With fossil fuels found to be the greatest contributor to climate change, the switch to renewable energy is imperative. One of the most convenient and popular renewable energies is hydropower: energy obtained from the movement of large quantities of water. While solar and wind power can only be harvested intermittently, hydropower supply is continuous, reducing the need to store the generated electricity (Nautiyal and Goel). In many cases, hydropower can also be multi-functional, helping with irrigation and flood control while also providing tourism opportunities (Ogino et al.).
In order to better understand the effects of hydropower, it is important to know how it works. Hydropower plants are built on or near an area where water flows downwards. The flowing water goes through a pipe, turns a turbine, and spins a generator. The three types of hydropower plants are a dam, a diversion facility (a series of canals that direct water to turbines), and a pumped-storage facility (water storage for times of high demand for electricity) (“Hydroelectric Energy”).
While the usage of energy generated from hydropower is sustainable, the construction and operation of a hydropower project can be devastating to the local ecosystem. “Large storage of water further causes biomass decomposition of flooded land which produces a significant amount of carbon dioxide (CO2) and methane (CH4) emissions” (Nautiyal and Goel). This poses the question: is hydropower as sustainable as it seems?
One way to determine the environmental impact of a hydropower plant is to look at carbon emissions from manmade sources and carbon absorption into environmental sinks. Construction period carbon sources can include building materials and fuel consumption as well as builders’ living activities, while operating period carbon sources can include operators’ living activity and permanent land occupancy. On the other hand, the vegetation at the site can be a carbon sink.
The total carbon footprint of hydropower during the construction phase is the summation of all individual carbon emissions during this time :
COEC = COEBM + COETL + COEW (1)
COEC = carbon dioxide released during construction
COEBM = carbon dioxide released by providing building materials
COETL = carbon dioxide released by temporary land occupancy
COEW = carbon dioxide released by builders’ living activities
Units for all variables are in tons (Zhang et al.).
The total carbon footprint of hydropower during the operating phase is the summation of all individual carbon emissions during this time :
COEo = – COEHR +/– COEPL + COEO (2)
COEo = carbon dioxide released during the operation period
COEHR = carbon dioxide emission from a thermal power station generating equivalent
power compared to hydropower
COEPL = carbon dioxide absorbed or released through permanent land occupancy
COEO = carbon dioxide released by workers’ living activities
Units for all variables are in tons (Zhang et al.).
Using these and other calculations, Zhang et al. investigated the carbon emission footprint of twenty-six small hydropower plants in China and found that “when the installed capacity increases by 1 kW, carbon emissions are reduced by 16.33 t.” Thus, “COEo is directly determined by hydropower” (Zhang et al.). While this was derived for small hydro plants, the same framework may be applied to think about hydropower projects’ carbon footprint in general.
The health of an ecosystem vs. energy harvested from the ecosystem
Beyond carbon emissions, hydropower has a multitude of direct impacts on the ecosystem it is built into, such as “water depletion downstream of the diversion, water quality deterioration, loss of longitudinal connectivity, habitat degradation, and simplification of the biota community composition” (Kuriqi et al.). Dams also have a detrimental impact on fish populations, who are blocked from swimming upstream and can get caught and die. However, new research is being conducted into gravity water wheels and fish-friendly turbines that do not hinder fish migration. For example, the Alden turbine has fewer blades and a slower rotational speed, leading to fish mortality rates as low as 2% for fish 20cm and smaller (Kougias et al.). Although not yet ready for commercial use, these hydropower advancements look to be promising.
In conclusion, a closer look at hydropower reveals that its environmental impact is more complicated than it may seem at first glance. While hydropower continues to be one of the most relied-upon sources of sustainable energy, factors such as carbon emissions from construction and operation, habitat destruction, and water depletion must be considered. The power generated must offset the damage caused. However, with modern technology and careful planning, hydropower can become a steady source of clean energy.
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