A study of photochemical air pollutants in the urban Airsheds of Edmonton and Calgary

Abstract

A small catchment in south‐central Ontario was divided into two zones to evaluate the effect of a small wetland on runoff response during spring snowmelt in 1980. Runoff from the downstream side‐slope zone was produced by a combination of saturation overland flow and subsurface flow. The response to individual snowmelt and rainfall events varied according to antecedent wetness conditions. Runoff delivery from the wetland zone was affected even more by antecedent conditions. For the first and largest event, the response of the wetland was very similar to that of the side‐slope zone, but as the runoff season progressed, the increasing storage capacity of the wetland resulted in more marked contrasts. Quickflow yields and peak flows were much lower from the wetland and response times were longer. Over the whole runoff season, the wetland yielded substantially less runoff mainly because the perched ground water system that sustained it became isolated from the regional ground water system, and this limited the extent of the runoff contributing area in the wetland zone.