Abstract
Pumped hydroelectric energy storage (PHES) projects are being considered worldwide to achieve renewable energy targets and to stabilize baseload energy supply from intermittent renewable energy sources. Unlike conventional hydroelectric systems that only pass water downstream, a feature of PHES schemes is that they rely on bi-directional water flow. In some cases, this flow can be across different waterbodies or catchments, posing a risk of inadvertently expanding the range of aquatic biota such as fish. The risk of this happening depends on the likelihood of survival of individuals, which remains poorly understood for turbines that are pumping rather than generating. This study quantified the survival of a globally widespread and invasive poeciliid fish, Eastern gambusia (Gambusia holbrooki), when exposed to three hydraulic stresses characteristic of those experienced through a PHES during the pumping phase. A shear flume and hyperbaric chamber were used to expose fish to different strain rates and rapid and sustained pressurization, respectively. Blade strike models were also used to predict fish survival through a Francis dual turbine / pump. Simulated ranges were based on design and operational conditions provided for a PHES scheme proposed in south-eastern Australia. All gambusia tested survived high levels of shear stress (up to 1853 s-1), extremely high pressurization (up to 7600 kPa gauge pressure) and the majority (> 93 %) were unlikely to be struck by a turbine blade. Given their tolerance to these extreme simulated stresses, we conclude that gambusia will likely survive passage through the simulated PHES scheme if they are entrained at the intake. Therefore, where a new PHES project poses the risk of inadvertently expanding the range of gambusia or similar poeciliid species, measures to minimize their spread or mitigate their ecosystem impacts should be considered.
Highlights
Pumped hydroelectric energy storage (PHES) projects are expanding worldwide, driven by the rising global demand for electricity, political renewable energy targets, security of supply, and upgrades to existing water infrastructure (Yang, 2016)
Mortality thresholds for these species generally ranged between 800 and 1,200 s−1, with blue gourami being the least tolerant (852 s−1) (Colotelo et al, 2018) and steelhead being the most tolerant [i.e., having no reported mortality at the highest strain tested (≥1,008 s−1)] (Neitzel et al, 2004). In comparison to these species, our results indicate that gambusia are a relatively tolerant species to shear strain, owing perhaps to their small size and body morphology (Neitzel et al, 2000)
The present study focuses on passage survival and was conducted based on the assumption that adult gambusia will become entrained in the PHES scheme
Summary
Pumped hydroelectric energy storage (PHES) projects are expanding worldwide, driven by the rising global demand for electricity, political renewable energy targets, security of supply, and upgrades to existing water infrastructure (Yang, 2016). Reversible turbines (usually a Francis dual turbine) pump water to a higher elevation reservoir during periods of low electricity demand. If a PHES facilitates the unintentional transfer of alien species to new areas, there can be flow on effects such as the loss of biodiversity, predation, and alterations of food webs (Strayer, 2010; Gallardo et al, 2016). Whether these impacts are realized will depend on whether a species will be entrained and survives passage through a PHES scheme
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