This review outlines the use of documentary evidence of historical flood events in contemporary flood frequency estimation in European countries.The study shows that despite widespread consensus in the scientific literature on the utility of documentary evidence, the actual migration from academic to practical application has been limited. A detailed review of flood frequency estimation guidelines from different countries showed that the value of historical data is generally recognised, but practical methods for systematic and routine inclusion of this type of data into risk analysis are in most cases not available. Studies of historical events were identified in most countries, and good examples of national databases attempting to collate the available information were identified. The conclusion is that there is considerable potential for improving the reliability of the current flood risk assessments by harvesting the valuable information on past extreme events contained in the historical data sets.

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The aim of this research is to analyse and project the effects of changing climate on Lithuanian river runoff and water temperature. Climate change is expected to affect the extremes of the major river indices that impact fundamental ecological processes in river ecosystems. The available runoff and temperature data of rivers from three different hydrological regions of Lithuania were used. HBV software was applied for modelling of hydrological processes in the selected river catchments. The expected future changes of runoff and water temperature were projected according to a new set of scenarios (called representative concentration pathways) presented in the Intergovernmental Panel on Climate Change Fifth Assessment Report. The projected extreme values of runoff (flood and low flow discharges) and water temperatures in the beginning and the end of the 21st century were compared to the ones from the past period. The results showed a decrease of spring flood discharges and summer low flows and an increase of river water temperature at the end of the 21st century. The results are going to be used for an integrated assessment of the impact of climate change on aquatic animal diversity and productivity.

Water temperature is one of the twelve physico-chemical elements of water quality, used for the assessment of the ecological status of surface waters according to the Water Framework Directive (WFD) 2000/60/ EC. The thermal regime of Lithuanian rivers is not sufficiently studied. The presented article describes the temporal and spatial variation of water temperature in Lithuanian rivers. Since a huge amount of statistical data is available (time series from 141 water gauging stations), the average water temperatures of the warm season (May-October) have been selected to analyse because that is the time when the most intensive hydrological and hydro-biological processes in water bodies take place. Spatial distribution of river water temperature is mostly influenced by the type of river feeding, prevalence of sandy soils and lakes in a basin, river size, and orography of a river basin as well as anthropogenic activity. The temporal distribution of river water temperature is determined by climatic factors and local conditions. The averages of the warm season water temperature for 41 WGS are 15.1°C in 1945-2010, 14.9°C in 1961-1990, and 15.4°C in 1991-2010. The most significant changes in water temperature trends are identified in the period of 1991-2010. For this period, the rates of increase of water and air temperature are 0.04 and 0.06°C/warm season, respectively. Therefore, air temperature is one of the most significant factors affecting the water temperatures of Lithuanian rivers.

Estimation of both the frequency and variation of spring floods is a key issue for the assessment and management of flood risks. Changes in river floods in Estonia, Latvia and Lithuania have been investigated in few national studies. However, there are no studies of the changes of flood patterns by using a common methodology for the rivers of this region. In this study flood pattern changes in the rivers of the Baltic countries were estimated applying trend and frequency analysis for the periods of 1922–2010, 1922–1960, 1961–2010 and 1991–2010, i.e. for the whole spring flood data sets, periods before and after 1960 (this year was considered as the beginning of the remarkable climate change), as well as for the two past decades. A comparative study of five probability distributions was performed in order to estimate which distribution at best represents statistical characteristics of the flood data. The results showed that maximum discharges of spring floods decreased over the whole studied period. Only some insignificant positive trends of maximum discharges were found in the last time period in continental and transitional rivers. Generalized extreme value distribution provided the best approximation to the maximum discharge data series of the rivers of Baltic countries for the whole observation period.

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The hydro-energy resources are considered as promising renewable energy sources, which emphasizes the need for assessment of theoretical hydrokinetic energy resources stored in Lithuanian rivers. This article presents the results of an investigation of the theoretical hydrokinetic energy in small and medium-size rivers. A total of 282 rivers (1487 segments) were examined and the relationships were established for evaluation of their hydrological and morphological indicators, such as river depth, width, and flow velocity. Only 41 rivers (328 segments) were identified as having a theoretical hydrokinetic potential. The total length of these valuable river segments reaches 2000 km. The estimated kinetic energy capacity calculated for a 1 km channel segment is 45.3 kW in South-eastern, 40.8 kW in Western, and 38.2 kW in Central Lithuania.