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The study evaluated climate change impact on water flows and nutrient loads to surface water bodies in Lithuania by applying the SWAT model. Seven RCM and GCM combinations were selected and RCP4.5 and RCP8.5 climate change representative concentration pathways were selected for the study. The study concluded that an annual and winter increase in most river water flows are expected. The change will be driven by rising precipitation, mainly in the regions where it is already high. Less snow would result in less surface runoff, substituted by increased lateral and groundwater flows because of more water percolating through the soils. As a result, water flows could be expected to increase by 9.7% for RCP4.5 and by 35.4% for the RCP8.5 climate scenario by the end-century. Whereas sediment transport and phosphorus loads would tend to decline a little bit (median results are -11.4% and -5.6% respectively for the RCP4.5 scenario, -13.3% and -7.4% for the RCP8.5 by the end of century). Conversely, temperature driven nutrient mineralization and increased leaching are expected to cause a significant increase in nitrogen loads (by 23.1% for the RCP4.5 scenario and by 64.4% for the RCP8.5 by the end of century). Overall, it could be concluded that climate change related hydrometeorological and water quality changes were found to be the most profound for the end-century RCP8.5 climate change scenario. [ABSTRACT FROM AUTHOR]

The potential effects of climate change on nutrient (total N and total P) loads in four large-scale (A=2940-6771 km2) river basins in Lithuania were analyzed. The climate impact assessment was based on an ensemble of four (RCP2.6, RCP4.5, RCP6.0 and RCP8.5) future climate projections, representing the averaged outputs from three (GFDL-CM3, NorESM1-M and HadGEM2-ES) global climate models. For each climate projection, near-future (2016-2035) and distant-future (2081-2100) time periods were compared to the baseline period (1986-2005) to distinguish future changes. The results have shown a decreasing trend in the annual nutrient loads in most of the studied rivers under the projected climate change. Seasonal changes in nutrient loads are also predicted with an increase occurring during the winter months and a fairly high decrease occurring in the spring and early summer months. These changes are consistent with the projected changes in the seasonal stream flow. [ABSTRACT FROM AUTHOR]

Although in Lithuania artificial land drainage is a common water management practice, there are still concerns about its downstream hydrological effects. Due to the complexity of flow driving factors, the hydrological effect of drainage is very uncertain, making it difficult to determine its relative importance. Aiming to distinguish between the influence of drainage and other factors in this study, the extent of changes of twenty hydrologic variables (flow magnitude, frequency, duration, timing and rate of change) downstream of drained areas and five explanatory factors that described different aspects of streamflow regimes in a non-redundant way were analysed. The resolution of the task involved the application of principal component and canonical correlation analyses. The results based on data collected from six tile-drained lowland river catchments (A=167-2290 km2) within the period 1940-1990 revealed that weather and catchment soil conditions were the primary factors determining the variability of most streamflow variables. The extent of the drained land area in river catchments affects only a few hydrologic variables - it tends to extend the duration of high pulses and causes later occurrence of annual peaks. The extended duration of high pulses along with the lag in occurrence of annual peaks are attributed to the "sponge effect" of drainage. The study also showed that artificial drainage results in a reduced number of low pulses by creating a more pronounced hydrological connection to groundwater. Most probably this occurs due to the greater depth of tile drains, providing a deeper outlet for shallow groundwater drainage. A larger groundwater inflow may also contribute through deepened streches of channelized streams and newly dug ditches collecting water from lateral tiles. [ABSTRACT FROM AUTHOR]

In Lithuania, artificial drainage is a common agricultural practice. The country remains one of the most extensively drained in the world. The total drained land area occupies 47% of the country's land area and 86% of the agricultural land area, of which 87% is tile-drained. Although the introduction of drainage has improved the quality of agricultural land, the benefits of drainage are associated with many changes in the local environment. Therefore, a review is presented of the results from various investigations and research studies conducted in Lithuania which have reported the historical and economic aspects of the development of agricultural drainage as well as its environmental effects on landscape structure, local hydrology and nutrient losses in the soil. Temporal changes in drainage run-off since the 1970s are also discussed. Furthermore, positive bidirectional effects of natural processes in and around open drain ditches on both environment and practice are highlighted which show the possibility of fostering them intentionally. [ABSTRACT FROM AUTHOR]

A study of precipitation, runoff and total annual nitrogen concentrations in streamflow was performed in three small stream catchments ( A = 1.66 ÷ 14.2 km 2 ) located in western, middle and southeastern parts of Lithuania during 1996–2010. The studied catchments belong to different geographic districts of Lithuania in which climate, soil, land use and farming conditions differ. The main objective was to present and analyse long-term data collected from three water-quality monitoring sites and to investigate the impact of various factors that may affect nitrogen losses. The results revealed the complex and dynamic nature of the various factors affecting nitrogen losses. The nitrogen contribution from wet deposition varied from 6.3 to 56.7 kg ha −1 per year and it was found to be significant factor controlling nitrogen export from the catchments. However, the proportions of arable land and pasture within the catchment, as well as the soil conditions were also found to be important. The annual runoff varied from 54 to 403 mm and exhibited strong spatial patterns among the catchments. The highest runoff was observed in the stream in southeast Lithuania, where sandy soils and a larger groundwater supply prevail. High runoff was also found typical in the stream in western Lithuania, the catchment of which received greater precipitation, exhibited hilly topography and a large drained area. The smallest runoff and highest instream nitrogen concentration (flow-weighted annual average was 7.0 mg l −1 compared with 3.3 and 2.8 mg l −1 in the other streams) was observed in the stream in the middle Lithuanian lowland, where more intensive agricultural activity occurs. The average annual load of total nitrogen in the stream in mid-Lithuania was 15.3 kg ha −1 , compared with 11.8 and 7.0 kg ha −1 for the streams in the southeast and west, respectively. The 15-year data did not show any statistically significant trend either in the dynamics of the annual nitrogen concentration or in the annual nitrogen load of the streams. [ABSTRACT FROM AUTHOR]

The statistical model MESAW was applied to simultaneously estimate export coefficients and retention of nutrients in four Lithuanian and three Estonian river basins (range 946-8,388 km²). This modelling approach uses non-linear regression to yield the export coefficients for total nitrogen and total phosphorus losses to surface waters, considering different land-use classes and retention of nutrients in the river network. The model was applied to data from 40 water quality monitoring sites and corresponding sub-basin data on land use, point sources and atmospheric deposition. The results showed that the studied river basins had a high nutrient retention capacity: 67-78 and 24-63% of total nitrogen and total phosphorus inputs remained in surface waters. The estimated retention was large in lakes: 27-59% for nitrogen and 11-31% for phosphorus. In-stream retention was apparently much lower, in the range 11-15% for total N and 3-12% for total P. Retention in lakes was lower in Estonia than in Lithuania due to the locations and smaller areas of the lakes in the Estonian basins. In Estonia, the highest relative retention in lakes was 46% for nitrogen and 35% for phosphorus. In-stream retention was also somewhat lower than in Lithuania, possibly because of the lower temperature in Estonian rivers in summer. [ABSTRACT FROM AUTHOR]

This study aimed at the evaluation of the change in the effectiveness of Best Management Practices (BMPs) for agricultural pollution control in terms of reduction of nutrient loads to surface water bodies in Lithuania in the context of climate change (CC). The SWAT model was used by applying two CC representative concentration pathways (RCP4.5 and RCP8.5), three time horizons (historical – 2000–2019, mid-century – 2040–2059, and end-century – 2080–2099), and five BMPs (arable land conversion to grasslands, reduced fertilization, no-till farming, catch-crops, and stubble fields throughout winter). The most effective (with the greatest nutrient reduction) BMPs include grasslands, stubble fields, and winter cover crops. No-plough farming and reduced fertilization BMPs appear to be the least effective ones. CC would increase the potential of reduced fertilization and conversion to grasslands BMPs up to 179% and 17%, respectively for total nitrogen (TN) reduction. Regarding total phosphorus (TP), the reduction potential would increase 226% for fertilization reduction, and remain approximate for grasslands (at median −4%). Due to winter reduction of loads, no-plough stubble fields, and winter cover crops would decrease by as much as − 50%, − 12% and − 26%, respectively for TN, and − 30%, − 11%, and − 17%, respectively for TP, compared to the historical period. The greatest change would be recorded for the most extreme CC scenario (RCP8.5) and the longest time horizon (end-century). The effectiveness of BMPs (except for no-plough) for TN load reduction would increase more, and on average would become greater in agriculture dominated areas (of central-northern Lithuania) than elsewhere, although the maximum reduction values would occur in western (and in some cases eastern) Lithuania (except for reduced fertilization). This suggests the importance of the application of the measures in both areas. BMPs (except for grasslands) are expected to have relatively little effect on the overall crop yield. • Climate change will alter the effectiveness of Best Management Practices. • Practices intervening surface runoff pathway is expected to lose effectiveness. • Nutrient reduction potential is predicted to increase in agricultural areas. [ABSTRACT FROM AUTHOR]