A warming world implies more precipitation, more rainfall, and, in turn, more water flowing down rivers into dams. This translates into higher generation of hydroelectric power, which is good; but on the flip side, it poses challenges to reservoir management and the likelihood of dam breaks.

Dipesh Singh Chuphal and Vimal Mishra of IIT-Gandhinagar decided to study the impact of 46 large dams in India and the effect of climate change on each of them. They examined dams in north, central and south India, for the near (2021-2040), mid (2041-2060) and far (2081-2100) terms against a reference period (1995-2014), for the best and worst global warming scenarios, and ‘SSP 1-2.6’ and ‘SSP 5–8.5’ (SSP, or ‘shared socio-economic pathways’, is a terminology used by the Intergovernmental Panel for Climate Change and refers to temperatures).

The study looked into questions such as how much warmer would each region get, what would be the precipitation, and what would be the impact on dams and on hydroelectric generation.

The result is quite revealing, showing both temporal and spatial variations. It shows that North India is likely to warm the most (around 5 degrees C); and Central and South India 3-4 degrees. However, dams in Central India are likely to receive higher inflows of water than those in the north and south. “Dams in Tapi, Narmada, Mahi, Godavari and Mahanadi river basins show a more remarkable rise in future hydropower potential,” says the study, published in  iScience magazine.

The projected change in ‘developed hydropower potential’, which is the maximum possible generation of electricity, ranges from –6.2 per cent to 39 per cent in the near period, -24 per cent to 58 per cent in the mid period, and –5 per cent to 63 per cent in the far period. Overall, India’s electricity generation from hydropower projects is projected to increase by 10-23 per cent.

So the good news is that global warming can lead to more hydropower generation in India, but the bad news is the potential impact on dam health.

More water flowing into dams poses challenges in terms of flood control when the reservoirs are full. “In the absence of reliable early warning and forecast systems, high inflow when reservoirs have already reached their total capacity may require quick release, which can cause flooding in the downstream regions,” the authors note. Further, the oversupply to reservoirs can also lead to the risk of dam breaks, they caution. They point out that the Machchhu dam failure in 1979 and the Kerala floods in 2018 were associated with reservoir storage.

Dams in central India are likely to be more challenged by inflows, while those in the south are likely to experience high inflows less frequently during the mid and far periods, they say.