Author(s): Maria Kamari; Eliisa Lotsari; Sirkka Tattari; Jari Koskiaho
Keywords: No Keywords
Abstract: The river ice cover periods have been indicated to shorten in Northern regions due to the warming climate. However, the river ice cover influence on water quality has not been thoroughly studied. Potential changes e. g. in turbidity and sediment loads may take place due to shortening ice cover duration and smoother discharge especially during freshet. The aim of the study is to analyze possible changes in water quality variables, i. e. turbidity, total organic carbon (TOC) and total suspended solids (TSS) during ice covered and open water periods at similardischarge levels. A large data set of monthly turbidity observations from the period 1973–2013 was available from the lower reach of the Kokem"aenjoki River (MQ=193 m s, 1983–2013) running into the Baltic Sea in SW Finland. In addition, new water quality monitoring technology was applied in the Vantaanjoki River (MQ=11 m s, 1983–2013) running into the Baltic Sea inSouthern Finland: automated water quality sensor recorded turbidity and TOC levels on hourly basis during 2011–2014. The results demonstrate that the ice cover is diminishing statistically significantly the river turbidity in the Kokem"aenjoki River. The conclusions of the analysis of data from automated and intensive sampling from the Vantaanjoki River are: 1) the ice covered river water turbidity is smaller compared to open water periods with similar discharges, 2) TOC levels did not differ notably depending on the season or ice situation, 3) the turbidity and suspended sediment concentrations of river water have a larger daily fluctuation during open water than ice covered days.