Duration and distribution of low flow periods in Lithuanian privers in 1960–2019

Changes in the intensity of climate events are becoming more and more pronounced and relevant today. One of the consequences of the effects of climate change is that more low flow periods of various intensities and durations are observed in Lithuanian rivers. The current legislation regulates the environmental flow of water as a minimum part of the 30 driest days. Environmental flow ensures only minimal conditions for the survival of aquatic ecosystems and is therefore suitable for the study of low flow conditions in the rivers. The article examines the distribution of environmental flow values (Q80%) in 1960–2019 and in separate (1960–1979, 1980–1999 and 2000–2019) periods according to continuous daily flow measurement data of 15 WGS, which represent different hydrological areas of Lithuania. This article discusses the interrelationships between the low flow periods and their dynamics in 15 WGS, examines the causes of low flow cases and distinguishes the periods with the highest number of low flow cases. The study revealed that since the 21st century cases of low flow are being recorded more frequently in Lithuanian rivers, and a significant prolongation of low flow periods is observed in many rivers during the warm season. Keywords: Lithuanian rivers, environmental flow, climate change, low flow