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The main object of the paper article is water resources of Lithuanian rivers, which were calculated using a long data series of the runoff. Water resources are based on the balance equation. This means that this equation includes only the runoff formed in the Lithuanian territory, from neighboring countries to Lithuania and through them into the sea. The average and dry annual water resources have been calculated at a 95% probability. The average perennial water resources of Lithuanian rivers are 24.844 km³ / year, of them 8.883 km³ / year is the transit from Belarus, Poland and Kaliningrad Region to Lithuania, 15.961 km³ / year is formed in Lithuania and 7.471 km³ / year are effluents through Latvia into the Baltic Sea from Kaliningrad Region into the Curonian Lagoon. The Nemunas basin floats 21.501 km³ / year to the Curonian Lagoon. The present water resources are by 4.5% less in comparison with water resources of in the year 1996. Cyclic water change is typical of the Lithuanian rivers. The Nemunas-Smalininkai hydrological station has noted 7 cycles in a long data series. The average term of a cycle is 27 years (14 years of a wet and 13 years of a dry period). The runoff of the Nemunas river differs in the duration of dry and wet periods (by about 16%). The runoff of rivers in Southeast and Western Lithuania differs by 21-23% and in Middle Lithuania by 28%. The long data series of the Nemunas-Smalininkai runoff have a negative trend because of a decrease in the last four decades. The runoff measured by this water management station consists of river runoff from the southeastern and middle parts of Lithuania. The annual runoff has a positive trend in the majority of Western Lithuanian rivers in the period 1961-2003. The minimum runoff of a dry period shows no trend in most Lithuanian rivers, except Western Lithuania where a positive trend was estimated in the period 1961-2003. [ABSTRACT FROM AUTHOR]

In 1957, the Laboratory of Hydrology under the leadership of the famous Lithuanian hydrologist professor Lasinskas began an extensive research of Lithuanian water bodies. A large number of different studies have been performed, important monographs have been published. In the last decades, the main research objects of the laboratory have remained the same; however, the research topics change, much longer datasets of hydrological data are available, and the modern research methods are applied. The article presents the contribution of the Laboratory of Hydrology (of Lithuanian Energy Institute) to the development of hydrology science; the most significant studies of the last decade related to climate change impact on Lithuanian water resources (rivers and the Curonian Lagoon) are described. An analysis of Lithuanian river runoff and the Curonian Lagoon water balance in the past was performed. Statistical methods helped identifying the changes of river runoff and its extreme values that already occurred. The prognosis of the river runoff in the Nemunas Basin area (that covers 75% of the Lithuanian territory) was accomplished applying the hydrological model HBV and using two global climate models (Echam5 and HadCM3) and three emission scenarios (A2, A1B, B1). The changes of the Curonian Lagoon water balance in the 21st century were assessed. [ABSTRACT FROM AUTHOR]

The neighbouring countries of Latvia and Lithuania should use common water assessment methodologies and measures for water management in the transboundary rivers according to EU Water Framework Directive, establishing a framework for community action in the field of water policy. However, there are no national and local legislative acts describing how to harmonise water policy and activities for good water status at the cross-border level. This study intends to propose practical measures for management of chemical pollution risk in the cross-border region by mixing zones. The transboundary basin of the Venta River was used as a case study. After initial assessment of water quality status on both sides (Latvian and Lithuanian) in Venta River Basin District, 12 hot spots of pollution were selected for evaluation of mixing zones. Chemical analysis of cadmium, lead, nickel, chromium, copper, zinc, arsenic, phenols, formaldehyde, mercury, benzene as well as total nitrogen and total phosphorus in the water samples from the selected sites was performed. The modelling, using the selected Discharge Test, ensured evaluation of mixing zone dimensions. Such joint investigations might benefit the evaluation of possibilities to integrate mixing zones to the overall transboundary water body for harmonisation of water quality management. [ABSTRACT FROM AUTHOR]