Summary
This hydrological modelling study used the Cold Regions Hydrological Modelling platform to simulate long-term water balance changes resulting from conversion of annual crop (canola) to perennial forage (smooth bromegrass) in a typical Red River Valley agricultural basin. The 22-year simulations (1992–2013) on clay soils in a cold continental climate indicated that forage conversion would substantially reduce annual water yield (36.5%) and peak discharge (29.9%), primarily through reduced overland flow and increased infiltration to frozen soil, whilst also increasing evapotranspiration. These hydrological changes could reduce both flooding risk and nutrient export to Lake Winnipeg, though the study focused on the water balance mechanism rather than direct nutrient measurements.
Regional applicability
Whilst this study is geographically specific to the Canadian Prairies (Red River Valley), the modelling approach and findings on perennial forage adoption reducing discharge and overland flow have potential relevance to United Kingdom clay-soil regions subject to winter flooding and nutrient runoff, particularly where grassland expansion or crop conversion is being considered for mitigation. However, the cold continental climate, permafrost dynamics, and spring snowmelt processes differ substantially from UK conditions, requiring model recalibration for direct application.
Key measures
Annual cumulative discharge (mm), peak discharge (m³ s⁻¹), overland flow (mm), snowpack (%), infiltration to frozen soil (mm), evapotranspiration (mm), soil moisture (%)
Outcomes reported
The study modelled long-term water balance components comparing annual canola cropping with perennial smooth bromegrass conversion in the La Salle River basin, measuring changes in discharge, runoff, snowpack, infiltration, and evapotranspiration. Results showed forage conversion reduced annual cumulative discharge by 36.5% and peak discharge by 29.9%, driven by reduced overland flow and enhanced infiltration.
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