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1.
Socio-economic and Environmental Implications of the Hydroelectric Projects in Uttarakhand Himalaya, India 总被引：1，自引：1，他引：0
This paper deals with detailed analysis of the fiasco created by the Tehri High Dam in Uttarakhand, India, particularly in terms of resettlement and rehabilitation of the local inhabitants. Aspects pertaining to the environmental issues are also discussed. Currently, the river valleys in Uttarakhand state of India are the targets of increasing hydroelectric projects. Virtually all rivers are being exploited for generating environmental friendly power. Having being learned the hard lesson from Tehri Dam, it has been decided to opt for such schemes in which comparatively little submergence and tempering with the fragile eco-systems is involved.However, our observations suggest that even in such schemes if due care is not taken they may turn out to be a failure. 相似文献
2.
Navin juyal Yaspal Sundriyal Naresh rana Shipra chaudhary Ashok k. Singhvi 《第四纪科学杂志》2010,25(8):1293-1304
The present study aims to explain the spatial and temporal variability in phases of aggradation/incision in response to changes in climate and seismicity during the late Quaternary in the Alaknanda River valley (a major tributary of the river Ganges or Ganga). Geomorphology, stratigraphy and optical dating of the fluvial sediment reveal that the oldest fluvial landforms preserved in the south of the Main Central Thrust are debris flow terraces developed during the early part of pluvial Marine Isotopic Stage 3. Following this, a period of accelerated incision/erosion owing to an increase in uplift rate and more intense rainfall occurred. In the Lesser Himalaya, three phases of valley fill aggradation around 26 ± 3 ka, 18 ± 2 ka and 15 ± 1 ka and 8 ± 1 ka occurred in response to changes in monsoon intensity and sediment flux. The last phase was regionally extensive and corresponds to a strengthening of the early Holocene Indian Summer Monsoon. A gradual decline in the monsoon strength after 8 ± 1 ka resulted in reduced fluvial discharge and lower sediment transport capacity of the Alaknanda River, leading to valley fill incision and the development of terraces. The study suggests that fluvial dynamics in the Alaknanda valley were modulated by monsoon variability and the role of tectonics was subordinate, limited to providing accommodation space and post‐deposition modification of the fluvial landforms. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
3.
Field stratigraphy, sedimentology and optically stimulated luminescence (OSL) dating have been used to reconstruct the southwest monsoon variability in the semi‐arid region of southern India during the late Holocene. Facies architecture and OSL dating of the water‐lain sediment suggest prevalence of a weak hydrological regime around 3 ka. Following this, a progressive strengthening of monsoon occurred till 2 ka. After 2 ka and until 1 ka fluvial activity was nearly dormant, indicating weakening of the monsoon. Presence of high‐magnitude flood deposits, overbank sedimentation and pedogenesis during 1–0.6 ka indicate intensification of the southwest monsoon in the basin. The onset of aridity was associated with episodic storm surge events that are manifested in the pond sedimentation and localised aeolian accretion. This phase is bracketed between 0.5 ka and 0.2 ka. A renewed phase of monsoonal activity was observed in the form of floodplain aggradation between 180 and 90 years ago. In the past 70 years no significant change in the monsoon performance has been observed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
Neeraj Singh Bankoti Navin Chandra Joshi Bimal Pande Seema Pande Wahab Uddin Kavita Pandey 《New Astronomy》2011,16(4):269-275
This paper presents the study of normalized north–south asymmetry, cumulative normalized north–south asymmetry and cumulative difference indices of sunspot areas, solar active prominences (at total, low (?40°) and high (?50°) latitudes) and Hα solar flares from 1964 to 2008 spanning the solar cycles 20–23. Three different statistical methods are used to obtain the asymmetric behavior of different solar activity features. Hemispherical distribution of activity features shows the dominance of activities in northern hemisphere for solar cycle 20 and in southern hemisphere for solar cycles 21–23 excluding solar active prominences at high latitudes. Cumulative difference index of solar activity features in each solar cycle is observed at the maximum of the respective solar cycle suggesting a cyclic behavior of approximately one solar cycle length. Asymmetric behavior of all activity features except solar active prominences at high latitudes hints at the long term periodic trend of eight solar cycles. North–south asymmetries of SAP (H) express the specific behavior of solar activity at high solar latitudes and its behavior in long-time scale is distinctly opposite to those of other activity features. Our results show that in most cases the asymmetry is statistically highly significant meaning thereby that the asymmetries are real features in the N–S distribution of solar activity features. 相似文献
5.
Land cover change over the last three centuries due to human activities: The availability of new global data sets 总被引：15，自引：0，他引：15
Land use and land cover change is an important driver of global change (Turner et al., 1993). It is recognized that land use change has important consequences for global and regional climates, the global biogeochemical cycles such as carbon, nitrogen, and water, biodiversity, etc. Nevertheless, there have been relatively few comprehensive studies of global, long-term historical changes in land cover due to land use. In this paper, we review the development of global scale data sets of land use and land cover change. Furthermore, we assess the differences between two recently developed global data sets of historical land cover change due to land use. Based on historical statistical inventories (e.g. census data, tax records, land surveys, historical geography estimates, etc) and applying different spatial analysis techniques, changes in agricultural land cover (croplands, pastures) were reconstructed for the last 300 years. The two data sets indicate that cropland areas expanded from 3–4 million km2 in 1700 to 15–18 million km2 in 1990 (mostly at the expense of forests), while grazing land area expanded from 5 million km2 in 1700 to 31 million km2 in 1990 (mostly at the expense of natural grasslands). The data sets disagree most over Latin America and Oceania, and agree best over North America. Major differences in the two data sets can be explained by the use of a fractional versus Boolean approach, different modelling assumptions, and inventory data sets. 相似文献
6.
Navin Chandra Joshi Neeraj Singh Bankoti Seema Pande Bimal Pande Kavita Pandey 《Solar physics》2009,260(2):451-463
In this article we present the results of a study of the spatial distribution and asymmetry of solar active prominences (SAP)
for the period 1996 through 2007 (solar cycle 23). For more meaningful statistical analysis we analyzed the distribution and
asymmetry of SAP in two subdivisions viz. Group1 (ADF, APR, DSF, CRN, CAP) and Group2 (AFS, ASR, BSD, BSL, DSD, SPY, LPS). The North – South (N – S) latitudinal distribution
shows that the SAP events are most prolific in the 21° to 30° slice in the Northern and Southern Hemispheres; the East – West
(E – W) longitudinal distribution study shows that the SAP events are most prolific (best observable) in the 81° to 90° slice
in the Eastern and Western Hemispheres. It was found that the SAP activity during this cycle is low compared to previous solar
cycles. The present study indicates that during the rising phase of the cycle the number of SAP events are roughly equal in
the Northern and Southern Hemispheres. However, activity in the Southern Hemisphere has been dominant since 1999. Our statistical
study shows that the N – S asymmetry is more significant then the E – W asymmetry. 相似文献
7.
Pradeep Srivastava Navin Juyal Ashok K. Singhvi Robert J. Wasson Mark D. Bateman 《Geomorphology》2001,36(3-4)
River adjustment and incision in the Sabarmati basin, Gujarat, India have been examined at a site near Mahudi. Towards this, the morphostratigraphy and depositional chronometry of the middle alluvial plains were investigated. The upper fluvial sequence, along with the overlying aeolian sand and riverbed scroll plains, provide clues to the evolution of the present Sabarmati River. Sedimentological analyses of the upper fluvial sequence indicate its deposition by a meandering river system during what is believed to be a persistent wetter phase. Luminescence chronology bracketed this sequence to between 54 and 30 ka, which corresponds to Oxygen Isotope Stage-3, during which the SW monsoon was enhanced. The overlying aeolian sand has been dated to 12 ka, indicating that dune accretion occurred simultaneously with the strengthening of the SW monsoon during the Early Holocene. Adjustment of the Sabarmati along a N–S transect is placed around 12 ka and the incision is bracketed between 12 and 4.5 ka. River adjustment could have been tectonic; however, the incision was facilitated by the availability of continuous flow in the river caused by the SW monsoon. The basin experienced two tectonic events at about 3 and 0.3 ka, as demonstrated by the morphology of the scroll plains. 相似文献
8.
Sanjay Kumar Navin Kumar Dwivedi R. P. Sharma Y.-J. Moon 《Astrophysics and Space Science》2018,363(10):204
We present an analytical model to explore the magnetic field turbulent spectrum by coupled high-frequency kinetic Alfvén wave (KAW) and slow mode of Alfvén wave (AW). The spectrum is computed as a realization of energy cascades from larger to smaller scales for a specific case of solar wind plasma at 1 AU. A two-fluid technique is implemented for the derivation of model equations leading two wave modes. These coupled, nonlinear equations are solved numerically. The nonlinearity in the system arises due to nonlinear ponderomotive force, which is believed to be responsible for the wave localization and magnetic islands formation. The numerical results show that the magnetic islands grow with time and attain a quasi-steady state after the modulation instability is saturated. The magnetic field spectrum and associated spectral indices are computed near the time of saturation of instability. The simulated spectrum in dispersion region follows a power-law with an index of ?2.5. The steeper spectrum could be attributed as energy transfer from larger to smaller scales and helps to study turbulence in solar wind. The magnetic field spectrum and spectral index show a good agreement with the observation of solar wind turbulent spectra. 相似文献
9.
Natural Hazards - Oceanic eddies span over a wide range of sizes and affect the thermodynamic properties of water column. By modifying the thermal structure of the upper ocean, these eddies... 相似文献
10.