Flow dynamics and the influence of atmospheric oscillations on the hydroclimate along the course of the West Morava River (Serbia)

Abstract

The West Morava River (length of 308 km), situated in Serbia’s Central region, boasts the largest reservoir of freshwater resources within the country. Research results for the period 1961-2023 revealed a significantly higher frequency of low flows on a monthly, seasonal, and annual basis. In the first part of the 21st century (2001-2023), there was an increase in the number of days with very high flows (Qd91th) and high flows (Qd75th), as well as very low flows (Qd9th) and low flows (Qd25th). This indicates a trend of decreasing average flows alongside an increase in the number of extreme flow days, both very high and very low, highlighting the impact of climate change. Compared to the 1961-2000 sub-period, the early 21st century (2001-2023) has seen slightly higher average precipitation and lower river flow, but significantly higher air temperatures. Summer months are now, on average, up to 2°C warmer than before. We conclude that this significant warming has led to increased evaporation, which has had a greater impact on river flow than changes in precipitation overall. The results further indicate that, in certain months, there is a significant relationship between  hydroclimatic elements (flow, precipitation, and air temperature) and variations in atmospheric oscillations: North Atlantic Oscillation  (NAO-slp and NAO-500hPa), North Sea-Caspian Pattern (NCP), Arctic Oscillation (AO), Mediterranean Oscillation (MO), Western  Mediterranean Oscillation (WeMO), East Atlantic-West Russian Oscillation (EAWR), Summer North Atlantic Oscillation (SNAO), East  Atlantic Oscillation (EA), and Scandinavian Oscillation (SCAND). Given the crucial importance of the River for Serbia, it is necessary to  define as soon as possible certain plans related to flow equalization and sustainable management of water resources, but also  mitigation and adaptation to current and specially projected future climate changes.