|De geschiedenis van het hydraulica laboratorium
Warmerdam, Piet ; Dommerholt, Anton - \ 2017
Wageningen : Wageningen University & Research, Leerstoelgroep Hydrologie en Kwantitatief Waterbeheer (HWM) - 137
hydraulica - geschiedenis - laboratoria - hydraulics - history - laboratories
Dit boek beschrijft een halve eeuw geschiedenis van het vakgebied van de Wageningse hydraulica, die de stroming van water in open waterlopen en gesloten leidingen bestudeert.
Handboek geomorfologisch beekherstel : leidraad voor een stapsgewijze en integrale ontwerpaanpak
Makaske, B. ; Maas, G.J. - \ 2015
Amersfoort : Stichting Toegepast Onderzoek Waterbeheer (Rapport / STOWA 2015-02) - ISBN 9789057736612 - 188
geomorfologie - waterlopen - herstel - hydraulica - landschapsbouw - natuurtechniek - geomorphology - streams - rehabilitation - hydraulics - landscaping - ecological engineering
Om de verschillende aspecten van beekherstel te belichten staat in dit deel de geologische en morfologische processen van beken centraal. Aanleiding voor dit boek is dat in veel beekherstelprojecten de beekbedding een nieuwe vorm krijgt. In de praktijk bestaan er veel vragen over het ontwerp en de vormgeving van deze nieuwe beddingen. Het gaat hierbij om de vraag wat het ‘juiste’ ontwerp is en wat de te verwachten afvoerdynamiek is van de herstelde beek. In dit handboek worden theorie en praktijk gecombineerd. U vindt een praktisch stappenplan voor het ontwerpproces, maar ook een theoretisch kader. Ook worden enkele praktijkvoorbeelden gegeven.
Hydraulic and operational performance of irrigation schemes in view of water saving and sustainability : sugar estates and community managed schemes In Ethiopia
Dejen, Z.A. - \ 2015
Wageningen University. Promotor(en): E. Schultz, co-promotor(en): S.B. Awulachew; L. Hayde. - Leiden : CRC Press/Balkema - ISBN 9789462571693 - 165
irrigatie - irrigatiewater-toedieningsschema - hydraulica - duurzaamheid (sustainability) - water - ethiopië - waterbeheer - irrigation - irrigation scheduling - hydraulics - sustainability - water - ethiopia - water management
The rate of global expansion of irrigated lands has been declining since the 1970s due to the fact that most of the potential for large and medium-scale irrigation schemes has been developed. This rate of decline is also expected to continue in the next decades. As such significant proportion of the expected increase in production would have to be supplied from the existing irrigated and /or cultivated lands. This in turn could be achieved by improving land and water productivity in the existing schemes through ensuring better performance and optimal operation and maintenance.
With less than 15% of over 5 million ha irrigation potential developed, irrigated agriculture in Ethiopia remained low. The largest proportion of the developed irrigation in the country belongs to small-scale irrigation by smallholder farmers. While accelerated development of new irrigation, particularly of large and medium-scale schemes is relevant in Ethiopia, performance and sustainability of existing schemes is equally important. The existing irrigation schemes in Ethiopia are generally characterized by overall performance and technical sustainability levels below expectation.
The research presented in this thesis evaluates the performance of two large-scale and two small-scale community-managed irrigation schemes located in the Awash River Basin of Ethiopia. The research focussed on hydraulic/water delivery performance in the large-scale schemes and on comparative performance assessment and internal irrigation service utility evaluation in the community-managed schemes. It was found that hydraulic, operational and institutional aspects play a significant role in the overall performance of the irrigation schemes. Major performance challenges were addressed and operational/water management options for improvement were proposed for each case.
Effect of flow discharge and median grain size on mean flow velocity under overland flow
Ali, M. ; Sterk, G. ; Seeger, K.M. ; Stroosnijder, L. - \ 2012
Journal of Hydrology 452-453 (2012). - ISSN 0022-1694 - p. 150 - 160.
shallow-water flow - semiarid hillslope - soil-erosion - channel flow - hydraulics - transport - surfaces - rills - rough
Precise estimation of mean flow velocity (U-mean) is imperative for accurate prediction of hydrographs and sediment yield. For overland flow, U-mean is normally estimated by multiplying the dye or salt based velocity measurement with a correction factor (alpha). A wide range of correction factors is available in the literature, all of which were derived under different experimental conditions. The selection of a suitable a has become a main challenge for accurate mean flow calculations. This study aimed to assess the variability of a with grain size (D-50) and slope (S), and to evaluate the dependency of U-mean on flow rate (Q), D-50 and S by regression analysis. Flume experiments were performed at Q varying from 33 to 1033 x 10(-6) m(3) s(-1), S ranging from 3 degrees to 10 degrees, and D-50 ranging from 0.233 to 1.022 mm. Flow velocities were measured directly with the dye tracing technique (U-dye), and derived indirectly from flow depth measurements (U-depth). The Udepth measurements were considered as U-mean. The derived alpha (U-depth/U-dye) values did not remain constant with sediment size and increase significantly with the increase of D-50. The mean alpha values for 0.230, 0.536, 0.719 and 1.022 mm sands were 0.44, 0.77, 0.82 and 0.82, respectively. Hence, due to the substantial variation of alpha with D-50, no absolute alpha value is applicable to all hydraulic and sedimentary conditions. However, mean alpha values for 0.230, 0.536 and 0.719 mm sands were found comparable with alpha values available in the literature for similar grain sizes. The influence of Q S. and D-50 on U-mean was studied by regression analysis. Regression analysis depicted the significant influence of Q and D-50 on U-mean. while the effect of slope was found to be non-significant. Comparison of the derived regression equation with five literature datasets showed that the model can predict mean flow velocities in overland flow at a reasonable accuracy as long as the mean velocity is below 0.4 m s(-1). At higher velocities the error becomes unacceptably large.
Toekomst van de Vecht als een halfnatuurlijke laaglandrivier : bouwstenen bij de grensoverschrijdende Vechtvisie 2009
Wolfert, H.P. ; Corporaal, A. ; Maas, G.J. ; Maas, K. ; Makaske, B. ; Termes, P. - \ 2009
Wageningen : Alterra (Alterra-rapport 1897)
ecologisch herstel - natuurontwikkeling - rivierregulering - geomorfologie - hydraulica - monitoring - rivieren - salland - ecological restoration - nature development - river regulation - geomorphology - hydraulics - monitoring - rivers - salland
Dit boekje wil bouwstenen aanreiken voor het proces dat herstel van de Vecht naar een halfnatuurlijke laaglandrivier beoogt. In combinatie vormen deze bouwstenen een samenhangend beeld van de Vecht, dat op lange termijn (over enkele decennia) gerealiseerd zou kunnen worden. De set van bouwstenen vormt een overkoepelende strategie, waarop kan worden teruggevallen bij planvorming en toekomstige uitvoeringsprojecten. Dit boekje is het resultaat van het herstelonderzoek Vecht, dat in de periode december 2008-maart 2009 is uitgevoerd door Alterra, HKV en KWR in opdracht van Waterschap Velt en Vecht, Waterschap Groot Salland en de Provincie Overijssel. DHV coördineerde het overleg tussen stuurgroep en projectgroep, alsmede de afstemming met het werk aan de Duits-Nederlandse Vechtvisie en het samenwerkingsprogramma Ruimte voor de Vecht.
Process description of SWQN : A simplified hydraulic model
Smit, A.A.M.F.R. ; Siderius, C. ; Gerven, L.P.A. van - \ 2009
Wageningen : Alterra (Alterra-rapport 1226.1) - 54
hydraulica - modellen - peilbeheer - stuwen - duikers - pompen - waterlopen - waterstroming - hydraulics - models - water level management - weirs - culverts - pumps - streams - water flow
SWQN is a simplified hydraulic model for surface water systems which computes water levels and flows in a network of nodes labelled as ‘volumes’ and segments labelled as ‘connectors’. The user can specify a variety of connectors like open water courses or structures such as weirs, gates, culverts or pumps. Water levels are calculated in the ‘volumes’ driving the one dimensional flows through the ‘connectors’ linking up the ‘volumes’. The assumption is that the flow between two nodes with an open connection in between is linearly dependent on the difference in water level, if necessary augmented with the difference in velocity head, the wetted profile, and a given resistance.
Estimating Manning's n for steep slopes
Hessel, R. ; Jetten, V.G. ; Zhang, G.H. - \ 2003
Catena 54 (2003)39479. - ISSN 0341-8162 - p. 77 - 91.
eroding rills - overland-flow - hydraulics - roughness - velocity
Hydrological and soil erosion models require calculations of flow velocity, for which either the Darcy-Weisbach or the Manning equation is generally used. A series of field experiments was carried out in a small catchment on the Chinese Loess Plateau to obtain reliable values of Manning's n. The soils are typically erodible loess soils. The experiments were conducted for a range of land uses as well as for different slope angles (6¿64%). Measurements were performed on a 2.5×0.4 m plot, on which flow was allowed to find its own path. Water was evenly applied to the top of the plot and discharge, surface velocity, flow width and slope were measured. The results show that Manning's n can, just like Darcy-Weisbach f, be estimated from Reynolds number. Furthermore, for croplands, there is an apparent linear increase in Manning's n (and f) with increasing slope angle (R2=0.70). As Manning's n is usually assumed to be constant, this must mean that either velocity increases with slope or hydraulic radius decreases. The measurements showed virtually no increase in velocity and a minor increase in hydraulic radius with slope, as flow was more concentrated on steeper slopes. Possible explanations for this lack of increase in velocity include increased roughness [Water Resour. Res. 37 (2001) 791], decreased effective slope angle because of the development of vertical head cuts and a shift in energy use. All three hypotheses only apply to situations involving erosion. The trend of Manning's n with slope implies that, in soil erosion models using Manning's equation (or Darcy-Weisbach), the value of n (or f) should be a function of the slope for erodible soils. For non-erodible soil (as in woodland), no increase in Manning's n with slope was observed.
Nutriënten in stromende wateren; een verkenning van ecologisch relevante hydrologische en hydraulische modelkenmerken
Verdonschot, P.F.M. - \ 2002
Wageningen : Alterra (Alterra-rapport 516a) - 80
hydrologie - waterlopen - ecologie - modellen - voedingsstoffen - hydraulica - simulatiemodellen - oppervlakkige afvoer - rivierafvoer - waterbeheer - milieu - nutriënten - oppervlaktewater - hydrology - streams - ecology - models - nutrients - hydraulics - simulation models - runoff - stream flow - water management
Het doel van deze studie was het zoeken naar ecologisch relevante modelkenmerken in een beperkt aantal beschikbare en goed beschreven hydrologische en hydraulische modellen die gebruikt kunnen worden als bouwstenen van een nieuw te ontwikkelen nutriëntenmodel voor stromende wateren. De algemene conclusie is dat alle onderzochte modellen en rekenpakketten min of meer een eigen keuze van relevante processen bevatten. Dit kan ingegeven zijn door de voorkeur van de bouwer, het doel van het model of de beschikbare informatie. Voor een advies over relevante processen in een nieuw te bouwen model geeft dit onderzoek weinig houvast. De bestaande modellen zijn niet gebouwd voor ecologische doelen en voldoen niet aan de eisen die nodig zijn bij toepassing voor een ecologische normering. Een raamwerk voor een nieuw te ontwikkelen laaglandbekenmodel wordt voorgesteld.
De relatie tussen de macrofauna in beken en de sleutelfactoren hydraulica en substraat bij veranderend klimaat
Higler, L.W.G. - \ 2002
Wageningen : Alterra (Alterra-rapport 230) - 59
waterlopen - klimaatverandering - temperatuur - regen - aquatische gemeenschappen - hydraulica - waterstroming - afvoer - macrofauna - aquatische ecosystemen - aquatische ecologie - beken - fauna - hydrologie - neerslag - piekafvoer - waterhuishouding - streams - climatic change - temperature - rain - aquatic communities - hydraulics - water flow - discharge - macrofauna - aquatic ecosystems - fauna
Klimaatverandering in stroomgebieden van de gematigde zone zal resulteren in hogere (zomer)temperaturen en veranderingen in het neerslagpatroon. In dit literatuuronderzoek wordt geanalyseerd welke effecten op kunnen treden op de macrofaunagemeenschappen in beken als gevolg van een veranderend neerslagpatroon. De macrofauna reageert op (veranderingen in) de hydraulische factoren als stromingspatroon en stroomsnelheid, die onder andere de substraatsamenstelling in beken bepalen. Verminderde wateraanvoer enerzijds en piekafvoeren anderszijds behoren eveneens tot de mogelijkheden bij klimaatverandering. Naar verwachting zullen kritische soorten, die alleen onder bepaalde condities in stromende wateren kunnen leven, minder vaak gaan voorkomen of helemaaluit Nederland verdwijnen.
Sediment transport in irrigation canals
Mendez V., N.J. - \ 1998
Agricultural University. Promotor(en): E. Schultz; L.C. van Rijn. - Rotterdam etc. : Balkema - ISBN 9789054104131 - 285
irrigatiewater - transport - waterverdeling - hydrodynamica - hydraulica - suspensies - sediment - irrigation water - transport - water distribution - hydrodynamics - hydraulics - suspensions - sediment
The world population is rapidly increasing and is expected to double to about 10 billion by the year 2050. To support an increasing population in terms of food sufficiency, more and more water will be required. Irrigation is the most critical component of the modern package of inputs to effect high crop production. Irrigation has been the largest recipient of public agricultural investment in the developing world. Hence, continued investment in irrigation along with reforms in institutional arrangements for management of water are very much necessary to ensure adequate supply of food. Simultaneously, water requirements for other purposes, domestic, industrial and hydropower will steadily increase as well. Under this competing situation irrigation will have to become increasingly more efficient in the future.
Improved management and operation activities must be implemented to prevent recurring degradation of irrigation projects. Clogging of turnouts and reduction of the conveyance capacity of canals by siltation are problems frequently met in irrigation systems. Annually, high investments are required for rehabilitation of irrigation systems in order to keep them suitable for their purposes. New development of irrigation projects or upgrading of existing schemes will require a better understanding of the sediment transport process under the prevailing flow conditions in irrigation canals. Applicability of the existing sediment transport relationships on irrigation canals has to be better understood. In this way predictions on sediment deposition in irrigation canals will be more reliable.
The present study is focused on sediment transport in irrigation canals which may have a serious impact on the operation and maintenance activities. The design of the canal system either should be based on the transport of all the in the water present sediment to the fields or to places in the canal system, where the deposition can be removed with least costs. Sedimentation should be prevented in canals and near structures, as it will hamper and endanger a proper irrigation management. In the design and operation of irrigation canals with sediment-laden water several aspects related to irrigation criteria and sediment transport must be taken into consideration. The need for conveying different discharges at a required water level to meet the irrigation requirement and at the same time to convey the sediment load with a minimum deposition and/or erosion in the canal system should be the main criteria for the canal design. Irrigation canals are generally designed upon the assumption of uniform and steady flow.
It is also assumed that there exists an equilibrium situation where the sediments entering into the irrigation canals will be transported without settling or erosion. However, uniform and steady flow are seldom found in reality. In the operation of an irrigation system the flow is predominantly non-uniform. While the sediment transport is highly dependent on the flow conditions it is obvious that the sediment transport capacity of the canals varies as well.
Development on sediment transport in open channels have been mainly focused on river engineering. Even though certain similarities between rivers and irrigation canals are present, these concepts are not fully applicable to irrigation canals. A description and analysis of the sediment transport concepts under the specific conditions of irrigation canals will contribute to improve the understanding of these concepts and will help to decide on the applicability of them on simulation of the sediment transport processes for particular conditions of water flow and sediment inputs. A mathematical model which includes sediment transport concepts for the specific conditions of irrigation canals will become an important and timely tool for designers and managers of those systems.
The aim of this research is to present a detailed analysis of the sediment transport processes, a physical and mathematical description of the behaviour of sediment transport under flow conditions encountered in irrigation canals and to develop a model to predict sediment transport and the deposition or entrainment rate for various flow conditions and sediment inputs.
Sediment transport processes
Sediment transport and water flow are interrelated and cannot be separated. From a mathematical point of view the interrelation can be described for a one-dimensional phenomenon without changes in the shape of the cross section by the following equations:
Water flow equations : although one-dimensional flow hardly can be found in nature, water flow in an irrigation canal will be considered to be one-dimensional. Under this assumption, the general equations for one dimensional flow can be described by the Saint Venant equations. The amount of water flowing into irrigation canals during the irrigation season and moreover during the life time of irrigation canals is not constant. For the time depending changes in the bottom of the canal the water flow can be easily schematized as quasi-steady which means that the time depending factors in the Saint Venant equations can be neglected.
Resistance to flow : the resistance to flow in open channels is affected by several factors, among which the development of bed forms play an important role. Determination of the friction factor of a movable bed is a complex problem that requires knowledge of an implicit process of flow conditions and bed form development. In order to predict the type of bed forms in irrigation canals the theories developed by Liu, Simons and Richardsons, Bogardi and van Rijn were compared to a selected set of laboratory and field data. Also a comparison of the most widely used methods to predict the resistance to flow with field and flume data has contributed to select an appropriate method for similar situations. The selected methods for predicting the resistance to flow were: White, Bettes and Paris (1979), Brownlie (1983) and van Rijn (1984c).The objective was to find the appropriate theories to describe the bed form and to estimate the resistance to flow (friction factor) in irrigation canals.
From the performance of each predictor of bed form type and friction factor method when compared with selected field and laboratory data some conclusions can be drawn:
Another important feature related to the resistance of water flow in irrigation canals is the estimation of the friction factor of a irrigation canal with composite hydraulic roughness. The development of bed forms on the bottom, different material on the bottom and side of the canal or vegetated side banks are typical situations for the composite roughness conditions in irrigation canals. The most common cross sections in irrigation canals are the trapezoidal and rectangular cross section with a relatively small value for the bottom width-water depth ratio. In these cross-sections the velocity distribution is strongly affected by the varying water depth on the side slope and the boundary condition imposed to the velocity at the side wall. A method to estimate the effective roughness in a trapezoidal canal with composite roughness along the wetted perimeter which uses the theoretical velocity distribution in the cross section, is proposed.
In order to predict the effective roughness in irrigation canals with composite roughness, the existing methods for predicting the effective roughness and the proposed method in this study have been compared with a selected set of laboratory data, which has been collected in the hydraulic laboratory of the Wageningen Agricultural University. The aim of the experiments has been to investigate the friction factor in a trapezoidal canal having varying roughness on side and bottom and to find an appropriate method to estimate the friction factor in a non-wide canal with different roughness along the wetted perimeter. From the comparison the main conclusion can be drawn that the proposed method gives better results than the other methods.
For rectangular cross sections with composite roughness the existing methods for estimating the effective roughness can not explicitly be used. Therefor it is proposed to estimate the composite roughness in rectangular cross sections by the same principle as used for the side wall correction. The procedure to estimate the effective roughness in rectangular cross sections has been tested with a selected set of laboratory data used by Krüger. The proposed method predicts more than 95% of the measured values of the composite roughness within a range of error of 15%.
Sediment transport equations : sediment transport equations are related to the way in which the sediment is transported: namely in equilibrium and non-equilibrium condition.
Sediment transport predictors for equilibrium conditions have been established for different conditions. The use of those equations should be restricted to the conditions for which they were developed. However a comparison of the different equations under similar flow and sediment characteristics, both in irrigation canals and from field and laboratory data will be a useful tool to evaluate the suitability of each equation under these particular flow conditions. In this study, five of the most widely used equations to compute sediment transport have been compared, namely the Ackers and White, Brownlie, Engelund and Hansen, van Rijn and Yang equations. These equations have been compared with field and laboratory data. The objective was to find more reliable predictors of the sediment transport capacity under the flow conditions prevailing in irrigation canals. From that evaluation some remarks can be drawn:
Sediment transport theories have been developed for wide, open channels. Most of the man-made irrigation canals are not considered as wide canals. Recommended values for the ratio of bottom width and water depth (B/h) in those canals are smaller than 8. Existing methods for calculating the total sediment transport capacity for the entire cross section of a non-wide canal do not take into account the velocity distribution over the cross section. A new method to compute the total sediment transport by using a cross section integrated method is proposed, which is based on the assumption of a quasi two-dimensional model. The objective is to consider the effect of the side banks on the distribution of velocities and to adapt the sediment transport predictors for computing the sediment transport for the entire cross section of a non-wide canal. The existing methods and the proposed method to compute the total sediment transport in non-wide canals were compared with a selected set of laboratory data. Based on the overall comparison the proposed method gives better results than the existing methods for computing the sediment transport capacity for the whole cross section.
An interesting phenomenon of the non-equilibrium sediment transport in irrigation canals is the adjustment of the actual sediment transport to the sediment transport capacity of the irrigation canal. To simulate the sediment transport under non-equilibrium conditions, the Gallapatti's depth integrated model for adaptation of the suspended load has been used. It has been assumed that the adaptation length for bed load is the same adaptation length for suspended load. Therefore the Gallapatti's depth integrated model can be used to describe the approach of the total sediment concentration to the transport capacity of the irrigation canal.
Application of mathematical modelling of sediment transport in irrigation canals
In order to simulate the sediment transport in irrigation canals, a computer program (SETRIC) has been developed. The computer program can simulate water flow, sediment transport and changes of bottom level in a network composed by a main canal and several laterals with/without tertiary outlets. Also some hydraulics structures are included in the program: overflow and undershot type, submerged culverts and inverted siphons, flumes and drops.
The computer program is based on a sub-critical, quasi-steady, uniform or non-uniform flow (gradually varied flow). The water flow can be simulated in open channels, with a rectangular or trapezoidal cross section with single or composite roughness. Only friction losses are considered. No local losses due to changes in the bottom level, cross section or discharges are taken into account. However, changes in the bottom level are included.
Sediment characteristics are defined by the sediment concentration at the head of the canal and sediment size is characterized by the mean diameter d 50 . The range of values is 0.05 mm≤d 50 ≤0.5 mm. A uniform sediment size distribution has been assumed.
The simulation periods take into account the variation of the irrigation water requirement during the growing season. The growing season is divided into four stages depending on the crop development and climate conditions. The program assumes a maximum of four different periods in which the discharges along the system can be varied.
Maintenance activities can also be included into the program. Those maintenance activities are referred to the obstruction degree due to weed growth on the banks and by its effect on the roughness condition of the canal. From that point of view three types of maintenance are included in the program: ideal maintenance, well maintained and poor maintained.
Some applications of the model to simulate sediment transport in irrigation canals are shown. The results can not be generalized so that they can only be applied for the local flow conditions and sediment characteristics of each application. The applications are meant to show the applicability of the model and to improve the understanding of the sediment transport process for situations usually encountered in irrigation systems. The sediment deposition in an irrigation canal during a certain period will be simulated for each of the different applications. The sediment transport capacity of the irrigation canal is computed according to the Ackers and White's predictor method. The adjustment towards the sediment transport capacity is according to the Gallapatti's depth integrated model. A sediment mass balance in each reach of the canal will give either the net deposition or net entrainment between the two boundaries of a specific canal reach. From the application cases some conclusions are drawn:
Changes of discharges : during the simulations for reductions of discharge to 80% of the design value (equilibrium condition), more than 40% of the incoming sediment load was deposited.
Changes in the incoming sediment load : the effect of changes in the incoming sediment load on the sediment transport include the effect of variations in the incoming sediment concentration and in the median sediment size during the irrigation season and/or the lifetime of an irrigation canal. For 100% of variation in the incoming sediment concentration about 30% of the incoming sediment load is expected to settle into the canal. A similar behaviour is observed for the case of changes in the design value of the median size of the incoming sediment. For instance a total of about 45% of the incoming sediment during the simulation period is deposited when the sediment size deviates 100% from the equilibrium size.
Controlled sediment deposition : two scenarios to concentrate the sediment deposition at the head reach of a canal were simulated. They can be described as: widening (scenario 1) and deepening (scenario 2). No additional considerations for optimizing economical cost and sediment deposition were done. For the specific flow and sediment transport conditions scenario 2 trapped 4 times more sediment than an irrigation canal without control and 1.3 times more than scenario 1.
Sediment transport predictor : large differences in the computed sediment deposition were observed among the sediment transport predictors. The hydraulic conditions during the simulation period gave a low sediment transport capacity for the Engelund and Hansen predictor and larger for Brownlie and Ackers and White predictors. By using the Engelund and Hansen's predictor the sediment deposition was 2 and 3 times more that the Brownlie and Ackers and White's predictors respectively.
Flow control structures : two types of flow control structures were compared: overflow type and undershot type. The observed total deposition in both cases is rather similar. A larger difference was observed in the distribution of the sediment deposition along the canal. That difference was mainly concentrated in the upstream part of the structure.
Maintenance activities : maintenance was related to weed infestation and it was simulated by assuming optimal maintenance and no maintenance at all during the irrigation season. No direct effect of the growth of the weed on the sediment transport is considered. More sediment deposition was observed in the ideally maintained canal than the non-maintained canal. Due to the constant water level at the downstream side of the irrigation canal the flow condition within the canal behaved as: in the ideally maintained canal a gradually varied flow (backwater curve) remained constant during the simulation period. A continuous deposition was observed during all the time along the irrigation canal. In the non-maintained canal the initial flow condition changed in time from a backwater curve to a drawdown curve due to the constant water level at the downstream end and due to the variation of the water level within the canal imposed by the variation of the roughness condition. A sediment deposition period followed by an entrainment period was observed during the irrigation season.
Operation activities : for simulating the effect of the operation procedures on the sediment deposition in the main canal four scenarios were investigated. The four scenarios are: scenario 1 (continuous flow); scenario 2 (rotational flow by hour); scenario 3 (rotational flow by day); scenario 4 (rotational flow by week). From the comparison the following conclusions can be drawn:
By considering the results of the applications of the mathematical modelling, it can be concluded that model is a useful tool for assessing the sediment deposition within irrigation canals under different flow conditions and sediment characteristics. Nevertheless, the mathematical model's performance can most probably be improved when it is applied in more situations. Monitoring of the sediment deposition in irrigation networks is required to evaluate the model under specific conditions and to investigate the response in time and space of the bottom level to determined water flows and sediment characteristics. Influences of the type and operation of flow control structures, geometrical characteristics of the canals, water flow and incoming sediment characteristics on the deposition, which the mathematical model predicts, will contribute to a better understanding of the sediment transport processes in irrigation canals.
Hydrodynamics, sediment transport and light extinction off Cape Bolinao, Philippines
Rivera, P.C. - \ 1997
Agricultural University. Promotor(en): L. Lijklema; W. van Vierssen. - Rotterdam : Balkema - ISBN 9789054104087 - 244
delta's - estuaria - hydraulica - hydrodynamica - rivieren - waterlopen - kanalen - water - geologische sedimentatie - kusten - modellen - theorie - onderzoek - oceanografie - deltas - estuaries - hydraulics - hydrodynamics - rivers - streams - canals - water - geological sedimentation - coasts - models - theory - research - oceanography
Observational and numerical modelling studies of the hydrodynamics, sediment transport, and light extinction were undertaken in the marine environment around Cape Bolinao in the Lingayen Gulf (Northwest Philippines). Abundant with ecologically important seagrasses and benthic organisms, Cape Bolinao is presently threatened with siltation and eutrophication problems. For this reason intensive field measurements of relevant enviromnental variables which include currents, tides, temperature, salinity, total suspended solids (TSS), ash-free dry weight (AFDW), sedimentation flux, grain size distribution and organic content of bottom sediments, gilvin absorption, phytoplankton concentration, and light extinction were executed from August 1993 to June 1995. Laboratory experiments were simultaneously undertaken to determine the sedimentation and light extinction characteristics of various sediment fractions. Using time series and regression analyses, the results were analyzed and presented. A set of numerical models were developed and applied in the area around Cape Bolinao and the Lingayen Gulf. A prognostic model for the hydrodynamics, driven by realistic wind and tide forces, was developed independently for the cape (fine-resolution model) and the gulf (coarse resolution model). An operational open boundary condition based on the method of wave propagation is discussed. The hydrodynamical predictions were used, in conjunction with a diagnostic surface wave model, to force the suspended sediment transport model. The transport model, which is based on the time-dependent advection-diffusion equation, is third order accurate in space and time. For a realistic description of the suspended sediment transport process in Cape Bolinao, resuspension and sedimentation fluxes were included in the numerical model using existing parameterizations. The predicted suspended sediment concentrations were used in a diagnostic model for light extinction. This later model is based on the assumption that the contributions of the optically active components to the attenuation of the photosynthetically available radiation (PAR) are linearly additive. Calibration of the numerical models using field observations produced a set of parameter values which is deemed representative for the area of investigation. Using these parameter values, the overall model predictions were in good agreement with field observations. Finally, using the integrated model, the impact of river sediment loads (treated as a conservative tracer) in the Bolinao reef system was quantified.
Morra park : voorlopige resultaten grond- en oppervlaktewater meetnet.
Arts, M.P.T. ; Dijksma, R. - \ 1995
Wageningen : Landbouwuniversiteit Wageningen (Rapport / Landbouwuniversiteit, Vakgroep Waterhuishouding 65) - 9
kanalen - hydraulica - hydrodynamica - hydrologie - instrumenten (meters) - meting - monitoring - rivieren - waterlopen - stedelijke gebieden - water - nederland - friesland - gemeenten - netwerken - canals - hydraulics - hydrodynamics - hydrology - instruments - measurement - monitoring - rivers - streams - urban areas - water - netherlands - friesland - municipalities - networks
Pyriet in afzettingen bij het Pompstation Vierlingsbeek : een micromorfologisch en geochemisch onderzoek
Bisdom, E.B.A. ; Breeuwsma, A. - \ 1990
Wageningen : Staring Centrum (Rapport / Staring Centrum 56) - 53
grondwaterwinning - horizontale bronnen - hydraulica - hydrodynamica - pyriet - monolietpreparatie - sediment - suspensies - slijpplaatje preparatie - nederland - noord-brabant - groundwater extraction - horizontal wells - hydraulics - hydrodynamics - pyrites - monolith preparation - sediment - suspensions - thin section preparation - netherlands - noord-brabant
Rivierdynamiek en vegetatieontwikkeling
Knaapen, J.P. ; Rademakers, J.G.M. - \ 1990
Wageningen : Staring Centrum (Rapport / Staring Centrum 82) - 84
kanalen - ecologie - inundatie - overstromingen - graslanden - hydraulica - hydrodynamica - hydrologie - landschap - landschapsecologie - natuurreservaten - plantengemeenschappen - polders - prairies - herstel - rivieren - waterlopen - vegetatie - water - wetlands - ecohydrologie - natuurtechniek - natuur - canals - ecology - flooding - floods - grasslands - hydraulics - hydrodynamics - hydrology - landscape - landscape ecology - nature reserves - plant communities - polders - prairies - rehabilitation - rivers - streams - vegetation - water - wetlands - ecohydrology - ecological engineering - nature
The fall velocity of grain particles.
Ieperen, H.J. van - \ 1987
Wageningen : Landbouwuniversiteit Wageningen (Research report / Agricultural University, Department of Hydraulics and Catchment Hydrology 83) - 17
kanalen - vloeistofmechanica - geologische sedimentatie - hydraulica - hydrodynamica - meren - vloeistoffen (liquids) - mechanica - plassen - reservoirs - rivieren - sediment - waterlopen - suspensies - water - canals - fluid mechanics - geological sedimentation - hydraulics - hydrodynamics - lakes - liquids - mechanics - ponds - reservoirs - rivers - sediment - streams - suspensions - water
De berekening van instationaire stroming in open waterlopenstelsels met een boomstructuur
Baalen, D.J.N. van; Witter, J.V. - \ 1985
Wageningen : Landbouwuniversiteit Wageningen (Nota / Landbouwuniversiteit, Vakgroep Hydraulica en Afvoerhydrologie 66) - 40
kanalen - kanalen, klein - stroming - doorstroommeters - vloeistoffen (fluids) - hydraulica - hydrodynamica - vloeistoffen (liquids) - wiskunde - meting - rivieren - rivierafvoer - waterlopen - turbulentie - water - waterwegen - wind - numerieke methoden - canals - channels - flow - flow meters - fluids - hydraulics - hydrodynamics - liquids - mathematics - measurement - rivers - stream flow - streams - turbulence - water - waterways - wind - numerical methods
|Het ontwerpen van hydrostatische overbrengingen = Designing hydrostatic transmissions
Straelen, B.C.P.M. van - \ 1982
Wageningen : I.M.A.G. (Publikatie / Instituut voor Mechanisatie, Arbeid en Gebouwen no. 175) - 74
besturingsonderdelen - ontwerp - verspreiders - aandrijfmechanismen - versnellingen - hydraulische krachtsystemen - hydraulica - theorie - tractie - kleppen - machines - control components - design - distributors - drives - gears - hydraulic power systems - hydraulics - theory - traction - valves - machines
Naslagwerk ten behoeve van ontwerpers van landbouwwerktuigen over de theoretische achtergronden en de mechanica van hydrostatische overbrengingen. Dergelijke overbrengingen vereisen meer achtergrondkennis dan mechanische overbrengingen
Metingen aan slootvegetaties bij Raalte
Pitlo, R.H. - \ 1981
Wageningen : LH (Nota / Laboratorium voor Hydraulica en Afvoerhydrologie. Landbouwhogeschool 51) - 30
aquatische gemeenschappen - waterplanten - drainage - hydraulica - hydrodynamica - waterlopen - salland - overijssel - aquatic communities - aquatic plants - drainage - hydraulics - hydrodynamics - streams - salland - overijssel
De werkgroep regulering slootvegetaties verrichtte in 1980 een aantal malen metingen in een tak van het Overijselsch Kanaal ten noorden van Raalte. Om passerende waterhoeveelheid per tijdseenheid (het debiet) te kunnen meten, werd door het Waterschap Salland in het kanaal een stuw gebouwd.
Hydrauliek in de landbouwmechanisatie
Straelen, B.C.P.M. van - \ 1978
Wageningen : Landbouwmechanisatie-pers - 110
hydraulica - hydraulische krachtsystemen - boerderij uitrusting - landbouwwerktuigen - mechanisatie - hydraulics - hydraulic power systems - farm equipment - farm machinery - mechanization
|Thermisch en hygrisch gedrag van enkele bouwconstructies en -materialen
Tol, J.C. - \ 1974
Wageningen : IMAG (Publikatie / Instituut voor Mechanisatie, Arbeid en Gebouwen 1) - 16
bouwconstructie - bouwnijverheid - bouwmaterialen - gebouwen - capillairen - chemische afbraak - civiele techniek - constructie - corrosie - effecten - vloeistofmechanica - warmte - hydraulica - vloeistoffen (liquids) - materialen - mechanica - daken - constructieonderdelen - oppervlaktespanning - theorie - thermische eigenschappen - thermodynamica - muren - grenslaag - oppervlakteverschijnselen - building construction - building industry - building materials - buildings - capillaries - chemical degradation - civil engineering - construction - corrosion - effects - fluid mechanics - heat - hydraulics - liquids - materials - mechanics - roofs - structural components - surface tension - theory - thermal properties - thermodynamics - walls - boundary layer - surface phenomena