EVALUATION OF EPICS SNOWMELT AND WATER EROSION SUBMODELS USING DATA FROM THE PEACE RIVER REGION OF ALBERTA

Water erosion due to snowmelt is a major form of erosion in boreal reg ions of the Canadian Prairie. Evaluation of erosion models is an essen tial step before recommending their use in local or regional assessmen ts of erosion rates and control methods. Using inputs fi om a runoff s tudy conducted at La Glace, Alberta(55 degrees 25'N, 119 degrees 10'W) from 1984 to 1986, we evaluated the Erosion-Productivity Impact Calcu lator (EPIC) for its ability to simulate runoff and sediment yield fro m snowmelt events. The model was initialized with soil profile data ac quired at the study site and complemented with data from standard soil databases (Albright series; loam, Dark Gray Chernozem). Daily weather data were acquired from the nearest climatological station (annual pr ecipitation = 475 mm). Management data were as reported and included c ombinations of conventional and reduced tillage, annual and perennial, and fallow cropping. Mean runoff volume measured in 1985 was 57 mm wh ile in 1986 it was 76 mm. EPIC over-predicted runoff volume by 25% in 1985 but under-predicted it by 7% in 1986. The period in which snowmel t occurred (mid-March - beginning of April) was predicted correctly. U nder the conditions of this study, with many cropping inputs obtained from different sources, the model was unable to reproduce the reported management effects on runoff and sediment yield. EPIC simulated sprin gmelt soil temperature trends at 9-cm depth, although the predicted te mperatures in 1985 were generally underestimated. Our results suggest that the EPIC model calculates adequate values of runoff volumes and s ediment yields during snowmelt.