scholarly journals Modelling Hydrological Performance of a Bauxite Residue Profile for Deposition Management of a Storage Facility

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1988
Author(s):  
Mandana Shaygan ◽  
Brent Usher ◽  
Thomas Baumgartl
Keyword(s):  
Bauxite Residue ◽  
Lower Boundary ◽  
Field Capacity ◽  
Climatic Conditions ◽  
Rainfall Event ◽  
Storage Facility ◽  
Predictive Tool ◽  
Moisture Profile ◽  
Lower Boundary Condition ◽  
Rainfall Events

Accurate scheduling of bauxite residue (red mud) deposition time is required in order to prevent the risk of storage facility failure. This study was conducted to precisely determine the hydraulic parameters of bauxite residue and investigate the capability of HYDRUS to accurately estimate the residue moisture profile and the timing for its deposition. The hydraulic properties of the bauxite residue profile were determined by solving an inverse problem. A one-dimensional hydrological model (HYDRUS-1D) was validated using a 300 mm long column filled with bauxite residue and exposed to a dynamic lower boundary condition. After numerical validation, the model was used to simulate the moisture profile of bauxite residue under the climatic conditions of an alumina refinery site in Queensland, Australia, as well as other scenarios (i.e., high (300 mm) and small (1.7 mm) rainfall events of the site). This study showed that the HYDRUS model can be used as a predictive tool to precisely estimate the moisture profile of the bauxite residue and that the timing for the re-deposition of the bauxite residue can be estimated by understanding the moisture profile and desired shear strength of the residue. This study revealed that the examined bauxite residue approaches field capacity (water potential −10 kPa) after three days from a low rainfall event (<1.7 mm) and after eight days from an intense rainfall event (300 mm) at the time of disposal. This suggests that the bauxite residue can be deposited every four days after low rainfall events (as low as 1.7 mm) and every nine days after high rainfall events (as high as 300 mm) at the time of deposition, if bauxite residue experiences an initial drying period following deposition.

scholarly journals The Effect of Soil and Vegetation Parameters in the ECMWF Land Surface Scheme

2004 ◽  
Vol 5 (6) ◽  
pp. 1131-1146 ◽  
Author(s):  
H. Richter ◽  
A. W. Western ◽  
F. H. S. Chiew
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Weather Prediction ◽  
Lower Boundary ◽  
Soil Parameters ◽  
Model Parameters ◽  
Lower Boundary Condition ◽  
Land Surface Scheme ◽  
Vegetation Parameters ◽  
Surface Scheme

Abstract Numerical Weather Prediction (NWP) and climate models are sensitive to evapotranspiration at the land surface. This sensitivity requires the prediction of realistic surface moisture and heat fluxes by land surface models that provide the lower boundary condition for the atmospheric models. This paper compares simulations of a stand-alone version of the European Centre for Medium-Range Weather Forecasts (ECMWF) land surface scheme, or the Viterbo and Beljaars scheme (VB95), with various soil and vegetation parameter sets against soil moisture observations across the Murrumbidgee River catchment in southeast Australia. The study is, in part, motivated by the adoption of VB95 as the operational land surface scheme by the Australian Bureau of Meteorology in 1999. VB95 can model the temporal fluctuations in soil moisture, and therefore the moisture fluxes, fairly realistically. The monthly model latent heat flux is also fairly insensitive to soil or vegetation parameters. The VB95 soil moisture is sensitive to the soil and, to a lesser degree, the vegetation parameters. The model exhibits a significant (generally wet) bias in the absolute soil moisture that varies spatially. The use of the best Australia-wide available soils and vegetation information did not improve VB95 simulations consistently, compared with the original model parameters. Comparisons of model and observed soil moistures revealed that more realistic soil parameters are needed to reduce the model soil moisture bias. Given currently available continent-wide soils parameters, any initialization of soil moisture with observed values would likely result in significant flux errors. The soil moisture bias could be largely eliminated by using soil parameters that were derived directly from the actual soil moisture observations. Such parameters, however, are only available at very few point locations.

ANALYSIS OF SUCTION DISTRIBUTION RESPONSE TO RAINFALL EVENT AND TREE CANOPY

2016 ◽  
Vol 78 (8-5) ◽  
Author(s):  
Mohd FakhrurazziIshak ◽  
Nazri Ali ◽  
Azman Kassim
Keyword(s):  
Matric Suction ◽  
Field Monitoring ◽  
Rainfall Event ◽  
Tree Canopy ◽  
Dominant Factor ◽  
Residual Soil ◽  
Initial Condition ◽  
Canopy Interception ◽  
Rainfall Events ◽  
Sloping Surface

This study provides an exploration of matric suction influenced by tree canopy interception on a single rainfall event. A field monitoring was carried out to measure matric suction at slope with two conditions; at toe of slope without tree and with a tree at toe of slope on a tropical residual soil. The variation in matric suction values and matric suction profiles response to the rainfall events on slope with and without a tree at toe were analysed to reveal the effect of the tree canopy. At initial condition, the matric suction was significantly higher at vicinity of tree compared to that of area without tree at toe of slope. However, a typical short and intense tropical rainfall has caused the matric suction to drop dramatically to a minimum value on slope without tree. This condition did not occur on slope with tree. Although, both slopes (with and without tree at toe) received the same amount of precipitation rainfall but the different responses in matric suction valueswere clearly shown at slope with tree at the slope toe. The short and intense rainfalls appeared to be the dominant factor to the suction variation at slope without tree, but not at slope with the tree. The tree canopy can be a factor to influence the suction variation at slope with tree as canopy interception reduced the amount of precipitation to the ground/sloping surface

scholarly journals Characteristics of rainfall events in regional climate model simulations for the Czech Republic

2017 ◽  
Vol 21 (2) ◽  
pp. 963-980 ◽  
Author(s):  
Vojtěch Svoboda ◽  
Martin Hanel ◽  
Petr Máca ◽  
Jan Kyselý
Keyword(s):  
Czech Republic ◽  
Regional Climate Model ◽  
Climate Model ◽  
Regional Climate ◽  
Rainfall Event ◽  
Spatial Average ◽  
Total Precipitation ◽  
Rainfall Events ◽  
The Czech Republic ◽  
Simulated Event

Abstract. Characteristics of rainfall events in an ensemble of 23 regional climate model (RCM) simulations are evaluated against observed data in the Czech Republic for the period 1981–2000. Individual rainfall events are identified using the concept of minimum inter-event time (MIT) and only heavy events (15 % of events with the largest event depths) during the warm season (May–September) are considered. Inasmuch as an RCM grid box represents a spatial average, the effects of areal averaging of rainfall data on characteristics of events are investigated using the observed data. Rainfall events from the RCM simulations are then compared to those from the at-site and area-average observations. Simulated number of heavy events and seasonal total precipitation due to heavy events are on average represented relatively well despite the higher spatial variation compared to observations. RCM-simulated event depths are comparable to the area-average observations, while event durations are overestimated and other characteristics related to rainfall intensity are significantly underestimated. The differences between RCM-simulated and at-site observed rainfall event characteristics are in general dominated by the biases of the climate models rather than the areal-averaging effect. Most of the rainfall event characteristics in the majority of the RCM simulations show a similar altitude-dependence pattern as in the observed data. The number of heavy events and seasonal total precipitation due to heavy events increase with altitude, and this dependence is captured better by the RCM simulations with higher spatial resolution.

scholarly journals Brief communication "Climatic covariates for the frequency analysis of heavy rainfall in the Mediterranean region"

2011 ◽  
Vol 11 (9) ◽  
pp. 2463-2468 ◽  
Author(s):  
Y. Tramblay ◽  
L. Neppel ◽  
J. Carreau
Keyword(s):  
Extreme Events ◽  
Heavy Rainfall ◽  
Climate Models ◽  
Extreme Event ◽  
Generalized Pareto Distribution ◽  
Climatic Conditions ◽  
Extreme Rainfall Events ◽  
Rainfall Events ◽  
The Future ◽  
Heavy Rainfall Events

Abstract. In Mediterranean regions, climate studies indicate for the future a possible increase in the extreme rainfall events occurrence and intensity. To evaluate the future changes in the extreme event distribution, there is a need to provide non-stationary models taking into account the non-stationarity of climate. In this study, several climatic covariates are tested in a non-stationary peaks-over-threshold modeling approach for heavy rainfall events in Southern France. Results indicate that the introduction of climatic covariates could improve the statistical modeling of extreme events. In the case study, the frequency of southern synoptic circulation patterns is found to improve the occurrence process of extreme events modeled via a Poisson distribution, whereas for the magnitude of the events, the air temperature and sea level pressure appear as valid covariates for the Generalized Pareto distribution scale parameter. Covariates describing the humidity fluxes at monthly and seasonal time scales also provide significant model improvements for the occurrence and the magnitude of heavy rainfall events. With such models including climatic covariates, it becomes possible to asses the risk of extreme events given certain climatic conditions at monthly or seasonal timescales. The future changes in the heavy rainfall distribution can also be evaluated using covariates computed by climate models.

scholarly journals Soil Management by Cover Crops in Vineyards for Climate Change Adaptation

Proceedings ◽  
2019 ◽  
Vol 30 (1) ◽  
pp. 26
Author(s):  
Marqués ◽  
Bienes ◽  
Ruiz-Colmenero
Keyword(s):  
Climate Change ◽  
Organic Matter ◽  
Soil Moisture ◽  
Soil Organic Matter ◽  
Climate Change Adaptation ◽  
Climatic Conditions ◽  
Water Infiltration ◽  
Soil Conditions ◽  
Grass Cover ◽  
Rainfall Events

The wine captures grapes’ variety nature and vinification techniques, but other aspects of soil, climate and terrain are equally important for the terroir expression as a whole. Soil supplies moisture, nitrogen, and minerals. Particularly nitrogen obtained through mineralization of soil organic matter and water uptake are crucial for grape yield, berry sugar, anthocyanin and tannin concentration, hence grape quality and vineyard profitability. Different climatic conditions, which are predicted for the future, can significantly modify this relationship between vines and soils. New climatic conditions under global warming predict higher temperatures, erratic and extreme rainfall events, and drought spells. These circumstances are particularly worrisome for typical thin soils of the Mediterranean environment. This study reports the effect of permanent grass cover in vineyards to maintain or increase soil organic matter and soil moisture. The influence of natural and simulated rainfalls on soils was studied. A comparison between minimum tillage (MT) and permanent grass cover crop (GC) of the temperate grass Brachypodium distachyon was done. Water infiltration, water holding capacity, organic carbon sequestration and protection from extreme events, were considered in a sloping vineyard located in the south of Madrid, Spain. The MT is the most widely used cultivation method in the area. The tradition supports this management practice to capture and preserve water in soils. It creates small depressions that accumulate water and eventually improves water infiltration. This effect was acknowledged in summer after recent MT cultivation; however, it was only short-lived as surface roughness declined after rainfalls. Especially, intense rainfall events left the surface of bare soil sealed. Consequently, the effects depend on the season of the year. In autumn, a rainy season of the year, MT failed to enhance infiltration. On the contrary, B. distachyon acted as a physical barrier, produced more infiltration (22% increase) and fewer particles detachment, due to increased soil structure stability and soil organic matter (50% increase). The GC efficiently protected soil from high-intensity events (more than 2 mm min-1). Besides, soil moisture at 35 cm depth was enhanced with GC (9% more than tillage). On average, soil moisture in GC was not significantly different from MT. These effects of GC on soil conditions created local micro-environmental conditions that can be considered advantageous as a climate change adaptation strategy, because they improved water balance, maintained a sustainable level of soil organic matter, therefore organic nitrogen, all these factors crucial for improving wine quality.

Modified electromyography-assisted optimization approach for predicting lumbar spine loading while walking with backpack loads

2020 ◽  
Vol 234 (5) ◽  
pp. 527-533
Author(s):  
Simon SW Li ◽  
Daniel HK Chow
Keyword(s):  
Boundary Condition ◽  
Lumbar Spine ◽  
Maximal Voluntary Contraction ◽  
Lower Boundary ◽  
Voluntary Contraction ◽  
Optimization Approach ◽  
Compression Force ◽  
Lower Boundary Condition ◽  
Force Profile ◽  
Mean Square Difference

This study modified an electromyography-assisted optimization approach for predicting lumbar spine loading while walking with backpack loads. The modified-electromyography-assisted optimization approach eliminated the electromyography measurement at maximal voluntary contraction and adopted a linear electromyography–force relationship. Moreover, an optimal lower boundary condition for muscle gain was introduced to constrain the trunk muscle co-activation. Anthropometric information of 10 healthy young men as well as their kinematic, kinetic, and electromyography data obtained while walking with backpack loads were used as inputs in this study. A computational algorithm was used to find and analyse the sensitivity of the optimal lower boundary condition for achieving minimum deviation of the modified-electromyography-assisted optimization approach from the electromyography-assisted optimization approach for predicting lumbosacral joint compression force. Results validated that the modified-electromyography-assisted optimization approach (at optimal lower boundary condition of 0.92) predicted on average, a non-significant deviation in peak lumbosacral joint compression force of −18 N, a standard error of 9 N, and a root mean square difference in force profile of 73.8 N. The modified-electromyography-assisted optimization approach simplified the experimental process by eliminating the electromyography measurement at maximal voluntary contraction and provided comparable estimations for lumbosacral joint compression force that is also applicable to patients or individuals having difficulty in performing the maximal voluntary contraction activity.

Assessment of the contribution of denitrification to N losses from compacted grassland soil by NO3− disappearance and N2O production during anaerobic incubation

1999 ◽  
Vol 79 (1) ◽  
pp. 57-64 ◽  
Author(s):  
M. K. Abbasi ◽  
W. A. Adams
Keyword(s):  
N Uptake ◽  
Field Capacity ◽  
Climatic Conditions ◽  
Grassland Soils ◽  
N Losses ◽  
N2o Production ◽  
Permanent Pasture ◽  
Net Mineralization ◽  
Simulated Field ◽  
C Limitation

Decreases in herbage production and of N uptake and utilization have been observed on Denbigh series soils in mid-Wales after several years in permanent pasture. Laboratory experiments were conducted to examine the contribution of denitrification to N loss from these wet grassland soils. Denitrification capacity was measured in seived soil following the addition of KNO3 and maintained at 20°C under anoxic conditions. Emission of N2O was measured from intact field cores equilibrated under conditions of simulated "field capacity" using glucose as C substrate. The rate of loss of NO3−–N decreased with depth and in the 0–2.5 cm layer all added NO3−–N was lost in 10 d incubation. Net mineralization of NH4+–N occurred at about one-sixth of the rate of NO3−–N disappearance. The presence of NO3− reduced the rate of decrease in redox potential (Eh) and the Eh did not fall below about +200 mV until all NO3−–N had been lost. Emission of N2O was greatest between 6 and 48 h and denitrification rate decreased with depth. Addition of glucose increased N2O emission in the 2.5–5.7 cm layers indicating that C limitation to denitrification may occur at shallow depths in the soil profile of compacted grassland. On average, the total denitrification ranged between 15 and 20 kg N ha−1, equivalent to 20–30% of applied N. The potential rates of denitrification change markedly over quite shallow depths in these compacted grassland soils. Furthermore, since denitrification occurred at substantial rates under simulated field capacity, conditions conducive to denitrification are likely to persist for quite long periods in the moist climatic conditions. Key words: Compacted soil, denitrification, glucose, grassland, nitrous oxide

scholarly journals Turbulent Flow over Steep Steady and Unsteady Waves under Strong Wind Forcing

2018 ◽  
Vol 48 (1) ◽  
pp. 3-27 ◽  
Author(s):  
Peter P. Sullivan ◽  
Michael L. Banner ◽  
Russel P. Morison ◽  
William L. Peirson
Keyword(s):  
Turbulent Flow ◽  
Lower Boundary ◽  
Breaking Waves ◽  
Wave Crest ◽  
Strong Wind ◽  
Wave Group ◽  
Wave Surface ◽  
Form Drag ◽  
Lower Boundary Condition ◽  
Wave Slope

AbstractTurbulent flow over strongly forced steep steady and unsteady waves is simulated using large-eddy simulation (LES) with time t and space x varying wave height h(x, t) imposed as a lower boundary condition. With steady waves, h(x, t) is based on measurements of incipient and active breaking waves collected in a wind-wave flume, while a numerical wave code is used to generate an unsteady evolving wave packet (group). Highly intermittent airflow separation is found in the simulations, and the results suggest separation near a wave crest occurs prior to the onset of wave breaking. The form (pressure) drag is most sensitive to the wave slope, and the form drag can contribute as much as 74% to the total stress. Wind and scalar profiles from the LES display log-linear variations above the wave surface; the LES wind profiles are in good agreement with the measurements. The momentum roughness increases as the water surface changes from wind ripples to incipient breaking to active breaking. However, the scalar roughness decreases as the wave surface becomes rougher. This highlights major differences in momentum and scalar transport over a rough wavy surface. For a rapidly evolving, strongly forced wave group, the form drag is highly correlated with the wave slope, and intermittent separation is found early in the packet evolution when the local wave slope −∂h/∂x(x, t) ≥ 0.22. The packet root-mean-square wave slope is 0.084, but the form drag fraction is 2.4 times larger than a comparably forced steady wave. Thus, a passing wave group can induce unsteadiness in the wind stress.

scholarly journals Nonlinear Dynamic Characteristic Analysis of a Landing String in Deepwater Riserless Drilling

2018 ◽  
Vol 2018 ◽  
pp. 1-17
Author(s):  
Jun Liu ◽  
Hongliang Zhao ◽  
Simon X. Yang ◽  
Qingyou Liu ◽  
Guorong Wang
Keyword(s):  
Boundary Condition ◽  
Dynamic Model ◽  
Marine Environment ◽  
Lower Boundary ◽  
Dynamic Responses ◽  
Characteristic Analysis ◽  
Lower Boundary Condition ◽  
Response Characteristics ◽  
Proposed Model ◽  
Nonlinear Dynamic Characteristic

The landing string is an important component of deepwater riserless drilling systems. Determination of the dynamic characteristics of the landing string plays an essential role in its design for ensuring its safe operation. In this paper, a dynamic model is developed to investigate the dynamic response characteristics of a landing string, where a landing string in a marine environment is modeled as a flexible slender tube undergoing coupled transverse and axial motions. The heaving motion of the drilling platform is taken as the upper boundary condition and the motion of the drilling bit caused by the interaction between the rock and the bit as the lower boundary condition. A semiempirical Morison equation is used to simulate the effect of the load imposed by the marine environment. The dynamic model, which is nonlinearly coupled and multibody, is discretized by a finite element method and solved by the Newmark technique. Using the proposed model, the dynamic responses of the displacement, axial force, and moment in the landing string are investigated in detail to find out the influences of driving depth of surface catheter, platform motion, bit movement, and marine environment on the dynamical characteristics of the landing string.

A review of the application of BRDF models to infer land cover parameters at regional and global scales

2001 ◽  
Vol 25 (4) ◽  
pp. 483-511 ◽  
Author(s):  
Gareth Roberts
Keyword(s):  
Land Surface ◽  
Lower Boundary ◽  
Terrestrial Ecosystems ◽  
Remotely Sensed Data ◽  
Area Index ◽  
Lower Boundary Condition ◽  
Surface Parameters ◽  
Case Examples ◽  
Global Circulation Models ◽  
Land Surface Parameters

This paper presents a review of the application of Bi-directional Reflectance Distribution Function (BRDF) models in the inference of land surface parameters at regional and global scales using remotely sensed data. Information on land surface parameters, such as Leaf Area Index (LAI), fraction of Absorbed Photosynthetically Active Radiation (fAPAR), aerodynamic surface roughness and albedo, are valuable for understanding the transfer of energy and mass between terrestrial ecosystems and the atmosphere (e.g., carbon, nitrogen and methane cycling) and for ingestion into the lower boundary condition of global circulation models (GCM)s. Conventional techniques for acquiring information on land surface parameters do not account for or utilize the directional nature of surface reflectance. This paper reviews empirical, semi-empirical and, to a lesser extent, physical BRDF models that describe the surface BRDF. In each case examples are given of their application in inferring land surface parameters. The review concludes by discussing the future prospects of BRDF modelling using spaceborne sensors.

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