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101.
The Indian subcontinent has the largest semi-arid tropical (SAT) area among developing nations. The State of Andhra Pradesh
falls under the SAT region in India and is mostly covered by compact and hard rocks, characterized by seasonal rainfall of
a highly fluctuating nature, in both space and time. As a consequence of the green revolution and an increase in industrial
activity, there has been an increase in the utilization of groundwater resources during the last two decades in Andhra Pradesh.
The development has also caused a number of problems, such as water table decline, decrease in well yields and seawater intrusion.
Although major irrigation projects have contributed to improved agricultural production, the associated problems of waterlogging,
salinization and loss of valuable bioresources have led to the gradual degradation of the land, affecting agricultural productivity.
Surface water and groundwater have also been polluted in several parts of the State because of untreated discharge of effluents
from the industries into nearby streams or open lands. A brief account of the overall scenario of the hydrogeological framework
and geo-environmental effects on the groundwater regime in Andhra Pradesh is presented. Possible management practices and
conservation methods are suggested.
Received: 9 August 1999 · Accepted: 10 July 2000 相似文献
102.
Steady plane flows of an incompressible rotating viscous fluid with infinite electrical conductivity are studied. Certain results of physical importance have been deduced for orthogonal flows. Lastly, the solutions to vortex and source flow problems are obtained. 相似文献
103.
D.K. Babu 《Advances in water resources》1977,1(2):111-116
The problem of vertical infiltration is solved by means of perturbation methods. The structure of the solution exhibits uniform validity for all times and all depths. For comparison between prediction and an exact result, the Burgers equation has been selected. This equation is mildly nonlinear and hence constitutes the most unfavourable known example. 相似文献
104.
The obstruction to flow around a pile placed in an erodible seabed causes scour leading to changes in the bed elevation in the vicinity of the pile. In the present investigation, scour around piles induced by the seabed current has been studied in a wave flume using model piles of diameters 50, 90 and 110 mm embedded in a silty clay soil bed. The particulate movement due to scour is time dependent and in case of sediments with particle sizes ranging upto clay fractions, the measurement of scour becomes extremely difficult. This paper presents a simplified experimental technique for the measurement of scour depth with time around a pile foundation in a silty clay soil. 相似文献
105.
The variations in CaCO3 and organic carbon and their inter-relationship in a core from the southeastern Arabian Sea (water depth 2,212 m) have been
used to demarcate the Holocene/Pleistocene boundary; an increased terrigenous deposition during Late Pleistocene has been
inferred. The higher contents of organic carbon and sulfide sulfur and their negative relationship clearly establish the existence
of a reducing environment below 65 cm subbottom depth. The occurrence of pyrite framboids and crystals, present only on the
surface of fecal pellets (80–85 cm), has been discussed in terms of significance of reducing microenvironment. 相似文献
106.
A three-dimensional numerical model is developed and used to study the coastal upwelling processes and corresponding seasonal changes in the sea level along the west coast of India. The upwelling and associated sea level variations are seen as a response of coastal ocean to pure wind stress forcing. The model is designed to represent coastal ocean physics by resolving surface and bottom Ekman layers as realistically as possible. The prognostic variables are the three components of the velocity field, temperature, salinity and turbulent energy. The governing equations together with their boundary conditions are solved by finite-difference techniques. Experiments are performed to investigate sea level fluctuations associated with the thermal response and alongshore currents of the coastal waters. The model is forced with mean monthly wind stress forcing of January, May, July and September representing northeast monsoon and different phases of the southwest monsoon. It is known from the observational study that the upwelling process reaches to the surface waters by May along the coastal waters of the extreme southwest peninsular region. The process is more intense in July compared to May and September and its strength decreases from south to north. However, during the northeast monsoon season, which is represented by January wind stress forcing in the model, downwelling is simulated along the coast. The model simulations of the coastal response are compared with the observations and are found to be in good agreement. The maximum computed vertical velocity of about 2.0 ×10 -3 cm s -1 is predicted in July in the southern region off the coast. 相似文献
107.
K. Krishna Moorthy S. K. Satheesh S. Suresh Babu C. B. S. Dutt 《Journal of Earth System Science》2008,117(1):243-262
During March–May 2006, an extensive, multi-institution, multi-instrument, and multi-platform integrated field experiment ‘Integrated Campaign for Aerosols, gases and Radiation Budget’ (ICARB) was carried out under the Geosphere Biosphere Programme of the Indian Space Research Organization (ISRO-GBP). The objective of this largest and most exhaustive field campaign, ever conducted in the Indian region, was to characterize the physico-chemical properties and radiative effects of atmospheric aerosols and trace gases over the Indian landmass and the adjoining oceanic regions of the Arabian Sea, northern Indian Ocean, and Bay of Bengal through intensive, simultaneous observations. A network of ground-based observatories (over the mainland and islands), a dedicated ship cruise over the oceanic regions using a fully equipped research vessel, the Sagar Kanya, and altitude profiling over selected regions using an instrumented aircraft and balloonsondes formed the three segments of this integrated experiment, which were carried out in tandem. This paper presents an overview of the ICARB field experiment, the database generated, and some of its interesting outcomes though these are preliminary in nature.
The ICARB has revealed significant spatio-temporal heterogeneity in most of the aerosol characteristics both over land and ocean. Observed aerosol loading and optical depths were comparable to or in certain regions, a little lower than those reported in some of the earlier campaigns for these regions. The preliminary results indicate:
相似文献
- low (< 0.2) aerosol optical depths (AOD) over most part of the Arabian Sea, except two pockets; one off Mangalore and the other, less intense, in the central Arabian Sea at ~18°N latitude
- High Ångström exponent in the southern Arabian Sea signifying steep AOD spectra and higher abundance of accumulation mode particles in the southern Arabian Sea and off Mangalore
- Remarkably low Ångström exponents signifying increased concentration of coarse mode aerosols and high columnar abundance in the northern Arabian Sea
- Altitude profiles from aircraft showed a steady BC level up to 3 km altitude with structures which were associated with inversions in the atmospheric boundary layer (ABL)
- A surprisingly large increase in the BC mass fraction with altitude
- Presence of a convectively mixed layer extending up to about 1 km over the Arabian Sea and Bay of Bengal
- A spatial off shore extent of <100 km for the anthropogenic impact at the coast; and
- Advection of aerosols, through airmass trajectories, from west Asia and NW arid regions of India leading to formation of elevated aerosol layers extending as far as 400 km off the east coast.
108.
Vijayakumar S. Nair K. Krishna Moorthy S. Suresh Babu K. Narasimhulu L. Siva Sankara Reddy R. Ramakrishna Reddy K. Rama Gopal V. Sreekanth B. L. Madhavan K. Niranjan 《Journal of Earth System Science》2008,117(1):315-323
Mass concentration and mass size distribution of total (composite) aerosols near the surface are essential inputs needed in developing aerosol models for radiative forcing estimation as well as to infer the environment and air quality. Using extensive measurements onboard the oceanographic research vessel, Sagar Kanya, during its cruise SK223B in the second phase of the ocean segment of the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB), the spatial distribution of the mass concentration and mass size distribution of near-surface aerosols are examined for the first time over the entire Arabian Sea, going as far as 58°E and 22°N, within a span of 26 days. In general, the mass concentrations (M T ) were found to be low with the mean value for the entire Arabian Sea being 16.7 ± 7 μg m?3; almost 1/2 of the values reported in some of the earlier campaigns. Coarse mode aerosols contributed, on an average, 58% to the total mass, even though at a few pockets accumulation mode contribution dominated. Spatially, significant variations were observed over central and northern Arabian Sea as well as close to the west coast of India. In central Arabian Sea, even though the M T was quite low, contribution ofs accumulation aerosols to the total mass concentration was greater than 50%. Effective radius, a parameter important in determining scattering properties of aerosol size distribution, varied between 0.07 and 0.4 μm with a mean value of 0.2 μm. Number size distributions, deduced from the mass size distributions, were approximated to inverse power-law form and the size indices (ν) were estimated. It was found to vary in the range 3.9 to 4.2 with a mean value of 4.0 for the entire oceanic region. Extinction coefficients, estimated using the number-size distributions, were well-correlated with the accumulation mode mass concentration with a correlation coefficient of 0.82. 相似文献
109.
The stable isotope analysis of all major rain events from Moinabad (MB), Rajendranagar (RN) and Osmanasagar (OS) reservoir, three closely placed locations in Hyderabad, India, were carried out during the 2005 to 2008 period. The OS station recorded the highest amount of rainfall with an average value of 1000 mm, whereas the MB station recorded the lowest average rainfall of 790 mm. The stable isotope (δ18O) values of the precipitation samples during these period varied from ?11.43‰ to ?0.03‰ for the MB station, ?8.21‰ to 0.54‰ for the RN station and ?11.47‰ to 0.72‰ for the OS station. The d‐excess of precipitation at the three stations also showed considerable variations and revealed that the precipitation in the region undergoes significant modification through secondary evaporation during its fall. The possible causes for these observed spatial and temporal variations in amount and the isotopic composition of precipitation in a small geographical area within the city were studied. The observed variations may be attributed to the regional scale differences in water budget induced by rapid urbanisation activities in the city coupled with the differences in secondary effects undergone by the falling drops. This study elucidating changes in precipitation patterns in the city and its possible causes may largely help in its water balance calculation. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
110.
Ajay Kumar A. S. Venkatesh P. V. Ramesh Babu S. Nayak 《Journal of the Geological Society of India》2012,79(3):279-286
Petrographic and EPMA studies reveal the presence of discrete grains of uraninite and pyrite are being reported for the first
time in quartz-pebble conglomerates from western margin of Bonai granite pluton, Sundargarh district, Orissa. Uraninite grains
(2–3 μ in size) are subrounded to muffin shaped which show variation in UO2 (63.86 to 71.73 wt %), ThO2 (5.48 to 6.42 wt %) and RE2O3 (1.57 to 2.23 wt %). Pegmatitic source of uraninite is revealed by comparing UO2, ThO2, PbO, CaO content and ratios of UO2/ThO2 and CaO/ThO2 in uraninites from pegmatite and other environments and areas. Subrounded to muffin shape of uraninite, their association
with subrounded pyrite and heavies like zircon, tourmaline, chromite, monazite, magnetite and their comparable chemistry with
well established quartzpebble conglomerates of India and world are indicative of their detrital origin. Pyrite, minor chalcopyrite
and rare galena are observed as sulphide phases in conglomerate. Variable shapes of pyrite, their low Co (up to 0.16 wt %)
and Ni contents (up to 0.09 wt %) and Co/Ni ratio less than 1.0 (mean= 0.63) favours sedimentary/diagenetic origin. 相似文献