Erosion processes alter water quality in a stream within a small catchment in the Upper Lusatia Region in Saxony

Abstract

This paper focuses on consequences of erosion processes on the water quality in a small catchment mainly used for agriculture. Due to the silty soils with small infiltration capacity and some steep slopes, much suspended sediment is carried with the surface runoff into the river. To gain detailed knowledge about the dynamic of suspended particle concentration in the stream, particularly the intensity and the duration of the pollution, continual measurements of turbidity and conductivity have been done. Additionally water samples have been automatically taken regulated by the streamflow and have been analysed in the lab to determine the particle concentration and some dissolved chemical substances such as nitrate and heavy metals. From those measurements a regression between turbidity and suspended particle concentration was derived as basis to calculate suspended load. Results showed a typical hysteresis with bigger particles being transported within the fast rising limb than in the falling limb of the flood waves. Moreover, it was also found, that nitrate concentration was lower during the summer and early autumn than in spring with the same discharge.