Positioning Water Retention for Phosphorus Reduction

The report advocates for the use of spatial targeting to maximize the water quality and climate adaptation benefits of water retention projects, such as wetlands and naturalized dams, in the Canadian Prairies. It highlights the PTMApp model and the necessity of high-resolution LiDAR-based digital elevation models (DEMs) to accurately map phosphorus loading and identify non-contributing areas. Using the Swan Lake study area as a demonstration, the document argues that strategic site selection improves cost-effectiveness and phosphorus interception, particularly during high-magnitude spring runoff events.

• 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.
• Water retention is presented as a high-return investment, with an estimated benefit of CAD 2.45 for every dollar spent.
• 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 typical daily rainfall event over 10 years.
• Effective spatial targeting requires the identification of 'non-contributing areas'—regions of a watershed that do not contribute to downstream runoff under average annual conditions—to avoid placing projects in areas that already effectively retain water and nutrients.
• High-resolution LiDAR-based digital elevation models (DEMs) are essential for detailed field-scale hydrologic analysis, as they allow for the precise mapping of terrain and water flow paths.
• The PTMApp model can be used to map feasible water retention projects and calculate cost-benefit ratios based on phosphorus reduction, and it can be applied to ungauged basins where measured data is limited.

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} }