Based on reports in the media, the Indus River Treaty between India and Pakistan is under scrutiny by the Indian government. While there may be a geo‐strategic case for scrutiny of the treaty, there are serious geographical, geological and ecological issues that a relook of the treaty raises.
If a relook at the Treaty involves new dams, as suggested by some commentators, planning should take note of lessons from earlier dam construction in the Himalayas. The key issue is that the Himalayas are a ‘hot spot’ for environmental hazards – particularly great earthquakes, landslides and floods.
It is also home to very high biodiversity, both on land and in the rivers and lakes. Building large dams to gain a geostrategic advantage over Pakistan may not be the best approach for the rivers governed by the Treaty or for the people living near those rivers. If criteria other than geo-strategy are taken into account then these rivers may not be easy candidates for big dams.
Although the whole Himalayan range is earthquake‐prone, some areas have experienced earthquakes with magnitudes greater than eight on the Richter scale, referred to as great earthquakes, while others experience much lower levels of seismicity.
It is one of the ironies of the Himalaya that those areas that experience low seismicity are also places where river flows are relatively small. So rivers that flow from the Indian territory into Pakistan may be eligible for only small dams, which may be safe but the reservoirs would be small and thereby not achieve the purposes imagined by those re‐examining the Treaty.
In locations prone to great earthquakes, the design of dams will have to be stringent and therefore the construction will be very costly. For example, in 1997, geologist KS Valdiya commented unfavourably on the location and design of the Tehri Dam – one of the world’s tallest dams situated on the Bhagirathi River in the earthquake‐prone state of Uttarakhand.
Landslides are also a major hazard in the Himalayas. Dangerous landslides can be caused by filling of reservoirs where adjacent hill slopes are destabilised. An extremely well documented case occurred in 1963 in Italy when about 30 million cubic metres of water was displaced from the Vaiont Reservoir by a landslide, sending a wall of water over the wall and killing 2000 people downstream.
Landslides from other causes can create waves that destabilise dams and overtop dam walls and spillways, like dropping a brick into a bath. Landslides also add sediment to reservoirs and shorten their useful lives. The Himalaya is home to great landslides, proof that the phenomenon of giant waves in reservoirs is not a figment of scientists’ fevered imaginations. In fact the Himalaya is not just a ‘hot spot’ of environmental hazards, is one the world’s 'great hot spots'.
And of course there are great floods. The most recent was the 2013 Kedarnath/Mandakini flood in Uttarakhand. This was not just 'great' but also a 'perfect storm'. The monsoon reached into the high mountains earlier than usual, and when it met cold and dry air from the Arctic it generated one of the most severe rainfall events in living memory.
The analysis of this event by the renowned Indian Institute of Tropical Meteorology (IITM) has made clear what happened. Floods of the magnitude of the 2013 event recur in the Alaknanda river on average every 40 years. Before the 2013 event, the largest flood was in 1970, which was one of the factors that spurred the 'Chipko Andolan'.
We know the average frequency of extreme floods from studying flood sediments from which it has been possible to reconstruct a flood history for the past 1500 years. However, the future may be bleaker than the past. The confluence of climatic phenomena that caused the 2013 flood will recur and possibly with greater frequency. As the Arctic warms, it will send out bursts of cold air more often.
It is particularly sobering to have found that most if not all of the large floods in the Alaknanda River over the past 1500 years have occurred when the Arctic was sending out such bursts into the Himalayas. Large floods can topple dams if the design is not sufficiently stringent. Floods also carry large amounts of sediment that reduce the lifespan of reservoirs.
Even more dangerous for people and dams are floods that are generated by the bursting of lakes made by landslides and glaciers. These are common in the Himalayas, another reason to see these mountains as a ‘great hot spot of hazards’.
Most of the Alaknanda floods were probably the result of landslide lake bursts, but glacial lake bursts also pose an increasing threat as glaciers are reduced by rising air temperatures that create lakes which eventually burst leading to a flood.
India clearly needs electricity for the good of its people. Hydroelectricity is more greenhouse gas friendly than thermal power stations, although not to the extent claimed by its proponents. Given the problems, actual and potential, of large dams it would be best to build small run‐of‐river dams for the generation of electricity; so‐called “hydels”.
Many are already built and a lot more are planned. However, once again the 2013 flood in Uttarakhand has lessons for the future. Many of the hydel dams were damaged and some destroyed. The hydels in the Himalayas are built too close together to provide for the aquatic ecosystem’s needs.
More dams in the Himalayas should be planned while honouring the safety of people and the ecology of the area. Learning from historical disasters, landslides, floods and earthquakes, the government should also adopt a 'disaster risk reduction' approach. A new Indus River Treaty can have long term impacts on the Himalayan mountain range. The impacts will be positive only if it is well planned in advance.
Dr Robert J Wasson is a Senior Research Fellow at the Lee Kuan Yew School of Public Policy, National University of Singapore
Shivani Ratra is a Research Associate at the Lee Kuan Yew School of Public Policy, National University of Singapore
First Published On : Oct 18, 2016 14:41 IST