Observations on some physical-chemical characteristics of river-ice breakup

Northern river breakups are a spectacular process capable of modifying hydrological, geomorphological, and biological regimes. To begin an assessment of the physical and chemical characteristics associated with river-ice breakup, some exploratory field studies were initiated on the Liard River, a large northern river. The primary objective was to conduct time series measurements of basic water chemistry parameters, suspended sediment concentrations and size, and associated trace elements during the active breakup period. Results show that, although water quality characteristics such as pH and specific conductivity remained relatively constant, dissolved oxygen increased rapidly as breakup progressed and reached a level of supersaturation. Just before breakup, a plume of fine-grained sediment developed leading to very high peak suspended sediment concentrations that far exceeded those produced under equivalent open-water discharge. Concentrations of select trace metal paralleled the rise in suspended sediment.