Model of spring runoff quantity and quality for urban watersheds

Abstract

Use of deicing chemicals to provide traffic safety during winter causes water quality problems for urban receiving waters. High chloride content from deicing salt changes partitioning between adsorbed and dissolved metals, increasing the dissolved (toxic) metal fraction in snowmelt. Abrasives generate large loads of suspended solids. A model was developed to evaluate the impact of snow removal and road deicing practices on water quality of urban receiving waters. The model was calibrated using data from the Lincoln Creek watershed (Milwaukee, Wisconsin), and verified on 30th Ave. watershed (Edmonton, Alberta). The watersheds differ in winter weather pattern as well as in winter road maintenance. Road salt is used exclusively in Milwaukee to maintain road safety while sand-salt mixture is applied in Edmonton. The quantitative part of the model is based on heat balance theory and describes the processes of snowpack formation, snow melting, infiltration, and runoff formation. The qualitative part calculates the accumulation of pollutants (atmospheric deposition, traffic emission, and deicing chemical application) in snowpack and resulting quality of snowmelt runoff. The mobility of pollutant in the snowpack is determined by partitioning to particulates and ice crystals. The results of simulation for chlorides, suspended solids, and lead are presented.