Hydropower is Not Universally Low-Carbon

Abstract:

There is mounting evidence that greenhouse gas emissions from hydropower energy generation can be far higher than what is broadly assumed. Hydropower is currently considered a low-carbon energy source on par with wind and solar, and thus far better for the climate than fossil fuels. However, our analysis shows that electricity generated by at least 100 hydroelectric facilities worldwide — out of 1,500 analyzed — may be more damaging to the climate than that by average coal and natural gas plants. Further, this number doubles to at least 200 facilities when considering climate impacts in the near-term.

This is concerning because thousands of new hydropower facilities are either planned or under construction globally, and the International Energy Agency predicts that hydropower could grow by nearly 80% by 2040 as society works to displace fossil fuels. Of additional concern is that many regions considered hotspots for future hydropower growth, such as Africa and India, have proportionally more facilities with high greenhouse gas emissions compared to the rest of the world. For example, of nearly 50 hydro plants in India with available estimates of greenhouse gas emissions, more than half are at least initially worse for the climate than coal per energy generated, and hydropower energy generation in India is projected to increase by 230% between 2015 and 2040.

There are enormous differences in the amounts of carbon dioxide and methane emitted from facility to facility due to a range of varying reservoir features and meteorological characteristics. If minimizing climate impacts are not a priority in the design, construction and geographic placement of new hydropower facilities, we could end up generating electricity that yields more warming — especially in the near-term — than fossil fuels. However, there are measures that can be taken to lower emissions (such as removing reservoir vegetation, minimizing reservoir surface area, avoiding development in particularly hot places, and deploying capture technologies). Overall, we must dispel the myth that hydropower is universally low-carbon, and be mindful of the potential for high emissions when developing new facilities.