The Keeyask dam construction site is situated on the lower Nelson River at the Gull rapids, in Manitoba. The Generating station is set for completion in 2021 with first power from the plant expected in 2019 (Pump Industry Analyst 2014). This will be the 5th dam built on the Nelson river and construction is already underway (Keeyask Generating Project, 2012b). Dams are commonly regarded as a safe solution to other carbon producing methods of power generating, however dams also come with a biophysical cost. In particular, some of the key negative variables that are associated with the presence of a new dam reservoir are loss in terrestrial habitat for sensitive species and increased mercury levels(Keeyask Generating Project, 2012b). There have been many studies conducted on the bio-physical effects of dams in Canada. An example of the bio-physical effect on dams is clear at the Elwha Dam in Washington State, where they were forced to remove the dam due to environmental implications. They concluded that 490 acres of various habitats were flooded, significantly effecting Elk and Deer populations (Winter and Crane, 2008). Another study by Fearnside (2015) observed significant impacts to 920 fish species following dam completion at the Maderia river in Brazil. This loss of fish species was due to the absence of fish passage around the dam.
Although the impacts of hydroelectric dams have been thoroughly established in the previous literature, determining the amount and severity of impacts is challenging based on the variability of hydroelectric dams and their surrounding areas. Dams of different sizes and different reservoirs are accompanied by differences in the severity of impacts they pose on their surroundings. Additionally, the river morphology and ecosystem characteristics may be more or less susceptible to disturbance from the dam based on their unique characteristics. More uncertainties arise from the impact of climate change, different environmental conditions and storm frequencies that will alter our current knowledge of hydroelectric dams (Power, 1996). Due to the variability of dams, specific assessments are necessary to accurately measure the impact a dam will pose on the surrounding environment. Seeing as how the Keeyask dam has already been approved and construction is currently underway, an environmental risk assessment has already been conducted. However, the risk assessment has only based findings on ideal water levels (159 m above sea level (ASL)). With the uncertainty of future climate change, flood events and drought events could occur in the future. These events may have additional risk associated with them, that have not been fully investigated by the original risk assessment.
Implementing a spatial risk assessment under drought and flood conditions will be necessary in understanding the range of impact that the Keeyask Generating station will have on the environment. Therefore, a multi-criterion evaluation (MCE) will be applied to the landscape under ideal, flood, and drought inundation levels to assess the potential risk associated with there respective water levels. The first evaluation will be based off of the projected minimum operating level (MOL). A minimum level will provide a water level of 158.0 m ASL, and the dam is expected to operate at this level for a small portion of time each week (1-2 days). The second evaluation will be based off of the normal full supply level (FSL), which will provide a water level of 159.0 m ASL and will operate the majority of the time. The final evaluation will be based off of the maximum surcharge level (MSL) and will provide a water level of 160.0 m ASL. The MSL will only occur in extreme flooding events (1:1000 year flood) and will only occur if the dam is not operating (Power Outage) (Keeyask Generating Project 2012a).
GIS application is necessary for preparing and implementing an MCE evaluation accurately and efficiently. The use of a spatial display and visualization will ease identification of the impacts, as well as measurement of the different extents of flooding based on a Digital Elevation Model (DEM). GIS also provides an easy way of manipulating the data based on future changes to the affected area. It is also important to use GIS to conduct an environmental based on the spatial distribution of major factors like the Aboriginal communities, sensitive species, endangered plants, and mercury levels.
Purpose of Research
The purpose of this research is to develop a GIS-based MCE model to assess the potential risk level associated with multiple inundation events of the Keeyask Generating Station’s reservoir.