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1.
Borehole data reveals that during Late Quaternary, the Ganga river was non-existent in its present location near Varanasi.
Instead, it was flowing further south towards peripheral craton. Himalayan derived grey micaceous sands were being carried
by southward flowing rivers beyond the present day water divide of Ganga and mixed with pink arkosic sand brought by northward
flowing peninsular rivers. Subsequently, the Ganga shifted to its present position and got incised. Near Varanasi, the Ganga
river is flowing along a NW-SE tectonic lineament. The migration of Ganga river is believed to have been in response to basin
expansion caused due to Himalayan tectonics during Middle Pleistocene times.
Multi-storied sand bodies generated as a result of channel migration provide excellent aquifers confined by a thick zone of
muddy sediments near the surface. Good quality potable water is available at various levels below about 70 m depth in sandy
aquifers. Craton derived gravelly coarse-to-medium grained sand forms the main aquifer zones of tens of meter thickness with
enormous yield. In contrast, the shallow aquifers made up of recycled interfluve silt and sandy silt occur under unconfined
conditions and show water-level fluctuation of a few meters during pre-and post-monsoon periods. 相似文献
2.
Subsurface dams to harvest rainwater— a case study of the Swarnamukhi River basin, Southern India 总被引：2，自引：0，他引：2
Declining water level trends and yields of wells, deterioration of groundwater quality and drying up of shallow wells are common in many parts of India. This is mainly attributed to the recurrence of drought years, over exploitation of groundwater, increase in the number of groundwater structures and explosion of population. In this subcontinent, the saving of water has to be done on the days it rains. India receives much of its rainfall in just 100 h in a year mostly during the monsoon period. If this water is not captured or stored, the rest of the year experiences a precarious situation manifest in water scarcity. The main objective behind the construction of subsurface dams in the Swarnamukhi River basin was to harvest the base flow infiltrating into sandy alluvium as waste to the sea and thereby to increase groundwater potential for meeting future water demands. An analysis of hydrographs of piezometers of four subsurface dams, monitored during October 2001–December 2002, reveals that there is an average rise of 1.44 m in post-monsoon and 1.80 m in the pre-monsoon period after the subsurface dams were constructed. Further, during the pre-monsoon month of June, much before construction of subsurface dams in October 2001, the water level was found fluctuating in the range of 3.1–10 m, in contrast to the fluctuation ranging from 0.4 to 3.1 m during the period following the construction of dams. Hence, the planning of rainwater harvesting structures entails thorough scientific investigations for identifying the most suitable locations for subsurface dams. 相似文献
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4.
N. Janardhana Raju 《Environmental Geology》2007,52(6):1067-1074
In the management of water resources, quality of water is just as important as its quantity. In order to know the quality
and/or suitability of groundwater for domestic and irrigation in upper Gunjanaeru River basin, 51 water samples in post-monsoon
and 46 in pre-monsoon seasons were collected and analyzed for various parameters. Geological units are alluvium, shale and
quartzite. Based on the analytical results, chemical indices like percent sodium, sodium adsorption ratio, residual sodium
carbonate, permeability index (PI) and chloroalkaline indices were calculated. The pre-monsoon waters have low sodium hazard
as compared to post-monsoon season. Residual sodium carbonate values revealed that one sample is not suitable in both the
seasons for irrigation purposes due the occurrence of alkaline white patches and low permeability of the soil. PI values of
both seasons revealed that the ground waters are generally suitable for irrigation. The positive values of Chloroalkaline
indices in post-monsoon (80%) and in pre-monsoon (59%) water samples indicate absence of base-exchange reaction (chloroalkaline
disequilibrium), and remaining samples of negative values of the ratios indicate base-exchange reaction (chloroalkaline equilibrium).
Chadha rectangular diagram for geochemical classification and hydrochemical processes of groundwater for both seasons indicates
that most of waters are Ca–Mg–HCO3 type. Assessment of water samples from various methods indicated that majority of the water samples in both seasons are suitable
for different purposes except at Yanadipalle (sample no. 8) that requires precautionary measures. The overall quality of groundwater
in post-monsoon season in all chemical constituents is on the higher side due to dissolution of surface pollutants during
the infiltration and percolation of rainwater and at few places due to agricultural and domestic activities. 相似文献
5.
Measuring and forecasting recruitment are central to the understanding and management of fish stocks. Kainge et al. (2013) studied the effect of spawning stock size and environmental fluctuations on the recruitment levels of the Cape hake Merluccius capensis in Namibia. However, their study contains some flaws that undermine the conclusion that Cape hake recruitment is under the influence of upwelling in summer. Until those flaws are properly addressed, this conclusion, in our view, should be treated with caution. 相似文献
6.
N. Janardhana Raju 《Journal of the Geological Society of India》2012,79(3):302-314
The study area covers an about 100 km2 of the middle Ganga plain in Uttar Pradesh, experiencing intensive groundwater extraction. In order to recognize the arsenic
contamination zones of the Varanasi environs, sixty eight groundwater samples have been collected and analyzed for major ions,
iron and arsenic. Twenty one sediment samples in the four boreholes were also collected to deduce the source of arsenic in
the groundwater. The preliminary survey reports for the first time indicates that part of rural and urban population of Varanasi
environs are drinking and using for irrigation arsenic contaminated water mostly from hand tube wells (<70 m). The study area
is a part of middle Ganga plain which comprises of Quaternary alluvium consists of an alternating succession of clay, clayey
silt and sand deposits. The high arsenic content in groundwater samples of the study area indicates that 14% of the samples
are exceeding the 10 μg/l and 5% of the samples are exceeding 50 μg/l. The high arsenic concentration is found in the villages
such as Bahadurpur, Madhiya, Bhojpur, Ratanpur, Semra, Jalilpur, Kateswar, Bhakhara and Kodupur (eastern side of Ganga River
in Varanasi), situated within the newer alluvium deposited during middle Holocene to Recent. The older alluvial aquifers situated
in the western side of the Ganga River are arsenic safe (maximum As concentration of 9 μg/l) though the borehole sediments
shows high arsenic (mean 5.2 mg/kg) and iron content (529 mg/kg) in shallow and medium depths. This may be due to lack of
reducing conditions (i.e organic content) for releasing arsenic into the groundwater. Rainfall infiltration, organic matter
from recently accumulated biomass from flood prone belt in the newer alluvium plays a critical role in releasing arsenic and
iron present in sediments. The main mechanism for the release of As into groundwater in the Holocene sandy aquifer sediments
of Varanasi environs may be due to the reductive dissolution of Fe oxyhydroxide present as coatings on sand grains as well
as altered mica content. The high societal problems of this study will help to mitigate the severity of arsenic contamination
by providing alternate drinking water resources to the people in middle Ganga plain and to arrange permanent arsenic safe
drinking water source by the authorities. 相似文献
7.
S.M. Moosavirad M.R. Janardhana M.S. Sethumadhav M.R. Moghadam M. Shankara 《Chemie der Erde / Geochemistry》2011,71(3):279-288
Lower Jurassic shales of the Shemshak Formation of Kerman Province, Central Iran, were analyzed for major and selected trace elements to infer their provenance, intensity of palaeoweathering of the source rocks and tectonic setting. Plots of shales on Al2O3 wt.% versus TiO2 wt.% diagram and Cr (ppm) versus Ni (ppm) diagram indicate that acidic (granitic) rocks constitute the source rocks in the provenance. Average CIA, PIA and CIW values (84%, 92%, 93%, respectively) imply intense weathering of the source material. Plots of shales on bivariate discriminant function diagram reveal an active continental margin setting for the provenance. The inferred tectonic setting for the Lower Jurassic shales of the Shemshak Formation of Kerman Province is in agreement with the tectonic evolutionary history of the Central Iran during the Jurassic period. 相似文献
8.
N Loiseau JJ Kiszka T Bouveroux MR Heithaus M Soria P Chabanet 《African Journal of Marine Science》2016,38(1):73-79
Bull sharks Carcharhinus leucas are common along the coast of Reunion Island (South-West Indian Ocean) and were suspected to aggregate in the vicinity of an aquaculture farm in Saint-Paul Bay on the west coast. In order to understand the behaviour and interaction of bull sharks near aquaculture cages at Saint-Paul Bay, we deployed an experimental unbaited stationary video camera. From 175 hours of recording during daylight hours from March to April 2012, eight individual female bull sharks (seven adults and one immature) were identified based on their natural markings. These sharks were resighted between 3 and 45 times. Residency analysis revealed site attachment under the aquaculture cages for at least three individuals over the course of the study. Recorded behaviours included intraspecific social interactions such as synchronised swimming. Social interactions and relatively strong paired associations for two pairs of females suggest some level of sociality among bull sharks around Reunion Island. Overall, our results demonstrate the utility of unbaited video systems to monitor the behaviour of adult coastal sharks. 相似文献
9.
S. M. Moosavirad M. R. Janardhana Houshang Khairy 《Environmental Earth Sciences》2013,69(7):2451-2467
Groundwater of an aquifer located in the vicinity of a large coal washery near Zarand City, Iran consists of two hydrochemically differing facies, which have been informally designated as groundwater (A) and groundwater (B). Groundwater (A) is native, brackish in composition and is characterized by Na+ > Mg2+ > Ca2+ > K+ and SO4 2? > HCO3 ? > Cl? > NO3 ?. Spearman’s rank correlation coefficient matrices, factor analysis data, and values of chloro-alkaline indices, C ratio and Na+/Cl? molar ratio indicate that in the groundwater (A), the ionic load of Ca2+, Mg2+, Na+, K+, SO4 2? and HCO3 ? is derived essentially from weathering of both carbonates and aluminosilicates and direct cation and reverse cation–anion exchange reactions. Groundwater (B) is the polluted variant of the groundwater (A), brackish to saline in composition, and unlike the groundwater (A), consists of HCO3 ? as the dominant anion. In comparison with the groundwater (A), the groundwater (B) contains higher concentrations of all ions, and its average ionic load (av. = 59.74 me/L) is 1.43 times higher than that of the groundwater (A) (av. = 41.54 me/L). Additional concentrations of Ca2+, Mg2+, K+, SO4 2?, Cl? and HCO3 ? in the groundwater (B) are provided mainly by downward infiltrating water from the coal washery tailings pond and reverse cation–anion exchange reaction between tailings pond water and exchanger of the aquifer matrix during non-conservative mixing process of groundwater (A) and tailings pond water. Certain additional concentrations of Na+, K+ and NO3 ? in the groundwater (B) are provided by other anthropogenic sources. Quality wise, both groundwaters are marginally suitable for cultivation of salt-tolerant crops only. 相似文献
10.
S. M. Moosavirad M. R. Janardhana M. S. Sethumadhav K. N. Prakash Narasimha 《Journal of the Geological Society of India》2012,79(5):483-496
Lower Jurassic sandstones of Shemshak Formation of Kerman basin, central Iran were analyzed for major and select trace elements to infer their provenance, palaeoweathering of source rocks and tectonic setting. Average modal framework components (Qt: F: L= 67.25: 2.41: 30.48) and chemical composition of the sandstones classify them as litharenites. The sandstones are quartz-rich (～ 67% quartz; 75.34 wt.% SiO2) and derived from a recycled orogen composed of quartzose sedimentary rocks. Average CIA, PIA and CIW values (69%, 76% and 80%, respectively) indicate moderate to intense chemical weathering of the source material. The inferred index of weathering/alteration is the sum total of intensities of weathering witnessed by the lithocomponents during atleast two cycles of sedimentation involving (1) chemical weathering of the source rocks («ultimate» granodiorite source and «proximal» quartzose sedimentary source), (2) chemical weathering during fluvial transport of the detritus, (3) chemical weathering of the detritus in depocenters, and (4) chemical weathering during diagenesis. Sandstones exhibit moderate maturity and were deposited under humid climatic conditions. Plots of the chemical analyses data on tectonic setting discrimination diagrams indicate active continental margin setting, which is in agreement with the tectonic evolutionary history of the Central Iran during Jurassic period. 相似文献