1. Bas Buddendorf1, Josie Geris1, Iain Malcolm2, Mark Wilkinson3, Chris Soulsby1 1Northern Rivers Institute, School of Geosciences, University of Aberdeen; 2Marine Scotland, Pitlochry; 3James Hutton Institute, Environmental and Biochemical Sciences, Aberdeen
Effects of river regulation on Atlantic salmon populations in Scottish rivers
Introduction
Figures
Copyright:
Figure 1: Flow requirements for different life-stages of Atlantic salmon.
Increase in number of large dams reduces percentage of rivers not impacted by river regulation to a mere 7%1,2 .
Many of Scotland’s rivers are regulated for hydropower (2020 Routemap3), yet also host substantial populations of Atlantic salmon .
In addition to habitat access, flow requirements of salmon are different for different life stages, Fig 1.
Smolts/autumn parr have a narrow window for migration, flow regulation could influence migration success.
Changes to natural flow regimes may affect sustainability of habitat at local and regional scales and ultimately conservation of the species.
Research is therefore needed to aid restoration and management of rivers impacted by previous hydropower development and guide new schemes to mitigate potentially adverse effects.
Figure 2: Overview of the Lyon catchment. 390km2; alt m; Q~2300mm/yr; 400mm ET/yr 1
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Figure 3: Effect of transverse barriers on longitudinal connectivity for different weighting approaches.
Use connectivity metrics to study effect of transverse barriers on longitudinal connectivity (catchment scale) in the River Lyon, Fig 2.
Determine importance of using different weighting approaches, Fig 3.
Use 2D-hydraulic models in combination with habitat suitability curves6 to study effect of flow regulation on habitat suitability for juvenile salmon (reach scale), Fig 4-6.
Characterise long term hydrological and temperature regimes in the Girnock and Baddoch Burn during the smolt/autumn parr migration period, Fig 7-8.
Model relevant endpoints of the migration run (e.g., 25th – and 75th percentiles of the run) in relation to environmental variables to determine environmental factors influencing run timing.
Methods
Figure 4: Flow duration curves. The left panel shows the flow duration curves for the 2008–2011 time series; moving to the right the panels show the flow duration curves for the spring, summer, and autumn/winter periods within the data set.
Figure 5: Variation of daily habitat quality values with daily discharge values for estimated natural and regulated flows. From left to right columns are displayed, respectively, the spring, summer, and autumn/winter periods. Scatterplots show daily quality values versus daily discharge, whereby plotted values can overlap. Vertical boxplots indicate spread in daily habitat quality values. Horizontal boxplots indicate the spread in daily discharge values. A ‘*’ indicates a significant difference in median for either habitat quality or discharge between regulated and estimated natural flow scenarios.
Figure 6: Coefficient of variation (CV) for discharge and habitat quality. Discharge variability is larger under estimated natural flows in all sites. In the RN- and C-site variability in habitat quality is larger under estimated natural flows, but in the HP-site this variability is larger under regulated flows.
Apply same approach for longitudinal connectivity at a national level
Do we see the same/similar effect of barriers at larger scales?
Poster presentation on environmental controls on smolt migration at the BES Ecology Across Borders conference, Ghent, December 2016
Future
Figure 7: Dendrogram showing clustering of years for environmental variables related to flow and temperature.
Figure 6: Prinicipal component analysis with groups identified by the dendrogram. Both axes display variables that had the highest axis loading.
Results
Wetted area could misinform management and planning of river restoration projects; inclusion of more relevant hydrogeomorphic and ecological details can improve our ability to identify those areas that are able to maintain high levels of connectivity.
Losing less but more suitable and productive areas can have a larger impact on connectivity than losing more but less suitable and productive areas.
Effects of regulation can vary substantially between reaches due to spatial differences in flow regime.
Comparison to natural flow regimes suggests that flow alteration has a variable influence on habitat quality depending on the type of regulation and season.
Flow rules should aim to incorporate seasonal flow preferences.
Caution needed when using discharge variability as habitat quality indicator.
KE output
1) Oral presentation WWC, Edinburgh 2015; 2) Poster at SEFS9, Geneva 2015; 3) Ooskanews panel member, RBS HQ 2015; 4) Oral presentation AGU, SF 2015; 5) HN panel member, World Water Day Dundee 2016; 6) Oral presentation EGU, Vienna 2016; 7) Oral presentation AGU, SF 2016; 8) Paper in Hydrol. Proc. 2017; 9) Paper in Sci.Tot.Env. 2017; 10) Paper in Ecol.Ind. 2017; 11) Poster at BES Ecology across borders conference, Ghent 2017
Acknowledgements
I would like express my gratitude to the Scottish Government and the Hydro Nation Scholarship program for funding my PhD research and providing a broad platform that stimulates research related to all aspects of the Food-Water- Energy nexus. I am also very thankful for the support, input, and feedback from my supervisors.
References
1: Zarfl et al., 2015; 2: Grill et al., 2015; 3: 4: Cote et al., 2009; 5: Millar et al., 2015; 6: Millidine et al., 2016.