverty and arrested the urbanisation trend besides ensuring food security and generation of cleanest and cheapest power generation.
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