Climate induced changes of Lithuanian rivers runoff in 1960–2009

Abstract

The primary objective of this study was the evaluation of runoff regime changes over the last 50 years in Lithuanian rivers. These changes were compared with the Neman river runoff regime changes in 1812–2009. On the basis of daily water discharge data, trends in the annual, maximum and minimum runoff characteristics as well as changes in the seasonal pattern of runoff were estimated. Regression analysis and the Mann-Kendall test were used to determine changes in the long-term hydrological regime. The magnitude of changes was estimated using Theil-Sen estimator. 1960–2009 runoff changes in Lithuanian rivers can be related to climatic changes. Sharp increases of January and February runoff during 1960–2009 were the largest changes throughout the observation period 1812–2009. The rate off runoff decrease in April was also among the largest decreases recorded. Spring flood and cold season minimum flow dates have become earlier than used to be.