Abstract
Extreme, short-duration fluctuations caused by hydropeaking occurs when hydropower is regulated to cover demand peaks in the electricity market. Such rapid dewatering processes may have a high impact on the downstream biological conditions, particularly related to stranding of fish and other species. The present work analyzes these fluctuations using a two-dimensional unsteady hydraulic modelling approach for quantification of two important hydro-morphological factors on fish stranding risk: the variation in wetted area and the dewatering ramping rate. This approach was applied on the two-kilometer-long reach of Storåne downstream of the Hol 1 power plant, where topo bathymetric LiDAR (Light Detection and Ranging) data was available providing a high-resolution digital elevation model. Based on this model, hydraulic conditions could be simulated in high detail allowing for an accurate assessment of the hydro morphological factors. Results show the dried area distribution at different flows and dewatering ramping rates. The attenuation of the water level fluctuation due to the damping effect along the river reach controls the dewatering rate. We recommend an alternative scenario operation which can reduce the impact of the peaking operation and estimate the operational mitigation cost. We find that the modelling based on the fine resolution grid provides new opportunities in assessing effects of hydropower regulations on the ecosystem.
Highlights
By 2050, the European Union (EU) should cut greenhouse gas emissions to 80% below 1990 levels [1]
The digital elevation model (DEM) could be made finer in areas where point density is higher but we considered our DEM
Evaluation of these impacts need high precision geometry like the light detection and ranging (LiDAR) data used in this study, which enables detailed 2D hydraulic modelling for evaluation of these problems
Summary
By 2050, the European Union (EU) should cut greenhouse gas emissions to 80% below 1990 levels [1]. Electricity generation, in all its forms, contributes to over a third of the global energy-related. CO2 emissions and energy transition is a fundamental step towards sustainability. In this frame, hydropower is expected to play a key role to balance the load of other renewable resources [2]. Norway has approximately half of the hydropower reservoir capacity in Europe [3], and thereby a large potential for load balancing. Short-term changes in electricity demands, for instance because of intermittent electricity generation from solar and wind energy, will increase hydropeaking production leading to higher fluctuations in discharge and water levels.
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