Positioning Water Retention for Phosphorus Reduction

This executive summary describes a spatial targeting strategy developed by the International Institute for Sustainable Development (IISD) to optimize the placement of water retention projects, such as wetlands and small naturalized dams, to reduce phosphorus loading in Canadian Prairie watersheds.

• Water retention infrastructure, including wetlands and small naturalized dams, provides significant climate adaptation benefits for the Canadian Prairies by reducing flood and drought risks, improving water quality, enhancing biodiversity, and reducing atmospheric carbon. These projects are estimated to provide a return of CAD 2.45 in benefits for every dollar spent.
• Spatial targeting allows for the strategic placement of water retention projects to maximize phosphorus interception and return on investment. This process is facilitated by models like the Prioritize, Target, and Measure Application (PTMApp), which utilize publicly available datasets such as LiDAR-based digital elevation models (DEMs).
• In the Canadian Prairies, spring runoff is a critical event for phosphorus loading; in the Swan Lake study area of the Living Lab Eastern Prairies, the average yearly spring runoff event is 78% larger by volume than the largest rainfall event typically estimated to occur in a single day over 10 years.
• Accurate hydrologic modelling in the Canadian Prairies requires high-resolution LiDAR-based DEMs to map terrain and flow paths, as well as detailed culvert inventories that include surveyed elevation and inlet/outlet coordinates. Additionally, PTMApp requires phosphorus export coefficients for different land types, which should be calibrated using measured data from events like spring runoff to ensure accuracy.
• The identification of 'non-contributing areas'—parts of a watershed that do not contribute to downstream runoff under average annual conditions—is essential for spatial targeting. Identifying these areas allows planners to deprioritize project development in regions that already effectively retain water and nutrients.
• IISD's spatial targeting strategy is designed to be replicable in ungauged basins where water quality and quantity data are limited. The strategy utilizes free and publicly available tools, with the exception of ArcGIS (Map or Pro), and can be expanded across Canada wherever high-resolution DEM data is available.

APA

Simoes, J., Vanrobaeys, J., & Morissette, R. (2025). Positioning Water Retention for Phosphorus Reduction. International Institute for Sustainable Development. https://www.iisd.org/system/files/2025-05/water-retention-spatial-targeting-canada-prairies-summary.pdf

Chicago

Simoes, Joey, Jason Vanrobaeys, and René Morissette. Positioning Water Retention for Phosphorus Reduction. International Institute for Sustainable Development, 2025. https://www.iisd.org/system/files/2025-05/water-retention-spatial-targeting-canada-prairies-summary.pdf.

Wikipedia

{{cite report |last1=Simoes |first1=Joey |last2=Vanrobaeys |first2=Jason |last3=Morissette |first3=René |title=Positioning Water Retention for Phosphorus Reduction |publisher=International Institute for Sustainable Development |date=May 2025 |url=https://www.iisd.org/system/files/2025-05/water-retention-spatial-targeting-canada-prairies-summary.pdf |access-date=17 August 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{simoes2025positioning, author = {Simoes, Joey and Vanrobaeys, Jason and Morissette, René}, title = {{Positioning Water Retention for Phosphorus Reduction}}, institution = {International Institute for Sustainable Development}, year = {2025}, month = may, url = {https://www.iisd.org/system/files/2025-05/water-retention-spatial-targeting-canada-prairies-summary.pdf}, urldate = {2026-08-17}, note = {Indexed by Climate Insights Directory} }