Physical Habitat Assessment of River Denwa Using GIS Techniques     

Vipin Vyas  Ankit Kumar  Vivek Parashar  Shailendra Tomar 《Journal of the Indian Society of Remote Sensing》2013,41(1):127-139

Physical habitat of any aquatic ecosystem is an integral part upon which the biological structures of resident communities are built. Degradation of the physical habitat has serious consequences on aquatic communities and is among the leading causes of stream impairment worldwide. Therefore, a sound habitat assessment approach is necessary to assess the condition of running water and to determine if habitat degradation is responsible for any degradation in biological condition. The present study was focused on Physical Habitat Assessment of Denwa River, a sub tributary of river Narmada in central India, for generating a Habitat Suitability map. The Denwa River originates from Satpura ranges in central India and flows through entire Pachmarhi plateau supporting a diversity of habitats for aquatic flora and fauna. A survey was carried out to assess the physical characteristic of Denwa river (84 kms) from its origin to the confluence point of Tawa Denwa river. Six reaches have been identified in study area on the basis of their physiographic conditions. For Habitat Assessment measurement, Rapid Bioassessment Protocols for Stream and Wadeable rivers by United States Environmental Protection Agency (USEPA, 841-B-99-002) have been used. Seven parameters from this protocol have been chosen for physical characterization. GIS techniques have been used to develop a Habitat Suitability Map of the study area based on scores to illustrate its suitability to support aquatic life. The present paper discusses in detail the suitability of the different reaches of the River Denwa for supporting the aquatic biodiversity.  相似文献   

Investigations related to scientific deep drilling to study reservoir-triggered earthquakes at Koyna,India   总被引：1，自引：0，他引：1  

Harsh Gupta  N. Purnachandra Rao  Sukanta Roy  Kusumita Arora  V. M. Tiwari  Prasanta K. Patro  H. V. S. Satyanarayana  D. Shashidhar  K. Mallika  Vyasulu V. Akkiraju  Deepjyoti Goswami  Digant Vyas  G. Ravi  K. N. S. S. S. Srinivas  M. Srihari  S. Mishra  C. P. Dubey  D. Ch. V. Raju  Ujjal Borah  K. Chinna Reddy  Narendra Babu  Sunil Rohilla  Upasana Dhar  Mrinal Sen  Y. J. Bhaskar Rao  B. K. Bansal  Shailesh Nayak 《International Journal of Earth Sciences》2015,104(6):1511-1522

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Predicting suitable habitat of an invasive weed Parthenium hysterophorus under future climate scenarios in Chitwan Annapurna Landscape,Nepal     

MAHARJAN Seerjana  SHRESTHA Bharat Babu  JOSHI Mohan Dev  DEVKOTA Anjana  MUNIAPPAN Rangaswamy  ADIGA Abhijin  JHA Pramod Kumar 《山地科学学报》2019,(10)

Chitwan-Annapuma Landscape(CHAL)in central Nepal is known for its rich biodiversity and the landscape is expected to provide corridors for species range shift in response to climate change.Environmental assessments have identified biological invasions and other anthropogenic activities as major threats to the biodiversity in the CHAL.One of the rapidly spreading Invasive Alien Plant species(IAPs)in the CHAL is Parthenium hysterophorus L.,a neotropical invasive weed of global significance.This study aimed to investigate the current and future projected suitable habitat of P.hysterophorus in the CHAL using MaxEnt modelling in three"Representative Concentration Pathways"(RCPs 2.6,4.5 and 8.5)corresponding to different greenhouse gases emissiontrajectories for the year 2050 and 2070.A total of 288species occurrence points,six bioclimatic variablesmean diurnal range,isothermality,annual precipitation,precipitation of driest month,precipitation seasonality,precipitation of driest quarter and two topographic variables(aspect and slope)were selected for MaxEnt modelling.Potential range shift in terms of increase or decline in the suitable habitat areas under the projected scenarios were calculated.Slope and annual precipitation were the most important variables that explained the current distribution of P.hysterophorus.Twenty percent of the total area of CHAL was predicted to be suitable habitat for the growth of P.hysterophorus in the current climatic condition.Highest gain in the suitable habitat of this noxious weed was found under RCP 4.5 scenario in 2050 and 2070.whereas there will be a loss in thesuitable habitat under RCP 8.5 scenario in 2050 and2070.Out of four physiographic regions present in CHAL,three regions-Siwalik,Middle Mountain and High Mountain have suitable habitat for P.hysterophorus under current climatic condition.The mountainous region is likely to be affected more than the Siwalik region by further spread of P.fhysteropfhorus in the future under low(RCP 2.6)to medium(RCP 4.5)emission scenarios.The suitable habitat for this weed is likely to increase in the protected areas of mountain regions(Langtang National Park,Annapurna Conservation Area and Manaslu Conservation Area)in the future.The results have revealed a risk of spreading P.hysterophorus from present localities to non-invaded areas in the current and future climatic condition.Such risk needs to be considered by decision makers and resource managers while planning for effective management of this weed to reduce its ecological and economic impacts in the CHAL.  相似文献   

Radiatively-driven general relativistic jets     

Mukesh K. Vyas  Indranil Chattopadhyay 《Journal of Astrophysics and Astronomy》2018,39(1):12

We use moment formalism of relativistic radiation hydrodynamics to obtain equations of motion of radial jets and solve them using polytropic equation of state of the relativistic gas. We consider curved space-time around black holes and obtain jets with moderately relativistic terminal speeds. In addition, the radiation field from the accretion disc, is able to induce internal shocks in the jet close to the horizon. Under combined effect of thermal as well as radiative driving, terminal speeds up to 0.75 (units of light speed) are obtained.  相似文献   

Parallel velocity shear instabilities in an inhomogeneous plasma     

K. M. Srivastava  D. N. Vyas 《Astrophysics and Space Science》1979,62(2):353-366

The stability of an inhomogeneous anisotropic plasma flowing along a straight magnetic field has been investigated. Both the flow velocity and the plasma density are spatially varying in a direction perpendicular to the magnetic field. The stability of an interface between an inhomogeneous anisotropic plasma flowing along the magnetic field and the non-conducting compressible gas of uniform density flowing parallel to the interface has also been discussed. The effect of gyroviscosity and inhomogeneity on the Kelvin-Helmholtz shear instability has been discussed in certain limiting situations.  相似文献   

Highβ, energy flux conserving equilibria for alfvén wave     

D. N. Vyas  Krishna M. Srivastava 《Astrophysics and Space Science》1983,95(1):87-97

Magnetohydrodynamic waves in a high β, collisionless plasma with smooth variations in plasma parameters across the boundary is studied. The heating of collisionless plasma is analyzed in one dimension, including the effects of shear magnetic field and compressibility of plasma. Energy absorption rate and dispersion relation between central plasma, surrounded by tenuous plasma have also been derived.  相似文献   

Microstructural interpretations of modern and Pleistocene subglacially deformed sediments: the relative role of parent material and subglacial processes   总被引：1，自引：0，他引：1  

Anjana Khatwa  Slawek Tulaczyk 《第四纪科学杂志》2001,16(6):507-517

Analysis of till micromorphology represents a relatively new technique that has been used most frequently to infer the importance of subglacial shear in till genesis. This study aims to calibrate the technique by comparing Pleistocene tills from United Kingdom with a modern till (the UpB till) from beneath Ice Stream B, West Antarctica. Despite the fact that all of the tills examined have been interpreted as deforming‐bed deposits, the modern till has significantly less abundant and diverse microstructures than those found in the Pleistocene tills. Seventeen examined thin‐sections of the UpB till contain recognisable microstructures over only 0–30% of individual thin‐section area. The most common microstructures are: (i) birefringent clay patterns that are interpreted as shear zones and (ii) adherent matrix structures, which we interpret as uncomminuted remnants of the parent glacial/glaciomarine diamictons. Fourteen thin‐sections of the Pleistocene tills were covered by microstructures in 10–95% of their area. The Pleistocene microstructures include birefringent clays and adherent matrix structures, as in the UpB till, but also laminations and deformed pods made of chalk and sorted sediments. We conclude that the same till‐forming process, i.e. subglacial deformation, may result in distinctly different till micromorphology. This is a consequence of the fact that microstructural characteristics are strongly influenced by factors other than shear deformation. We identify three controls that may be important for forming contrasting microstructural assemblages: (i) strain magnitude, (ii) the degree of heterogeneity of parent material, and (iii) relative importance of sediment sorting by flowing water in the subglacial environment. Thus till micromorphology is sensitive to multiple factors, which with proper calibration may enhance the existing capability to interpret past subglacial conditions from microstructures. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Non-linear analysis of the stability of the Screw Pinch     

Krishna M. Srivastava  D. N. Vyas 《Astrophysics and Space Science》1982,86(1):71-89

Non-linear effects on the stability of the Screw Pinch in cylindrical system surrounded by a uniform pitch magnetic field in an incompressible pressureless plasma have been studied. A linear dispersion relation governing the stability of interface has been obtained with the help of normal mode analysis. Perturbation technique has been used to obtain the non-linear Schrödinger equation for the time variation of amplitudeA(t) which evolves according to . This can lead to non-linear stabilization, explosive instability or eventual decay, depending on the sign of . The whole calculations have been made form=1, kink modes in a sharp boundary plasma pinch. Non-linear analysis for -pinch (0) andz-pinch () have also been discussed in detail. It has been found that non-linear theory have a destabilizing influence on both - andz-pinches.  相似文献   

Daily variations ofE andF region drifts over Tiruchirapalli     

G D Vyas  H Chandra  R G Rastogi 《Journal of Earth System Science》1978,87(11):215-224

Daily variations of the E-W and N-S components of ionospheric drifts, measured using closely spaced receiver method over Tiruchirapalli near magnetic equator, are described for the periods 1973–75 forE region and 1974–75 forF region. N-S component is not observed except for a few occasions during summer months for theE region. E-W component is generally eastward during night hours and westward during day hours. There is a large day-to-day variability in the magnitude as well as in the evening reversal time. Daily variations primarily consist of the diurnal component with average amplitude of about 90 m/sec forF region and of about 80 m/sec forE region. The drift speeds are found to decrease with magnetic activity. It is concluded that the abnormal electrojet region extends upto north of Tiruchirapalli in the Indian zone and drifts here can be used as a monitor of electric field.  相似文献   

Geomagnetic disturbance effects on equatorial spreadF     

R G Rastogi  G D Vyas  H Chandra 《Journal of Earth System Science》1978,87(7):109-113

Geomagnetic disturbance effects on the occurrence of range and frequency spread at Huancayo are studied for the period 1957–74. The occurrence of frequency spread is decreased on disturbed days forD-months andE-months while duringJ-months an increase is noted in the post-midnight period. The occurrence of range spread is decreased on disturbed days in the pre-midnight hours duringD andE-months. Post-midnight hours ofD andE-months and all hours of night duringJ-months show an increase of range spread on disturbed days, which is most prominent during low sunspot years. The mean occurrence of frequency spread (2300–0100 LT) and range spread (2000–2300 LT) decrease with increasing ΣKp. On the other hand, occurrence of range spread (0300–0500 LT) increases with increasing ΣKp, and is suggested as the consequence of the changes of the horizontal electric field in theF-region associated with the geomagnetic storms.  相似文献