Formation of variability of flow quality in the top of the Luga river in inter-annual and short-term time. Part 1. Interannual variability

Abstract

The study of the interannual variability of the flow quality of the Luga River was carried out in the section of the village of Tolmachevo 3 km downstream of the confluence of the Oredezh River according to the data of the North-West UGMS 2000–2017. Water pollution in the runoff was assessed in accordance with RD 52.24.643-2002. For 11 years out of 18, the water in the effluent was “very polluted”, 2 years – “dirty”, 3 – “polluted”, and only in 2016 and 2017 – “slightly polluted”. The use of factor analysis showed that the variation of Vzag% of the runoff of the most polluted water of classes 3 and 4 is influenced by factor 1 (33% of the total variance), which is associated with the value of the highest water discharge. Factor 2 (22%) has a positive relationship with the variation in average and lowest water discharges. Four components Mn2+, Fetot, COD and Cu2+ are distinguished, polluting most of the volume of water flow annually. Factor 1 (21%) affects Vzag% of water contaminated with single components. It has a negative relationship with Vzag% of water, the oxygen saturation of which is below normal. This, possibly, can serve as a marker of the contribution of the Oredezh River to the formation of runoff in the section of the village of Tolmachevo. Factor 2 (18%) showed an inverse relationship between the variation of Vzag% of the runoff of water contaminated with Cu2+ and the average annual water discharges