Nutrient Release and Transport In Snowmelt and Rainfall-Generated Runoff On the Canadian Prairies.

On the Canadian prairies, snowmelt runoff typically occurs over frozen soils during a 2-week period in late March or early April.  Although snow usually accounts for less than one-third of annual precipitation, snowmelt runoff accounts for more than 80% of surface water recharge.  Nutrient transport during snowmelt differs from that during rainfall-induced runoff because low infiltration into frozen soils results in runoff from lower intensity events and reduces soil-runoff interaction. Sources of nutrient may also differ between the two types of events as soil detachment is less during snowmelt, and freeze-thaw processes in fall and spring may release nutrients from vegetation into the snowpack.

These differences in nutrient sources and transport processes between snow and rain result in a greater proportion of dissolved nutrients in snowmelt than in rainfall-induced runoff and have implications for development of beneficial management practices for the protection of water quality.  We have studied snowmelt runoff at a range of scales during the past 20 years and will present and discuss data collected at the bench, plot, edge of field, farm and small watershed scales to illustrate the differences between snowmelt and rainfall-induced runoff.