The Boyne Valley Water Initiative: Natural Infrastructure and the Treherne Dam feasibility study

The Municipality of Norfolk Treherne (pop. 1,751), a rural municipality in south central Manitoba, will be carrying out a climate adaptation feasibility study to assess the technical and financial feasibility of constructing a dam on the Boyne River in order to reduce the municipality’s vulnerability to drought and flooding. Southern Manitoba's vulnerability to climate change was highlighted by recent events in 2017. In early April, spring flooding along the Boyne River forced Carman's water treatment plant to shut down due to high turbidity levels, and in early June, flooding occurred while farmers were spraying their fields. These events coupled with the increased demand for water left the municipality struggling to supply the local community with their water requirements. The Boyne River has reached its maximum license capacity for summer flow conditions, which is of specific concern for the supply of potable water in the region.The Treherne Dam was first proposed in 1965 by the Prairie Farm Rehabilitation Administration and was designed as an impoundment on the Boyne River in order to intercept runoff in the headlands of the river for irrigation and livestock watering purposes. In the 1980s, the project was reconceptualised to include pumping water from the Assiniboine River into the reservoir during spring freshet to increase water supply. This feasibility study will re-analyze the Treherne Dam proposal in light of water harvesting infrastructure within the context of climate change. The new storage capacity created by the new dam would provide greater flexibility in the management of the limited water resources in the watershed and surrounding region. Given the water shortages experienced in the past, this increased supply and management flexibility is required under existing hydrologic conditions, and becomes even more critical under any modified hydrologic conditions that may arise as a result of climate change.The feasibility study will include a review of existing reports and studies and a comprehensive analysis of impacts and benefits of the project in the context of climate change. This analysis will include a cost-benefit analysis, a modern multifunctional reservoir operations strategy based on simulation modelling and climate model projects, and a recommended institution model for long-term project management. The analysis will also include an assessment of the key environmental impacts of the reservoir construction; include the frequency of low flows with and without the reservoir construction and the impact of construction on aquatic and terrestrial habitat impacts. The Municipality of Norfolk Treherne will oversee the development of this feasibility study in partnership with Eco-West Canada, the International Institute for Sustainable Development (IISD) and the Prairie Climate Centre (PCC).