The research of the draining surface water from drained areas has become relevant with an increase of drainage system areas. In order to maintain sufficient drainage efficiency by the draining surface water from the drained fields the density of open inlets for the surface water had to be increased to 5.5 u 100 haE-1. That was determined by the density decline of the open ditches. The observations of the technical condition of open inlets for the surface water in the drained fields of the country have been performed since 1986. It was established that prevalent type of the inlets is F-5 design. Such inlets amounts over 90% of all tested ones. The article discusses the condition of the inlets of such type, evaluates the selection of the installation location, conditions of surface water running to an inlet and the condition of water inlet openings. The research demonstrated some disadvantages of inlet designs, quite a few mistakes of installation and breakdowns during operation. A clear increasing tendency of water inlet openings being blocked by the ground and vegetation was established: in 1986 11.1% of water inlet openings were completely blocked, in 1996 the percentage was 20.8% and in 2007 it was 42.9%. On the basis of this it can be stated that the inlets with halfway blocked openings will stop functioning soon as well if the maintenance work is not carried out in good time and an appropriate way.

The main objective of this study is to demonstrate the use of artificial neural network (AN) modelling tool to predict the risk of phosphorus (P) loss from the fields to nearest water body. The attention is drawn to AN as an alternative approach to the P index calculation for prediction of the P losses. The specific tasks of this study were to determine risk classes of P loss by linking together source and transport factors that accelerate P losses and to evaluate AN model performance for predicting risk classes via nutrient transport. AN was trained with a Levenberg-Marquardt algorithm, and Scaled Conjugate Gradient algorithm was used to estimate the possible risk of P losses from agricultural land. Two small agricultural watersheds in Auce and Bauska were chosen to determine field parameters, and expert's evaluation was used for description of the risk classes' of P loss. Finally these values were used as inputs for the neural network model. The model was trained and validated by assessing its predictive performance on a testing set of data excluded from the training set. The research results highlight the capabilities of AN to predict risk for a particular field and suggest that future research on application of other algorithms is required.

Pollution and treatment efficiency of surface (rain) wastewater, forming in the production territory of meat processing company LTD ‘Krekenavos mėsa’ (centre of Lithuania in Kėdainiai district), were investigated in the period 2004-2009. On the surface of the company territory the precipitation water turns to surface wastewater, which is collected and sent down to treatment equipment. Wastewater samples were taken before and after biological treatment. The samples were investigated in the Chemical Analysis Laboratory of the Water Research institute of Lithuania University of Agriculture certified by the Environment Ministry of the Republic of Lithuania The following indices have been determined: biochemical oxygen demand (BOD7) – by titrometric method, suspended solids (SS) – by gravimetric method, having filtered the substance through a mid-thickness filter. Concentrations of oil pollutants were determined with the help of a spectrophotometric device of infrared rays IKAN-1 in the Analytical Department of Agrochemical Study Center of Lithuanian Agricultural Institute. During six years of investigation average wastewater pollution with suspended materials was 35.0 mg LE-1, which by 14% exceeded the BAC. Suspended solids determined BOD7 concentrations in surface wastewater by 46%. The best treatment effect was received in the purification of oil products - 96%, suspended solids - 60%, organic pollutants - 59%. The wastewater discharged from the company production territory to natural environment was clean as concentrations of the investigated oil hydrocarbons, biochemical oxygen demand and suspended solids in the surface wastewater were 26, 4 and 2 times respectively lower than biggest available concentration.

The paper overviews the research material related to occurrence of sinkholes and change of their water quality in the conditions of increasingly natural environment and minimal anthropogenic impact. Sinkholes create favourable conditions for interaction of surface and groundwater. Identification of possible sources of sinkholes pollution is very important in solution of groundwater safety problems. Water quality investigations are carried out in 4 sinkholes, which are of different age and have differently overgrown slopes. Sinkhole water quality may worsen due to accumulation of organic materials (increasing peat content) or natural changes of environment (abrasion of slopes, overgrowth, etc.), while anthropogenic impact is minimal. Water quality in peat-filled sinkholes and young sinkholes with mineral slopes is different. Water of peat-filled sinkholes has bigger amounts of N-NO3, PTotal, SO4 and BOD7 than water in young sinkholes. The highest N-NO3 and SO4 concentration is observed in the sinkhole that is overgrown with trees and shrubs.

The change in landscape is a never-ending process. In this article information regarding watermills and small-scale hydroelectric power plants historical development in Latvia has been summarized. The research was conducted from September 2010 till April 2011 with the aim of summarizing information regarding impacts to landscape from changes occurring from 12th century till 21st century. The research had a detailed view about the usage history of the watermills, small-scale hydroelectric power plants buildings, and energy producing constructions. The fundamental changes in energy producing mechanisms and legislation regulations changes that have an impact on river open space landscape and on landscape use in surrounded territories of watermills and small-scale hydroelectric power plants landscape were analyzed and studied carefully. The territories were described and analysed using historical, monographic, and comparative methods. The paper gives possible descriptive historical classification of these industrial landscape elements. The historical progress and legislation evolution until the 21st century has also been summarized.

Surface water runoff, formed in the company areas due to changing wastewater discharge and pollution fluctuations can be treated in retention ponds. Pollutants, released into the ponds, mineralize during complex natural biochemical processes in the aquatic environment. The paper presents the long-term observation data (2004 – 2016 m.) on the purification of surface wastewater, formed in the company’s production territory, in retention ponds. The aim of this work is to identify surface wastewater purification efficiency in retention ponds. Wastewater samples were taken before and after biological treatment. The samples were investigated in the Chemical Analysis Laboratory of the Water Research Institute of Lithuania University of Agriculture. Biochemical oxygen demand (BOD7 ) was determined with titrometric method, suspended solids (SS) – with gravimetric method, having filtered the substance through a mid-thickness filter. Concentrations of oil pollutants were determined with the help of a spectrophotometric device of infrared rays IKAN-1 in the Analytical Department of Agrochemical Study Center of Lithuanian Agricultural Institute. Although the suspended solids, BOD7, and oil hydrocarbon concentrations, released into the natural environment, were below the MAC when they are collected from the company’s production areas, they are often contaminated; therefore, it is necessary to treat them. The purification efficiency of researched materials was satisfactory and reached 61, 64 and 91%.

This paper aims to deal with the phytoremediation approach for protection of environment and preventing the streaming of contaminant flows to hydrological systems. Phytoremediation is a cost-effective environmentally friendly clean-up technology, which uses plants and microorganisms in rhizosphere for soil and groundwater treatment. Phytoremediation is enhancing degradation of organic pollutants and improving stabilization of inorganic contaminants where plants can be used to treat soil and water polluted with hydrocarbons, chlorinated substances, pesticides, metals, explosives, radionuclides as well as to reduce the excess of nutrients. Selection of species for this type of treatment processes is based on evapotranspiration potential and ability to bioaccumulate contaminants. The project entitled “Phytoremediation Park for treatment and recreation at glassworks contaminated sites” (PHYTECO) aimed at cross-sector international partnership. The challenge of project was to develop remediation strategy where negative consequences from centuries long anthropogenic influence are turned to be something positive – development of the recreation park from the glass dump. New “Knowledge in Inter Baltic Partnership Exchange for Future Regional Circular Economy Cooperation” (PECEC) project is sequential continuation.

The article provides the research data on the variation of organic matter in the Jaugila Stream, which flows through drained fields fertilized with organic fertilizers. The aim of the research was to determine the effect of manure application in drainage basin to the changes of organic matter concentration in the Jaugila Stream. Water samples for chemical analysis were taken once a month from the drainage water and the river. The samples from the river were taken upstream and downstream manure fertilized fields and the drainage water – from the outlets of the drainage system, which drains the fertilized area. Water analysis was performed by the Analytical Laboratory of Chemical Analysis of the ASU Water Research Institute. BOD7 was determined by titrimetric method. The research has shown that a greater impact on the increase of BOD7 concentrations in the Jaugila Stream was due to the stream water, saturated with the organic matter, flowing from the upstream areas, rather than the drainage water flowing into this stream from manure fertilized area. The assessment of BOD7 concentrations according to the water quality requirements for surface waters determined that in most cases the water of the Jaugila Stream, both in above and below fertilized areas, was in a very good or good ecological status. The impact of manure fertilized areas on the organic matter concentration in the stream was determined to be minimal, as the statistical analysis of the data has shown that the difference between BOD7 concentrations above and below fertilized areas is negligible.

The paper presents the study material and analysis of the distribution of woody vegetation of regulated streams in southeast Lithuania. The studies were carried out in 110 randomly selected slope strips of regulated streams in the Neris River basin in the Baltic Highland within the period of 2005 to 2006. During the studies 32 species of woody vegetation were found, from which 14 species of trees and 18 species of bushes. In regulated streams different species of willows are most common. However their distribution on channel slopes is different. For most species of woody vegetation the conditions are most favourable in the lower and middle part of slopes. Here their density is highest (0.34 +- 0.89 and 0.73 +- 0.139 units mE-2 respectively), the frequency is 0.56 and 0.64 respectively. As it was determined, the frequency of woody vegetation on slope strips of regulated streams is na = 0:61. On the slope the lower overgrowth limit of woody vegetation is ra = 1:58 +- 0:16 m, the upper limit is rv = 4:13 +- 0:22 m. In southeast Lithuania, in discharge network of drainage systems there are more possibilities for planning of ecological means, when trees and bushes are allowed to grow on slopes.

The objective of the present studies has been to estimate wastewater treatment efficiency of surface-flow wetlands for finishing treatment of secondary effluent. The studies have been carried out within the reconstructed wastewater treatment facilities in Babenai (Kedainiai district, Lithuania), where, after the initial wastewater treatment in the septic tanks and biological ponds, a plant filter has been set for finishing the wastewater treatment. The removal efficiency of the main pollutants in the filter like BOD5, suspended solids, total N (nitrogen), and total P (phosphorus) has become the focus of the analysis as well. Wastewater treatment efficiency analysis was done on base measurements taken in all seasons of the year within the period 2003-2006. Surface-flow wetlands are characterised by good removal efficiency of the organic pollutants. At the average load of the examined plant filter - 0.9 mg O2 lE-1 BOD5 (biochemical oxygen demand), the removal efficiency reached up to 61.2%. Low winter temperatures reduce the rate of removal for BOD and the biological reactions responsible for nitrification and denitrification. During the warm period of the year, the treatment efficiency of BOD5 was 70.8%, and during the cold one - 52.4%. However, the total N constituted up to 16.7% and 9.7% respectively. Due to the anoxic and anaerobic conditions in the filter, wastewater after the treatment on average contains 66.0% of ammonium nitrogen of the total N concentration. After a year, with the growth of plants the phosphorus removal efficiency improved and at the average load of the examined plant filter according to P 0.063 g mE-2 dE-1, on average 0.018 g mE-2 dE-1 of the total P was removed, i.e., the removal efficiency constituted 28.6%.