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71.
Groundwater flow and solute transport at the Mourquong saline-water disposal basin, Murray Basin, southeastern Australia 总被引:5,自引:0,他引:5
Craig T. Simmons Kumar A. Narayan Juliette A. Woods Andrew L. Herczeg 《Hydrogeology Journal》2002,10(2):278-295
Saline groundwater and drainage effluent from irrigation are commonly stored in some 200 natural and artificial saline-water
disposal basins throughout the Murray-Darling Basin of Australia. Their impact on underlying aquifers and the River Murray,
one of Australia's major water supplies, is of serious concern. In one such scheme, saline groundwater is pumped into Lake
Mourquong, a natural groundwater discharge complex. The disposal basin is hydrodynamically restricted by low-permeability
lacustrine clays, but there are vulnerable areas in the southeast where the clay is apparently missing. The extent of vertical
and lateral leakage of basin brines and the processes controlling their migration are examined using (1) analyses of chloride
and stable isotopes of water (2H/1H and 18O/16O) to infer mixing between regional groundwater and lake water, and (2) the variable-density groundwater flow and solute-transport
code SUTRA. Hydrochemical results indicate that evaporated disposal water has moved at least 100 m in an easterly direction
and that there is negligible movement of brines in a southerly direction towards the River Murray. The model is used to consider
various management scenarios. Salt-load movement to the River Murray was highest in a "worst-case" scenario with irrigation
employed between the basin and the River Murray. Present-day operating conditions lead to little, if any, direct movement
of brine from the basin into the river.
Electronic Publication 相似文献
72.
The Gondwana successions (1–4 km thick) of peninsular India accumulated in a number of discrete basins during Permo-Triassic period. The basins are typically bounded by faults that developed along Precambrian lineaments during deposition, as well as affected by intrabasinal faults indicating fault-controlled synsedimentary subsidence. The patterns of the intrabasinal faults and their relationships with the respective basin-bounding faults represent both extensional and strike-slip regimes. Field evidence suggests that preferential subsidence in locales of differently oriented discontinuities in the Precambrian basement led to development of Gondwana basins with varying, but mutually compatible, kinematics during a bulk motion, grossly along the present-day E–W direction. The kinematic disparity of the individual basins resulted due to different relative orientations of the basement discontinuities and is illustrated with the help of a simple sandbox model. The regional E–W motion was accommodated by strike-slip motion on the transcontinental fault in the north. 相似文献
73.
Variations in long term wind speed during different decades in Arabian Sea and Bay of Bengal 总被引:1,自引:0,他引:1
A study has been carried out by comparing the extreme wind speeds estimated based on NCEP/NCAR reanalysis data for 100 years
return period using Fischer Tippet-1 (commonly known as Gumbel) and Weibull distributions for three locations (off Goa, Visakhapatnam
and Machilipatnam) in the north Indian Ocean. The wind dataset for Goa is compared with that from ERA-40 data. For higher
wind speeds (12–20m s−1), NCEP wind speed has higher percentage of occurrence than that of ERA-40. Analysis has shown slight upward trend in the
annual maximum wind for location off Machilipatnam with an increase of 1.2 cm s−1 per year and a decreasing trend of −1.3 cm s−1 per year in the case of Goa. The Weibull distribution with shape parameter 2 fits the annual maximum wind data better than
FT-1 distribution. 相似文献
74.
In the middle of 2007, a severe flood affected the People’s Republic of Bangladesh. This is a natural disaster that takes
people’s lives, destroys livestock, infrastructures and communication systems and, damages crops and fish ponds. Despite many
adverse impacts, the flood situation is an accepted phenomenon to the citizens of Bangladesh, due to the immense increase
of soil fertility due to the flood, plus, the recharge of aquifer, ecosystem and fish. The flood of 2007 was the 5th major
flood of the last 20 years when more than thirty-five percent of the area of the country was inundated with flood water. As
in the past, the flood of 2007 had its own significance. The geography of the country contains a floodplain delta of three
major river basins: the Ganges, the Brahmaputra and the Meghna (GBM). The mean monthly rainfall plot from the TRMM satellite
data has shown that for both the Meghna and Brahmaputra basins, the rainfall was higher during July 2007 than any other months
of the last 2 years. This excess rainfall had accumulated in the Brahmaputra and Meghna rivers and carried downstream to Bangladesh.
This was the main cause of the flooding in 2007. The first crossing above the danger level of the river waters was observed
at Durgapur station of the Someswari and at Sunamganj station of the Surma on the nineteenth of July, 2007 inside Bangladesh.
In terms of magnitude of the peak and duration of the flood, the Brahmaputra was higher in 2007 than during 2004. However,
the Ganges river water level never crossed the danger level during flood of 2007. The Meghna was lower during the flood peak
for the duration of the flood in 2007. The year–to-year variability in both the magnitude and duration of the flood suggests
changes in rainfall and landuse pattern of the catchment. 相似文献
75.
Jagadish Prasad Sahoo Pradip Kumar Pradhan 《Geotechnical and Geological Engineering》2010,28(6):889-897
An experimental investigation was undertaken to study the effects of lime-stabilized soil-cushion on the strength behavior
of expansive soil. In the present investigation, a series of laboratory tests (Unconfined compression tests and CBR tests)
were conducted on both expansive soil alone and expansive soil cushioned with lime-stabilized non-expansive cohesive soil.
Lime contents of 2, 4, 6, 8 and 10% by dry weight of cohesive non-swelling soil was used in the stabilized soil cushion. Both
expansive soil and lime stabilized soil cushion were compacted to Standard Proctor’s optimum condition with thickness ratio
2:1. Tests on cushioned expansive soils were conducted at different curing and soaking periods i.e., 7, 14, 28 and 56 days.
The test results revealed that maximum increase in strength was achieved after 14 days of curing or soaking period with 8%
of lime content. 相似文献
76.
The concept of the equivalent free surface has been extended to determine the seismic horizontal pullout capacity of shallow
vertical strip plate anchors buried in sand. The analysis has been done rigorously by using the method of stress characteristics.
The results have been expressed in the form of non-dimensional charts. The pullout resistance has been found to reduce quite
extensively with increase in the magnitude of horizontal earthquake acceleration. The results were compared with the previously
published data, and it was seen that the computed pullout resistance with the proposed method was found to be lowest.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
77.
In this paper we present a method for computing the equilibrium structures and various physical parameters of a primary component
of the binary system assuming that the primary is more massive than the secondary and is rotating differentially according
to the law of the w2 = b0 + b1 × s2 + b2 × s4, w being the angular velocity of rotation of a fluid element distant s from the axis of rotation and b0, b1, b2 suitably chosen numerical constants. This method utilizes the averaging approach of Kippenhahn and Thomas (1997) and the
concept of Roche equipotentials in a manner earlier used by Mohan et al. (1997) to incorporate the effects of rotation and
tidal distortions on the equilibrium structures of certain rotationally and tidally distorted stellar models. The use of the
method has been illustrated by applying it to obtain the structures and some observable parameters of certain differentially
rotating and tidally distorted binary systems whose primary component is assumed to be a white dwarf star. 相似文献
78.
A model of the predawn bulge ionosphere composition and structure is constructed and compared with the ion mass spectrometer measurements from the Pioneer Venus Orbiter during orbits 117 and 120. Particular emphasis is given to the identification of the mass-2 ion which we find unequivocally due to D+ (and not H2+). The atmospheric D/H ratio of 1.4% and 2.5% is obtained at the homopause (~ 130 km) for the two orbits. The H2+ contribution to the mass-2 ion density is less than 10%, and the H2 mixing ratio must be <0.1 ppm at 130 km altitude. The He+ data require a downward He+ flux of ~2 × 107 cm?2 sec?1 in the predawn region which suggest that the light ions also flow across the terminator from day to night along with the observed O+ ion flow. 相似文献
79.
A discrete time-delay control (DTDC) law for a general six degrees of freedom unsymmetric autonomous underwater vehicle (AUV) is presented. Hydrodynamic parameters like added mass coefficients and drag coefficients, which are generally uncertain, are not required by the controller. This control law cancels the uncertainties in the AUV dynamics by direct estimation of the uncertainties using time-delay estimation technique. The discrete-time version of the time-delay control does not require the derivative of the system state to be measured or estimated, which is required by the continuous-time version of the controller. This particularly provides an advantage over continuous-time controller in terms of computational effort or availability of sensors for measuring state derivatives, i.e., linear and angular accelerations. Implementation issues for practical realization of the controller are discussed. Experiments on a test-bed AUV were conducted in depth, pitch, and yaw degrees of freedom. Results show that the proposed control law performs well in the presence of uncertainties. 相似文献
80.
Planar waves events recorded in a seismic array can be represented as lines in the Fourier domain. However, in the real world, seismic events usually have curvature or amplitude variability, which means that their Fourier transforms are no longer strictly linear but rather occupy conic regions of the Fourier domain that are narrow at low frequencies but broaden at high frequencies where the effect of curvature becomes more pronounced. One can consider these regions as localised “signal cones”. In this work, we consider a space–time variable signal cone to model the seismic data. The variability of the signal cone is obtained through scaling, slanting, and translation of the kernel for cone‐limited (C‐limited) functions (functions whose Fourier transform lives within a cone) or C‐Gaussian function (a multivariate function whose Fourier transform decays exponentially with respect to slowness and frequency), which constitutes our dictionary. We find a discrete number of scaling, slanting, and translation parameters from a continuum by optimally matching the data. This is a non‐linear optimisation problem, which we address by a fixed‐point method that utilises a variable projection method with ?1 constraints on the linear parameters and bound constraints on the non‐linear parameters. We observe that slow decay and oscillatory behaviour of the kernel for C‐limited functions constitute bottlenecks for the optimisation problem, which we partially overcome by the C‐Gaussian function. We demonstrate our method through an interpolation example. We present the interpolation result using the estimated parameters obtained from the proposed method and compare it with those obtained using sparsity‐promoting curvelet decomposition, matching pursuit Fourier interpolation, and sparsity‐promoting plane‐wave decomposition methods. 相似文献