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Dollar spot is caused by the fungus Clarireedia spp. and is the most economically important disease of golf course turfgrass in temperate regions of the United States. Previous research has demonstrated that nitrogen (N) fertilization may reduce dollar spot severity, but the results have been inconsistent, and the impact of N as part of repeated foliar fertilization applications to golf course putting greens remains unclear. Two independent trials were replicated in Madison, Wisconsin and Glenview, Illinois in the 2015, 2016, and 2017 growing seasons. The objective of the first trial was to evaluate the effect of four different N rates applied as urea (4.9, 9.8, 19.4, and 29.3 kg N/ha applied every 2 weeks) on dollar spot severity, and the objective of the second trial was to evaluate the effect of three N sources (calcium nitrate, ammonium sulfate, and ammonium nitrate applied every 2 weeks) on dollar spot severity. Results from the N rate trial at both locations indicated that only the highest (29.3 kg N/ha) rate consistently reduced dollar spot severity relative to the nontreated control. Nitrogen source had minimal and inconsistent impacts on dollar spot severity based on location and year. Although these results show that meaningful reductions in dollar spot severity can be achieved by manipulating N fertilizer application rates, the rate of N needed for disease suppression may be impractical for most superintendents to apply and result in undesirable nontarget impacts.

[1] Most rivers exhibit regions of strong channel curvature that are characterized by more complex and variable flow and erosion patterns, compared to regions of lower curvature. Studies investigating high-curvature bends using eddy-resolving techniques have been limited, and the effect of bend angle on flow and erosion has rarely been investigated. This study investigates flow in a 135° nonerodible bank open channel bend of high curvature: ratio of radius of curvature, R, to channel width, B, is 1.5. The bathymetry is obtained during the final stages of a clear water scour experiment. Large Eddy Simulation is used to investigate the effect of secondary flow on the redistribution of streamwise momentum, the details of coherent structures, and mechanisms leading to erosion within the bend. Results are compared with those from a similar numerical study of a 193° sharply curved open channel bend with R/B = 1.35. The angle of the 135° bend is representative of typical regular meander geometry, while the larger angle of the 193° bend is representative of a tortuous meander geometry. The different bathymetries induced important quantitative and qualitative differences in the vortical and turbulence structure within the open channel for the two cases. Inner bank streamwise-oriented vortical (SOV) cells formed in both cases, but the position and extent of shear layers forming between regions of fast and slow moving fluid differed, and flow did not separate at the inner bank in the 135° bend. An outer-bank cell was observed in the 135° bend, but not in the 193° bend. Distributions of predicted boundary shear stresses indicated the capacity of the flow to erode the outer bank of a sharply curved bend under two representative regimes found in the field.

This paper presents the results of an experimental investigation into the hydraulic efficiency of a vertically oriented water intake. Under low submergence conditions, the operation of such an intake is affected significantly by the formation of surface vortices, which result in significant flow reduction and the downstream entrainment of air and swirl. The experimental work considered the fact that vortex formation is governed by the geometrical characteristics of the intake, including the diameter, local shape, submergence, surrounding boundary, etc, and the velocity distribution in the approaching flow. Therefore, an experimental study was conducted to investigate the influence that the local shape and the proximity to nearby boundaries have on the hydraulic performance of a vertical water intake. The results of this experimental investigation will hopefully lead to a better understanding of the phenomena governing the flow in such structures and to the elaboration of improved engineering design guidelines.

A three-dimensional numerical model was used to examine the turbulent flow field and associated sediment transport due to a series of barbs (submerged groynes) in a channel bend. Model results were in good agreement with measured laboratory data and adequately simulated the important features of sediment transport. Statistical comparison of the predicted and measured equilibrium bed geometry found average regression coefficients of determination of 0.77 and 0.72 for the 90° and 135° channels, respectively. The predicted velocity data followed expected trends. The capability of a three-dimensional numerical model to simulate sediment transport through bend sections of a channel containing barbs was verified. This included the simulation of the effects of different arrangements of barb groups and an analysis of the data to determine the relation of the flow field to associated scour and deposition in a complex fluvial environment. These novel results are useful for improved analyses of the bank-protection capabilities of these structures and for the development and improvement of design guidelines.Key words: three-dimensional models, numerical models, movable bed models, channel bends, turbulence, secondary flow, scour, barbs, groynes.

Phase 1 of an ongoing laboratory study of a novel form of stream-bank protection structure is described. "Barbs" are dike-like stone structures designed to protect the (usually unstable) outside-bank regions of channel bends. These low-profile structures point upstream into the flow and typically extend to about 1/4-way across the channel. By disrupting near-bank velocity gradients they promote sediment deposition along the eroding outside-bank region. Their presence also modifies the "helicoidal"-type flow pattern of the bend such that secondary currents, which would otherwise attack the outside-bank, are redirected towards the center of the channel. This novel form of bank protection structure is currently undergoing field tests on selected bends on a number of shallow "wide" streams in Illinois, USA. While initial results are encouraging, additional studies are necessary to develop design criteria for their wider application. In phase 1 of this study, the effectiveness of different arrangements of barb groups, in both 90° and 135° moveable-bed bend sections of a hydraulically "narrow" rectangular channel, are investigated. For each hydraulic condition considered, the channel-bed scour profiles generated by the different barb groups are compared to corresponding "reference" profiles generated in the absence of barbs. Judging the effectiveness of the different barb groups in promoting long-term stability of the outside-bank region is based on two criteria: (i) percent reduction achieved in scouring in the vicinity of the outside-bank and (ii) degree to which the channel thalweg (deepest portion) is moved from the outside-bank region towards the center of the channel.Key words: barb, channel bends, local scouring, bank erosion, bank protection, secondary currents.

In view of the selfcalibrating feature, the brink depth generated at the entrance to a freelydischarging drop structure in a prismatic open channel is widely used for estimating channel discharge. ...

In this paper we describe the development and validation of a 2-D finite-difference mathematical model for simulating inert pollutant transport in compound channels. In its formulation the model couples depth-averaged (depth-integrated) versions of the classical 3-D Navier-Stokes equations and the advection-diffusion equation with constant eddy-viscosity model. The numerical solution scheme is Platzman’s space-staggered scheme, and a double time step operation is employed in the analysis. The model is initially validated using laboratory data of continuous-injection dye tracer experiments performed in a large asymmetrical compound-shaped channel at the Hydraulics Laboratory, University of Ottawa. Comparison between predicted and observed dye concentration curves indicates generally good agreement in the overall shapes of the curves, as well as in the peak concentrations and the times to peak.

Most previous laboratory studies of local scour at bridge abutments were performed in rectangular channels in which the distributions of flow velocity and bed shear stress were considered uniform in the transverse direction. In reality, however, bridge abutments usually terminate in the flood plain zone of rivers where velocity and shear stress are not uniformly distributed. This paper presents the results of a laboratory study performed to investigate the impact of lateral momentum of flow intercepted by abutment and flow related to a specific channel width at the abutment end, is a significant parameter to account for lateral momentum transfer and should be incorporated in the scour prediction formulation. Also, based on the discharge ratio, Froude number, and critical Froude number associated with the sediment size, a relationship for predicting maximum local scour depth at bridge abutments was proposed. (A)

L'objectif principal de cette etude etait d'optimiser l'horaire de pompage et de relâchement du reservoir d'approvisionnement d'eau dans la Municipalite regionale d'Ottawa-Carleton (MROC), dans le but de reduire les couts d'operation relies. Les demandes horaires doivent etre satisfaites avec un cout minimum de pompage. L'article precedent (partie 1) decrit le systeme de la MROC et le modele numerique utilise dans l'analyse d'optimisation. Le present article (partie 2) presente les principaux resultats obtenus de l'optimisation, et rapporte sur l'objectif de la seconde etude, qui etait d'examiner l'impact sur les couts d'operation d'augmenter : (i) la capacite d'emmagasinage du reservoir, (ii) la capacite de la station de traitement ; et (ii) la demande d'eau des consommateurs. En general, la programmation lineaire s'est averee une bonne option pour generer des horaires optimises de pompage et de relâchement de service du reservoir. Les analyses des alternatives de gestion d'eau ont confirme que le systeme d'approvisionnement d'eau de la MROC etait dimensionne pour des demandes journalieres maximales, cependant, les operations jours-a-jours seraient simplifiees si les amenagements actuels d'emmagasinage et de traitement seraient elargies. Il serait economiquement difficile de justifier les couts de construction a partir des economies potentielles d'energie obtenues de cette etude. Il semble ainsi qu'il est important de commencer la gestion de la demande.

The principal objective of this study was to optimize pump scheduling and reservoir releases in the Regional Municipality of Ottawa-Carleton's (RMOC) water supply system with a view to reducing electricity-related operating costs. Pump schedules and reservoir releases for enhanced operation were obtained using a linear programming optimization model that incorporated Ottawa Hydro's electricity tariff structure for "large" users. A second objective was to investigate the impact on system operating costs of increasing (i) reservoir storage capacity, (ii) treatment plant capacity, and (iii) water demand by consumers. This paper (part I) describes the RMOC distribution system and reviews the model development. The next paper (part II) presents the analyses performed for the two study objectives, and important results. Key words: water supply system, pump scheduling, pumping costs, optimization, modelling.

Floodplain conveyance in compound channel flows is examined through applications of the dynamic flow routing model DWOPER to both laboratory and field data sets. Three different approaches regarding the modelling of off-channel storage are considered, namely, the single-channel approach and two interface-plane methods, which artificially separate main channel flows from floodplain flows, using (i) vertical and (ii) diagonal interface planes. The single-channel method, which views composite flow fields as single units without storage, produced significant differences between simulated and observed stage and discharge hydrographs. The vertical interface method gave generally good results in the case of the laboratory data, but was less successful when applied to the field data. The diagonal interface method, which in this instance applied outward-facing diagonal interface planes at the junctions of the main channel and floodplain zones, produced superior results overall. Key words: floodplain, conveyance, unsteady flow, compound channels, off-channel storage, interface planes.

The seasonal and annual global distributions of diabatic heating during the First GARP Global Experiment (FGGE) are estimated using the isentropic mass continuity equation. The data used are from the FGGE Level IIIa analyses generated by the United States National Meteorological Center. Spatially and temporally coherent diabatic heating distributions are obtained from the isentropic planetary scale mass circulation that is forced by large-scale heat sources and sinks. The diabatic heating in the Northern Hemisphere is closely associated with the distribution of land and ocean. While cooling prevails over Eurasia and North America and heating occurs along the east coasts of these two continents during northern winter, a contrasting situation exists during northern summer with heating over most of the continents and cooling over the oceans where subtropical anticyclonic circulations prevail. Heating in the tropics, mostly from moist convection, has considerable longitudinal variations which change seasonally. Of particular importance is the seasonal progression of the primary centre of heating within the planetary scale Asiatic monsoon which is located over the western equatorial Pacific during northern winter and near the Philippines and Southeast China during northern summer. DOI: 10.1111/j.1600-0870.1983.tb00201.x

[1] Detailed mapping of bathymetry and three-dimensional water velocities using a boat-mounted single-beam sonar and acoustic Doppler current profiler (ADCP) was carried out in the vicinity of two submerged wing dikes located in the Lower Missouri River near Columbia, Missouri. During high spring flows the wing dikes become submerged, creating a unique combination of vertical flow separation and overtopping (plunging) flow conditions, causing large-scale three-dimensional turbulent flow structures to form. On three different days and for a range of discharges, sampling transects at 5 and 20 m spacing were completed, covering the area adjacent to and upstream and downstream from two different wing dikes. The objectives of this research are to evaluate whether an ADCP can identify and measure large-scale flow features such as recirculating flow and vortex shedding that develop in the vicinity of a submerged wing dike; and whether or not moving-boat (single-transect) data are sufficient for resolving complex three-dimensional flow fields. Results indicate that spatial averaging from multiple nearby single transects may be more representative of an inherently complex (temporally and spatially variable) three-dimensional flow field than repeated single transects. Results also indicate a correspondence between the location of calculated vortex cores (resolved from the interpolated three-dimensional flow field) and the nearby scour holes, providing new insight into the connections between vertically oriented coherent structures and local scour, with the unique perspective of flow and morphology in a large river.

A series of seven stream barbs were installed at two consecutive channel bends in Sawmill Creek, a semi-alluvial stream located in Ottawa, Canada. Stream barbs (also known as submerged groynes) are low-profile linear rock structures that extend from the outside bank regions of channel bends in an upstream direction, to redirect the attacking currents and prevent erosion of the bank. As well as providing bank protection, these structures promote vegetated stream banks, create resting pools and scour holes for fish habitat, and increase biodiversity for aquatic species. Despite these benefits, because of their relative novelty as river training structures, stream barbs are not a common means of stream bank protection in Canada and are possibly non-existent for semi-alluvial or clay channels. Three years of monitoring and measurement of flow conditions (discharge, water velocity and depth) and bathymetry, before (2 years) and after (1 year) the construction of the barbs, have been collected at the Sawmill Creek study site, providing valuable data for understanding their performance in a semi-alluvial channel. Sawmill Creek has a predominately clay bed and banks, presenting a rare opportunity to study the unique dynamics between flow and sediment transport within a clay channel. This paper reports on (i) the unique site conditions and monitoring methodology; (ii) preliminary results of the 3 year monitoring program; and (iii) recommendations for future design and implementation of these structures.

Des methodes d'optimisation sont utilisees pour estimer les donnies de propagation des crues par des canaux ouverts mixtes (canaux principaux avec pkrimtttres d'inondation). Ces donnees incluent la geometrie des sections de canal irregulittres et la rugosite limitrophe. Les icarts entre les debits et les niveaux simulis et ceux observes sont reduits en utilisant trois algorithmes d'optimisation : la methode de Powell, I'algorithme de Rosenbrock et la methode Simplex de Nelder et Meade. La methode de Powell a produit des resultats mediocres alors que les methodes de Rosenbrock et Simplex ont permis d'obtenir de bons resultats. Les donnies estimies a I'aide des mithodes de Rosenbrock et Simplex ont Cte utilisees pour calculer differentes propagations des crues observies dans un canal en laboratoire. On a constate une bonne concordance entre les debits et les niveaux de pointe simulis et ceux estimes a I'aide de donnkes reelles.

A three-dimensional numerical model Simulation in Intakes with Multiblock option (SSIIM) was used to model the effects of placing a series of barbs along an unstable section of Sawmill Creek, a small urban stream in the city of Ottawa, Canada. Stream barbs (a type of submerged groyne) are low-profile linear rock structures that prevent the erosion of stream banks by redirecting high velocity flow away from the bank. As they can be built at a relatively low cost and also provide significant ecological benefit, these structures are an important and relatively new method of stream bank protection. The numerical model was used to assess various design alternatives for a series of seven stream barbs at two consecutive channel bends requiring stabilization measures along their outer banks. Design criteria were principally based on the goals of reducing local velocities, shear stress and subsequent erosion at the outside bank of each bend, and on moving the thalweg away from the (existing) outside bank regions towards the centre of the channel. This paper reports on (i) the unique site conditions and environmental protection requirements, (ii) the results of the numerical simulation, and (iii) the design methodology.

The subject of flow through rockfill is of increasing interest in Canada. Rockfill drains are presently used by mining companies in order to permit existing creeks to flow through the base of mine waste dumps. There is potential for the use of flow through rockfill dams for mini-hydro schemes because the adoption of a costly concrete spillway may be unnecessary in some cases. An important issue in the design of flow through rockfill structures is the pore pressure distribution and the associated hydraulic gradients, neither of which are associated with Darcy's law. For such determinations the finite difference scheme of Curtis and Lawson, which is based on the partial differential equation presented by Parkin et al., was investigated. However, expressions for edge nodes under this non-Darcy finite difference scheme do no exist. This paper presents the effect on the results of using more direct expressions for the edge nodes. Analytical results are compared with observed piezometric heads in the case of two model flow through rockfill dams. Further, it is shown that through the use of a standard electronic spreadsheet, piezometric heads for non-Darcy flow in porous media and the associated hydraulic gradients can be modelled directly without the need of complex computer programming. Key words: flow through rockfill embankment, piezometric head, finite difference method, non-Darcy flow.

Barbs (or submerged groynes) are low-profile linear rock structures that are primarily used to prevent the erosion of stream banks. They are a variation of a groyne, similar to spur dikes and bendway weirs. Barbs are typically anchored, in series, to the outside bank in stream bends and extend in an upstream direction from the bank into the flow. This configuration redirects flow away from the outer stream bank and disrupts the velocity gradient close to the outer bank, encouraging sediment deposition adjacent to the barb. These interactions between the flow pattern and the sediment transport around the barb prevent erosion of the bank. Furthermore, vortices generated by the barb create local scour holes that can enhance aquatic habitat. A three-dimensional numerical model, Sediment Simulation in Intakes with Multiblock option (SSIIM), was used to examine the turbulent flow field and associated scour and depositional patterns due to a series of barbs in a mobile-bed channel bend. Previous physical model observations were used for model calibration and verification. Barb design was optimized to minimize scour. The parameters considered in the optimization were channel bend angle, barb alignment angle, and barb spacing. In this paper the spatial distribution of the three-dimensional flow field through a series of barbs in a 90o channel bend are mapped and the impact on the flow field of subtle differences in barb geometry are examined. Special emphasis is placed on the influence of barb design on secondary currents in the meander bend and the generation of three-dimensional vortices, and the consequent impact on scour.

In this paper, the simulation of the violent impact of tsunami-like bores with a square column is performed using a single-phase, weakly compressible three-dimensional Smoothed Particle Hydrodynamics (SPH) model. In order to avoid large fluctuations in the pressure field and to obtain accurate simulations of the hydrodynamic forces, a Riemann solver-based formulation of the SPH method is utilized. Large-scale physical experiments conducted by the authors are reproduced using the numerical model. Time-histories of the water surface elevation as well as time-histories of the pressure distribution and net total force acting on the column are successfully compared. As observed in previous breaking wave impact studies, results show that the magnitude and duration of the impulsive force at initial bore impact depend on the degree of entrapped air in the bore-front. Although ensuring a stable pressure field, the Riemann solver-based SPH scheme is believed to induce excessive numerical diffusion, as sudden and large water surface deformations, such as splashing at initial bore impact, are marginally reproduced. To investigate this particular issue, the small-scale physical experiment of Kleefsman et al. (2005) is also considered and modeled.

The mass circulation of the zonally averaged global circulation is investigated in isobaric and isentropic coordinates through the use of a FGGE Level IIIa data set. The isobaric mass circulation during the First GARP Global Experiment is consistent with previous results, i.e., direct Hadley cells in low latitudes and indirect Ferrel cells in midlatitudes of both hemispheres. Within the isentropic framework, the combination of a geostrophic mean mode of mass transport within the baroclinic wave structure of extratropical latitudes, and an ageostrophic mean mode in tropical latitudes, yields an isentropic mass circulation spanning the hemisphere. The asymmetric structure of midlatitude baroclinic waves provides the degree of freedom for a geostrophic mode of mass transport that is fundamental to the direct Hadley-type circulation in isentropic coordinates. This direct Hadley-type circulation is explicitly linked to heat sources and sinks on a planetary scale. The diabatic heating estimated from th...

The time-averaged structure of global monsoonal circulations and planetary scale transport processes are determined from the FGGE Level IIIa operational data set generated by the US National Meteorological Center. Through isentropic diagnostics, rotational and irrotational components of the horizontal mass transport and the distribution of heating for the planetary scale are analyzed for the months of January. April, July and October of 1979. The global monsoonal circulations coupled with the planetary scale of differential heating occur in the form of large scale Hadley-type and Walker-type circulations. Net heating within a given region and net cooling in another region in association with latent heat release and differences in boundary flux of energy through the earth's surface and the top of the atmosphere result in forcing of isentropic mass circulations that link energy source with energy sink regions, a result basic to thermally forced circulations. The primary planetary source of energy in the region of Indonesia-Philippines-Southeast Asia is linked through isentropic mass transport with sinks of energy in the regions of the two circumpolar vortices, the Sahara and subtropical anticyclonic circulations. This primary center of the source of energy in the Indonesia-Southeast Asia area moves seasonally from one hemisphere to the other. Other source regions of energy occur over Brazil in January and Central America and Africa in July. Through horizontal transport of mass and energy, the winter Asiatic monsoonal circulation links radiative cooling over Asia to sensible and latent heat release within mid-latitude baroclinic waves and also to latent heat release in the Indonesia, Philippine and New Guinea regions. The role of mid-latitude baroclinic waves in providing for mass and energy exchange between polar and subtropical regions within the time-averaged isentropic structure is briefly discussed. DOI: 10.1111/j.1600-0870.1985.tb00274.x