Time-dependence of salinity in monsoonal estuaries   总被引：1，自引：0，他引：1  

V. Vijith  D. SundarS.R. Shetye 《Estuarine, Coastal and Shelf Science》2009

The theories and classification schemes commonly used for understanding estuarine dynamics often refer to a steady state of the estuary in which the salinity field is time-independent. In this state salinity-ingress into the estuary due to different processes (diffusion, gravity current formation, impact of tidal asymmetries, etc.) is balanced by salinity-egress induced by runoff. Here we point out that the salinity field of the estuaries that are located on the coasts of the Indian subcontinent and come under the influence of the Indian Summer Monsoon (ISM) is never in a steady state. We refer to such estuaries as “monsoonal estuaries”, an example of which is the Mandovi estuary located on the west coast of India. We describe the annual cycle of the salinity field in this estuary and conclude that the essential unsteadiness of the salinity field arises from two features of the runoff into it. First, most of the runoff occurs as a series of episodes of highs and lulls spread over about 4 months of the wet summer monsoon. Second, the total runoff is large, well over an order of magnitude larger than the estuarine volume. We define two parameters to represent these two features, and show that they can be used to distinguish the monsoonal estuaries from others.  相似文献   

Study of stream temperature dynamics and corresponding heat fluxes within Miramichi River catchments (New Brunswick,Canada)     

Cindie Hebert  Daniel Caissie  Mysore G. Satish  Nassir El‐Jabi 《水文研究》2011,25(15):2439-2455

Water temperature is a key physical habitat determinant in lotic ecosystems as it influences many physical, chemical, and biological properties of rivers. Hence, a good understanding of the thermal regime of rivers and river heat fluxes is essential for effective management of water and fisheries resources. This study dealt with the modelling of river water temperature using a deterministic model. This model calculated the different heat fluxes at the water surface and from the streambed using different hydrometeorological conditions. The water temperature model was applied on two watercourses of different sizes and thermal characteristics, but within a similar meteorological region, namely, the Little Southwest Miramichi River and Catamaran Brook (New Brunswick, Canada). The model was also applied using microclimate data, i.e. meteorological conditions within the river environment (1–2 m above the water surface), for a better estimation of river heat fluxes. Water temperatures at different depths within the riverbed were also used to estimate the streambed heat fluxes. Results showed that microclimate data were essential to get accurate estimates of the surface heat fluxes. Results also showed that for larger river systems, the surface heat fluxes were generally the dominant component of the heat budget with a correspondingly smaller contribution from the streambed. As watercourses became smaller and groundwater contribution more significant, the streambed contribution became important. For instance, approximately 80% of the heat fluxes occurred at the surface for Catamaran Brook (20% from the streambed) whereas the Little Southwest Miramichi River showed values closer to 90% (10% from the streambed). As was reported in previous studies, the solar radiation input dominated the contribution to the heat gain at 63% for Catamaran Brook and 89% for Little Southwest Miramichi River. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Delineation of fresh aquifers in tannery belt for sustainable development — A case study from southern India     

Sahebrao Sonkamble  V. Satish Kumar  B. Amarender  P. M. Dhunde  S. Sethurama  K. Raj Kumar 《Journal of the Geological Society of India》2014,83(3):279-289

The tannery effluents discharged by the existing units on either side of the Palar river at Ambur town (known for tannery industry), has resulted in vertical and lateral spread of pollution. The study area of 55.3 km² is situated on a granitic terrain of Archaean age with undulating topography and hillocks. The shallow aquifers, in flood plain and valley fills of the river are highly polluted (with EC: 15340 μS/cm) by tannery effluents making groundwater unfit for any use, hence the local population (20000) face health hazards and shortage of potable water. Hydrogeological, geophysical and in-situ groundwater quality measurement were carried out to demarcate fresh groundwater zones and to delineate lateral and vertical extent of pollution. The results show, brackish aquifer was characterized by low order of resistivity (<20 Ω-m) with a thickness of 8.5 to 28 m located in the flood plains, valley fills, and partially in hard rock formations, whereas the fresh water aquifer resistivity varying from 23 to 216 Ω-m in hard rock. Further, these results were correlated with the water quality data and Ground Penetrating Radar (GPR) signals. The integrated studies revealed that pollution due to tannery effluents has spread over an area of 33.4 km² (60.4 %) on either side of the river and only a small area of 21.9 km² (39.6 %) was identified as fresh groundwater zone, which has to be conserved and exploited in sustainable manner for future generations.  相似文献   

Hyperspectral Radiometry to Characterise Dunite Alteration and Magnesite Deposits of Salem,South India     

Satish Kumar Jayabal  Sanjeevi Shanmugam  Govindan Sukkiri 《Journal of the Indian Society of Remote Sensing》2011,39(4):497-505

This work reports the results of insitu surveys, hyperspectral-radiometry and geochemistry for dunite-alteration and magnesite mapping in the Salem, southern India. Spectral parameters such as the strength of absorption in the 865 nm and 2,300 nm range for Fe²⁺ and CO3^2- respectively, and the position of absorption trough were derived from the laboratory spectra for 13 samples. It is observed that dunite alteration and conversion to magnesite produce measurable changes in the VIS-NIR-SWIR spectra due to a transition from the silicate-dominated rocky composition to carbonate-dominated industrial mineral composition. Relationship between the spectra and mineralogy suggests that we can identify the varieties of magnesite using hyperspectral radiometry.  相似文献   

Terrestrial invertebrates of dry river beds are not simply subsets of riparian assemblages     

Alisha L. Steward  Jonathan C. Marshall  Fran Sheldon  Bronwyn Harch  Satish Choy  Stuart E. Bunn  Klement Tockner 《Aquatic Sciences - Research Across Boundaries》2011,73(4):551-566

Dry river beds are common worldwide and are rapidly increasing in extent due to the effects of water management and prolonged drought periods due to climate change. While attention has been given to the responses of aquatic invertebrates to drying rivers, few studies exist on the terrestrial invertebrates colonizing dry river beds. Dry river beds are physically harsh and they often differ substantially in substrate, topography, microclimate and inundation frequency from adjacent riparian zones. Given these differences, we predicted that dry river beds provide a unique habitat for terrestrial invertebrates, and that their assemblage composition differs from that in adjacent riparian zones. Dry river beds and riparian zones in Australia and Italy were sampled for terrestrial invertebrates with pitfall traps. Sites differed in substrate type, climate and flow regime. Dry river beds contained diverse invertebrate assemblages and their composition was consistently different from adjacent riparian zones, irrespective of substrate, climate or hydrology. Although some taxa were shared between dry river beds and riparian zones, 66 of 320 taxa occurred only in dry river beds. Differences were due to species turnover, rather than shifts in abundance, indicating that dry river bed assemblages are not simply subsets of riparian assemblages. Some spatial patterns in invertebrate assemblages were associated with environmental variables (irrespective of habitat type), but these associations were statistically weak. We suggest that dry river beds are unique habitats in their own right. We discuss potential human stressors and management issues regarding dry river beds and provide recommendations for future research.  相似文献   

A Comparative Evaluation of the Geotechnical Index Properties of Clayey Sediments along the West Coast of India     

Thomas Mathai  M. Suresh Chandran  S. B. Nair  M. R. Asoka Kumar  Satish Kumar  P. Praveen Kumar 《Marine Georesources & Geotechnology》2013,31(3-4):151-165

Sediment core samples collected during geotechnical surveys along the West Coast of India in the near shore areas of Arabian Sea have generated data on the geotechnical index properties of clayey sediments up to nearly 5 m depth below seafloor. A comparative study of three sectors within themselves is attempted before carrying out a final evaluation between the sectors. Cohesive clayey sediments of Gujarat sector are comparable though widely variant in a few aspects; in the Maharashtra-Goa-Karnataka sector though, plasticity levels and clay type vary, and activity and consistency levels are quite similar. Though broadly comparable, the clayey sediments of Kerala-Tamilnadu sector have quite diverse characteristics that fail to conform to any particular pattern as each area has an exclusive set of geotechnical properties.  相似文献   

Understanding Conspicuous Gravity Low Over the Koyna–Warna Seismogenic Region (Maharashtra,India) and Earthquake Nucleation: A Paradigm Shift     

A. Vasanthi  K. Satish Kumar 《Pure and Applied Geophysics》2016,173(6):1933-1948

  相似文献   

Rock mass classification and assessment of stability of critical slopes on national highway-22 in Himachal Pradesh     

Satish Kumar  Kishor Kumar  N. N. Dogra 《Journal of the Geological Society of India》2017,89(4):407-412

Rock slopes require geo-engineering evaluation to assess the instability of critical slopes leading to landslides particularly in Himalayan terrain where rocks are highly jointed, fractured and weathering prone. Interplay of discontinuities in the rocks coupled with other parameters is one of the prime causes of failure of slopes. Engineering rock mass classification, such as, rock mass rating (RMR) and slope mass rating (SMR) along with geological strength index (GSI) have widely been used for stability assessment of rock slopes above tunnel portals, and these classifications are employed here for assessment of stability of slopes of critical nature along Rampur-Powari highway in Himachal Pradesh. In the present study, out of 154 numbers of slopes, a total of 29 have been selected for assessment of their criticality by employing RMR, SMR and GSI.  相似文献   

Burrowing activities of goby fish in the recent intertidal mud flats along the Navinal coast,Kachchh, Western India     

Nishith Y. Bhatt  Satish J. Patel  Dipal A. Patel  Hardik P. Patel 《Journal of the Geological Society of India》2009,74(4):515-530

Behavioural activities of the goby fish-Periophthalmodon septemradiatus were observed in the intertidal zone around Navinal coast in the Gulf of Kachchh, western India. Intertidal zone is broad, and comprise of creeks, which are muddy and vegetated by mangrove on eastern side and ridge runnel systems on western side of the study area which are hospitable for the goby fish. Different types of biogenic activities are observed such as crawling, pellet making, grazing and burrowing. The crawling activity is part of movement of the goby fish from one burrow to another burrow and pellet making activity is part of burrow modification. The grazing activity is feeding on the surface mud after receding of tide and exposure of the tidal flat by left and right movement of the front part of the body. The most conspicuous activity is burrowing, they construct unlined, vertical to incline ‘I’, ‘J’ and ‘Y’ shaped branched, circular to oval burrows with varying diameter and depth. In the muddy sediments goby fish produced circular to oval rimmed muddy lumps as surfacial expression around the burrows and further produced funnel shape depression and downward extended cylindrical holes, while in the runnels burrows are usually small and simple. The trail is consisting of fin marking on either side of the tail marks (grooves) which are radiate around the burrows. Occasionally burrows are interconnected in more than one burrow system which is nested within single funnel structure on the surface. The burrow systems of the goby fish in the intertidal sediments serves for protection and dwelling purpose and most importantly these burrows are irrigated by water which supply the oxygen and keep body surface wet. The overall dimensions of the burrow decrease towards the lower intertidal zone. In all, behavioural structure produced by the goby fish marks the combined activity of dwelling, feeding and grazing. The complex behavioural mechanisms have helped the goby fish to survive and flourish in the harsh intertidal environments along the Navinal Coast, in the Gulf of Kachchh.  相似文献   

Two-dimensional full wavefield inversion of wide-aperture marine seismic streamer data   总被引：3，自引：0，他引：3  

Richard M. Shipp  Satish C. Singh 《Geophysical Journal International》2002,151(2):325-344

  相似文献