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Volunteer native pastures on widespread sodic texture contrast soils in northern New South Wales slopes and plains are known for their limited agricultural production. Fertilised tropical grass pastures on these soils are reported to have much increased pasture production, deeper, more abundant root mass and greater soil profile moisture storage. The subsoil physical differences between native and tropical grass pastures are not well understood. This observational study compared root abundance, soil structure and soil physical parameters (dispersion, bulk density, porosity and pore distribution) in sodic texture contrast soils under native and adjacent, well established and fertilised tropical pastures in a 14-year chronosequence. The physical differences observed may have contributed to improved soil water storage reported by other authors. Fourteen years after establishment, mean root abundance was significantly lower in soils under native pasture and greater in the tropical grass pasture system with 4600 and 8400 m of roots [m.sup.-3] respectively. Dispersion values were high in native pastures but soils under tropical pastures had to be physically worked to cause dispersion. Bulk density under native pasture was significantly higher than in tropical grass pastures by 0.08 g [cm.sup.-3] at 0-10 cm and by 0.2 g [cm.sup.-3] in the upper B horizons. Total soil porosity of topsoils and upper B horizons was consequently lower in native than in tropical grass pasture. Tropical grass pasture upper B horizons had a three-fold greater macroporosity (pores > 30 [micro]m), than under native pastures. This is equivalent to significantly greater potential water flow through stable macropores in dense sodic B horizons in tropical pastures. These findings indicate that pasture system selection and management positively affects deep soil structural properties which promote pasture productivity. The study contributes to a better understanding of mechanisms of published deeper water storage in tropical grass pasture systems on these normally low production soils. Additional keywords: root abundance, sodicity, soil structure, tropical pastures. Received 3 June 2019, accepted 5 November 2019, published online 4 December 2019, Introduction Sodic texture contrast soils Sodic-soils with a strong texture contrast between A and B horizons are extensive in the northern New South Wales (N NSW) slopes and plains on [...]

Riverine macrophytes play diverse and foundational ecological roles, directly influencing ecosystem properties from local biodiversity to flows of water, energy, nutrients, and sediment, many of which in turn are central to river management. Numerical modeling is thus a crucial tool for understanding macrophyte and ecosystem responses to environmental, ecological, or management changes. However, riverine macrophytes have received relatively limited modeling attention compared to plants in many other aquatic or terrestrial systems. We conducted a systematic review of riverine macrophyte growth models, focusing on mechanisms of macrophyte growth, biomass loss, and feedback effects on river ecosystems. Processes such as light availability, thermal tolerance, nutrient limitation, and mortality were widely included in almost all models meeting the review criteria. However, models varied widely in their inclusion of processes such as shading, scour, and the roles of macrophytes in stream nutrient cycles. There has been relatively little consideration of factors such as dispersal, carbon sources, herbivory, burial, desiccation, and competition for space or nutrients, indicating directions for future modeling work. In light of this, we present a conceptual framework to help guide future macrophyte growth modelers through a thorough consideration of macrophytes' myriad interactions with their ecosystems. We also emphasize the importance of modularity and accessibility toward improving efforts to model, and in turn manage, riverine ecosystems. • Riverine macrophytes play diverse ecological roles and often merit modeling. • Existing models consistently include light, temperature, and nutrients. • Fruitful future directions include dispersal, herbivory, burial, and desiccation. • Growth measurement, requirements, influences, and feedbacks can guide future models. • Modularity and accessibility can accelerate progress in river macrophyte modeling. [ABSTRACT FROM AUTHOR]

Abstract Sandstones of the Agbada Formation deposited in Eocene serves as the main hydrocarbon reservoirs of the Niger Delta Basin. PZ-2 well and PZ-4 well that penetrated sections of the formation were investigated for their reservoir heterogeneity, to understand the hydraulic flow units and better assessment of the reservoirs. Reservoir quality and pore throat sizes encountered in the sandstones vary from poor to excellent quality and macroscopic. Greater heterogeneities permeability and homogeneous porosity distribution occur in the bioturbated sandstone facies in the PZ-4 well and sandstone facies in the PZ-2 well. Four hydraulic flow units (FZ-1, FZ-2, FZ-3, FZ-4) and three hydraulic flow units (FZ-1, FZ-2, FZ-3) were recognized in the PZ-2 and PZ-4 wells respectively. These flow zones are characterised by good reservoir qualities and adjudged as a better reservoir candidate for probable prospects.

Mucilage produced by myxodiaspores has been mainly studied for its role in seed ecology. This work investigates changes due to mucilage in soil structure and stability in the spermosphere of the myxodiaspore crop chia (.Salvia hispanica L.). In sandy-loam (S) repacked soil sown with chia and subjected to wetting-drying (DW), Computer Assisted X-ray micro tomography showed that extrusion of a mucilage capsule formed a pore of volume twice that of the seed, surrounded by a shell of particles with higher porosity and lower pore size than the bulk soil. In three soils (S; loam, L; and clay-loam, C) the aggregate stability index to wet sieving (Stw) decreased with one and two DW cycles. Application of 2% w/w mucilage increased Stw before and after DW, from 29% in C to more than 60-fold in S. Mucilage-amended samples after DW had higher or equal Stw compared with unamended soil before DW. Soil retained at the surface of hydrated diaspores exposed to water flow changed with soil texture (11.3, 90.5 and 91.7 mg on each hydrated seed for S, L and C respectively) and chia genotype (6.7, 9.9 and 12.8 mg per hydrated seed in BC and G8 long-day flowering mutants and commercial Black chia respectively). Our results showed that myxodiaspores affected soil structure by providing a microenvironment of altered porosity and high stability around the mucilage capsule extruded by the hydrated seed. This finding characterises a transient but crucial time of crop production around sowing when physical properties of soil surrounding seeds are relevant to stability, germination and plant-microorganism relations. Additional keywords: aggregate stability, germination, soil-plant interactions, soil porosity., Introduction Soil structure and related properties are affected by plants (Roose et al. 2015). Many studies focus on the effect of roots or polysaccharides produced by roots and associated microorganisms [...]

Remnant populations of Betula papyrifera Marshall have persisted in the Great Plains after the Wisconsin Glaciation along the Niobrara River Valley, Nebraska. Population health has declined in recent years, which has been hypothesized to be due to climate change. We used dendrochronological techniques to assess the response of B. papyrifera to microclimate (1950-2014) and the normalized difference vegetation index (NDVI) derived from satellite imagery (Landsat 5 TM (1985-2011) and MODIS (2000-2014)) as a proxy for population health. Growing-season streamflow and precipitation were positively correlated with raw and standardized tree-ring widths and basal area increment increase. Increasing winter and spring temperatures were unfavorable for tree growth, while increasing summer temperatures were favorable in the absence of drought. The strongest predictor for standardized tree rings was the Palmer Drought Severity Index, suggesting that B. papyrifera is highly responsive to a combination of temperature and water availability. The NDVI from the vegetation community was positively correlated with standardized tree-ring growth, indicating the potential of these techniques to be used as a proxy for ex situ monitoring of B. papyrifera. These results aid in forecasting the dynamics of the species in the face of climate variability and change in both remnant populations and across its current distribution in northern latitudes of North America. Key words: paper birch, tree rings, riparian, MODIS, Landsat, NDVI, water, temperature, Nebraska Sandhills. Des populations reliques de Betula papyrifera Marshall ont persiste dans les grandes plaines apres la glaciation du Wisconsin le long de la vallee de la riviere Niobrara, au Nebraska. L'etat de sante des populations s'est deteriore au cours des recentes annees, vraisemblablement a cause des changements climatiques. Nous avons utilise les techniques dendrochronologiques pour evaluer la reaction de B. papyrifera au microclimat (1950-2014), ainsi que l'indice de vegetation NDVI derive de l'imagerie satellitaire (Landsat 5 TM (1985-2011) et MODIS (2000-2014)) en tant que substitut refletant l'etat de sante des populations. La precipitation et l'ecoulement fluvial durant la saison se croissance etaient positivement correles avec l'augmentation de l'accroissement de la surface terriere et la largeur brute et standardisee des cernes annuels. L'augmentation des temperatures hivernales et printanieres etait defavorable pour la croissance des arbres tandis que l'augmentation des temperatures estivales etait favorable en l'absence de secheresse. Le meilleur predicteur pour les cernes annuels standardises etait l'indice de severite de la secheresse de Palmer, ce qui indique que B. papyrifera est tres sensible aune combinaison de temperature et de disponibilite de l'eau. L'indice NDVI de la communaute vegetale etait positivement correle a la croissance des cernes annuels standardises, ce qui indique que ces techniques peuvent etre utilisees comme substitut pour le suivi ex situ de B. papyrifera. Ces resultats vont aider a predire la dynamique de cette espece face aux changements climatiques tant dans les populations reliques que partout dans son aire de repartition actuelle sous les latitudes septentrionales de l'Amerique du Nord. [Traduit par la Redaction] Mots-cles: bouleau blanc, cernes annuels, riverain, MODIS, Landsat, indice de vegetation NDVI, eau, temperature, dunes du Nebraska., 1. Introduction Paper birch (Betula papyrifera Marshall) is a widely distributed deciduous tree species across continental North America. It grows in the boreal forest from Newfoundland in eastern Canada all [...]

Cofferdams are widely used temporary structures at construction sites. Two of the main parameters required in designing a cofferdam are the flow rate and exit hydraulic gradient at the bottom of the excavation. Commonly, these two parameters are evaluated by using two-dimensional (2D) ground water flow models. However, when the flow pattern is threedimensional (3D), such as flow into the square or rectangular cofferdams, predictions by the 2D models underestimate the flow rate and exit gradients considerably. Therefore, it is necessary to incorporate the 3D flow effect through a correction factor. It is shown that treating a square cofferdam as a circular one of the same width or treating a rectangular cofferdam as a 2D double-walled cofferdam significantly underestimates the flow rate. In this study, simple expressions are developed and validated for accurately estimating the flow rate and exit hydraulic gradient values of square and rectangular cofferdams, based on hundreds of finite element simulations in both 2D and 3D. It is suggested that the expressions given in the Canadian foundation engineering manual be improved. Key words: flow rate, exit hydraulic gradient, square cofferdam, rectangular cofferdam. Les batardeaux sont des structures temporaires largement utilisees sur les chantiers de construction. Deux des principaux parametres requis pour la conception d'un batardeau sont le debit et le gradient hydraulique de sortie au fond de l'excavation. Generalement, ces deux parametres sont evalues en utilisant les modeles bidimensionnels (2D) d'ecoulement des eaux souterraines. Cependant, lorsque le modele d'ecoulement est tridimensionnel (3D), tel que l'ecoulement dans les batardeaux carres ou rectangulaires, les predictions par les modeles 2D sous-estiment considerablement le debit et les gradients de sortie. Par consequent, il est necessaire d'incorporer l'effet de flux 3D grace a un facteur de correction. Il est montre que le traitement d'un batardeau carre comme un circulaire de la meme largeur ou le traitement d'un batardeau rectangulaire en tant que batardeau 2D a double paroi sous-estime significativement le debit. Dans cette etude, des expressions simples sont developpees et validees pour estimer avec precision le debit et les valeurs de gradient hydraulique de sortie des batardeaux carres et rectangulaires, sur la base de centaines de simulations d'elements finis en 2D et en 3D. Il est suggere que les expressions donnees dans le Canadian foundation engineering manual soient ameliorees. Mots-cles : debit, gradient hydraulique de sortie, batardeau carre, batardeau rectangulaire., Introduction Cofferdams are widely used in construction sites as temporary structures to keep excavations safe and dry, reducing the water seepage into the excavations. They are constructed by making enclosures [...]

A fluid-solid interaction model has been implemented by coupling two numerical methods--computational fluid dynamics (CFD) and discrete element method (DEM)--that capture the mesoscale behaviors of the fluid-solid system. The model is first validated by comparing the results of simulations with two types of experiments: free settling of a single sphere in water and formation of angle of repose of particles under water, which show its capability in modeling the behaviors of both particle phase and fluid phase. The verified model is then used to study factors affecting the soil erodibility, where case studies are designed for soil particles deposited inside a pipe and subsequently subjected to water flow-induced surface erosion. Influencing factors for soil erodibility, including particle diameter and interparticle bond, are analyzed. For cohesionless soils without bond strength, the critical shear stress is found to be linearly related to particle size; while for soils with bond strength, simulation results show that interparticle bonding largely decelerates the erosion process and causes a much lower erosion rate. To further the understanding of soil surface erosion under turbulent flow, the 'k-e' turbulence model has been successfully implemented for the fluid phase. Comparison between the laminar model and the turbulence model shows turbulence significantly accelerates the erosion process. Key words: fluid-particle interaction, computational fluid dynamics--discrete element method (CFD-DEM) model, k-e turbulence model, soil erosion, multiphase flow. Un modele d'interaction fluide solide a ete mis en oeuvre en couplant deux methodes numeriques, la dynamique des fluides computationnelle (CFD) et la methode des elements discrets (DEM), qui capturent les comportements a l'echelle meso du systeme fluide solide. Le modele est d'abord valide en comparant les resultats des simulations avec deux types d'experiences: le depot libre d'une sphere unique dans l'eau et la formation de l'angle de repos des particules sous l'eau, qui demontrent sa capacite a modeliser les phases. Le modele verifie est ensuite utilise pour etudier les facteurs affectant l'erodabilite du sol, ou des etudes de cas sont concues pour les particules de sol deposees a l'interieur d'une canalisation et ensuite soumises a l'erosion de surface induite par l'ecoulement de l'eau. Les facteurs d'influence de l'erodabilite du sol, y compris le diametre des particules et la liaison entre particules, sont analyses. Pour les sols sans cohesion sans resistance de liaison, la contrainte de cisaillement critique est liee lineairement a la taille des particules; tandis que pour les sols ayant une force d'adherence, les resultats de la simulation montrent que la liaison entre les particules ralentit considerablement le processus d'erosion et entraine un taux d'erosion beaucoup plus faible. Pour mieux comprendre l'erosion de la surface du sol sous ecoulement turbulent, le modele de turbulence <> a ete mis en oeuvre avec succes pour la phase fluide. La comparaison entre le modele laminaire et le modele de turbulence montre que la turbulence accelere de maniere significative le processus d'erosion. Mots-cles: interaction fluide-particules, modele dynamique des fluides computationnelle--methode des elements discrets (CFD-DEM), modele de turbulence k-e, erosion du sol, ecoulement polyphasique., 1. Introduction Interactions between fluid and particulate solid materials are very common yet complicated processes involved in multiple engineering fields, such as geotechnical engineering, mining, mechanical engineering, manufacturing, and chemical [...]

Numerical simulations of coupled groundwater flow and heat transport are used to address how hydrogeological conditions can affect permafrost dynamics. The simulations are based on a two- dimensional vertical-plane conceptual model of a study site at the Iqaluit Airport, Nunavut, Canada, which includes a 50 m deep permafrost terrain with a shallow active layer, overlain by a paved taxiway with winter snow-covered embankments. Coupled groundwater flow and advective-conductive heat transport with freeze-thaw dynamics, temperature-dependent pore-water freezing functions, and latent heat are included in the model. The simulation results show that a smooth (low-slope) freezing function with a higher residual unfrozen moisture content produced a deeper thaw front compared to that using a steeper freezing function, generating a maximum increase in the depth to permafrost of 17.5 m after 268 years. Permafrost thaw rates in high- permeability zones within a heterogeneous system were also relatively higher compared to an otherwise equivalent homogeneous soil, resulting in a maximum increase of 2.6 m in the depth to permafrost after 238 years. As recharge water cools while flowing along the upgradient permafrost table, advectively driven heat transport is paradoxically shown to temporarily increase the height of the permafrost table in downgradient areas. Key words: permafrost, groundwater, numerical modelling, heterogeneity, freezing function. Des simulations numeriques du debit d'eau souterraine couple et du transport de chaleur sont utilisees pour determiner comment les conditions hydrogeologiques peuvent affecter la dynamique du pergelisol. Les simulations sont basees sur un modele conceptuel en deux dimensions a plan vertical d'un site d'etude a l'aeroport d'lqaluit, au Nunavut, qui comprend un terrain de pergelisol de 50 m de profondeur avec une couche active peu profonde, recouverte d'une voie de circulation pavee. L'ecoulement d'eau souterraine couplee et le transport de chaleur par advection- conduction avec la dynamique de gel-degel, les fonctions de congelation de l'eau interstitielle dependant de la temperature et la chaleur latente sont inclus dans le modele. Les resultats de la simulation montrent qu'une fonction de congelation lisse (faible pente) avec une teneur residuelle en eau non gelee plus elevee produit un front de degel plus profond compare a une fonction de congelation plus raide, generant une augmentation maximale de la profondeur jusqu'au pergelisol de 17,5 m apres 268 ans. Les taux de degel du pergelisol dans les zones a haute permeabilite dans un systeme heterogene etaient egalement relativement plus eleves comparativement a un sol homogene par ailleurs equivalent, ce qui a entraine une augmentation maximale de 2,6 m dans la profondeur du pergelisol apres 238 ans. Au fur et a mesure que l'eau de recharge se refroidit en s'ecoulant le long de la table de pergelisol ascendante, on constate paradoxalement que le transport de chaleur entraine par advection augmente temporairement la hauteur de la table de pergelisol dans les zones en aval. [Traduit par la Redaction] Mots-cles: pergelisol, eaux souterraines, modelisation numerique, heterogeneite, fonction de congelation., 1. Introduction Permafrost terrain, which covers about 24% of the land surface in the Northern Hemisphere (Zhang et al. 2003), is among the most sensitive environments to climate change, especially [...]

Torrent Ducks (Merganetta armata) inhabit fast-flowing rivers in the Andes. Rainfall causes rivers to swell, increasing water velocity, turbulence, and turbidity. These changes may affect the ducks' foraging ability because of the harsher conditions or alteration of the aquatic macroinvertebrate resource base. We examined the relationship of Torrent Duck time budgets with food availability and rainfall in the central Andes of Colombia. Time spent foraging was not correlated with total macroinvertebrate density but was negatively correlated with density of 4 preferred families. Monthly precipitation was negatively correlated with total macroinvertebrate density but not correlated with the 4 preferred families. Time spent foraging correlated with rainfall the day before. Torrent Duck time budgets result from interactions among several factors: the ducks' foraging tactics, prey type, and river conditions that affect ducks directly, and indirectly through prey availability. Three of the 4 preferred invertebrate families are filter-feeding larvae that adhere to rocks and are therefore less affected by changes in river flow than other prey types. Thus, Torrent Duck foraging time is independent of overall invertebrate abundance but responds strongly to changes in the density of the 4 most-consumed families. Foraging time is also affected by previous-day rainfall, suggesting that increases in water flow or turbidity have a direct effect on the ducks' foraging efficiency. We conclude that physical conditions of the river habitat impose restrictions on the ducks' activities, both directly and through an indirect interaction with food availability. Received 7 July 2017. Accepted 11 September 2017.Key words: Anatidae, Andean river, aquatic macroinvertebrate, Colombia, foraging behavior.Los Patos de Torrentes (Merganetta armata) habitan rios torrenciales de alta montana. La lluvia aumenta el caudal de estos rios, lo que incrementa la velocidad del agua, la turbulencia y la turbiedad. Estos cambios pueden afectar la capacidad de forrajeo de los patos porque alteran las caracteristicas fisicas del rio o disminuyen la disponibilidad de su alimento, los macroinvertebrados acuaticos. Examinamos la relacion de los patrones de actividad de los patos con la disponibilidad de alimento y la precipitacion mensual en la cordillera Central dc Colombia. El tiempo invertido en alimentacion no estuvo correlacionado con la densidad total de macroinvertebrados acuaticos, pero si lo estuvo con la densidad de las cuatro familias de presas preferidas por los patos. La precipitacion mensual se correlaciono negativamente con la densidad total de macroinvertebrados, pero no con la densidad de las cuatro familias preferidas. El tiempo invertido en alimentacion tambien se correlaciono con la cantidad de lluvia caida el dia anterior. Los patrones de actividad de los Patos de Torrentes son el producto de las interacciones entre varios factores: las estrategias de alimentacion, el tipo de presa y las caracteristicas fisicas del rio. Estas ultimas afectan a los patos de manera directa, pero tambien lo hacen indirectamente por su efecto sobre la disponibilidad de alimento. Tres de las cuatro familias mas consumidas son larvas de insectos filtradoras que se adhieren a las rocas y son menos afectadas por los cambios en el caudal del rio que los otros tipos de presas. Por lo tanto, el tiempo que los patos invierten en alimentacion es independiente de la densidad total de macroinvertebrados, pero responde fuertemente a cambios en la densidad de sus presas principals. EI tiempo invertido en alimentacion tambien es afectado por la cantidad de lluvia del dia anterior, sugiriendo que los incrementos en el caudal o la turbiedad tienen un efecto directo sobre la eficiencia en la busqueda y obtencion de su alimento. Concluimos que las caracteristieas fisicas del habitat fluvial imponen restricciones directas a las actividades de los patos durante el ciclo anual, pero tambien restricciones indirectas debido a su efecto sobre la disponibilidad del alimento.Palabras clave: Anatidae, Colombia, comportamiento de alimentacion, macroinvertebrado acuatico, rio andino., Torrent Ducks (Merganetta armata) inhabit fast-flowing rivers in the Andes from Venezuela to Argentina and Chile, where they feed on invertebrates obtained from the river bottom or scraped from rocks [...]

Sandstones of the Agbada Formation deposited in Eocene serves as the main hydrocarbon reservoirs of the Niger Delta Basin. PZ-2 well and PZ-4 well that penetrated sections of the formation were investigated for their reservoir heterogeneity, to understand the hydraulic flow units and better assessment of the reservoirs. Reservoir quality and pore throat sizes encountered in the sandstones vary from poor to excellent quality and macroscopic. Greater heterogeneities permeability and homogeneous porosity distribution occur in the bioturbated sandstone facies in the PZ-4 well and sandstone facies in the PZ-2 well. Four hydraulic flow units (FZ-1, FZ-2, FZ-3, FZ-4) and three hydraulic flow units (FZ-1, FZ-2, FZ-3) were recognized in the PZ-2 and PZ-4 wells respectively. These flow zones are characterised by good reservoir qualities and adjudged as a better reservoir candidate for probable prospects. [ABSTRACT FROM AUTHOR]

Introduction: Because of the fairly simple equations for accurate flow measurement and controlling the water level, weir and gate method is more useful than the separate weir, gate and partial flume methods. Since the flowing water in the channel always contains sediment particles and floating debris, they are deposited at the gate inlets and behind the weirs which reduces the size of the channel in the structure range and which reduces some problems such as neighboring land flooding due to overflow of water from the channel banks, threatening the structure stability and reducing the measurement accuracy. Using a combination of weir- gate model, in comparison with other conventional devices, will make it possible to get the actual conditions closer two main hypotheses derived from the relations and accurately measure the discharge coefficient. In this model, the deposited materials are easily passed through the gates and the suspended debris are easily passed over the weirs. One of the combined weir- gate structures is semi cylindrical weir- gate structure. Regarding about the form of the combined weir- gate structures, it has some advantages , including simple design, sediments and floating material flow, high flow discharge coefficient compared with other replaceable structures and its being economic. Semi Cylindrical gate turning around center Axis, for reason of rotation the center becomes Conversion to wire, wire gate with opening with different height. Materials and Methods: The experiments were conducted in a rectangular flume with the length of 8 m, width of 0.282 m and height of 0.3 m in Soil Conservation and Watershed Management Research Institute. In this research, PVC pipes were used as semi cylindrical gate structures. The experiments were conducted for three diameters 70, 120 and 160 mm with height of the opening between zeros until radius, angles zero, 30, 45, 60 and 90 degree and differently discharging. Experiments were performed at a discharge limit of 2-27 l/s. In order to decrease turbulence of the flow, the gate was installed at the end 4 m of the flume. The ratio of cylindrical structure diameter to channel width (D/B) was in the range of 0.25 to 0.57 and the Froude number was in the range of 0.08 to 0.55. Results and Discussion: Coefficient discharge of semi cylindrical structure and then dimensionless parameters of [H/P], [a/H], [ /H] and [Fr] against the discharge coefficient in the studied gate opening between zero until radius were investigated. According to result with decrease dimensionless parameter of a/H, discharge coefficient increased, So that the maximum Coefficient discharge rate of angle 90 degrees and minimum angle 0 degrees. Also in a constant of a/H for the curvature of the downstream and upstream, with increasing the diameter of semi cylinder, discharge coefficient remains and has no change, shows that changes in diameter of semi cylinder have no significant impact on discharge coefficient. With increasing H/P for both curves upstream and the downstream, discharge coefficient increased. Also in a constant of H/P for the curvature of the downstream and upstream, with increasing the diameter of semi cylinder, discharge coefficient remains. With constant of angles with increasing Freud for all angles, both the curvature of the downstream and upstream, /H decreased. Also in a constant of Freud and angles, with increasing the diameter of semi cylinder, /H remains. According to the result, discharge coefficient of semi cylindrical gates varies, in Experimental limit, from 0.45 to 1.45 which is more than that of sluice gates reported by the USBR. One of the reasons, this is ascribed to this is the difference between the amount of entrance, head loss in this structure, because when the flow approaches cylindrical gate, due to curvedness of the wall upstream, a gradual gathering of flow lines gives the aerodynamic method to entrance section, thus decreasing resistance against the flow and entrance head loss and increasing discharge coefficient. However, in sluice gates the vertical wall in entrance section is conducive to fast gathering of flow line, thereby increasing resistance against flow, increasing entrance head loss, and decreasing discharge coefficient relative to a semi cylindrical method. Conclusion: The results showed that increasing Froude coefficient and decreasing the a/H (ratio of gate opening to upstream water depth) dimensionless parameter decrease, respectively increase the discharge coefficient and decrease head loss in all aspects of structural alignment. Within addition by increasing the H/P dimensionless parameter (ratio of upstream water depth to structure diameter) discharge coefficient increased. Results showed that the maximum and minimum values of discharge coefficient are related respectively to 90 degree and 0 degree angle.

The Iowa Flood Center (IFC), established following the 2008 record floods, has developed a real-time flood forecasting and information dissemination system for use by all Iowans. The system complements the [...]

Computational simulations suggest that future losses of tidal wetlands attributable to sea-level rise could be greatly offset by the landward advance of these ecosystems into newly sea-inundated areas.Simulations of the effects of sea-level rise on tidal wetlands., Author(s): Jonathan D. WoodruffAuthor Affiliations:Future of tidal wetlands depends on coastal management Figure 1 | Tidal marshes at Jamaica Bay, New York. Schuerch and colleagues' modelling study[sup.1] suggests that coastal [...]