Hydropeaked rivers need attention

Abstract

Hydropower is considered a renewable form of energy production, but generating electricity from rivers is not always environmentally benign. The global demand for renewables is increasing rapidly as fossil fuels are gradually phased out, so rivers will continue to be subjected to the pressures imposed by hydropower for decades to come. Finding ways of operating hydropower plants that limit impacts on downstream river ecosystems is therefore a pressing global concern. Usually, these plants cause marked and rapid fluctuations in flow in downstream river reaches, termed ‘hydropeaking’. Hydropeaks result in a variety of ecological changes in the dynamic mountain rivers they typically affect; declines in fish and insect populations are evident, especially in reaches immediately downstream from the plant. While these changes are often acute and readily apparent, the underlying causal mechanisms remain unclear. We argue here that riverbed sediments are a critical but neglected causal link between hydropeaking flow regimes and ecological changes. We outline how a variety of tools from different branches of river science can now be brought together to understand precisely why hydropeaking alters sediment dynamics; these tools provide a mechanistic explanation for changes in bed sedimentary conditions and channel form across multiple scales and, consequently, a better understanding of ecological changes. By allowing us to simulate the effects of flow fluctuations on sediment dynamics and channel form, these tools also allow us to develop ways of releasing water from hydropeaking dams that limit impacts on aquatic habitat and species.

Mitigation of environmental effects of frequent flow ramping scenarios in a regulated river

“…Upper left panel: an overview of the sites used for dewatering computations; upper right panel: Trekanten site (regions 2-5); middle right panel: side channel site (region 1); lower right panel: Stryket site. Adapted from Kenawi(2021).…”

Hydroelectric plant effects and climate change/land use impacts on flow regime in the tropical headwater watershed

“…( than 20% of the daily flow, as recommended by Richter et al (2012), to minimize changes from the natural regime and to reduce the low pulse count; (b) the date of minimum flow should occur in the dry season, preferably in September, at the same time when it used to occur during the predam period; and (c) because the significant change in the number of reversals, it is also recommended that dam operation occurs without significant hydropeaking by applying a combination of structural, operational and morphological approaches including reengineering dams, changing the timing and rate of hydropeaking, and implementation of hydraulic structures for energy dissipation and habitat refugia (Batalla et al, 2021).…”

Reflexión sobre dinámica morfosedimentaria. Implicaciones para la gestión fluvial en un contexto de cambio global

“…El consenso internacional para reducir las emisiones de gases de efecto invernadero garantiza un papel importante para la hidroelectricidad a medio plazo. Pero a pesar de ser clasificada como una forma verde de producción de energía, esta tecnología no está libre de impactos ambientales (Batalla et al, 2021). Las presas y las infraestructuras asociadas para la producción imponen presiones específicas en los ríos.…”