Chin Reservoir Update: Environmental Impact Assessment Released

September 3, 2024

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• Grasslands
• Rivers
• Wildwater

The Environmental Impact Assessment (EIA) for the Chin Reservoir Expansion Project has been published by the Natural Resources Conservation Board (NRCB), following an application submitted by the St. Mary River Irrigation District to the NRCB on July 31, 2024. The Chin Reservoir Expansion is one of the few projects under the Alberta Irrigation Modernization Program that has been required to undergo an EIA since the initial funding announcement from the Government of Alberta back in October 2020.

The Chin Reservoir is an existing reservoir in southeast Alberta, storing 176,475 acre-feet of water and contained by two dams that were completed in 1955. The project proposes to increase storage to 257,820 acre-feet, nearly a 50 percent increase. This change would flood an additional 1000 acres of land within Chin Coulee.

Chin Coulee is classified as a High Value Landscape by Prairie Conservation Forum, identifying mainly intact tracts of native prairie, an ecosystem that is highly endangered and under-protected in Alberta, and vital habitat for wildlife. The reservoir expansion “will result in a decrease in vegetation habitat quantity, including loss of native grassland vegetation communities, traditional use plants, rare plants and rare plant communities, and increased fragmentation of vegetation communities.” As the EIA notes, “Chin Coulee is a relative island of native prairie in a sea of agricultural and industrial land uses.” These areas of native prairie likely provide wildlife corridors for many plants and animals, and the flooding of these lands could present a significant barrier to movement, in addition to the direct loss of native grasslands and rare plants.

As well as the loss of prairie vegetation, the project would result in a loss of prairie habitat, displacing many wildlife species. The Breeding Bird Survey conducted for the EIA detected 87 bird species, including the Endangered chestnut-collared longspur, as well as widespread use by amphibians and reptiles, such as boreal chorus frog, plains spadesfoot, wood frog, prairie rattlesnakes, and bullsnakes. A likely active snake hibernaculum was located just east of the dam site. Clearly, this is a site that supports high biodiversity, and the flooding of these lands would destroy a substantial amount of habitat, displacing and potentially killing several animals residing in the area.

The expansion of Chin reservoir could also further damage the already degraded river health in the South Saskatchewan River basin. Although the project summary suggested “an increase in water diversion from naturally occurring watercourses will not be required,” the description also stated that expansion of the Chin Reservoir was selected to “meet the need of the increased demand for irrigation.” River health in southern Alberta is already at risk, with the World Wildlife Fund (WWF) Watershed Reports noting that the South Saskatchewan Watershed, where the project is located, is already at high risk from overuse of water and aquatic habitat fragmentation due to roads and dams. Many of Alberta’s rivers are overdrawn, often failing to meet Water Conservation Objective (WCOs) established to maintain river flows and unable to sustain river health. Considering the scarcity of water in southern Alberta, and the already vulnerable state of our rivers, expanding irrigation appears irrational.

The expanded reservoir could severely degrade the quality of nearby rivers, groundwater, and soils. The EIA acknowledges that expanding the Chin Reservoir is “expected to lead to an increased rate of groundwater flow” and that this may “lead to a low magnitude change in groundwater quality through transport of salts.” In Alberta, groundwater resources are poorly understood, and it is irresponsible to assume the magnitude of negative impacts, as well as allowing potentially harmful actions without realizing the full extent of harm. The EIA also acknowledges that “a heightened water table in the presence of evapotranspiration can result in the increased salinization of surface soils.” For surface water, there is “expected to be an increase in suspended sediment concentrations,” a result of eroding the shoreline. As well, although not fully discussed in this EIA, the increase of still water and the greater surface area of the reservoir will likely increase evaporation rates, which could concentrate compounds, including phosphorous, nitrogen, mercury and other toxins, and salts. Changes to any of these components can significantly alter water chemistry and damage the aquatic habitat, as well as degrading nearby groundwater and soils.

The impact on fish and other aquatic life is another concern not fully addressed in the EIA. Fish entrainment due to dams and irrigation canals is a major threat for many species, and higher dams can be greater barriers to fish movement. The EIA notes, “Fish will be excluded from the expanded reservoir during initial filling, which will avoid exposure to sediment during the period of highest potential for mobilization.” However, this does not solve the long-term problem of fish and other aquatic organisms becoming trapped in the reservoir and in irrigation canals. Without strong mitigation measures, including fitting intake screens and installing bypass facilities, fish will become trapped, further threatening already declining populations.

Climate change is also not entirely explored in the assessment of the project. While the benefits of reservoir expansion for climate change are addressed, the negative impacts are largely ignored. While increasing storage may improve agricultural resilience, reservoir expansion is likely to also have negative impacts that exacerbate climate change. The EIA acknowledges a “loss of carbon sequestration potential” in soils, although it does not discuss the release of carbon due to destruction of native grasslands, or the release of greenhouse gases created by reservoirs. Reservoirs are estimated to release millions of tonnes of greenhouse gases per year due to decomposing vegetation, and microorganism activity, as well as during construction when disturbance of soils and vegetation releases stored carbon. In addition, the expanded surface area of larger reservoirs increases evaporation, removing water from an easily accessible state and potentially exacerbating drought. These potential impacts that contribute to worsening climate change must be considered alongside any benefits.

These environmental impacts should all be considered with total cumulative impacts in the region. Although relative cumulative impacts are mentioned, the additional effect of this project with all other developments and disturbances is not discussed. For instance, there is high agricultural conversion in the region, and scarce native prairie remaining. As a result, any remnant prairie is likely to be in high use by grassland-dependent species, and the removal of additional prairie may have disproportionate effects on overall biodiversity. Additionally, the impacts of irrigation are not addressed, despite the intent to increase irrigated acres by expanding Chin Reservoir. All impacts of the project need to be considered in determining whether the project is in the public interest.

Finally, the socio-economic costs are incompletely assessed. The EIA focuses on the agricultural benefits, increasing jobs and gross domestic product (GDP); despite the lack of attention to environmental impacts, it incorporates the benefits of increasing irrigated agriculture. However, it does not address the socio-economic costs associated with losing native grassland and grazing lands, the costs expected due to worsening climate change, or discuss the ability of the project to support food and sustenance for local communities. This uneven approach to socio-economic costs provides a biased and incomplete assessment of the project.

The EIA for the Chin Reservoir does not provide enough justification to allow this project to proceed. It states, “Given the potential for the enhancement of regional drought resiliency and flood mitigation, the SMRID believes the Project is in the public interest.” Given the loss of native prairie, displacement of wildlife habitat, damage to rivers and aquatic ecology and potential contribution to climate change and cumulative effects, we disagree.