Seasonal Dynamics of Phosphorus Partitioning and Export in Two Streams in Alberta, Canada

Abstract

In 1983, phosphorus (P) export was quantified for two streams in Alberta, Canada. The influence of changes in discharge on P concentration and partitioning was examined on an annual and seasonal basis and these data were used to develop empirical models to predict P concentrations. Phosphorus export peaked during summer storms; 68% of annual total P loading was transported during 12 d in early summer. Phosphorus increases were larger during storms in early summer than during storms in late summer. Annual total P exports were 7.5 and 13.0 mg/m2 (watershed area) for the two streams, primarily in the fine particulate fraction. The empirical models presented are the first based on detailed data from watersheds with the following characteristics: (1) trees predominantly coniferous, (2) deep glacial till overlying sedimentary bedrock, and (3) climatic regime where most P is exported during summer storms. These results underscore the need for intensive sampling regimes in streams in a variety of regions (especially at high discharge) so factors controlling P levels can be better understood.