EFFECT OF TELECONNECTION PATTERNS ON THE RUNOFF
FORMATION OF LITHUANIAN RIVERS DURING THE WARM PERIOD

River discharge and flow dynamics are influenced by numerous natural and anthropogenic factors, which implies the need for comprehensive studies to reach sustainable water resource management and enhance predictions and preparedness for extreme events, especially droughts. Talking about warm season risks, anthropogenic activities in rivers create additional challenges in water management. In human-regulated rivers, maintaining ecological flow downstream of technical structures is essential to balance anthropogenic and ecosystem needs and reach EU WFD goals. Therefore, it is important to understand the conditions of runoff formation and its natural causality. Previous research in Lithuania has established that the multi-annual average of low-flow discharge (Q30_average) could be assumed as the potential value of ecological flow. However, the causality of this parameter was not sufficiently investigated because this measure can be influenced by multiple large-to-local scale driving forces that govern discharge volume and flow patterns. This study focuses on investigating teleconnections, which represent long-distance effects between large-scale atmospheric oscillations and regional climatic anomalies, as significant drivers of the hydrological cycle. Teleconnections are well-known to impact temperature and precipitation, thereby affecting discharge volumes and flow regimes. However, their influence may vary significantly on spatial and temporal scales. Specifically, this study examines five Northern Hemisphere teleconnection patterns (North Atlantic Oscillation (NAO), East Atlantic (EA), East Atlantic/Western Russian (EATL/WRUS) Scandinavian (SCAND), Polar/Eurasian (POL)), which manifest themselves through a variety of influences on the climate of Europe. Lithuanian rivers from three hydrological regions exhibiting diverse feeding patterns were studied to assess the relationship between teleconnections and the formation of low-flow parameters. Non-parametric Wilcoxon sum rank test was applied to assess the connections between the selected teleconnections and the low-flow of the warm period. The findings of this study indicated that some of the indices showed only an occasional effect, however, the SCAND index was revealed to be closely related to the runoff variability in the warm period. Consequently, the results of this study contribute to a better understanding of the impact of teleconnections on the formation of low-flow parameters that one day might be assumed as ecological flow, as well as providing valuable insights for sustainable water resource management.

Keywords: teleconnection patterns, flow formation, low-flow, ecological flow.