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ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) THE ESTIMATION OF DRAINAGE AGE AS OF THE FACTOR OF FAILURE RISKNijolė BASTIENĖ, Virgilijus BUOŽISSummaryIn this article one of the most important reliability measures of drainage - its functioning until failure - is analyzed. The means of drainage functioning until failure have been calculated on the basis of probability theory and mathematical statistics. The distribution regularities have been established for the drainage objects functioning under different land-reclamation conditions. This may help to determine the failure probability of drainage of certain age as well as to foresee the time and extent of repair work. Keywords: drainage, reliability, time before damage probability.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) PERSPECTIVE REAGIONS FOR THE MAIN AGRICULTURAL PLANTSVilma SUDONIENESummaryThe material of soil investigations, the structure of farming lands and the crop structure of agricultural enterprises, the areas of cultivated plants and their dynamics in the period of 1994-2000 have been analyzed in the article. The zoning has been fulfilled while estimating the collocation of the main agricultural plants in the zones most suitable for them in comparison with the material of soil investigations, peculiarities of agriculture in separate territories, the collocation of recast enterprises of agricultural produce as well as while evaluating other factors. In produced pictures one can see: the intensity of the use of arable land in Lithuanian Republic, the cultivating of grain, flax, sugar-beet, rape, potatoes, herbage food in the period of 1994-2000 and the most suitable regions for their cultivation. Most of the derelict agricultural landed properties are in the places where the productivity point of landed properties is low. It shows the link between the intensity of land usage and economical conditions of agricultural produce. Traditional agriculture is characteristic to the regions with efficient soils and in the farms with low efficiency it would be promising to try unconventional farming. The produced analysis shows the differences of land efficiency in the territory of Lithuania as well as the most suitable regions for the cultivating of agricultural plants. There is no vivid farm specialization in Lithuania yet. Miscellaneous plant-growing and animal husbandry farms predominate. While trying to secure the best usage of the land it is necessary to join farming and the local, ecological, economical and market conditions. Keywords: zoning, regions, crops, soils, agricultural plants.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) EVALUATION OF DRAINAGE PERFORMANCE ACCORDING TO WATER ENTRANCE RESISTANCEAleksandras RIMIDISSummaryEvaluating the state of drained areas we encounter some spots where it is difficult to determine drainage system functioning only by supervising them or carrying out solitary measurements of drainage water levels and its runoff. Therefore the functioning of such drainage systems should be evaluated according to special parameters, one of which is considered to be water entrance resistance and is related to the calculation of hydrostatic head loss in the vicinity of drain per unit of discharge. The aim of the researches was to investigate the changes of drainage hydrological functioning in the course of time as well as to estimate water entrance conditions in view to water head loss occurring near drains. The researches were carried out in the object characteristic to the Middle zone of Lithuania. This object was arranged in Kėdainiai district, in the plot of land which belongs to the Experimental department of Lithuanian Institute of Water Management. Hydrological functioning of different drainage variants in reconstructed and non-reconstructed systems was observed during the researches. It was established that not only hydrological conditions, soil permeability, protective filtering material properties and depth of drains predetermine water entrance resistance. It also depends on the change of water level, with the rise of which water resistance decreased in the vicinity of drains. At the beginning of reconstructed drainage functioning as water level had subsided down to minimal draining rate (50-60 cm) the water resistance was the biggest. It fluctuated from 13.1 to 21.3 d/m in clay tile drainage systems and from 8.3 to 12 d/m in polyethylene ones. When new soil macropore system formed in trenches after 5-6 years, the conditions of water entrance into drains ameliorated because the resistance limits fluctuated from 8.22 to 19.58 d/m in clay tile drainage systems and from 4.49 to 7.44 d/m in polyethylene ones, which was about 2-2.5 times less. Water resistance in a non-reconstructed drainage system which has been functioning for 41 year already makes up 7.6-10.3 d/m on average, which corresponds to the one in reconstructed drainage system with polyethylene pipes. According to the functional criteria applied in Western Europe the functioning of this drainage system was evaluated as satisfactory. A strong and moderate correlation connection of linear dependence was established between hydrostatic head loss of water entering the drains and total water head between drains. Keywords: drainage systems, draining functioning, hydrostatic head, resistance, functional criteria.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) METHOD OF SUSPENDED PARTICLE FRACTIONATIONRomas PUKŠTAS, Saulius VAIKASAS Summary Great theoretical and practical difficulties of accuracy occurred when the well-known pipette method of soil particle fractionation was used for the suspended sediment concentration measurement in the Nemunas delta. It refers to some quantity of measured water samples, especially to small particles of clay and silt. For the study of fraction of such suspended particles a new method and equipment for turbidity measuring was adapted. The infrared device of suspended sediment concentration measurement was applied and a new modification for particle fraction according to A. Rimkus was used. This equipment was adapted in order to work with high frequency of electricity and it can eliminate the negative impact of sunshine rays. The framework scheme is presented in the paper and the examples of fractionation method of suspended sediment particles are presented. The possibilities of the new device application for the investigation of suspended sediment particle fall velocity and for the specification of existing formulas are also mentioned in the article. Keywords: suspended sediment, fractions, measurement.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) RIVULETS WATER QUALITYGinutis KUTRA, Ausra RACKAUSKAITESummary Rivers (and also the Baltic Sea) are polluted by nutrients and especially by nitrogen due to agricultural activity. Previous investigations determined that diffuse agricultural pollution is increasing during transition to market economy in Lithuania and other countries. In this article we analyse farming impact on rivulets water quality in the Middle Plain region of intensive agricultural activity (Graisupis watershed) and in the hilly Baltic and Žemaičiai Highlands Highlands (Vardas and Lyžena watersheds). Crop structure is worst from a nutrient leaching point in Graisupis watershed. Perennial grasses occupy only 15 % of the watershed territory. In Vardas and Lyžena watersheds 50 % of the area is occupied by perennial grasses. In order to evaluate fertilisation impact on environment we have calculated nitrogen balance on the watersheds’ level. Surplus nitrogen accumulates only in Graisupis watershed: it was equal to 28.5 kgN/ha in 1996 and it increased up to 34.5 kgN/ha in 2000 year. In Vardas watershed the balance remained negative: -28.2 and -26.1 kgN/ha. Nitrogen concentration every year and nitrogen runoff in 2000 year was considerably bigger in Graisupis watershed than in Vardas, only in 1996 nitrogen runoff was smaller in Graisupis watershed because of particularly low water flow. There were analysed territories that gave the highest nutrient leaching. The highest nitrogen concentrations (24 mg/l on average) were determined in drainage water coming from the surroundings of barns and farmsteads. 11 mg/l on average were found in drainage water from ploughed lands and 4.8 mg/l of total nitrogen from perennial grasses fields. Data on crop structure, nutrient balance on a farm and a watershed level (when proper book keeping is performed on farms) could be used for rivulets water quality management. Keywords: river pollution, nitrogen, balance, farming activity, runoff.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) PECULIARITIES OF NITROGEN AND PHOSPHORUS LEACHING IN AGRO-ECOSYSTEMSKazimieras GAIGALIS, Aušra RACKAUSKAITESummaryThe article presents an investigation that has been continued for five years in three small agricultural watersheds that represent a different Lithuanian physical geographic zone each. In the installed river water monitoring posts water flow is measured continuously, river and precipitation water quality is determined every month, besides, land use is registered throughout the whole territory of the watersheds. The research evaluates diffuse nitrogen and phosphorus pollution on a watershed level that originates in agricultural areas and determines peculiarities of the nutrient leaching in the different physical geographic zones of Lithuania at different time of a year. The research has approved that the highest nutrient leaching occurs in spring when the biggest water flow happens and when high nutrient concentrations are usually observed. Only in western Lithuania the highest nitrogen and phosphorus leaching occurs in winter. It was evaluated that the average runoff of total nitrogen is from 6.1 to 14.4 kg/ha per year and the runoff of total phosphorus is from 0.153 to 0.382 kg/ha. Precipitation brings 14-18 and 0.61-0.88 kg/ha of nitrogen and phosphorus per year to the territory of the watersheds. Keywords: flow, nutrient runoff, nitrogen, phosphorus, watershed.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) THE INVESTIGATIONS OF DRAINAGE RUNOFF OF DIFFERENT INTENSITYValentinas Saulys Summary When drained land is used intensively it is important to let excess water out of drained areas. The overdue sowing reduces the harvest, therefore it was aimed to increase the efficiency of drainage functioning particularly in clay soil. Soil liming is one of the means which ameliorate the permeability of trench filling in clay soil. In this paper the efficiency of drainage functioning is analysed, when filter properties of drainage trench filling are ameliorated by liming the soil. A drainage was arranged in Kanujai object (Pasvalys district). Filter properties of trench filling of this drainage were ameliorated by liming the soil. Three experimental variants were arranged there. In variants 2 and 3 the filling of drainage trench was mixed with lime and 0.6 % of active CaO was added for ground mass. In the 1 control variant the trench filling was made of local soil which was mixed up when digging trenches with a multi-scoop excavator ETC-202. In variants 1 and 2 the draining distances were 16m, and the ones in variant 3 were broadened 1.5 times and reached 24 m. Each variant was repeated four times. Their total areas covered 5.27, 4.77, and 4.55 ha accordingly. The length of the drains arranged were 2717, 2384 and 1688 m accordingly. Light loam and clay soils prevail in the research object. The average amount of physical clay particles (<0.01mm) in ground make up 43 %, ground density is 1.58 g/cm3, frame density is 2.63 g/cm3 and porosity is of 39.67 %. Maximum comparative discharge was 1.3 times bigger in intensively drained systems with extra lime to compare with the one in control systems. It was also 1.52 times bigger in intensively drained limed systems to compare with the variant where draining distances were broadened 1.5 times. In spring of the year 2000, ground water level of 10 cm remained on ground surface for 11 days in the control variant, at the depth of 20 cm it remained for 20.5 days and at the depth of 30 cm it remained for 24 days. Ground water rose up to the level of 30 cm in intensively drained systems with extra lime (variant 2) as well as in the systems where draining distances were broadened 1.5 times (variant 3) and remained here for 5.5 and 6.0 days accordingly. The draining intensity of the area gets more efficient when draining intensity is reduced in the systems, i.e. when draining distances are broadened 1.5 times and when filter properties of trench filling are ameliorated by mixing the trench filling with lime (adding 0.6 % of active CaO for ground mass). Keywords: drainage, trench filling, draining intensity.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) INVESTIGATION OF DRAINAGE RUNOFF REGULATION Vytautas MORKUNAS, Edmundas RAMOSKA Summary In this papier the possibilities of the regulation of drainage runoff are analysed seeking to make the most efficient use of water resources and to reduce the pollution of environment. The aim of the researches was to establish the efficiency of damming in drainage systems, at the same time solving the problems on relief, plant yield, soil properties and moisture regime regulation. The investigations were carried out in damming and natural drainage systems arranged in Calc (ar)i-Endohypogleyic and Hapli – Endo hypogleyic Levisols in sandy-loam and loam soils in Middle Lowland of Lithuania. On the basis of the data obtained in the period of two years it was established that at the begining of plant vegetation the retained runoff accumulates in drainpipes through which it penetrates into the soil and makes up a water irrigation fringe. This rezults a better provision of plants with water. Having damming the drainage in spring water retained there for the period of 30-40 days. The factors predetermining the afflux height include microrelief and infirltration properties of the soil. The beginning of spring damming is predetermined by the position of soil water level in between drains as well as by landuse and climatic conditions. The damming may be started a month earlier in the areas where winter crops are grown to compare with the ones with summer crops. At the period of plant vegetation, having ponded the drainage during drought the water reserves of the soil increased by 12 mm on the average. Meanwhile, they changed insignificantly when there was a sufficient amount of precipitation. In dry spring crops grew more intensity in ponded areas of drainage. There was obtained an extra yield of grain. The height of stems and coarsenness of grain depended on the afflux height (r=0,71 and r=0,59). Keywords: regulation of drainage runoff, head, moisture reserves.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) ON PRECONDITIONS FOR THE DEVELOPMENT OF NATURAL FUNCTIONS OF DRAINAGE CHANNELSRomanas LAMSODIS SummaryDrainage channels were deprived (or almost deprived) of natural functions which they had contained as natural watercourses before regulation: the diversity (as well as protection) of species induced by abiotic conditions of river bed and riparian ecotones, and the role of natural watercourses related to this variety (abiotic and biotic one) when trying to stop erosion and the migration of its products in geosystem. In this paper preconditions for the development of natural functions of drainage channels are being discussed on the basis of different materials obtained in period 1995-2000, as well as the results of other authors. These materials include the facts of the phenomena occurring in drainage channels and their vicinities (slops covering with woody vegetation, sediment accumulation, beaver activity, changes of water quality, soil water regime at impounded channels). It was established that both woody vegetation and beavers inhabiting the channels increase biodiversity. Overgrown channels accumulate sediment much more slowly. The concentrations of nutrients in water flowing via dammed up channels as well as in channels flowed from fields into forests show a certain downward tendency of nutrients. There exist technical means for the control of the impact of beavers as well as woody vegetation upon drainage systems. Keywords: biological diversity, water quality, sediment, soil water, woody vegetation, beavers.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) THE INVESTIGATIONS OF HOUSEHOLD WASTEWATER PURIFICATION IN RETENTION PONDSSimanas AŠKINIS Summary The dynamics of household wastewater purification efficiency in retention ponds under the conditions of biocenosis is presented in this paper. The researches were carried out in wastewater treatment facilities of Tiskūnai. The facilities contain a septic-tank and three retention ponds. This treatment method was chosen due to several reasons: it is cheap, easy to carry out, and it gives the possibility to treat a big amount of wastewater regardless of its pollution degree. Already in the first half-year after its arrangement, the system was functioning efficiently enough: the amount of suspended sediment was reduced by 63 %, the amounts of Nb and Pb decreased by 55 % and 58 % accordingly. A high average BOD7 (49.0 mgO2/l) was predetermined by the rise of BOD7 at the end of August and at the beginning of September, when it reached 131.0 mgO2/l. This was caused by the sudden spreading of microorganisms, which had consumed the greatest amount of soluble oxygen from wastewater. The quantity of oxygen which remained in wastewater was insufficient for the oxidation of pollutants. This phenomenon was characteristic to warm periods of the researches, however such a high BOD7 was never met again: in 2000 the maximum BOD7 reached 45.5 mgO2/l, in 2001 (from January to June) it was 51.0 mgO2/l. The average pollution slightly exceeded the biggest permitted limit (25 mgO2/l). The biocenosis formed in ponds in the second study year, and the efficiency of wastewater treatment remained almost the same in the third year, too. The researches have shown that the more polluted wastewater is, the more efficiently it can be treated. In May, 2001, urine got into the wastewater, therefore the concentration of total nitrogen reached 113.0 mg/l. The pollution of the stream was reduced 2.25 times, though the urine was not treated to the permitted limit. The concentrations of nutrients in wastewater flowing out of a septic-tank were lower in the second and the third study years to compare with their concentrations in the first study year. Therefore, the efficiency of their purification in ponds was less: the amount of Nb decreased by 29.0 % and 31.8 %, the amount of Pb was reduced by 20.0 % and 10.5 % accordingly. The amount of total nitrogen was reduced to the permissible limit in wastewater, meanwhile the quantity of phosphorus was twice as big in wastewater running out of the treatment facilities. The amount of the soluble oxygen increased by 90.0 % and 17.4 % accordingly in these years. The concentration of suspended sediment in wastewater flowing out from the third pond never exceeded the permitted limits (the average - 30 mg/l; the maximum - 40 mg/l). Despite the wastewater flow and pollution fluctuations, the retention ponds are really efficient carrying out wastewater treatment works. The quality of wastewater flowing out of the last pond into the stream corresponds to the ecological requirements made for such kind of wastewater treatment facilities. Keywords: retention ponds, purification efficiency, household wastewater, biocenosis.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) THE INVESTIGATION OF PRIMARY WASTEWATER TREATMENT IN MEAT-PROCESSING COMPANIESZenonas STRUSEVIČIUS, Sigita Marija STRUSEVIČIENĖSummaryToday meat is beeing processed in 240 private companies most of which are located in rural areas. Ten companies out of the mentioned ones process from 5.0 to 30.0 t of meat production per day. The amount of wastewater reaches 30-180 m3 per day. Foreign technologies made for the treatment of wastewater are of high technical quality but very expensive, therefore at present they are not applied widely in Lithuania. Having estimated chemical and biological properties of wastewater as well as the pollutant transformation processes occuring at the time of wastewater treatment, we have created the technology of primary wastewater treatment. This technology is based on physical and chemical means of wastewater treatment and is 4-5 times cheaper, therefore it is acceptable by all meat-processing companies. This experimental technology was first applied in Agricultural company "Nematekas" in 2000. Wastewater from meat-processing companies is heavily polluted with grease and other organic matter. The amount of grease in it is on average 1100 mg/l BOD7 – 1720 mgO2/l. Therefore, before wastewater gets into the level of biological treatment, first of all it should be cleaned from grease and its pollution with organic matter should be reduced down to at least 400-600 mgO2/l (according to BOD7) in the primary treatment facilities. Laboratory investigations have shown that wastewater treated in gravitational grease separator by adding some lime (0.4 kg CaO/m3) contains less than 90 % of grease, and its contamination with organic compounds decreases down to 50 % according to BOD7. The investigations of the functioning capacity of our technology have shown that grease separation efficiency increases up to 98.4 %, and the removing efficiency of organic matter from wastewater increases up to 72.7 % (according to BOD7) when oxygen participates in floculation processes of wastewater. Our technology of the primary treatment of wastewater from meat processing industry includes gravitational grease separator, device for physical and chemical cleaning and sedimentation pond. This technology helps to remove up to 91 % of organic pollutants (according to BOD7), 57 % of biogenic pollutants Nb and Pb, and up to 100 % of fat from wastewater. The implantation of our technology requires about 4-5 times less expenditure and 2.5 times less input to compare with the technologies of similar efficiency in foreign countries. Therefore, they are hoped to be in great demand. Keywords: wastewater, pollutants, lime, floculation, treatment efficiency.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) ANALYSIS OF TOTAL LOAD IN LITHUANIAN RIVERSZenonas RIMKUS Summary The article deals with problems of total load analysis, which is one of the main factors in riverbed formation. It is observed that earlier investigators have interpreted total load rather differently and in most cases without restraint. Some of investigators used to attribute only the loads that flow in water to total load, some of them considered total load as both flowing and moving in riverbed loads, others thought that all substances dissolved in water had to be attributed to total load too. There were many occasions when one of structural forms was pointed out: suspended load (most frequently), bed load, or loads generally. Therefore, the conception of total load and terminology of component parts are concretised already in the beginning of the article, and the principal forming scheme is presented. The analysis of total load of Lithuanian rivers in chronological order was carried out for the first time. This will help much for future investigations. It was established that suspended load of Lithuanian rivers is being investigated satisfactorily. These results of investigation can be used in future scientific research and in solving practical problems. There is not enough data about bed load of Lithuanian rivers. Therefore, attention in the article is drawn to the importance of ratio between suspended load and bed load. Meanings of the ratio that occur in Lithuania were compared with corresponding meanings of some rivers of the world. At present the dimensions that are got calculating ratios between suspended load and bed load in Lithuania are too large in comparison with suchlike ratios of rivers in other regions. Therefore, the conclusion can be made that in future it is important to develop investigation of bed load in nature and to search bed load calculating methods that are the most suitable in Lithuania. The data about total load of rivers collected by Lithuanian hydrometeorological-service station is summarized in this article. Unfortunately the information about total load of Lithuanian rivers is comparatively spare, observations in nature are still narrowed down. Statistical distribution of average monthly discharge of suspended load and their connection with analogical change of water discharge in the period of a year have been analysed. Present and earlier investigations of total load of Lithuanian rivers are important for both hydro engineering needs and theoretical investigation of riverbed processes. Keywords: total load, suspended load and bed load, load distribution.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) CROPPING INTENSITY CONNECTION BETWEEN AGROECOSYSTEM PRODUCTIVITY AND MATTER MIGRATIONSaulius GUŽYS, Elena Aldona ARLAUSKIENĖSummaryDuring the period 1995–1998 in the Vezaiciai Branch of the Lithuanian institute of Agriculture the organic – biological and intensive cropping systems investigations on autonomous drainage plots in limed moderately podzolized sod podzolic (Jv2) and gleyic sod podzolic (JPv1) as well as non acid podzolized sod-gleyic (VG1j) soils were carried out. This paper presents the summarized investigation results of field crop productivity, soil biological activity, drainage runoff and migration of elements and compounds in the conditions of mentioned cropping systems. Cultivation of intensive cropping system permits to receive 38-77 % higher average yields of all crops comparing with organic – biological cropping system. In the conditions of intensive cropping system in all soil types was observed tendency of microorganism spreading increasion. Liming had a stronger influence on soil biological activity than fertilization. But and after liming, microflora of Jv2 soil was a poorly, comparing with JPv1 and VG1j soils. VG1j soil during all period of investigation divorced a richer and stabiler microflora. The influence of cropping intensity on microorganisms spreading depended on soil genetical type. Drainage runoff depended on amount of precipitation and average air temperature (R=0,61). Cultivation of intensive cropping system drainage runoff decreased from 6-63 to 23-57 %, comparing with organic – biological cropping system. Cropping intensity has no influence on Ca2+, Mg2+, K+, SO42-, PO43- concentration in drainage and Ca2+, Mg2+, K+, HCO3-, SO42-, PO43- concentration in ground water. Concentration of Ca2+, HCO3- and SO42- in drainage water as well as concentration of Ca2+, K+, HCO3- in ground water on geochemical soil media and increasęd in such sequence: Jv2ŕJPv1ŕVG1j. Increase of fertilization efficiency on crop yield decreasing nitrate concentration in drainage and ground water. The leached amounts of elements and compound depended on drainage water runoff and cropping intensity. Under the conditions of intensive cropping system lower amounts of Ca2+, Mg2+, HCO3-, Cl-, K+, PO43- are leached. According to these and other (Bakhsh et al., 2001; Kristensen et al., 1994; Lind et al., 1995) investigations intensive cropping system should not considered the strengthened pollutant of geosystem to compare with organic cropping system. However, the data of investigations allow us to think that fertilization recommendation in Lithuania estimate the migration processes of biogens insufficiently. In order to reduce non-point source pollution of geosystem it should be aimed to reach maximum efficiency of fertilizers and to carry out others agricultural means irreproachably at the same time. Keywords: organic-biological agriculture, intensive agriculture, yield, soil, soil biological activity, drainage water, ground water, runoff, nitrates, water quality, leaching.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) THE DRAINAGE AND SCREEN – DRAINAGE MODULES AS THE MEANS OF SOIL WATER REGIME REGULATION IN HUMID AREALeonid Fiodorovich KOZHUSHKO, Nikolaij Nikitovich TKACHUK, Natalija Andrejevna REVCHUKSummaryThe paper deals with the means of soil water regime regulation in humid area with help of drainage and screen drainage modules. The relative position of screen and drain (the main elements of the module) has been proved on the basis of laboratory and natural researches. Quantitative characteristics of screen and drain common operation are presented in the paper. More efficient modules for humidity surplus zones have been established. The proposed constructions allow to retain a maximum amount of filtration water and guarantee the possibility for the lowering of ground water level in drainage systems. Moreover, the mentioned modules may be applied for the increase of canal and dike slope stability in the case when there is a high depression curve. They can also be used for the protection of territory against water head and in order to avoid the impact of land-reclamation systems upon the environment. Key words: draining, regulation, drainage module, water head, screen-drainage module.
Article received 09 2001, given to print 12 2001. ISSN 1392-2335 Transactions of the Lithuanian University of Agriculture and Lithuanian Institute for Water Management 2001 vol. 16(38) INFLUENCE OF NUTRIENT MIGRATION PROCESSES ON SURFACE WATER QUALITYPetras MILIUS, Giedrius BAIGYSSummary Farming activity is a very important factor for leakage of nutrients and pollution of water bodies, because the biggest part of nutrients reaches rivers with water leached from agricultural land in a form of non-point source pollution. A monitoring post is installed in the watershed of L-1 rivulet (Šilalė municipality) to investigate nutrient migration processes. L-1 rivulet is a left tributary of the Lyžena river, and its watershed belongs to the eastern edge of the Žemaičiai Highland. The watershed is inside Karklėnai–Bijotai micro region that is characterised as a massive flat hilly talus loamy landscape. The water monitoring post is installed in Kumečiai village on L-1 rivulet (0.87 km above rivulet’s mouth) at the outfall of tile drainage system 41. In order to calculate the amount of leached nutrients in the rivulet and the drainage system, water quality samples are taken at runoff measuring places of L-1 rivulet and tile drainage system 41. Areas of the watersheds at the monitoring post cover 166 ha and 14 ha accordingly. Another drainage runoff measuring post is installed in Dauba village on the standard tile drainage system 1, at the outfall of collector 1-b. It measures runoff from the area of 10 ha. Loam soils dominate and land is occupied by meadows and pastures in this territory When investigating the water quality, the attention is to be paid mainly to nitrate and phosphate leaching. Nitrate nitrogen is leached most quickly (because soil absorbs it most weakly). The amount of nitrates in L-1 rivulet is typical to average polluted water (purity class IV) according to the indicators of surface water general pollution. When investigating water quality dependence on meteorological conditions and peculiarities of runoff formation, it was determined that nitrate nitrogen concentration in the rivulet depended on water discharge, air temperature and nitrate concentration in drainage water. In the watershed of L-1 rivulet two leaching maximums of nitrate nitrogen showed up: in late autumn – early winter and winter – early spring. It was determined that the highest amount of nitrate nitrogen got into the rivulet via tile drainage. During winter – early spring period, when soil adsorptive capacity dropped down significantly because of low air temperature and freezing, nitrate increase was determined by precipitation and activity of nitrificators. In November-December, when the amount of nitrate in precipitation was small, high nitrate leakage was determined by mineralisation processes of autochthonous organic material. The available average five-year comparable data on nitrate nitrogen transported via L-1 rivulet do not show that nitrate nitrogen leakage fluctuates remarkably, i.e. increases or decreases. Similar conclusions can be made for phosphorus leakage. Phosphorus is leached by infiltration water, but the landscape of the investigated water ecosystem is not characterised as the one with high infiltration capacity. Phosphorus migration dependence on meteorological, hydrological factors and land use was not clear. The highest phosphorus concentrations are determined in autumn and winter, when due to high soil acidity a fair amount of soluble phosphates reaches the rivulet via drainage and surface water in the watershed. Five-year investigations show that nutrient changes in river water are determined by landscape physical properties, climatic factors, local hydrological conditions and agricultural activity. Nutrient migration mostly depends on infiltration capacity of the watershed: bigger nitrate nitrogen and less phosphorus amounts inflow, when infiltration conditions become worse. Keywords: monitoring, nitrate nitrogen, phosphatesi, leaching,, runoff, drainage.
Article received 09 2001, given to print 12 2001. |
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