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CONTENT ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 5–14 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture INFLUENCE OF DRAINAGE RUNOFF REGULATION ON SOIL WATER REGIME Edmundas RAMOŠKA*, Vytautas MORKŪNAS Summary The investigated issues are related to the agricultural and nature protective function of the drainage. The paper reviews the operation of drainage during different seasons of the year, as well as the effect of affluent on the regime of drainage water. The investigations were carried out in damming and natural drainage systems arranged in Endocalcari-Endohypogleyic Cambisols and Hapli-Epihypogleyic Luvisols in sandy-loam and loam soils in the Middle Lowland of Lithuania in 2003–2006. The studies included the observations of the formation and abatement of affluent in drainage network, also drainage water levels, drainage hydrological functioning. The paper also analyzes the requirements and technical solutions for regulated drainage systems. In loam-sandy loam soil of Middle Lithuanian Plain the functioning and regulation of drainage are related to climatic conditions and cover spring and autumn–winter periods. When analyzing the functioning of dammed drainage it was determined that during the rush hour the runoff module is evenly lower in less dammed area and unevenly lower in larger dammed area; here after the rush hour the runoff module was decreasing slower, however in the run of time it was rapidly decreasing and stopped earlier than that in non-dammed area. Having discharged the water for sediment to be removed, higher runoff module was observed in dammed area. The part of suspended runoff depended on the season of the year, occupation of fields with crops, and the evenness of affluent rise. When damming in spring, insignificant part of runoff is suspended. However, much larger amount of runoff is suspended during autumn-winter period. Annual runoff is on the average 11–19 mm (8–28%) lower in dammed areas. Drainage functioning often had no significant effect on MWL in-between the drains. Under extreme cold conditions the affluent advanced the flooding of the top soil layer. When the height of water pressure level in the outfall becomes stable, MWL was fluctuating in respect of the climatic factors. The height of affluent depended on the runoff and meteorological conditions. After the rush hour, the designed height of the affluent formed during 1–2 days; after spring sowing period and after water level abatement the affluent reached half of the designed height. In drainage network the affluent lasts 30-60 days; higher and longer affluent occurs in larger dammed area. The abatement of the affluent usually matches with the end of the runoff. A medium linear relation was determined between the duration of the affluent and meteorological conditions. The suspended runoff may be estimated as the means protecting water resources and ecosystem. Keywords: affluent, control drainage, runoff, water levels. *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 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 15–27 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture Tendencies and reasons of the changes of phosphorus concentrations in water of the Nemunas and its tributaries Antanas Sigitas ŠILEIKA*, Kazimieras GAIGALIS Summary There are discordant results on trends in nutrient river water quality from the economical transition countries in Europe. The present study assessed the impact of those economical changes on the load and concentration at 17 monitoring stations along the Nemunas and its major tributaries (Lithuania and Belarus). Three time periods were evaluated: the Soviet period 1986–1991, the transfer to market economy period 1992–1996 and the post reform period 1997–2002. The area-specific load of PO4-P decreased significantly from the first to the third period at all sites along the Nemunas (31–86%). Seasonal (SMK) and Partial (PMK) Mann-Kendall tests on PO4-P concentrations also showed significant downward trend at 14 from all 16 investigated sites. The decrease of PO4-P levels was attributed to the reduction of municipal and industrial point source emissions and to the decreased livestock numbers. This study showed that trend analysis at multiple sites in a river basin is crucial for the understanding of the variability in time and space. Such analysis is also important for our interpretation of underlying sources and fluxes in a drainage basin over time. This is particularly important for compounds that have different source origin. Keywords: concentration, load, monitoring, phosphorus, river, trend. *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 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 28–35 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture DISPERSION OF WATER STEAM IN PROFILED SOIL SURFACE DURING THERMAL REMOVAL OF WEEDS Povilas Algimantas SIRVYDAS*, Paulius KERPAUSKAS, Sigitas ČEKANAUSKAS, Rasa ČINGIENĖ Summary Damp water steam is an ecologic high temperature media, destroying a plant, which can substitute herbicides used for weed extermination. Extremely difficult weed control is in cultural plants crops of long germinating seeds. The crop is destroyed together with the weeds when it is not protected from the thermal effect. The studies of water steam scatter in profiled soil surface in thermal weed control showed that the surface of the soil in the sowing time can be profiled so that the germinating cultural plant was protected from thermal destruction. 9 possible soil surface profiles were examined in respect of the place of water steam releasing (4 variants), height of the profile (3 variants) and width of the profile (2 variants). Total – 196 cases. By experiment it was determined that only one profile of the soil surface fits for the protection of germinating cultural plants from thermal destroy in thermal weed extermination. In the sowing time on the profiled surface of the soil with constitutive profile with triangular emersions which descent is 45°, a good compatibility of profiling of the soil with thermal weed control with water steam technology is obtainable, which allows protecting the germinating cultural plant from thermal destruction. Keywords: soil profile, thermal weed control, water steam. *contact person Habil.dr. Povilas Algimantas Sirvydas, professor, Lithuanian University of Agriculture, Heat and Biotechnological Engineering Department. Research interests – plant energetics, heat engineering. Address: Studentų g. 15, LT-53361 Kaunas-Akademija, Lithuania. Phone: +370 37 75 22 40, e-mail: algimantas.sirvydas@lzuu.lt. Dr. Paulius Kerpauskas, assoc.prof., Lithuanian University of Agriculture, Heat and Biotechnological Engineering Department. Research interests – plant energetics, environment engineering. Sigitas Čekanauskas, ph. d. student, Lithuanian University of Agriculture, Heat and Biotechnological Engineering Department. Research interests – heat engineering. Rasa Čingienė, ph. d. student, Lithuanian University of Agriculture, Heat and Biotechnological Engineering Department. Research interests – heat engineering. Received 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 36–43 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture REMOVAL OF AMMONIA AND NITRITE NITROGEN DURING WASTEWATER TREATMENT IN CONSTRUCTED WETLANDS Zenonas STRUSEVIČIUS*, Valerijus GASIŪNAS, Sigita Marija STRUSEVIČIENĖ Summary In companies “Pastogė” and “Nikola constructed wetlands of vertical flow are arranged, while LTD “Agaras” contains two-stage constructed wetlands of horizontal flow. In all the objects the supplied wastewater is prie-treated (primary treatment). Wastewater discharge was measured daily in all the objects, wastewater samples were taken once per month. Having compared the efficiency of ammonium and nitrite nitrogen removal in two types of constructed wetlands (VFCW and HFCW) it was determined that larger amounts of total nitrogen are removed in HFCW (38.1%) rather than in VFCW (24.4%), however in VFCW smaller amounts of ammonium and nitrite nitrogen are discharged with wastewater. In VFCW, the efficiency of ammonium and nitrite nitrogen removal is of seasonal character: during the warm period of the year (05–10 months) when filter load according to Ntotal is fluctuating from 0.45 to 3.4 m-2 d-1, ammonium nitrogen concentrations in treated wastewater outflow were changing from 0.4 to 7.5 mg l-1 , while nitrite nitrogen concentrations were changing from 0.01 to 0.15 mg l-1; during the cold period of the year when filter load was fluctuating from 0.65 to 2.6 g m-2 d, ammonium and nitrite nitrogen concentrations in wastewater outflow were much higher and were fluctuating from 4.5 to 17.5 and from 0.1 to 1.15 mg l-1 respectively. No significant effect of the fluctuations of ambient temperature for the removal of ammonium and nitrite nitrogen was observed in HFCW (difference of average values of cold and warm periods was 3–8%). Rather reliable relation (R2 = 0.738) was determined between ammonium nitrogen concentrations in wastewater outflow and HFCW load according to total nitrogen, however ammonium nitrogen amounts in treated wastewater (when filter load according to total nitrogen is 0.3 to 4.6 g m-2 d) exceeded the maximum allowable rate and were fluctuating from 6 to 32 mg l-1. Keywords: ammonium, constructed wetlands, nitrites, nitrogen, wastewater treatment. *contact person Dr. Zenonas Strusevičius, senior researcher, Water Management Institute of Lithuanian University of Agriculture. Research interests: ecology and landscape management, the impact of the handling of wastewater and manure on the environment, investigation of pollutant transformation processes. Address: Parko 6, Vilainiai, LT-5048 Kėdainiai district, Lithuania. Phone: +370 34768020. E-mail: zenonas@water.omnitel.net. Valerijus Gasiūnas, senior researcher, Water Management Institute of Lithuanian University of Agriculture. Research interests – natural wastewater treatment methods. Dr. Sigita Marija Strusevičienė, scientific researcher of Water treatment laboratory at the Water Management Institute of Lithuanian University of Agriculture. Research interests: ecology and landscape management, the impact of the handling of manure, urine and wastewater on the environment. Received 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 44–56 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture CHANGES OF NITROGEN AND PHOSPHORUS CONCENTRATIONS IN STREAMS OF AGRICULTURAL CATCHMENTS Kazimieras GAIGALIS*, Antanas Sigitas ŠILEIKA, Aušra ŠMITIENĖ Summary Pollution sources in agriculture are outspread within a large area, therefore sometimes it is difficult to distinguish it without special observations. Since 1995, our institute has been carrying out investigations on the changes in surface water quality in different Lithuanian geographical regions depending on the variation of natural and agricultural conditions. Reasons of water quality changes in three agricultural catchments of the Graisupis (Lithuanian Middle Plain), the Vardas (Baltic Upland, Eastern Lithuania) and the Lyžena (Samigitian Upland, Western Lithuania) are analysed. The mean water runoff was 167, 241 ir 200 mm in the Graisupis, the Vardas and the Lyžena streams respectively during the period of 1996–2005. The mean total N concentration ranged from 8.0, 5.3 and 2.4 mg l-1 respectively and phosphorus oncentration was 157, 88 and 106 µg l-1 respectively. Positive correlation was found between yearly nitrogen (Ntotal and NO3-N) concentration in the Graisupis stream water and precipitation and the negative one was observed between nitrogen concentration in stream water and specific stream water runoff. Negative correlation occurs between total phosphorus concentration in the Graisupis stream water and the amount of precipitation, too. No correlation was established between the Vardas stream water nitrogen concentration and precipitation, temperature or water runoff. Some correlation exists between Ptotal concentration in stream water and precipitation, as well as water runoff and temperature. Only weak correlation was found between Ntotal concentration and air temperature in the Lyžena catchment. Other natural factors do not show any correlation. Current investigations show that natural factors have different impact on water quality in agricultural catchments located in different Lithuanian natural-geographical regions. Rather weak correlation between stream water quality and nature factors shows that other than natural factors regulate nitrogen and phosphorus losses into Lithuanian surface waters. Relation established between water quality in stream water and percentage of arable land in catchments shows that land use intensity influences water quality, too. Keywords: catchment, concentration, nitrogen, phosphorus, stream. *contact person 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. Address: Mituvos str. 9, LT–50134 Kaunas. E-mail: syzak@kaunas.init.lt. 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. Aušra Šmitienė, ph. student, Water Resources Sector, Water Management Institute of the Lithuanian University of Agriculture. Research interests – valuation and modeling of streams water quality. Received 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 57–66 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture MID-SIZED RIVER SPECIFIC WATER RUNOFF INFLUENCE ON NITRATE NITROGEN CONCENTRATION Saulius KUTRA*, Laima BERANKIENĖ Summary When predicting the pollution of river water, little attention is paid on the dependence of the pollution on water runoff from the basin. This is not the only criterion affecting river water pollution; however it is rather important and actually uncontrolled. Therefore when modeling pollution fluctuation processes in the river basin, it is fundamental to recognize and evaluate this relation. The paper presents the dependences of nitrogen concentrations and runoff module of four rivers: the Venta, the Lėvuo, the Šušvė and the Nevėžis upper reaches. The dependences were determined on the basis of the analysis of the whole year and divided it into the warm and the cold periods. As it was determined, when analyzing the whole year, the relation of nitrate nitrogen concentrations and runoff module is best reflected by the second-range polynomial mathematical model. When the year is divided into the warm and the cold periods, the relation mentioned is best reflected by the logarithmic model during each separate period. It was determined that for the evaluation of the pollution of the river basin a sensitivity criterion may be used, showing how the changing runoff module may induce changes of nitrate nitrogen concentration in the river water. This criterion is distinct for its individual fluctuation peculiarities that may be determined on the basis of the selected mathematical model of the relation. The sensitivity criterion may be expressed by a fixed figure – a constant, a straight line or a curve. As it was determined, increasing runoff module results in the decreasing sensitivity criterion and, if floods are evaluated, it may obtain negative values. From all the rivers studied under the conditions of low runoff module the most susceptible is the river Lėvuo, while the river Venta is the least sensitive one. Keywords: concentration, nitrate nitrogen, sensitivity to flow, specific flow. *contact person Dr. Saulius Kutra, the head of Water Protection Department, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, GIS, pollution modeling, application of remote sensing. Address: Parko 6, Vilainiai, LT-58102 Kėdainiai district, Lithuania. E-mail: kutra@water.omnitel.net. Dr. Laima Berankienė, senior researcher, Water protection department, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, hydrology, river pollution. Received 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 67–74 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture INFLUENCE OF DYKES on the dynamics of fine sediments and nitrate concentrations in the valley of the river Minija Alfonsas RIMKUS, Saulius VAIKASAS*, Summary When flood water overflows into the river, the valley is limited having arranged dykes of non-flooded winter polders. Water of the main river bed becomes more turbid and contains higher concentrations of nitrates due to the deposition of silt particles transported by the flow, decrease of water area and increase of the velocities of other parts of water flow. Using a mathematical hydrodynamic module DELTA, investigations of sedimentation and nitrate retention processes in the valley of the river Minija near Priekulė were carried out. As the study results have shown, dykes of the arranged winter polder Stragnai reduced the deposition of clay and silt particles as well as nitrate retention from 15 to 5 % (i.e., about 3 times). The arrangement of the additional non-flooded partition dyke of the valley has no major impact on those processes. The paper also discusses other possible variants of the arrangement and reconstruction of polders in the river valley. Keywords: dykes, flood flows, nitrate retention, sedimentation. *contact person Dr. habil. Alfonsas Rimkus, freelance researcher, Exploitation Laboratory, Water Management Institute of Lithuanian University of Agriculture. Research interests – hydraulics of hydrostructures, river bed processes. Dr. habil. Saulius Vaikasas, senior researcher, Exploitation Laboratory, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and landscape management, hydraulic modeling, river bed processes. Address: Parko 6, Vilainiai, LT–58102 Kėdainiai district, Lithuania. Phone: +370 347 6 81 09. E-mail: s.vaikasas@delfi.lt. Received 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 75-81 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture INVESTIGATIONS ON THE CHANGES OF SOIL PHYSICAL CHARACTERISTICS IN Earth DAM Povilas ŠUKYS*, Edmundas RAMOŠKA, Vaclovas POŠKUS Summary The paper presents the results of the studies of soil physical characteristics of the earth dam. With the help of the results obtained the authors have been trying to achieve the statistical substantiation or rejection of the changes of characteristics after 25 years of exploitation of the dam. As it was determined, soil density near the wet slope is higher in the lower part of the investigated layer, however further from the mentioned slope the density becomes higher in the upper part of the layer. Weak direct relation was determined between ground bulk density and skeleton contained in the ground in the investigated medium of the dam. In the fluctuation zone of the depression curve the ground bulk density is less than that in layers below or above this zone. The soil in the lower part of the layer situated below the depression curve is more saturated with water than the soil in the upper part. The regularity of changes of soil grain-size composition in the cross-sectional dam profile was determined: further from water surface of the pond towards the lower slope the amount of the finest particles is increasing. Such changes of grain-size composition is characteristic not only for the soil situated below the depression curve, but also for the soil above this curve that is affected by the filtration flow of gravitational water resulting from the precipitation. Keywords: earth dam, grain-size composition, ground bulk density, water filtration. *contact person Dr. Povilas Šukys, head of Geofiltration Research Department, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering, geofiltration, relations between the regime and pollution of surface and subsurface water. Address: Parko 6, Vilainiai LT-58102, Kėdainiai district, Lithuania. Phone: +370 687 74785. E-mail: lygis@water.omnitel.net. Dr. Edmundas Ramoška, senior researcher, Sector of Geofiltration Investigation, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering, regulation of water regime in mineral soils. Vaclovas Poškus, junior researcher of Exploitation Laboratory, Water Management Institute of Lithuanian University of Agriculture. Research interests – environmental engineering and natural processes in hydraulic engineering constructions. Received 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 82-87 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture APPLICATION OF CONSTRUCTED WETLANDS FOR THE TREATMENT OF WASTEWATER FROM MILK COLLECTION POST Simanas AŠKINIS Summary In 2003, an experimental wastewater treatment facilities of the milk collection post were arranged in Padargupiai village, in Ariogala (Raseiniai district). As the pollution of such kind of wastewater after primary treatment is twice higher than that of domestic wastewater, the filtration path in constructed wetlands was made twice longer (i.e. up to 10 m long). On the basis of the study results, dependence equations have been derived according to which the amounts of the main pollutants contained in wastewater after the filtration through the sand media of different depth have been calculated. As the calculations have shown, the treatment of wastewater from milk collection posts up to the allowable limits depends on the constructed wetlands with the filtration path of 7 m. After the filtration of wastewater through such kind of sand media, the removal of organic pollutants is 97.2%, the removal of total nitrogen and total phosphorus is 68.7% and 91% respectively. In order to reach a normative treatment level of wastewater from milk collection post according to BOD5, the reaction constant must be 0.12 when calculating the necessary area of constructed wetlands. The experimental wastewater treatment facilities release 4562 m3 of pre-treated wastewater per year. Together with wastewater, the natural environment receives 18 kg of organic pollutants, 30 kg of nitrogen and 0.8 kg of phosphorus per year. The reduction of wastewater filtration path in the constructed wetlands to 7 m would result in the increase in released pollutants amounts by 64, 20 and 2.6 kg respectively. Keywords: constructed wetlands, filtration path, primary wastewater treatment, treatment efficiency.
Dr. Simanas Aškinis, senior 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 and wastewater on the environment, researches on the transformational processes of pollutants. Address: Parko 6, Vilainiai 5048, Kėdainiai district, Lithuania. Phone: +370 347 6 80 20. E-mail: s.askinis@takas.lt. Received 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 88-94 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture EFFECT OF LAND USE ON THE RUNOFF Henrikas PAULIUKEVIČIUS Summary The paper analyzes changes of the runoff in basins of small creeks under the conditions of Middle Lithuania. The objective of the study was to determine how and how much runoff characteristics are influenced by the composition of land use. The study objects include two channels with different land use, i.e. the Kraujupis (basin area 1,75 km2, arable land covers 85%) and the Kolupė-1 (basin area 0,74 km2, woodedness is 99%), the total runoff observation period of which is 38 years. Historical material (i.e. data of measurements taken in small creeks of the Nevėžis basin within the period of 1968 to 1995) was also used during the research. During the whole study period the annual runoff depth was higher in the Kraujupis basin; the most significant difference was observed in dry years. However, the relation between the runoff depth relation Kraujupis/Kolupė and abundance of the year in water is not very close (r = 0.46). The most significant differences between the seasonal runoff of both channels occur in summer and autumn periods. The Kraujupis has never been totally dry during the whole season. Meanwhile the Kolupė-1 14 times was totally dry during the whole summer and 21 times was dry in autumn (more than a half of all cases). In this case the differences of basin areas as well as more intensive evaporation in forested basin might be influential. In 1959–1990, spring rates of discharge were nearly similar, while since 1990 rates of the Kolupė-1 discharge were lower all the time. Perennial changes of the peak rates of discharge of spring flood runoff were similar in both channels, however higher rates of discharge occurred in the Kraujupis more often. In forested basin during the study period the spring flood occurred 5,6 days later on the average, however the duration of the flood was similar in both river basins. At the end of the period of low abundance in water and at the beginning of the period abundant in water, in basins of Middle Lithuanian channels with different land use, weak and average inverse correlation of annual rate of discharge with woodedness of the basin was observed (r = -0.238 -0.525), and direct correlation of annual rate of discharge with the areas of arable land was determined (r = 0.199 -0.551). No significant correlation between annual runoff rate of discharge and basin area was observed (r = -0.238 -0.401). Relations of the peak spring rate of discharge with land use areas are weak and unreliable. Keywords: land use, runoff, woodedness.
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 12 2006. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 95-103 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture INVESTIGATIONS ON THE EFFECT OF CONDITION OF DITCHES ON THE EFFICIENCY OF USAGE OF DITCH MAINTENANCE TECHNIQUE Stasys Ragauskas Summary When doing the mechanized maintenance of ditches, one of the factors of efficient work is suitable machine driving conditions along the ditch stretches. To evaluate objectively the mentioned conditions, 680 randomly selected ditch stretches (100 m each) were investigated. As it was determined, machine driving conditions depend on many different obstacles: unevenness of the micro relief of driving strip, its transverse declination and the appearance of vegetation cover on it. Using the Dutch ditch maintenance equipment in stretches of analogous condition, the effect of different factors of ditch condition on the indices of efficiency was determined using different work equipment. Due to obstacles occurring every 206 meters, when mowing slopes with a disc mower the working velocity decreases by 7.5% on the average; while due to inappropriate micro relief enhancing the transverse conversion of the machine the working velocity is reduced 1.9 to 3.3 times. In the slope strips where there is no enough space of ditch protection belt to drive the machine, and its one wheel must go on the arable land, the working velocity as well as other capabilities of the machine decrease due to the difference of track heights as well as due to the insufficient adhesion of wheels with the ditch slope. When using cycle operations (when mowing or bed treatment are performed when the tractor is standing across the ditch), to overtake obstacles made by mowing bucket about 0.5% of total time are needed; meanwhile, no effect of ditch micro relief and vegetation cover on low working velocity of the machine (when the length of the bucket is fitted) were observed. When making ditch maintenance, it is enough to use this equipment only once; however, when mowing with a disc mower this mostly depends on the number of swathes on the slope and the possibility to mow both slopes during one track. In the case if only one slope is mown (due to the absence of spillway or swampy ditch slope), the number of drives is doubled. In such case the work efficiency due to purposeless drives is almost as much. During the investigations it was determined that the ditch stretch necessary to drive any of the machinery mentioned is to be no narrower than 3 meters. Keywords: cross-declination, driving track of the ditch, micro-relief, working velocity. ISSN 1392–2335 Water Management Engineering, 30(50), 2006, 104-108 © Lithuanian University of Agriculture © Water Management Institute of Lithuanian University of Agriculture calculation of water-supply CIRCULAR networks EVALUATING THE effect OF adjacent rings Rymantas PEKUS Summary Complex calculation of water-supply, ventilation and water heating systems is performed in accordance with the methods of Lobachiov and Cross using simple software applications. There are cases when it is impossible to match the network. This article deals with the analysis of the source where it is impossible to match network and a new calculating method evaluating the effect of adjacent rings is recommended. This method is accelerating the iteration process and can possibly adapt circular networks for all calculated cases. Keywords: circular pipe network, Cross method, correction for discharge, iteration. |
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