The paper deals with monitoring results of nitrate nitrogen (NO3 --N) run-off in three small agricultural catchments in Latvia (Berze, Mellupite, and Vienziemite) during the period of 1995 - 2007. Continuous flow measurements and water sampling were carried out in two scales - catchment and drainage field. Water quality data was analyzed statistically to identify outliers at various intensity agricultural production systems. The results indicated that with increase of agriculture intensity outlying values are higher and scattered from the rest of the data set thereby the risk of NO3 --N leaching is higher. It can be explained by application of different rates of organic and inorganic fertilization. To analyze water discharge data, cumulative distribution was used. The results show that main part of the water discharge is observed from late autumn to spring, whereas in summer period it is low and stable. The dependence of NO3 --N concentrations on the discharge is expressed by Spearman's correlation coefficient - at catchment scale it is 0.37 in Vienziemite site, 0.39 - in Berze, and 0.44 in Mellupite. Calculated correlation coefficients are statistically reliable.

The research was made in the Šušvė river basin fertilized with organic fertilizer in the vicinity of a pig complex 'Litpirma' Ltd (25.0 thousand fattening pigs per year), Šiaulėnai local administration, Radviliškis district, in 2001-2006. This article presents total nitrogen concentrations and its amounts leaching from the complex to the basin, in the field drainage water and the Šušvė River (at a distance of 11.6 km from the pig complex). In the investigated Šušvė section, biologically treated wastewater from Šiaulėnai Township and the areas fertilized with organic fertilizers comes into the river. In total, 11.8 t of nitrogen come into the river, of which 4% (0.49 t) come from the township's wastewater, and the rest major part (96% or 11.3 t) is the drainage water coming from fertilized agricultural fields. The dynamics of nitrogen concentrations both in the river and in the drainage outlet is of a seasonal nature: in winter (January – March) concentrations were higher, and in warm season (April – November) – lower. The Šušvė pollution by total nitrogen, both above and below the pig complex activities range, almost all the research period was exceeding the limit (2 mg lE-1). Due to the pig complex activities and intensive agriculture, the runoff of nitrogen pollutants increases from 14.9 to 29.3% in the Šušvė River. This proves that the processes of spontaneous purification are not intensive enough to neutralize completely the pollution from such size pig complex in this particular section of the river.

Due to the recently increasing frequency of extreme changes in river runoff regime, scientific literature deals with the characteristics of runoff formation. Works are carried out in analyzing climate changes and a lot of attention falls on land–use structures. Following thorough analysis of the lithological structure of river basins in separate costal zones, this article aims at evaluating river runoff formation characteristics. The basin lithological factor was calculated based on Quaternary map of Lithuania M 1:200000 and Lithuanian river map M 1:50000 using ArcGis software. In order to carry out more thorough analysis of the influence of lithology in given territories, sections of 0–20 m, 50–200 m, 200–500 m, 500–800 m, 800–1000 m and is greater than 1000 m were established, calculating the distance in meters from the riverbank. Eight river basins of typical lithological structure (sandy, loamy, argillaceous) were selected and examined. The period of the years 1960–2007 was analyzed as this period saw the greatest amount of precipitation (up to 33% probability), and relation between the runoff and precipitation was established as well as that with the lithological structure, established following the derivation of a hydromodule.

Global warming undoubtedly influences the flow of rivers. It is essential to observe the climate changes, trace, analyse and forecast how they could influence the environment and, especially, how it can influence the flow of rivers. In this article two maximum flows of basins of two different rivers are analyzed: the river Venta (above Papile) and the river Krazante (above Pluskiai) during the period 1968–2008. Climatic parameters, such as the precipitation and the average air temperature, observed in the weather stations of Siauliai and Laukuva, influence the changes in flows the most. The correlation between the precipitation and maximum change of the flow was estimated though it was not strong: the ratio of correlation in the river Venta was 0.66, in the river Krazante the same ratio was 0.72. Significant negative trends of the both analyzed rivers during the spring period and significant negative trends of the river Venta during the period of winter have been established by the use of statistical analysis of the results obtained from a non-parametric Mann-Kendall test and linear regression test. This specific analysis is performed by using TREND programme. The collected data which were obtained to show that the most watery decade of the rivers Venta and Krazante were during the period 1978–1987, which formed 36% flow in the river of Venta and 35% in the river of Krazante for the whole period of forty years.

Hydro-physical properties of heavy or presses soil as well as water regime may be improved by various ways, taking into account the texture of soil and climatic conditions. Drainage is the tool for productive farming and economic benefit generation. Hydrological activity of drainage typically depends on project installation quality, anthropogenic and climatic factors. It is important to assess drainage activity under different meteorological conditions. One of methods to improve drainage performance is its installation with thickened humus layer. Lithuanian soil humus layer is close to arable layer and is equal to approximately 20–25 cm. The impact of humus on heavy-textured soil is multiple, since not only moisture regimes, biological activity, sorption capacity, chemical and biological characteristics, stability of plant nutrition are related with its quantity. The dynamics of drainage activity in soil with thickened (up to 40–50 cm) humus layer and with humus layer of natural thickness (20–30 cm) during various seasons of period of 1989–2009 is reviewed. Especially important indicator of drainage functioning – water runoff dynamics. The present article analyses the variation of climatic conditions and drainage runoff in the object. It is determined that the lowest quantity of precipitation in the researched territory during the research period is in spring and winter but the highest – in summer and autumn. During the research period the highest drainage runoff in the field I was during winter season (46.3%), in the field II – in winter and spring almost the same (32–33%).

Kriging is a method of interpolation, which predicts unknown values from data observed at known locations. This method uses a variogram to express spatial variation, and it minimizes the error of predicted values which are estimated by spatial distribution. The objective of the current work was to investigate how the accuracy of predicted runoff average depth values ranges by applying ordinary Kriging interpolation method when parameters of the method are altered. The simulation was tested by the following method parameters on: fitted semivariogram model, lag size, neighbouring points; the number of sectors of the circle. The best results of the spatial distribution of runoff average depth were received applying the ordinary Kriging method when the exponential variogram is used, the lag size being 27 km while 6 contiguous points and the orbicular scheme divided into sectors in 45° angle are taken. Applying the Ordinary Kriging method having selected all parameters with probability p = 0.95 the model described about 74% of all investigated values.

Wet soils play an important role in hydrological, biological and chemical processes, and knowledge on their spatial distribution is essential in forestry, agriculture and similar fields. Digital elevation models (DEM) and various hydrological indexes are used to perform water runoff and accumulation processes. The prerequisite for the calculation of the hydrological indexes is the most accurate representation of the Earth’s surface in the DEM, which must be corrected as necessary to remove surface artefacts that create a dam effect. In addition, different resolutions for DEM give different results, so it is necessary to evaluate what resolution data is needed for a particular study. The aim of this study is to evaluate the feasibility of using existing ditch vector data for DEM correction and the resulting implications for soil moisture prediction. Applied methodology uses a network of available ditch vectors and creates gaps in the overlapping parts of the DEM. The data were processed using open source GIS software QGIS, GRASS GIS and Whitebox GAT. Ditch vector data were obtained from JSC Latvian State Forests and the Latvian Geospatial Information Agency. The results show that by applying the bottomless ditch approach in forest lands on moraine deposits, depending on the accuracy of the ditch vector data, the values of the prediction of the soil wetness both increase and decrease. On the other hand, in forest lands on graciolimnic sediments it is visible that predicted soil wetness values increase in the close proximity of ditches. For forest lands on glaciofluvial and eolitic sediments there were no visible changes because of lack of ditches.

Pollution of surface (rain) wastewater forming in the production territory of a pig-breeding enterprise was investigated in the period 2007–2011. The surface water is collected from the production territory from yards with a hard covering and from roofs, enters the rain sewerage, and is released untreated into the natural environment. The aim of this work is to find out what influence on the environment is exerted by surface wastewater released into the natural environment from the production territory of pig-breeding enterprises. Surface wastewater pollution indices and the research frequency were identified according to the requirement to carry out surface water monitoring: surface wastewater samples are collected three times per year. Because of the uneven rainfall distribution during the year, less surface wastewater runoff occurred during the cold period; however, concentrations of indices were higher compared to the end of the warm period (TSS – 18 %, BOD7 – 39 %, Ntotal – was unchanging, oil products – 12.5 %). Only Ptotal concentrations were higher in the end of the warm period in 14 %. The organic pollution in surface wastewater was increased by total suspended solids. The increased concentrations of TSS and biochemical oxygen demand (BOD7 ) were related to a higher precipitation level. The indices’ TSS, BOD7 , Ntotal, Ptotal and oil products concentrations in the surface wastewater runoff from the pig breeding enterprise‘s production territory complied with the requirements for surface water which is collected from this area and released into the environment.

During the period 1995-1998, in the western part of Lithuania, the organic and intensive (conventional) cropping systems were compared on small autonomous drainage plots in limed Bathihypogleyi-Albic Luvisols (LVa-gld-w) and Dystri-Endohypogleyic Cambisols (CMg-n-w-dy) as well as non-acid Endocalcari-Endohypogleyic Cambisols (CMa-n-w-can) soils. This paper presents the summarised results of field crop productivity and the factors determining drainage water runoff as well as the migration and balance of elements in the organic and intensive cropping systems.