Simulating the hydrological impacts of land use conversion from annual crop to perennial forage in the Canadian Prairies using the Cold Regions Hydrological Modelling platform

Abstract. The Red River is one of the largest contributing sources discharge and nutrients to world's 10th freshwater lake, Lake Winnipeg. Conversion large areas annual cropland perennial forage has been proposed as a strategy reduce both flooding nutrient export Such reductions could occur either via reduction in concentration runoff or through changes basin-scale hydrology, resulting lower water yield concomitant nutrients. This study assessed latter mechanism by using physically based Cold Regions Hydrological Modelling platform examine hydrological impacts land use conversion from crops subbasin La Salle basin Canada. typical agricultural Valley, characterised flat topography, clay soils, cold subhumid, continental climate. Long-term simulations (1992–2013) major components balance were compared between canola smooth bromegrass, representing cropping systems forage. An uncertainty framework was used represent range fall soil saturation status (0 % 70 %), which governs infiltration frozen subsequent spring. model indicated that, on average, there 36.5 ± 6.6 (36.5 7.2 mm) cumulative 29.9 16.3 (2.6 1.6 m3 s−1) peak due over period. These driven reduced overland flow 52.9 12.8 (28.8 10.1 mm), increased snowpack (8.1 1.5 %, 7.8 enhanced soils (66.7 7.7 141.5 15.2 mm). Higher evapotranspiration (ET) (34.5 0.9 94.1 2.5 also predicted simulations. Overall, daily moisture under 18.0 (57.2 1.2 higher than that crop simulation, likely snow equivalent (SWE) infiltration. However, impact varied interannually. Soil stands be crops, depending antecedent spring snowmelt volumes.