Hydropeaking declining in North America, scientists find

Consistent river flows benefit aquatic species and habitat

Hydropeaking operations Median water level (top graph) versus median electricity demand (bottom) from Brazil's Operator of the National Electricity SystemHydroelectric generation in North America is producing steadier river flows, which benefit aquatic species, according to a paper by Dr. Stephen Déry, Professor of Environmental Science at the University of Northern British Columbia (UNBC).

Déry and collaborators Marco Hernández-Henríquez, UNBC; Dr. Tricia Stadnyk, University of Calgary; and Dr. Tara Troy, University of Victoria studied hydropeaking, the sharp rise or fall in water levels in managed rivers due to increases or decreases in electricity demand.

Their paper, "Vanishing weekly hydropeaking cycles in American and Canadian rivers,” published in the journal nature communications, details the decline of hydropeaking over recent years.

“There is a very consistent, overall decreasing pattern in the index values we’ve formulated for hydropeaking in this study, and the pattern crosses various jurisdictions, watersheds, and power grid interconnections,” Déry commented.

“A reduction in ramping up and ramping down in river flows benefits aquatic species and improves their habitat.”

The researchers analyzed at 100 years of data from 500 sites across Canada and the U.S. They found instances of hydropeaking increasing in the mid-20th Century and then decreasing in the 21st Century.

Results suggest that hydroelectricity demand and generation is changing, with less reliance on hydropower to support peak demand during daytime and weekdays,” Déry said.

Several other reasons may contribute to the decrease in hydropeaking:

  • the addition of wind and solar energy to the grid
  • improved regulatory oversight
  • an increasingly interconnected grid that helps load balancing, and
  • lifestyle changes that have resulted in more even electrical demand.

Déry added, “Recent reductions of the weekly hydropeaking cycle provide evidence that hydropower operations are indeed being modified to improve ecosystem health and well-being.”

The next phases of research include assessing the seasonal variation in hydropeaking and overall extremes.

Déry remarked, “We also hope at some point to directly correlate electricity production with weekly hydropeaking cycles.”


The image shows hydropeaking: graph (A) median water level, (B) discharge change at Abunã (upstream from two dams) & Porto Velho (5km downstream of Santo Antônio dam) based on hourly data, (C) median electricity demand based on hourly data for the same time period as in graphs A & B. Demand data are publicly available from Brazil’s Operator of the National Electricity System. Figure 7 credit: Almedia et al, "Hydropeaking operations of two run-of-river mega-dams alter downstream hydrology of the largest Amazon tributary," frontiers in environmental science

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