Nordic socio-recreational ecosystem services in a hydropeaked river system

Zeeshan Tahir Virk^a, Faisal bin Ashraf^a,b, Ali Torabi Haghighi^a, Bjorn Klove^a, Seppo Hellsten^c, Hannu Marttila^a

^a University of Oulu, Faculty of Technology, Water, Energy, Environmental engineering Research Unit

^b Stockholm Environment Institute (SEI)

^c Finnish Environment Institute (SYKE)

 

 

 

Fluctuating energy prices in the Nordic region call for short-term river flow regulation at hydropower plants (HPPs). This short-term regulation leads to Hydropeaking – the pulsating water flow downstream of an HPP. Hydropeaking is detrimental to the overall health of the river, impacting all riverine and riparian ecosystem services. One of the major ecosystem services affected by hydropeaking in Nordic rivers is the socio–recreational ecosystem service (SRES), which holds significant value for Nordic culture and human wellbeing. We examine how SRES are affected by hourly hydropeaking events in a large Nordic River reach. Employing two indicators based on normalized daily maximum flow difference and sub-daily flow ramping we estimated annual and seasonal trends of hydropeaking in the studied reach of the Kemijoki River system. The study reach was found to be under “High Pressure” peaking class in all seasons. For SRES impact assessment, we applied a novel methodological approach to multiple layers of high-resolution spatio-temporal data. An overlay analysis of inundation maps derived from 2D-hydrodynamic modeling and a customized land classification map based on a machine learning algorithm resulted in identification of SRES areas under influence of sub-daily hydropeaking within the study reach. The degree of impact on SRES corresponded to seasonal variations of sub-daily hydropeaking where the highest impact was observed in the summer season The most affected recreational land uses were the shore and litorine areas. Furthermore, as intraday flow ramping results in peaking waves downstream of the HPP, our results show that most part of the river channel becomes hydraulically unsafe during hydropeaking events, especially in summer, which is popular in the context of Nordic culture and tourism. Consequently, hydropeaking can seriously impact the social, and recreational services offered by Nordic rivers; therefore, regulation practices at the HPPs should also consider SPES aspects.  We recommend further research to evaluate these services so that tradeoffs between energy production at HPPs and ecosystem services of rivers can be balanced.