Rainstorms impacts water, sediment and trace elements loads in an urbanized catchment within Moscow city: case study of summer 2020 and 2021

Abstract

Abstract In 2020 and 2021 the city of Moscow, Russia, has experienced two historical rainfall events that had caused major flooding of small rivers. Based on long-term observation datasets from the surrounding weather stations, regional mesoscale COSMO-CLM climate model results, and a detailed hydrological and water quality monitoring data collected in 2019–2021, we performed pioneer climate change and urbanization impact assessment on flooding hazard and water quality of case study urban Setun river. Statistically significant rise of moderate extremity indices and absence of significant trends for the most extreme indices was revealed for the 1966‑2020 period. The combined impact of climate change and increased urbanization is highly non-linear and results in as much as a four-fold increase in extreme floods and shift of water regime features which lead to formation of specific seasonal flow patterns. The rainstorm flood wave catchment response, involving infiltrated and hillslope-routed fraction of rainfall, is accounted as 6 to 11 hours, which it is more than twice as rapid as compared to the non-urbanized nearby catchments. Behaviour of four types of chemicals in the river water during rainstorms was identified, as well as main differences compared to the spring freshet period revealed. Based on the obtained results we conclude that lack of research focused on the combined impacts of climate change and urbanization on flooding and water quality in the Moscow urban area is a key problem in water management advances.