Hydropeaking in small hydropower in Norway—Compliance with license conditions?

Abstract

AbstractHydropeaking involves rapid changes in water flow, causing negative effects on aquatic organisms. To reduce these effects, hydropower licenses contain restrictions on hydropeaking. The owners of a hydropower plant are obliged to follow the requirements in the license. This study was conducted to understand the effect of environmental policies in small hydro licenses. We studied the occurrence of hydropeaking by analysing 256 high‐head, small Norwegian hydropower plants in relation to a set of characteristics that define each plant. We selected plants that were online during 2005–2014 and chose 2015 as a year for hourly production patterns. We counted the number of starts, that is, the moment when the hydro facility starts to produce energy, as an indicator of hydropeaking. Among the analysed plants, 75.8% had restrictions to practice hydropeaking. Production typically showed daily, weekly, and annual cycles though shapes varied depending on turbine type and location. The number of starts was independent on having or not having a license to practice hydropeaking. The average duration of periods with production and the average production in these periods were higher for plants without restrictions. The number of starts varied widely among plants. The number of starts was lower for installed Pelton turbines than for Francis and Kaplan turbines, which was in agreement with the characteristics of the turbines. Overall, these results show that hydropeaking restrictions given in the licenses are rarely followed. The high number of starts may be explained by failure in the grid system, improper maintenance, and financial interests. Their relative importance should be subject to further investigation.