Declining water levels at Lake Powell have prompted the US Bureau of Reclamation (USBR) to disrupt invasive fish spawning at the Glen Canyon Dam. In a significant move to safeguard the delicate ecosystem surrounding the dam, USBR says it is developing alternative operational strategies that may extend until 2027.
The lake’s declining water levels have led to the epilimnion, the upper layer of the lake where most fish are located, drawing nearer to the water intakes of the Glen Canyon Dam. This shift has increased the likelihood of non-native fish passing through the dam and into the Colorado River. Moreover, the epilimnion, when discharged downstream, raises the river’s temperature, creating ideal spawning conditions for the smallmouth bass, a predatory invasive fish species that poses a threat to the federally protected humpback chub and other native fish.
USBR says it will assess various reservoir releases, considering temperature and flow velocity combinations and these analyses will encompass a flow option that does not utilise the dam’s river outlet works to reduce water temperatures. The goal is to determine the effectiveness of these strategies in disrupting smallmouth bass spawning behaviour and preventing their establishment below the dam. Furthermore, USBR will update the high-flow protocol sediment accounting process, incorporating the latest scientific findings.
Safe passage
A new A$7m fishway project is set to revolutionise the Fitzroy Barrage System and facilitate the safe movement of 31 native fish species to 545 hectares of habitat in Australia. Construction of the fishway will be undertaken by Queensland-based construction firm, Pensar Infrastructure, and is one of six additional projects within the Rookwood Weir Project which is designed to enhance water infrastructure while promoting ecological well-being.
The landmark Rookwood Weir, located upstream of the Fitzroy Barrage, introduces a pioneering fish lock system, providing a mechanism for species migration. The new fishway will further amplify this effort, with its design incorporating ‘cone’ type blocks to enable seamless migration of smaller fish upstream and downstream, effectively connecting fish population across the river.
In conjunction with road upgrades and bridge construction, this fish passage initiative is a key component of the Rookwood Weir Project’s comprehensive approach to fostering regional growth, environmental health, and water security. “
With the Queensland and Australian Governments contributing a total of A$367.2 million and Sunwater financing the remainder, amounting to A$568.9 million, the Rookwood Weir Project is a substantial investment in the region’s future.
Fish funds
The US Department of Energy (DOE) has announced funding exceeding US$6.3 million is to be allocated to six research and development projects focused on the advancement of fish passage and protection technologies, ultimately reducing the environmental impact of hydropower on aquatic ecosystems.
Jeff Marootian, Principal Deputy Assistant Secretary for Energy Efficiency and Renewable Energy, emphasised the dual importance of clean energy and biodiversity protection, stating: “Hydropower is a flexible renewable energy resource that has a central role as we move toward a clean electricity sector and economy. But the climate crisis is also a biodiversity crisis, and we need to protect species as we move toward a clean energy system. This investment in fish passage and protection technologies will help fish move safely through hydropower facilities while reducing the overall environmental impact of hydropower and restoring fish population levels.”
The US$6.3 million investment will drive the development of innovative fish passage and protection technologies through six selected projects:
- Electric Power Research Institute’s Fishheart Hydraulic Fishway will deploy and assess a novel fish entry and transport system at the Santee Spillway hydropower project in Pineville, South Carolina.
- MarineSitu’s Automated Fish Passage Monitoring will create an automated tool to track and classify fish navigating fish ladders.
- Natel Energy’s Safe Downstream Fish Passage will evaluate Natel Energy’s Restoration Hydro Turbine as a secure downstream passage for American Eel.
- Percheron Power’s Helical Fish Passage will test the Stralkin Helix. This is a novel fish passage approach utilising a rotating helix that seeks to significantly reduce costs compared to conventional methods while improving multi-species fish passage.
- University of California, Davis’ White Sturgeon Passage Assessment is focused on assessing the safe turbine passage of White Sturgeon population. This laboratory research aims to provide valuable insights to turbine designers, operators, and fish regulators, balancing renewable energy production and biodiversity protection.
- University of Massachusetts Amherst’s D-Cylinder Fish Ladder Evaluation will address the limitations of existing fish ladder designs.
Work at Holyoke Dam
Kleinschmidt Associates, an engineering, regulatory, and environmental consulting firm, has been selected by Holyoke Gas and Electric (HG&E) to conduct an extensive study on the movement and upstream passage of the Shortnose Sturgeon at the Holyoke Dam in Massachusetts, US.
The study aims to assess the efficiency of the fish passage infrastructure at the dam in facilitating the safe and timely migration of adult Shortnose Sturgeon. Kleinschmidt’s team plans to employ an acoustic telemetry monitoring system to track approximately 70 sturgeons as they approach the dam and navigate through a fish lift to move upstream.
Bryan Apell, Project Manager and Senior Fisheries Ecologist at Kleinschmidt, emphasised the critical role of habitat connectivity for the Connecticut River ecosystem, particularly for diadromous and potamodromous fish species that rely on it for their life cycles.
“The Holyoke dam is the first mainstem dam on New England’s largest river, supporting a host of migratory fish runs,” he said. “HG&E has been at the heart of the effort to improve habitat connectivity through safe and timely fish passage and protection at their hydroelectric facility.”
Kleinschmidt has assisted with the project since 2017 and is now helping to bring this intricate multi-year effort to fruition. The study is expected to conclude in 2024.
Concern over Mekong Fish
New research claims to have revealed “an alarming decline” in the number of fish species in the Mekong River system in Southeast Asia where two tributaries have shown declines in fish species, while an increase in diversity was noted in a third, largely free-flowing tributary.
Sarah Null, a water resources expert in the Utah State University’s Department of Watershed Sciences, and an author on the study, says that this is one of the first pieces of research to show reduced fish diversity following dam construction, contrasted with increased diversity in less fragmented rivers in the Mekong River system.
Flowing through six Asian countries, the Mekong supports the highest levels of fish harvest from any inland fishery in the world, sustaining the livelihoods of tens of millions of people. The authors claim that the region’s rapid pace of hydropower development, which includes 129 commissioned dams in the Lower Mekong Basin, will disrupt and block fish migrations and alter fish communities and aquatic ecosystems, leading to decreased biodiversity, abundance, and biomass, according to the authors.
The team focused on the Sesan, Srepok and Sekong Rivers which make up just 10 per cent of the Mekong watershed geographically, but provide as much as 25 per cent of the main river’s flow, supporting 40 per cent of the more than 1000 species of fish found in the Mekong River system.
The diversity of select fish species decreased alarmingly in the more heavily dammed Sesan and Srepok Basins, the study found, from 60 and 29 species in 2007 to 42 and 25 species in 2014. During the same period, it increased from 33 to 56 species in the Sekong, the basin with the fewest dams.
The results show the importance of keeping rivers like the Sekong free-flowing, said Ratha Sor, a researcher at Utah State University and Chea Sim University of Kamchaymear in Cambodia, and lead author of the study.
“The Sekong Basin plays an important role as a free-flowing river corridor for fish migration and can potentially compensate for environmental changes and habitat loss in the Sesan and Srepok Basins,” said Sor.
To preserve biodiversity and stem the potential decline in fish species, the researchers urge policymakers to focus on developing other renewable sources of energy and optimising hydropower at existing dams as alternatives to the construction of new dams in the Mekong region.
This article first appeared in International Water Power magazine.
