The river discharge changes in three Baltic States and its relation to changes in the main climatic variables such as precipitation and air temperature were analyzed using observed data and methods of empirical slatistical analysis. The study is important for the development of efficient waler resource management systems and validation of climate change impact models. The application of the Mann-Kendall test reveals that a significant increasing trend in winter air temperature and precipitation was determined for all 3 investigated periods (1923-2003, 1941 -2003 and 1961-2003). The same trend was found for the winter and annual discharge ttme series. No trend was obsen/ed for the spring, summer and autumn seasonal streamflow and summer low flow series for most of the Baltic region. In general the relation between the main meteorological and hydrological parameters and the tendency in river discharge trends is common for all of the Baltic States, and might be associated with the regional impacts of global climate change.

Extreme floods can be caused by various combinations of hydrological and meteoroiogicai factors and river basin conditions that have not been observed for a long time. Long-term observational series permit estimation of both the frequency and variation of spring floods -the key issues of protection systems. Fortunately, Baltic States have a long-term record of hydrological data for the last 80 years. In this research, spring flood parameters (maximum discharge, height of maximum discharge and its timing) for the Baltic countries were assessed for four periods (1922-. In total, 70 hydrological data series of spring flood parameters were used. To detect trends in time series for these periods, the Mann-Kendall test and the nonparametric Sen's method for the magnitude of the trend were used. The index flood method was used to estimate the maximum discharge in ungauged catchments. The results showed that maximum discharges and heights of spring floods decreased over a longer period. Spring flood peaks took place on earlier dates. Only some significant trends of maximum discharges and their timing were found in the last time period (1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008). Ali these changes could be caused by the increasing ambient temperature and precipitation in the later decades.