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CONTENTS
ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 5–14 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture LEACHING OF NITROGEN COMPOUNDS IN THE CONDITIONS OF CROP ROTATIONS Saulius Gužys*, Zita Petrokienė Abstract The investigations were carried out in the land of the Water management institute of LUA, in the village of Lipliūnai on Endocalcari Endohypogkeyic Cambisol (CMg-n-w-can). The base of investigations is 3 drainage systems, which contain Norpholc, row crops and grasses crop rotations. The row crop rotation was distinguished by the highest productivity as well as by highest amount of mineral nitrogen in soil. The amount of mineral nitrogen in soil was determined by many natural and anthropogenic factors (fertilization, yield, drainage runoff). The most productive row crop rotation was distinguished by the least mean annual drainage runoff. When applying a less productive crop rotation the drainage runoff increases. The row crop rotation was distinguished by the highest mineral and total concentration nitrogen in soil and the highest leaching. Nitrogen leaching is reduced under the conditions of Norfolc and grasses crop rotations. The leaching of mineral and total nitrogen under the conditions of crop productivity, its fertilization, nitrogen balance and nitrogen balance compensation of nitrogen fertilization varies by parabolic (y=a-bx+cx2) regularity. The minimal nitrogen leaching is gained under the following conditions: fertilization – 66–71 kg ha-1 a.m., agroecosystem productivity – 30–94 GJ ha-1 and moderate negative nitrogen balance – (-48; -32 kg ha-1). Independent of applying crop rotation nitrogen balance was essentially dependent on mineral fertilization. Keywords: balance, drainage water, leaching, mineral and total nitrogen, soil, yield.
*contact person Dr. Saulius Gužys*, senior researcher, Water protection department, Water Management Institute of Lithuanian University of Agriculture. Research interests – agrochemistry, agroecology, agricultural hydrology. Address: Parko 6, LT-58102, Vilainiai, Kėdainiai district, Lithuania. Phone: +370 671 06124. E-mail: s.guzys@water.omnitel.net. Zita Petrokienė, junior researcher, Water protection department, Water Management Institute of Lithuanian University of Agriculture. Research interests – investigations on plant nutrient migration and balance, water protection. Received 05 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 15–26 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture VARIATION OF NITROGEN AND PHOSPHORUS COMPOUNDS IN NEVĖŽIS RIVER Antanas Sigitas ŠILEIKA*, Kazimieras GAIGALIS, Giedrius BAIGYS Abstract The article analyses the variation of nitrogen and phosphorus compounds in the Nevėžis from its headwaters to the mouth and in the lower courses of its tributaries during the periods of autumn and winter of 2004–2007. The investigations established that nitrogen and phosphorus get into the Nevėžis from different pollution sources. The concentration of ammonia nitrogen in the Nevėžis headwater is very high. In autumn and spring in the Nevėžis upstream Laukagaliai the concentration of this element exceeded the allowed maximum 0,39 mg l-1. The concentration of nitrate nitrogen is also quite high – in the autumn of 2004 it was 4,1 mg l-1. The concentration of ammonia nitrogen and phosphates in the Nevėžis depends highly on the river discharge. During the spring flood the concentration is much lower than in autumn. An extremely dry and hot summer of 2006 increased the nitrate nitrogen concentration in the Nevėžis markedly. The concentration of phosphate phosphorus in the headwater of the Nevėžis is comparatively low. In autumn and spring it rarely exceeds 0,02 mg l-1, but below Panevėžys sometimes the phosphate phosphorus concentration actually exceeds the allowed maximum (0,08 mg l-1) 10 times. The biggest amount of phosphorus reach the Nevėžis from Panevėžys, Naujamiestis, Krekenava and Kėdainiai towns as well as from the Nevėžis‘ tributaries the Lokauša, the Obelis and the Šušvė. The Lokauša is mainly polluted by a huge pig husbandry complex in Račionys, the Obelis‘ pollution is determined by the run-off of Kėdainiai plant of phosphorus fertilizers. In the estuary of the Šušvė the phosphorus concentration is high due to the run-off from Vainikai village and a pig husbandry complex near Josvainiai. The pollution by nitrate nitrogen in the Nevėžis decreases going down from the headwaater to Panevėžys, but the towns and tributaries below increase it noticeably again. In order to restore a good water quality of the Nevėžis River the non-point pollution by nitrogen compounds from agriculture and the concentrated pollution by phosphorus from towns, villages and animal husbandry enterprises have to be reduced. To reduce the concentrated pollution, first of all, waste water treatment plants in Panevėžys, Naujamiestis, Krekenava, Kėdainiai and Josvainiai have to be reconstructed. With a view to reducing pollution by animal husbandry the fields for slurry spraying in the Lokauša and the Šušvė watersheds have to be expanded substantially. Keywords: ammonia nitrogen, concentration, nitrate nitrogen, observations, phosphate phosphorus, river.
*contact person Dr. Antanas Sigitas Šileika, director, Water Management Institute of Lithuanian University of Agriculture. Research interests – valuation and monitoring of river water quality, modeling of river water quality. Address: Parko 6, Vilainiai, LT-58102 Kėdainiai district, Lithuania. Phone:+370 347 6 81 00. E-mail: sigitas@water.omnitel.net. Dr. Kazimieras Gaigalis, the head of Water Resources Sector, Water Management Institute of the Lithuanian University of Agriculture. Research interests – hydrology, monitoring and evaluation of water runoff of small streams. Giedrius Baigys, ph. d. student, of Water Resources Sector, Water Management Institute of Lithuanian University of Agriculture. Research interests – monitoring and evaluation of water runoff of rivers and drainage systems. Received 06 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 27–35 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture INFLUENCE OF FERTILIZING ON NITROGEN VARIATION AND LOSSES IN A FIELD’S CROP ROTATION Stefanija MISEVIČIENĖ Abstract The article discusses the results of the research carried out at WMI of LUA trial field in 1999–2003. The influence of fertilizing on nitrogen balance and nitrogen leaching into drainage water was researched. To calculate nitrogen balance the amounts of this element with precipitation, seed, fertilizer, biological nitrogen fixations and plant residues taken with the yield (secondary and main production) and drainage water were fixed. Nitrogen supplies in the soil were established. It was established that nitrogen leaching into drainage water increased at surplus or least deficit balance of this element. The greatest amount of nitrogen leached out (32,3 kg/ha-1), at surplus balance (+39,79 kg/ha-1) and the least amount (4,1 kg/ha-1) – at deficit balance (-82,74 kg/ha-1). Keywords: balance, leaching, nitrogen.
Dr. Stefanija Misevičienė, scientific researcher of Water treatment laboratory, Water Management Institute of Lithuanian University of Agriculture. Research interests – ecology and environmental engineering, the impact of the management and usage of slurry on the environment, researches on the transformational processes of pollutants. Address: Parko 6, LT-58102, Vilainiai, Kėdainiai district, Lithuania. Phone: +370 347 6 80 20. E-mail: s.miseviciene@takas.lt. Received 09 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 36–46 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture INFLUENCE OF NATURAL AND ANTHROPOGENIC FACTORS ON NITROGEN LEACHING IN STREAM CATCHMENTS Antanas Sigitas ŠILEIKA*, Kazimieras GAIGALIS, Abstract Studies of water runoff changes and total nitrogen (N) leaching were carried out in West, Middle and Southeastern part of Lithuania. Catchments are different in climate, soil, land use and farming intensity. Water runoff and N concentration varied very widely in the mouth of all three studied streams during 1996–2006. Mean yearly water runoff has fluctuated from 159 to 240 mm and N concentration – from 2.4 to 5.9 mg l-1. The largest runoff was in the hilly Southeastern part where stream beside precipitation was fed by groundwater. The highest N concentration was in the stream of the Middle Lithuania where agriculture is the most intensive and the stream is fed almost only by precipitation. Applying non-linear user-specified regression for the yearly observation data were defined that N concentration in all three streams depends on variation of precipitation, weather temperature and N concentration in precipitation (R2=0.92; 0.83 and 0.56). Relation of monthly observation data between natural variables and N concentration in streams is weak. Natural factors in different parts of Lithuania influenced differently on variation of N concentration in streams. Analyses of the natural factors separately, showed that precipitation play the key role in N concentration of the Middle and South-eastern Lithuanian streams (R2= 0.72 and R2= 0.61). N concentration in the Western stream depend mostly on N concentration in precipitation and weather temperature (R2= 0.58 ir R2= 0.54). The largest mean annual N load in 1996–2006 was in the Middle Lithuanian stream, – 13.5 and the lower in Western stream – 5.5 kg ha-1. The N load in studied streams in some years differs 4–5 times. In the Middle and South-eastern streams, which are further from the Baltic Sea, the largest load usually are influenced in spring after snow melting. In the Western part of Lithuania, closer to the sea were winters are milder, the largest load is in winter. To separate anthropogenic impact from natural variation in the collected data the Visual Basic programme FLOWNORM developed by A. Grimvall from Linkoping University was used. Using semiparametric flow normalisation model N load increase was determined in two of the three streams but to state that intensification of agriculture has influenced higher N load is not possible. Thorough investigation showed that significant increase of N concentration in precipitation in 2006 could determine such trend. Keywords: catchment, concentration, load, stream, runoff, nitrogen.
*contact person Dr. Antanas Sigitas Šileika, director, Water Management Institute of Lithuanian University of Agriculture. Research interests – evaluation and monitoring of river water quality, modeling of river water quality. Address: Parko g. 6, LT-58102 Vilainiai, Kėdainiai district, Lithuania. Phone: +370 347 6 81 00. E-mail: p. sigitas@water.omnitel.net. Dr. Kazimieras Gaigalis, the head of Water Resources Sector, Water Management Institute of the Lithuanian University of Agriculture. Research interests – hydrology, monitoring and evaluation of water runoff of small streams. Received 10 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 47–57 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture NUTRIENT LEACHING FROM CONTROLLED DRAINAGE SYSTEMS Edmundas RAMOŠKA,* Vytautas MORKŪNAS Abstract During the production intensification under the conditions of planned economy drainage systems were installed on large areas in Lithuania and they still have an impact on environment. In an even more balanced agricultural system relatively controlled in an environmental way it is important to evaluate the perspective of the drainage system management by reducing the impact on the environment. The efficiency of regulated drainage in terms of environmental protection was analysed in 2003–2006 in the middle part of the central Lithuania’s flat on Endocalcari Endohypogkeyic Cambisol. The drainage hydrological activity, the variation in the concentrations of biogenic substances in the run-off and leaching in two normally functioning systems of regulated drainage in the two fields were observed and meteorological conditions analysed. The nitrate nitrogen concentration in the drainage run-off was lower in cold period and in the beginning of run-off, and it partly depended on the nature of drainage functioning, meteorological conditions and plants grown. In the run-off of regulated drainage in the first field the annual nitrate nitrogen concentration was lower for three years and for one year after dry periods it was higher compared with the run-off of normally functioning drainage. By regulating the drainage due to a lower nitrate nitrogen concentration and a decreased drainage run-off the average annual rate of nitrate nitrogen leached was by 31% lower than in normally functioning drainage. The environmental effect by regulating drainage functioning in the second field was not achieved due to earlier applied different amounts of nitrogen in fertilizing experiment plots and nitrogen accumulated in the soil. The annual nitrate nitrogen concentration in the run-off of regulated drainage was 2,4–7,8 mg l–l higher and the leaching of this element on average was 51% higher than that in area of the normally functioning drainage. The average annual ammonia nitrogen concentration in drainage run-off (0,05–0,16 mg l–l) and the amount of this element leached annually (39–45 g ha–1) was not significantly different. Instantaneous concentration of ammonia nitrogen in the drainage run-off of both variants increased when ground water levels rose to the arable layer and the concentration of this element in slack water of the regulation mechanism increased one hundred times. Regulation of drainage had no substantial impact on the average annual concentration of phosphorus phosphates and potassium and the average annual leaching of this element. In dry years phosphate concentration in the run-off of flooding drainage was lower compared with the normally functioning drainage and it was respectively higher in years of average humidity. Potassium concentration in the run-off of both variants was higher in dry years compared with the years of average humidity. By regulating the drainage the annual leaching of potassium was by 8–33% lower on average compared with normally functioning drainage. By drainage regulation the biogenic substances existing in the run-off stopped remain in the soil and a smaller amount of them reach water sources. In such a way it is possible to reduce a negative impact on the environment and apply a more rational way of farming. Keywords: concentration of biogenic materials, control drainage, leaching, run-off.
*contact person Dr. Edmundas Ramoška, senior researcher, Sector of Geofiltration Investigation, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, regulation of water regime in mineral soils. Address: Parko 6, Vilainiai, LT-5048 Kėdainiai district, Lithuania. Phone: +370 347 6 80 08. E-mail: e.ramoska@takas.lt. Dr. Vytautas Morkūnas, Deputy Director for Science, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, land draining. Received 10 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 58–65 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture Relative significance of the runoff formating factors and possibilities to apply the regression equations Henrikas PAULIUKEVIČIUS Abstract The influence of the 12 climatic, physiographical and antropogenic factors on the mean characteristics of the annual runoff depht, spring peak diurnal and 30 days minimum modulus of flow is investigated. The data of the 25 Lithuanian river basins are used. The area of river basin changes from 71 to 3600 km2, 22130 km2 overall. The simple and multiple correlation and regression methods are used when investigating how the mean runoff characteristics depend on the different factors and their groups. The climatic factors are main contributors to the mean annual runoff. The dependence of the annual runoff on the factors related to the watershed characteristics and human impact is rather weak. In case of the spring peak flow the significance of all groups of factors investigated becomes nearly equal while climatic factors determinate less than 50% the peak daily flow change. The dominant factors affecting the minimum modulus of flow are physiographycal and human. 12 factors investigated determinates 87,9% of the annual runoff depht, 84,8% of the maximum modulus of flow and 91,6% of the minimum modulus of flow changes in the river basins investigated, when considering that the coefficient of determination reflects the segment of the influence of factors or their group. Remaining 8,4 to 15,2% belongs to the factors not investigated in this work, errors of estimation of characteristic of river basin, the measurement of the climatic characteristic and the runoff itself. Data of the two river basins in the Middle Lithuania and one in the West Lithuania is used to verify the regression equations. The relative errors of the calculation of runoff depth for the Middle Lithuanian rivers were from 2 to 4%, for the West Lithuanian river Akmena – 6,8%. The relative errors are larger in case of the extreme runoff but in most occasions less than 40%. The land use and tile drenage area are strong enough and statistically significant factors affecting the maximum and minimum discharge. The multiple regression equations, therefore, would be suitable means off evaluating changes of the mean runoff characteristic associated with land use activities in the river basin. Keywords: modulus of flow, normal annual runoff, regression equation.
Dr. Henrikas Pauliukevičius, senior researcher, Water Protection Department, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, geography, hydrology. Address: Parko 6, Vilainiai, LT-58102 Kėdainiai district, Lithuania. E-mail: h.pauliukevicius@takas.lt. Received 09 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 66–73 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture PERMANENT AND RANDOM POLLUTION BY TOTAL PHOSPHORUS IN MEDIUM SIZE RIVERS Saulius KUTRA*, Laima BERANKIENĖ Abstract The article analyses pollution by phosphorus of four Lithuanian rivers or their sections with basin areas of about 1000 km2 in 1997–2004. According to the peculiarities of variation in pollutant concentrations two pollution types were identified: permanent and random. Simulation of permanent and random pollution by total phosphorus is carried out separately. The model of simulating permanent pollution is specified by mean permanent pollution expressed by concentration in water, standard deviation and lognormal distribution. The simulation model of random pollution consists of the highest and the lowest concentration of pollutants typical for a river, incident probability and uniform distribution. The main simulation parameters of permanent pollution in the analysed rivers are as follows: the Venta: mean concentration of total phosphorus – 0,089 mg l-1, standard deviation – 0,033; the Lėvuo: – 0,088 mg l-1 and 0,017 respectively, the Nevėžis – 0,086 mg l-1 and 0,067, the Šušvė – 0,051 mg l-1 and 0,028. The simulation parameters of random pollution are as follows: the Venta: the highest concentration – 0,26 mg l-1, the lowest – 0,20 mg l-1, probability – 0,037; the Lėvuo: the highest concentration – 0,88 mg l-1, the lowest – 0,38, probability – 0,081; the Nevėžis: the highest concentration – 0,77 mg l-1, the lowest – 0,32 mg l-1, probability – 0,066; the Šušvė: the highest concentration – 0,20 mg l-1, the lowest – 0,14 mg l-1, probability – 0,039. Keywords: permanent pollution, phosphorus concentration, pollution simulation, random pollution, total phosphorus.
*contact person Dr. Saulius Kutra, head of Water Protection Department, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and land management, GIS, pollution modelling, application of remote-sensing. Address: Parko 6, Vilainiai, LT-58102 Kėdainiai, Lithuania. Phone: +370 347 6 82 47. E-mail: kutra@water.omnitel.net. Dr. Laima Berankienė, senior research of Water Protection Department, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and land management, hydrology, river pollution. Received 10 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 74–80 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture VARIATION OF INDICATORS OF WATER PUMPING IN POLDERS AND THEIR DEPENDENCE ON HYDROLOGICAL FACTORS Arvydas Povilas MALIŠAUSKAS Abstract Due to changed land-ownership, farming and financing conditions the operation regime of polder pumping stations was changed as well. The amount of water pumped decreased as well as pump capacity and duration of activity in certain places, therefore, the amount of electric power used decreased too. In 1991–1995 the energy consumption decreased 2–3 times. In these latter years the activity of pumping stations in winter polders has increased again and it reached 60–80% of energy consumption corresponding to the consumption of intensive polder drainage in the period before 1990. The pumps in summer polders operate under a limited regime, only ensuring the drainage of the average and higher areas of the soil surface during the warm season of the year. The electric power consumption in polder pumping stations depends on the amount of water required to pump out, which is determined by the fixed water level regime in the channels and the soil as well as meteorological conditions. Guideline consumption of electric power in different polders is recommended depending on the amount of water pumped and the water- level in canals and in the soil. Keywords: polder, pumping station, electric power consumption, amount of pumped water, water-level.
Dr. Arvydas Povilas Mališauskas, senior researcher, Water Protection Department, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, hydraulic engineering and hydrology. Address: Parko 6, Vilainiai, LT-58102 Kėdainiai district, Lithuania. Phone: +370 347 6 80 09. E-mail: a.malisauskas@water.omnitel.net. Received 05 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 81–87 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture CONDITION OF SURFACE WATER INLETS IN DRAINED LAND AREAS Valentinas šaulys*, Nijolė bastienė, Alvyda šaulienė Abstract The investigations of surface water removal from the drained land areas have become relevant with the increase of drained areas. In order to maintain adequate draining efficiency, while evacuating surface water from the drained lands, the density of surface water inlets had to be increased up to 5,5 units 100 ha-1. That was determined by the density reduction of the open drains. Observations of the technical condition of surface water inlets in the drained lands of the country have been carried out since 1986. It was established that over 90% of inlets were of F–5 construction. The article analyses the condition of the inlets of such design and evaluates the installation location, conditions of water flow towards an inlet and the state of water inflow openings. The research proved some drawbacks of the design, a number of installation errors and failures that had occurred during the operation period. A clear increasing tendency of silting of water inflow openings and overgrowing with vegetation was established: in 1986 there were 11.1%, in 1996 – 20.8%, and in 2007 – 42.9% of inlets with complete siltation of water openings. On this ground it can be stated, that the inlets with partial siltation of water inflow openings will fail soon, if there are no timely and appropriate maintenance works carried out. Keywords: damages, drainage maintenance, surface water inlets.
*contact person Doc. dr. Valentinas Šaulys, senior researcher, Head of Exploitation Laboratory, Water Management Institute of the Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, processes of surface water seepage, water quality, water management policy. Address: Parko 6, Vilainiai, LT–58102, Kėdainiai district, Lithuania. Phone: +370 347 68109. E-mail: valentinas@water.omnitel.net. Dr. Nijolė Bastienė, senior researcher at Water Management Institute of the Lithuanian University of Agriculture. Research interests – environmental engineering, efficiency of drainage systems operation. Alvyda Šaulienė, junior researcher, Geofiltration Research Department, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering, relations between the regime and pollution of surface and subsurface water. Received 10 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 88–95 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture FIELD MEASUREMENTS OF THE REGIME OF CURRENTS AND SEDIMENTS IN THE RIVER NEVĖŽIS IN KĖDAINIAI Saulius VAIKASAS*, Vaclovas POŠKUS Abstract On the basis of field measurements it has been established that there is a 1–5 cm pebble bed formed self-armouring. The bed sediments do not move usually, while the suspended sediments are brought down by the flow. As a matter of fact, the bed processes are not intensive and have reached the dynamic balance. In winter 2006 the biogenic contamination of the River water in view to nitrogen (N) and phosphorus (P) concentration significantly exceeded the allowed maximum rate in a carp-breeding pond. Although the water quality was rather satisfactory in view to BDS7 (<5,35 mg/l), it was poor in view to Q2 (=1÷2,5 mg/l). It has been established a particularly great distributive biogenical pollution along the River banks (Nł12,60, P – 1,97– 2,13 mg/l). The River is very sensitive to eutrophication and easily affected by both antropogenic and industrial pollution, because it is not deep and is mainly fed by surface discharge and melting snow water only. As a result, environment-friendly water discharge during the dry season is 0,6 m3/s only. Besides, industrial water consumption in Kėdainiai (0,24 m3/s) can make up even to 30% of this discharge. As a result, during the dry season it is not sufficient to properly dilute the partially treated sewage discharged by both Panevėžys and Kėdainiai industrial companies. Keywords: bed process, field measurements, pollution, river Nevėžis.
*contact person Habil. dr. Saulius Vaikasas, senior researcher, Exploitation Laboratory, Water Management Institute of Lithuanian University of Agriculture. Research interests – investigations and modeling of flood currents and riverbed processes. Address: Parko 6, Vilainiai, LT-58102 Kėdainiai district, Lithuania. Phone: +370 347 6 81 09. E-mail: s.vaikasas@delfi.lt. Vaclovas Poškus, junior researcher of Exploitation Laboratory, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and natural processes in drainage channels. Received 10 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 96–101 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture MATHEMATICAL MODELLING OF FLOW DYNAMICS OF THE URBAN RIVER NEVĖŽIS IN KĖDAINIAI Alfonsas RIMKUS, Saulius VAIKASAS* Abstract The dynamics of flow velocities and water level in the River Nevėžis in Kėdainiai has been estimated by applying a hydraulic-mathematical model DELTA. It was established that there were no conditions for a non-desirable layer of silt to form in the examined section, because silt and clay particles from fields were not transported during minimal discharges. Besides, accumulated bed sediments are washed away by the discharge during a flood (flow velocity in the examined section does not exceed 0,5 m/s when the usual discharge during the dry season is m3/s. When the discharge affects the formation of the river bed m3/s, the flow velocity reaches 1,2–1,3 m/s). Next, it has been also estimated that a two-meters high dam near Skongalis does not stimulate the bed silting too, because it is not high and is flooded during floods. As a result, it can barely influence the bed formation processes. When the water level is low and the flow velocity is small (0,1 m/s), the water in the River is only slightly turbid, i. e., the water is relatively clean (the turbidity is 2–6 mg/l) and the formed self-armoring prevents the bed from a flood erosion. Finally, it has been established that in order to improve esthetical view of the river and reduce the riverside overgrowth, it is advisable to regulate the river bed within the examined section by reducing the river width at its wide sections up to 30 m. Keywords: modelling, river-bed process, vegetation and deposits.
*contact person Dr. habil. Alfonsas Rimkus, freelance researcher, Exploitation Laboratory, Water Management Institute of Lithuanian University of Agriculture. Research interests – hydraulics of hydrostructures, riverbed processes. Habil. dr. Saulius Vaikasas, senior researcher, Exploitation Laboratory, Water Management Institute of Lithuanian University of Agriculture. Research interests – investigations and modeling of flood currents and riverbed processes. Address: Parko 6, Vilainiai, LT-58102 Kėdainiai district, Lithuania. Phone: +370 347 6 81 09. E-mail: s.vaikasas@delfi.lt. Received 10 2007. ISSN 1392–2335 Water Management Engineering, 31(51), 2007, 102–110 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture ANALYSIS AND EVALUATION OF MAINTENANCE EXPENSES OF POLDER SYSTEMS IN NEMUNAS LOWLAND DURING THE LAST DECADE Nijolė BASTIENĖ*, Valentinas ŠAULYS Abstract. Based on the economic, ecological and social points of view, the polder systems in the Nemunas lowland are considered to be the unique ones requiring a great deal of annual state subsidies. According to the land reclamation programme during the period of 2006–2008 Lithuanian polder system are planned to be yearly granted 7425 thousand Lt from the State budget, the local administration of Šilutė municipality, which is maintaining the polders of the Lower Nemunas, being awarded a grant containing more than half of the sum (75%). The article includes the analysis of maintenance expenses and statistical estimation of the Lower Nemunas polders during the period of 1996–2006. The statistical average of the expenditure on the polder systems of Šilutė municipality is revealed to amount to 2.34±0.48 million Lt a year. The average annual expenses on the pump stations, dikes, ditches and roads during the research period were determined. The analysis of the previous decade’s expenses shows that the statistical average of the expenditure on the polder systems of Šilutė municipality amounts to 2.34±0.48 million Lt a year. The analysis of the expenses shows that 1 ha of polder lands should be obviously awarded a grant of the state subsides including the amount at an average of 112 Lt. The increase in the financing must be based on the economic necessity. It’s a district municipality to determine and legitimate the priorities of the means redistribution according to the needs of the economic subjects. Keywords: maintenance expenses, polder systems, state subsidies.
*contact person Dr. Nijolė Bastienė, senior researcher, Exploitation Laboratory, Water Management Institute of the Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, researches of drainage system reliability and exploitation efficiency. Address: Parko 6, Vilainiai, LT-58102 Kėdainiai district, Lithuania. Phone: +370 347 6 81 09. E-mail: vegelyte@delfi.lt. Doc. dr. Valentinas Šaulys, senior researcher, Head of Exploitation Laboratory, Water Management Institute of the Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, investigation of the usage and maintenance of land reclamation equipment. Received 06 2007. |
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