Water Retention Beneficial Management Practices

The report details a spatial targeting strategy for phosphorus reduction in the Canadian Prairies, using the Swan Lake study area as a pilot. It integrates the PTMApp model with HEC-HMS and HEC-RAS to account for regional hydrological specifics, such as spring runoff and non-contributing areas. Key findings highlight that default PTMApp settings may overestimate BMP efficiency during spring runoff and that high-quality land-use data is critical to avoid significant errors in nutrient load estimates. The report also discusses the practical application of these models for government and First Nations stakeholders, emphasizing the value of local knowledge and the need for compensation programs to encourage BMP adoption on high-value cropland.

• The 2-year spring runoff event in the Swan Lake study area is estimated to be approximately 78% larger in total volume than the runoff generated from a 10-year 24-hour rainfall event using the SCS curve number method.
• Default PTMApp methodology for farm pond/wetland BMPs can be inaccurate for large flow events because the decay coefficient is too low, potentially overestimating treatment efficiency when most water spills untreated.
• In the Swan Lake study area, 21.1% of farm pond/wetland BMPs (106 out of 503) have reduction ratios lower than 1.0 for the 2-year spring runoff event, meaning their efficiency is sensitive to the inflow scenario.
• Incorrect land-use data can lead to significant overestimations of nutrient reduction; in one case, a downstream farm pond/wetland BMP's TP reduction was overestimated by 47.7% due to an erroneous barren land assignment.
• The use of HEC-RAS to identify non-contributing areas provides a critical filtering criterion for BMPs, as many highly feasible and effective sites overlap with areas that contribute little to no flow during average years.
• There is a significant conflict between the most cost-effective BMP locations and high-value agricultural land, suggesting that compensation programs are necessary to make BMP implementation viable for producers.
• Local knowledge from Indigenous communities, such as the Swan Lake First Nation, can identify non-contributing areas that models may miss, highlighting the importance of engaging stakeholders early in the modelling cycle.

APA

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

Chicago

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

Wikipedia

{{cite report |last1=Simoes |first1=Joey |last2=Vanrobaeys |first2=Jason |last3=Morissette |first3=René |title=Water Retention Beneficial Management Practices |publisher=International Institute for Sustainable Development |date=May 2025 |url=https://www.iisd.org/system/files/2025-05/water-retention-spatial-targeting-canada-prairies.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{simoes2025water, author = {Simoes, Joey and Vanrobaeys, Jason and Morissette, René}, title = {{Water Retention Beneficial Management Practices}}, 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.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }