Impacts
One highly significant impact of hydroelectric power generation projects is the entrainment of fish that pass through the spillways and turbines in their habitat use and migratory patterns that results in injury and mortality (Nalcor 2009, Vol. 2A; Zhong and Power, 1996) With respect to spillway passage, direct injury can be caused by rapid pressure change, rapid deceleration, shearing effects, turbulence and shearing forces in tail-water, the striking force of fish on the water from their free fall, and scraping or abrasions. Indirect injury also has the potential to occur as a result of gas bubble disease due to the atmospheric gas super-saturation in tail-water. There is also the risk of predation above and below spillways as a result of increased fish concentrations, thermal stress from changes in water temperature below the spillways, and the effects of stress, which can impact species survival and propagation (Nalcor 2009, Vol. 2A) With respect to the turbine passage, the main sources of injury and mortality include mechanical damage due to contact with equipment, cavitation and/or pressure-induced damage from exposure to low pressures within the turbines, and shearing damage from passage through particularly turbulent areas (Nalcor 2009, Vol. 2A).
Mitigation
(Nalcor 2009, Vol. 2A)In order to minimize the incidence of fish injury and morality, Nalcor has developed mitigation measures to address the complications associated with spillways and turbines. There is to be as minimal use of the spillways as possible so that the frequency of injuries is reduced. Furthermore, adaptive management techniques will be applied to deter fish from approaching the spillways themselves (Nalcor 2009, Vol. 2A). In addition, Nalcor invokes fish friendly design considerations throughout the Project. At Gull Island, the spillways will be of the ski jump type to direct the water horizontally and thereby reduce the potential for abrasions of the fish on the spillway surface. This particular design detail is unnecessary at Muskrat Falls though, because the elevation is much lower (Nalcor 2009, Vol. 2A) In addition to the careful spillway design, the turbine design will be as efficient at possible to lessen the effects of fish passage and thereby increase survival rates. The use of Francis turbines will entail relatively low runner speed, a high efficiency, and a maximum clearance between the trailing edge of the gates and the leading edge of the runner blades. This design also maximizes the tail-water elevation, which helps to reduce the incidence of cavitation (Nalcor 2009, Vol. 2A).
Assessment
The assessment of the effects of spillways and turbines was conducted by gathering information from several existing studies to identify the cause and level of injury and mortality on fish from similar projects (Nalcor 2009, Vol. 2A) Nalcor also completed a literature review on the construction of facilities with an emphasis on the fish friendly practices that they will then implement in their own designs. In particular, several studies on the merit of different types of turbines were examined to aid in fish friendly facility design (Nalcor 2009, Vol. 2A) In addition, the radiotelemetry program that was used to assess fish habitat was also used to determine the movement of fish and to ensure low fish movement in the vicinity of generation facilities (from Lower Churchill River to Goose Bay) (Nalcor 2009, Vol. 2A).
Critique
There are several elements of the assessment and mitigation methods for fish entrainment that appear problematic. First, there was a low sample size in the radiotelemetry monitoring program (Fisheries and Oceans Canada, 2009). Nalcor tagged and tracked 248 fish (Nalcor 2009, Vol. 2A) However, this represents a very low proportion of fish in the river system. This is an issue of concern because the measurements in this system should be, if anything, extra precise because the fish habitat use has already been described as atypical due to the high flow velocities and thus the system cannot be generalized and compared as readily to existing data. Furthermore, fish passage was not assessed at Muskrat Falls, because there is no migration across it - there is a complete migration barrier (Fisheries and Oceans Canada, 2009; Nalcor 2009, Vol. 2A) This is problematic, however, because some baseline needs to be established to determine the trajectory of fish after they pass Goose Bay. It is important to understand where they travel in close proximity to Muskrat Falls in order to assess where they will travel after development alters the fish habitats and river flows and specifically if there is a likelihood of them traveling into the Muskrat Falls area. To continue, Nalcor could have elaborated on their strategies to deter fish from spillways and turbines. In the review of other project proposals and methods of operation, it was found that the Dunvegan Hydroelectric Project specifies that their spillway design will include horizontal release of water, which is in line with the provisions of Nalcor. However, the proponent of the Dunvegan Hydroelectric Project goes further in outlining the positioning of sluiceways near spillways and turbine units to direct fish towards less turbulence in addition to the use of fish exclusion racks to minimize entrainment and guide fish towards sluices (Joint Review Panel, 2008).
One highly significant impact of hydroelectric power generation projects is the entrainment of fish that pass through the spillways and turbines in their habitat use and migratory patterns that results in injury and mortality (Nalcor 2009, Vol. 2A; Zhong and Power, 1996) With respect to spillway passage, direct injury can be caused by rapid pressure change, rapid deceleration, shearing effects, turbulence and shearing forces in tail-water, the striking force of fish on the water from their free fall, and scraping or abrasions. Indirect injury also has the potential to occur as a result of gas bubble disease due to the atmospheric gas super-saturation in tail-water. There is also the risk of predation above and below spillways as a result of increased fish concentrations, thermal stress from changes in water temperature below the spillways, and the effects of stress, which can impact species survival and propagation (Nalcor 2009, Vol. 2A) With respect to the turbine passage, the main sources of injury and mortality include mechanical damage due to contact with equipment, cavitation and/or pressure-induced damage from exposure to low pressures within the turbines, and shearing damage from passage through particularly turbulent areas (Nalcor 2009, Vol. 2A).
Mitigation
(Nalcor 2009, Vol. 2A)In order to minimize the incidence of fish injury and morality, Nalcor has developed mitigation measures to address the complications associated with spillways and turbines. There is to be as minimal use of the spillways as possible so that the frequency of injuries is reduced. Furthermore, adaptive management techniques will be applied to deter fish from approaching the spillways themselves (Nalcor 2009, Vol. 2A). In addition, Nalcor invokes fish friendly design considerations throughout the Project. At Gull Island, the spillways will be of the ski jump type to direct the water horizontally and thereby reduce the potential for abrasions of the fish on the spillway surface. This particular design detail is unnecessary at Muskrat Falls though, because the elevation is much lower (Nalcor 2009, Vol. 2A) In addition to the careful spillway design, the turbine design will be as efficient at possible to lessen the effects of fish passage and thereby increase survival rates. The use of Francis turbines will entail relatively low runner speed, a high efficiency, and a maximum clearance between the trailing edge of the gates and the leading edge of the runner blades. This design also maximizes the tail-water elevation, which helps to reduce the incidence of cavitation (Nalcor 2009, Vol. 2A).
Assessment
The assessment of the effects of spillways and turbines was conducted by gathering information from several existing studies to identify the cause and level of injury and mortality on fish from similar projects (Nalcor 2009, Vol. 2A) Nalcor also completed a literature review on the construction of facilities with an emphasis on the fish friendly practices that they will then implement in their own designs. In particular, several studies on the merit of different types of turbines were examined to aid in fish friendly facility design (Nalcor 2009, Vol. 2A) In addition, the radiotelemetry program that was used to assess fish habitat was also used to determine the movement of fish and to ensure low fish movement in the vicinity of generation facilities (from Lower Churchill River to Goose Bay) (Nalcor 2009, Vol. 2A).
Critique
There are several elements of the assessment and mitigation methods for fish entrainment that appear problematic. First, there was a low sample size in the radiotelemetry monitoring program (Fisheries and Oceans Canada, 2009). Nalcor tagged and tracked 248 fish (Nalcor 2009, Vol. 2A) However, this represents a very low proportion of fish in the river system. This is an issue of concern because the measurements in this system should be, if anything, extra precise because the fish habitat use has already been described as atypical due to the high flow velocities and thus the system cannot be generalized and compared as readily to existing data. Furthermore, fish passage was not assessed at Muskrat Falls, because there is no migration across it - there is a complete migration barrier (Fisheries and Oceans Canada, 2009; Nalcor 2009, Vol. 2A) This is problematic, however, because some baseline needs to be established to determine the trajectory of fish after they pass Goose Bay. It is important to understand where they travel in close proximity to Muskrat Falls in order to assess where they will travel after development alters the fish habitats and river flows and specifically if there is a likelihood of them traveling into the Muskrat Falls area. To continue, Nalcor could have elaborated on their strategies to deter fish from spillways and turbines. In the review of other project proposals and methods of operation, it was found that the Dunvegan Hydroelectric Project specifies that their spillway design will include horizontal release of water, which is in line with the provisions of Nalcor. However, the proponent of the Dunvegan Hydroelectric Project goes further in outlining the positioning of sluiceways near spillways and turbine units to direct fish towards less turbulence in addition to the use of fish exclusion racks to minimize entrainment and guide fish towards sluices (Joint Review Panel, 2008).