Hydropeaking Impacts and Mitigation

Abstract

Flow is a major driver of processes shaping physical habitat in streams and a major determinant of biotic composition. Flow fluctuations play an important role in the survival and reproductive potential of aquatic organisms as they have evolved life history strategies primarily in direct response to natural flow regimes (Poff et al. 1997; Bunn and Arthington 2002). However, although the organisms are generally adapted to natural dynamics in discharge, naturally caused flow fluctuations may entail negative consequences (e.g., stranding, drift, low productivity), especially if the intensity is exceptionally high or the event timing is unusual (Unfer et al. 2011; Nagrodski et al. 2012). Aside from natural dynamics in discharge, artificial flow fluctuations with harmful impacts on aquatic ecology can be induced by human activities. Hydropeaking-the discontinuous release of turbined water due to peaks of energy demand-causes artificial flow fluctuations downstream of reservoirs.

Cover or Velocity: What Triggers Iberian Barbel (Luciobarbus Bocagei) Refuge Selection under Experimental Hydropeaking Conditions?

“…The ecological impacts of hydropeaking can result in the reduction of fish suitable habitat and favorable areas for refuge [5,6,69]. Under those conditions, fish may benefit from the presence of instream structures for flow-refuging [11,15,25]. Thus, when designing morphological mitigation measures, it is strongly recommended to create habitats that remain stable during rapid flow variation, while assuring flow refuge areas during high velocities and water connectivity with the main channel [14].…”

“…Those impacts are site-specific and, therefore, mitigation measures should be adapted considering the river morphology together with species-specific ecological requirements [6] such as life-stage [10]. Hydropeaking mitigation measures can be grouped into direct and indirect measures [11]. Direct measures include specific operational schemes (e.g., decrease the flow ratio), as well as structural measures such as the construction of retention basins or hydropeaking diversion hydropower plants (e.g., [12,13]).…”

Life Stage-Specific Hydropeaking Flow Rules

“…Fish can be affected by changes in various components of the hydrograph, whereby the most common responses-stranding, drift, and dewatering of spawning grounds-are mostly related to up-and downramping rates [5,6], peak flow magnitude [5], and baseflow duration [7].Considering the large capacity of existing storage hydropower plants [8], as well as new ones that are currently being planned and installed [9], it is imperative to develop appropriate and transferable management measures to mitigate these ecological impacts. Many structural (e.g., constructing retention basins) and operational (e.g., reducing flow fluctuation rates) mitigation measures have been proposed [10,11], but implementation remains difficult, among other issues, because of significant reductions in the energy yield when setting ecological thresholds [2,12]. Therefore, well-targeted mitigation measures have to be developed to avoid energy losses and to guarantee ecological efficiency.Freeman et al [13] argue that adverse effects can be minimized by either restoring vital features of the natural flow regime or by implementing a flow management scheme which avoids hydropower-induced habitat bottlenecks.…”

“…Considering the large capacity of existing storage hydropower plants [8], as well as new ones that are currently being planned and installed [9], it is imperative to develop appropriate and transferable management measures to mitigate these ecological impacts. Many structural (e.g., constructing retention basins) and operational (e.g., reducing flow fluctuation rates) mitigation measures have been proposed [10,11], but implementation remains difficult, among other issues, because of significant reductions in the energy yield when setting ecological thresholds [2,12]. Therefore, well-targeted mitigation measures have to be developed to avoid energy losses and to guarantee ecological efficiency.…”

Habitat Enhancement Solutions for Iberian Cyprinids Affected by Hydropeaking: Insights from Flume Research

“…These rapid flow fluctuations result from the distinct stages of hydropeaking: base-flow discharge (no electricity production), increasing discharge or up-ramping (powering-on of the turbines), continuous high discharge (peak electricity demand), and decreasing discharge or down-ramping (powering-off of the turbines) [2,3]. This continuous flow variability alters the downstream river morphological and hydrological processes [4][5][6][7][8][9], with consequences to the ecological integrity of the river system [10]. Notwithstanding, new hydropower plants are planned or under construction [11,12].…”