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Hydro power creates more greenhouse gases than first thought: study

Last Updated Oct 6, 2016 at 9:41 am PDT

The Williston Reservoir near Hudson's Hope. (Courtesy BC Hydro)

Researchers analyzed studies dating back to 2000

Study concludes the world's reservoirs produce about 1 gigaton of carbon dioxide annually

VANCOUVER (NEWS 1130) – It’s billed as a clean, green source of electricity — it’s what lights up most of our province — but a new study out of Washington State University raises some serious concerns about our reliance on hydroelectric power.

Researchers have determined that manmade reservoirs are a much larger source of greenhouse gases than previously thought.

The report, which is being published this week in the journal Bioscience, concludes the world’s reservoirs, whether they are used for power generation, drinking water or irrigation, produce roughly 1 gigaton of carbon dioxide a year — or 1.3 per cent of all greenhouse gases produced by humans.¬†“If all the reservoirs were a country, they would have a similar emission to the population of Canada,” says co-author John Harrison, an associate professor at WSU’s School of Environment.

The report reveals that reservoirs are a particularly important source of methane, which is produced when areas are flooded and organic material decomposes.

The researchers analyzed studies dating back to 2000, tracking the carbon footprint of manmade reservoirs and co-author Bridget Deemer says they were surprised to find how much greenhouse gases, particularly methane, were being produced.

“A large number of papers have come out over a relatively short time period and we have pulled all that information together,” says the recent WSU research associate, pointing to data suggesting some hydroelectric dams are even bigger carbon-emitters than certain fuel-burning power plants.

“About 10 per cent of the dams in one study were producing more greenhouse gases per unit of energy generation than the natural gas combined cycle,” she tells NEWS 1130.

Over 90 per cent of BC’s power comes from hydro-electric sources, mostly generated by major dams. So, what does that mean for the province’s “clean” electricity grid? BC Hydro¬†says it’s getting an expert to look over the study.

BC Hydro Statement

“Reservoirs have very low GHG emissions when compared to other sources and emissions decrease over time. Last year, 98 per cent of the electricity generated in B.C. was from clean sources,” writes BC Hydro spokesperson Simi Heer in an email to NEWS 1130, adding that the province’s energy portfolio includes hydroelectric, run-of-river, wind and solar.

“Our big reservoirs were built decades ago but we took a look at this issue recently during the environmental assessment process for Site C. Potential GHG emissions were studied and modeled and the Joint Review Panel concluded that Site C will have the lowest greenhouse gas emissions, per gigawatt hour, compared to all other electricity generation options, except nuclear,” she says.

“Since the study is international, it’s also important to note that evidence shows that hydroelectric reservoirs in northern environments, like British Columbia, emit much lower quantities of GHG emissions when compared to reservoirs in tropical environments that release high levels of methane.”