Hydrological variability affects particulate nitrogen and phosphorus in streams of the Northern Great Plains

•Hydroclimatologic changes affected P and N concentrations and fractions.•Greater fractions of particulate P and N were observed during snowmelt in 2013.•Greater proportions of dissolved P were observed during snowmelt + rainfall in 2014.•Effective actions are needed to reduce dissolved P and N export to Lake Winnipeg. The study area is located in southern Manitoba, in the prairie region of Canada This study examined the impact of hydrological variability on the timing and magnitude of nutrient export from seven agriculturally-dominated watersheds in the Red River Valley, Manitoba, Canada. In 2013, discharge showed a seasonal pattern typical of streams traversing the Canadian prairies: high discharge during snowmelt followed by cessation of flow in early June due to lack of precipitation. In 2014, discharge still peaked during snowmelt but, compared to 2013, was 49% lower during snowmelt yet 21% higher during summer and fall due to greater rainfall. These hydrologic differences were associated with differences in fractionation of nutrients between years. Thus, higher concentrations and loads of particulate phosphorus (P) and nitrogen (N), and a greater (p