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The present study records the triangular-shaped Ediacaran fossil identified as Thectardis avalonensis from the Sonia Sandstone of Jodhpur Group, Marwar Supergroup, western India. These Ediacaran fossil specimens are preserved in convex (positive) relief, but one is in negative relief on the bedding planes of sandstone in the Sursagar mines area. T. avalonensis is well-preserved, unskeletonized, elongated and triangular in shape, with sharp, raised marginal rims or ridges that widen at the triangular base and taper towards the apex of the organism. This Ediacaran triangular-shaped T. avalonensis organism is recorded for the first time from India. The phylogenetic affinity of T. avalonensis is still uncertain, as some have interpreted it as a sponge based on a body plan consistent with the hydrodynamics of the sponge water-canal system, which lacked a mouth or movement and its length-width ratio of more than 1.6. As well as these, T. avalonensis may also belong to Diskagma-like lichen or living Cladonia-like lichen group and the Auroralumina-like cnidarian organisms of the Ediacaran crown group. [ABSTRACT FROM AUTHOR]

A comprehensive review of state of the art numerical modeling in the field of sea bed morphology during cyclonic events is of vital importance. In this study a high impact and devastating cyclone, Vardah (2016) is considered to understand the hydrodynamic conditions, whereas, the recent cyclone, Nivar (2020) is considered for investigating the morphodynamic changes along the continental shelf region off the state of Tamilnadu, India. Three different models are coupled intrinsically to simulate hydrodynamics of tides and surges, waves and morphodynamic conditions. Initially, the hydrodynamic and wave models are established and validated with field measurements for an extreme event. Then, morphodynamic model is coupled with validated wave and tide model. Furthermore, the validation of bed evolution is performed for two cases viz., currents only and combination of waves and currents. The combined effect of tides, waves and surges improves the morphodynamic predictions. The present paper emphasizes the spatial and temporal morphological changes along the radius of cyclone pertaining to the shelf region. It is observed that the impact of cyclone on morphodynamics is predominant upto half the radius of the cyclone along the coast and upto 25 m contour from the coast across the shelf region. In this study, the bed evolution and its rate of change at various locations along the coast and across the shelf are extensively discussed. [ABSTRACT FROM AUTHOR]

The coastal sediments contain heavy minerals originating from the offshore and hinterland. We investigated the heavy minerals on different sediment layers of three trenches such as the Dhanushkodi open coast and Manoli island beach in India to identify the pervasiveness and depositional environment of the sediments. The primary objectives of this study are to identify the source rock and to establish the impact of hydrodynamics on the vertical textural trends of heavy mineral distribution. This is in conjunction with sediment deposits. The mineral array consists mainly of ilmenite, sillimanite, garnet, and pyroxene. Both surface and sub‐surface sediments indicate their origin, primarily from metamorphic and igneous rocks. To achieve the goal of the present study, during the low tide time, three shallow‐depth trenches, such as Trench‐1 (Palk Bay Side) and Trench‐2 (Gulf of Mannar side) were dug at Dhanushkodi beach and Trench‐3 excavated at Manoli island beach. The tip of the Dhanushkodi is called Arichalmunai and it is a continuously growing dynamic sandspit whereas Manoli Island has massive reefs with both live and dead corals on its Southern and Northern borders and it includes lagoonal lakes and extensive mudflats. The fine and very fine sand fractions of Trenches 1 and 2 contain a high concentration of ilmenite and sillimanite. Due to high energy sorting by the wave action, Trench 3 contains relatively high concentrations of mineral assemblages with very fine sand particles. Provenance relationships are established based on the mineralogical contents of trench sediments, and the observation of down‐core variation of heavy mineral assemblages implies that they were sourced from various igneous and metamorphic rocks of nearby land areas, such as the East and West coasts of India, as well as the Sri Lankan coast. [ABSTRACT FROM AUTHOR]

This research bears significant implications for river management, flood forecasting, and ecosystem preservation in the Lower Narmada Basin. A more precise estimation of Manning's Roughness Coefficeint (n) will enhance the accuracy of hydraulic models and facilitate informed decision-making regarding flood risk management, water resource allocation, and environmental conservation efforts. Ultimately, this study aspires to contribute to the sustainable management of perennial river systems in India and beyond by offering a robust methodology for optimizing Manning's n tailored to the complex hydrological dynamics of the Lower Narmada Basin. Through a synthesis of empirical evidence and computational modelling, it seeks to empower stakeholders with actionable insights toward preserving and enhancing these invaluable natural resources. Using the new HEC-RAS v 6.0, a one-dimensional hydrodynamic model was developed to predict overbank discharge at different points along the basin. The study analyzes water levels, stream discharges, and river stage, optimizing Manning's n and required flood risk management. The model predicted a strong output agreement with R 2 , NSE, and RMSE for the 2020 event as 0.83, 0.81, and 0.36, respectively, with an optimum Manning's n of 0.03. The lower Narmada Basin part near the coastal zone (validation point) appears inundated frequently. The paper aims to provide insights into optimizing Manning's coefficient, which can ultimately lead to better water flow predictions and more efficient water management in the region., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Sandy beaches generally are influenced by various coastal dynamic processes and undergo constant changes. The present study is an attempt to understand the hydromorphodynamic characteristics of a sandy pocket beach situated along the central west coast of India through field observation and numerical modeling. Multiple oceanographic instruments are deployed to capture the actual nearshore hydrodynamics, and sediment transport is measured using the streamer trap method suggested earlier during the premonsoon season. The observed vertical distribution of sediment fluxes showed a typical upward decrease from the seabed to the water surface. It is also noted that nearly 75% of the trap measurements showed that near-bed transport is higher than the depth-integrated values, confirming that the maximum sand remobilization is in the vicinity of the seabed rather than in suspension. The beach profiles of selected transects were measured during the pre- and postmonsoon seasons to understand the bed evolution. A one-dimensional numerical model, developed using XBeach and validated with field-observed values, demonstratively captured the effect of monsoon hydrodynamics on the beach profiles with fair accuracy. The various significant numerical parameters that govern the morphodynamics in the sandy beach are evaluated through a comprehensive analysis. In the end, the simulated beach profile that captures the effect of monsoon and storm are in good agreement with that obtained from field observations, with Brier Skill Scores (BSSs) of 0.69, 0.76, and 0.74 for Profiles 1, 2, and 3, respectively. [ABSTRACT FROM AUTHOR]

The movement of the ship-generated waves on restricted shallow waterways creates complex river dynamics. The irregular bathymetry increases the bed shear stress in the waterway, causing significant sediment resuspension. In order to investigate the impact of the ship-generated waves on the sediment resuspension, field measurements were performed at the Falta stretch of the Hooghly river, India (National Waterway 1). The present study applied the acoustic backscattering intensity of a horizontally-looking ADCP to quantify the sediment resuspension generated by ship waves. Based on the low-pass filter, the primary and secondary waves were separated. Based on the analysis, the low-frequency primary waves are less significant compared to the high-frequency secondary waves. The correlation study suggested that the ship-induced sediment resuspension is highly influenced by irregular bathymetry, river geometry, depth Froude number and ship speed. Finally, two new empirical models were proposed to estimate the sediment resuspension due to ship-generated waves by using correlation study and regression analysis. • The ship-generated waves and their sediment resuspension were reported based on the field measurements. • The primary and secondary waves are separated by using the principle of the frequency difference. • The primary waves were less significant than the secondary waves for suspended sediment concentration (SSC). • Parametric study of the ship-induced SSC was explored. • Two new empirical models were proposed to predict ship-generated SSC. [ABSTRACT FROM AUTHOR]

This study presents a Coupled Coastal Monitoring Framework (CCMF) that integrates remote sensing (CoastSat), video beach monitoring system (VBMS), and numerical modelling to analyse the morphology and hydrodynamics of a structure-influenced beach. A 10.2 km stretch of straight beach with an artificial breakwater along the Kozhikode coast of Kerala, India, is selected for the study. The shoreline change analysis revealed that 38% of the total coast is under erosion, with the northern sector of the breakwater being highly erosive and the southern sector being stable. Continuous monitoring from the VBMS confirmed the stability of the southern sector with varying erosion accretion trends during 2018–21. Coastal morphological features such as double bars, cusps, and rip-like formations were identified through the VBMS, validated and analysed in detail with distinct wave-current interactions and sediment transport through numerical modelling. The study concludes that the breakwater is effectively protecting the beach adjacent to the south but has disturbed longshore transport, potentially leading to increased erosion to the north. The proposed CCMF provides real-time and post-performance monitoring of structure-influenced beaches, enabling timely decision-making at critical locations and appropriate remedial measures for efficient coastal management. • Coupling of satellite remote sensing, coastal video monitoring and numerical model. • Hydrodynamics of breakwater influenced medium energy coast. • Analysis of coastal erosion trends and identification of erosion hotspots. • Extraction of morphological features viz. double bar, cusp and rip channels. • Identification of two less intensity rip hotspots at Kozhikode beach, India. [ABSTRACT FROM AUTHOR]

Tsunami numerical model studies are mostly focused on inundation and run-up onto the coast. Fewer studies have been aimed at investigating the role of submarine canyons on tsunami heights, currents and run-up. The tsunami hydrodynamics in the vicinity of submarine canyons and ridges in the Palar–Cauvery region off the southeast coast of India on 26 December 2004 is considered in this study. Numerical modelling was carried out to study tsunami heights and currents in the vicinity of the submarine canyons as well as the variation of tsunami heights at 10 m water depth. Comparisons between the tsunami wave energy density at 10 m depth and the onshore run-up height observations showed good correlation for select locations, with the run-up heights being about 3% of the wave energy density. However, the local topography in the run-up zone also strongly influences the local run-up, which reduces direct correlations between run-up and nearshore tsunami height. [ABSTRACT FROM AUTHOR]

Soft bottom macrobenthos are highly diverse benthic invertebrates, and their diversity depends mainly on the health of the benthic habitat. The impact of anthopogenic stress and port related activites on macrobenthos diversity was studied in New Mangalore port, a tropical monsoon influenced environment. A shift in the macrobenthos abundance and diversity was observed with seasons, along with shift in the dominance of opportunistic species. The ecological quality status (EcoQS) indicated 'poor' to 'moderate' and also 'bad' status of benthic habitat, and this changed with the seasons and regions within the port. Higher diversity of macrobenthos at stations located in the high circulation area (HCA) compared to low circulation area (LCA) and oil and fertilizer wharf (OFW) indicated pivotal role of local hydrodynamics and activities within the port in structuring macrobenthos diversity. The occurrence of opportunistic species within the port demonstrated the role of anthropogenic stress in structuring macrobenthos community. • Benthic Ecological quality status (EcoQS) was assessed at New Mangalore Port. • Benthic EcoQS was 'bad'- 'high', and it changed with seasons and region within port. • Seasonal shift in macrobenthos community changed with regions within port. • Dominance of opportunistic species reflected anthropogenic stress within the port. • Local hydrodynamics and port activities determine benthic habitat health. [ABSTRACT FROM AUTHOR]

Sensitivity analysis determines how perturbation or variation in the values of an independent variable affects a particular dependent variable. The present study attempts to comprehend the sensitivity of the static input parameters on the accuracy of the outputs in a hydrodynamic flood model, which subsequently improves the model accuracy. Hydrodynamic flood modeling is computationally strenuous and data-intensive. Moreover, the accuracy of the flood model outputs is extremely sensitive to the quality of hydrologic and hydraulic inputs, along with a set of static parameters that are traditionally assumed and primarily used for calibration. Therefore, we focus on developing a framework for global sensitivity analysis (GSA) of static input parameters in a 1D-2D coupled hydrodynamic flood modeling system. A set of numerical experiments is conducted by perturbing various combinations of input parameters from their standard (or observed) values to generate flow hydrographs. Nonparametric probability density functions (PDFs) of the river discharge at different locations are compared to calculate the Kullback-Leibler (KL) entropy or KL-divergence, which is used to quantify the sensitivity of the input parameters. We demonstrated the proposed framework on a highly flood-prone rural catchment of the Shilabati River in West Bengal, India, and infer that the sensitivity of the static input parameters is highly dynamic, and their importance varies spatially from the upstream to the downstream of the river. However, Manning's n values of the channel and the banks are significantly sensitive irrespective of the location in the river reach. We suggest that any flood modeling exercise should accompany a GSA, which sets a guideline for the modelers to prioritize the set of sensitive static input parameters during data monitoring, collection, and retrieval. This study is the first attempt at a GSA in a 1D-2D coupled hydrodynamic flood modeling system, whose importance cannot be over-emphasized in any flood modeling platform. The proposed novel framework is generic and can be implemented prior to flood risk analyses for any floodplain management exercise. All free and commercially-available flood models can incorporate the proposed framework for a GSA as an extension toolbox., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Glacier-associated hazards are becoming a common and serious challenge to the high mountainous regions of the world. Glacial lake outburst floods (GLOFs) are one of the most serious unanticipated glacier hazards, with the potential to release a huge amount of water and debris in a short span of time, resulting in the loss of lives, property, and severe damage to downstream valleys. The present study used multi-temporal Landsat and Google earth imageries to analyze the spatio-temporal dynamism of the selected glacial lake (moraine-dammed) in the Satluj basin of Western Himalayas. Furthermore, GLOF susceptibility of the lake was assessed using a multi-criteria decision-based method. The results show that the lake area has increased from 0.11 to 0.26 km 2 over the past 28 years from 1990 to 2018. The susceptibility index value for the lake was calculated as 0.75, which indicates that the lake is highly susceptible to the GLOF. The depth and volume of the lake were estimated to be 16 m and 57 × 10 5 m 3 , respectively, using an empirical formula. HEC-RAS, HECGeo-RAS, and Arc-GIS software were utilized in this study to perform unsteady flow analysis and to determine the GLOF impact on the downstream area. The worst-case GLOF scenario (breach width of 75 m) was revealed during an overtopping failure of the moraine dam, resulted in a peak discharge of 4060 m 3 /s and releasing a total water volume of 57 × 10 5 m 3 . The breach hydrograph has been routed to calculate the spatial and temporal distribution of peak flood, inundation depth, velocity, water surface elevation, and flood peak arrival time along the river channel. The analysis further reveals that the routed flood waves reach the nearest settlement, i.e., Rajpur town, situated at a distance of 102 km in the downstream valley of the lake at 6 h after the beginning of the lake breach event with a peak discharge/flood of 1757 m 3 /s and maximum flow velocity of 1.5 m/s. With the ongoing climate warming and glacier retreat, moraine-dammed lakes are becoming more hazardous and thus increasing the total threat. Therefore, it is mandatory to monitor and assess such lakes at regular intervals of time to lessen the disastrous impacts of GLOFs on the livelihood and infrastructure in the downstream valleys. The findings of this study will aid in the creation of risk management plans, preparatory tactics, and risk reduction techniques for GLOF hazards in the region., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Weaver, R.J.; Johnson, J.E., and Ridler, M., 2016. Wind-driven circulation in a shallow microtidal estuary: The Indian River Lagoon. Studying wind-driven fluctuations in the surface elevation along the Indian River Lagoon (IRL) allows researchers to better understand the best methods for managing sustainable water quality in a microtidal estuary. Water quality has a direct effect not only on the marine life, but also on tourism. This study improves the knowledge of circulation and surge in a shallow, microtidal estuary while enabling validation of numerical modeling efforts. Two submersible pressure sensors were deployed in the IRL for 7 months. Data collected from these gauges is analyzed in conjunction with data from permanent gauges at Haulover Canal and Sebastian Inlet, with an emphasis placed on the relationship between surface elevation and meteorological forcing. A time series analysis was employed to correlate periods of harmonic oscillations with wind events. Analysis focused on the direction of the wind with respect to the along-estuary and cross-estuary orientation of the lagoon. Results indicate that the water rises or falls uniformly in the cross-estuary direction and is transported to the south during Nor'easter events, piling up at the constriction south of Sebastian Inlet. Study results will be used to provide a better understanding of circulation in shallow-water estuaries, as well as improve numerical models to better predict wind-driven circulation in the IRL. [ABSTRACT FROM AUTHOR]

Microplastic pellets (MPPs) are ubiquitous contaminants, recognised as a serious threat to the biota in coastal, estuarine and marine environment. The distribution, abundance, weathering and chemical characteristics of MPPs on the beaches of Goa, and their transport to the coast during the southwest (SW) monsoon are discussed in this paper. MPP samples collected from six sandy beaches were categorised based on colour and polymer types using Stereoscope microscope and FTIR-ATR spectroscopy, respectively. White colour MPPs were the most abundant, and Polyethylene (PE) and Polypropylene (PP) were the dominant polymer types of MPPs deposited on all the beaches. Carbonyl index values showed that MPPs collected in June 2015 (representing SW monsoon) were ‘new’, whereas the MPPs collected in January 2015 were ‘aged’, showing that MPPs are arriving at Goa coast only during SW monsoon due to conducive hydrodynamic conditions. Characteristics of MPPs suggest that they could be originated primarily from ocean-based sources. The winds and surface currents during SW monsoon are the driving forces for the transportation and deposition of MPPs on the Goa beaches. The results of this study will be useful to the National ‘Clean India’ program for effective plastic debris removal management. [ABSTRACT FROM AUTHOR]

The sources, distribution, surface features, polymer composition and age of microplastic pellets (MPPs) in surface sediments along the Chennai coast during March 2015 (pre-Chennai flood) and November 2015 (post-Chennai flood) were characterised using a Stereoscopic microscope and FTIR-ATR spectroscopy. White MPPs were the most abundant, and specifically polyethylene (PE) and polypropylene (PP) were the dominant polymer types of MPPs found on the coast during both the times. The abundance of MPPs in November 2015 was three-fold higher than those found in March 2015, confirming that huge quantity of fresh MPPs washed through Cooum and Adyar rivers from land during the flood. The winds and surface currents during November were the driving forces for the transportation and deposition of MPPs from the sea to beaches. The results of this study will be useful to formulate beach MPPs litter management policies to effectively create long-term solutions. [ABSTRACT FROM AUTHOR]

Tidal inlets along the Maharashtra coast on the central west coast of India were classified according to three methods available in the literature. Two classification methods viz., (i) Hydrodynamic classification (Hayes, 1979) and (ii) Classification based on dimensionless parameters (Vu, 2013) used for the classification are compared with the morphological classification of de Vriend et al., (1999). The hydrodynamic classification of Tidal inlets along Maharashtra coast is carried out considering mean annual significant wave height. The classification is also extended considering significant wave heights obtained for South-West monsoon, North-East monsoon and Fair Weather seasons. It has been observed that 74% of the inlets are tide dominated as per morphological classification whereasconsidering annual mean wave heights in Vu (2013) method, 67% of the inlets are wave dominated. [ABSTRACT FROM AUTHOR]

Integrated Coastal and Marine Area Management – Project Directorate (ICMAM-PD), Ministry of Earth Sciences, Govt of India is implementing a project on ecosystem modelling for SW Coast of India to study the anthropogenic and natural influences on ecosystem character of SW Coast of India during the 12th plan period (2012-17). The study area covers the coastal stretch from Goa to Kanyakumari including the offshore waters, the estuarine and the inlet waters. In order to develop an ecosystem model for the SW Coast, extensive data sets on various physical and biogeochemical parameters (water level s , currents, temperature, salinity, nutrients, DO, chlorophyll, primary production etc) have been collected since 2012 through various field measurements. The available past data from ICMAM database, COMAPS datasets, institutional reports etc have also been collected to understand the hydrodynamic behaviour of the SW Coast. The hydrodynamic processes such as tidal propagation, currents and circulation, density distribution, etc have been studied to understand the dispersal mechanisms of particulate matter derived from land run off. Model simulations were carried out to investigate the dynamics of the shelf flow response to the spatial and temporal variability of the tidal forcing along the SW Coast. An attempt has been made to understand the variability of the surface circulation and associated SSC in different seasonal condition during 2013 and 2014 as a response of wind and tidal forcing under variable land run off conditions. Temperature, salinity, and density profiles were used to study the variability in circulation and stratification characteristics along the coast. Tide models were utilized to study the tidal excursion along the coast and the results were validated with the tide data from the survey of India. The regions of hydraulic heads, and zones of possible accumulation of particulate matter along the coast and the subsequent influences on ecosystem character has been studied and discussed. [ABSTRACT FROM AUTHOR]

Coastal inlets are the openings along the coastline that provide a linkage between the open ocean and the hinterland water bodies. These coastal inlets are varied in nature depending on many influencing parameters such as tide, wind, river flow and waves. Amongst these parameters, the tides are the most regular while waves and freshwater flow are more seasonal. The tidal inlets have to be examined and studied to understand the nearshore coastal processes. The inlet remains stable (i.e. open) as long as the alongshore sediment bypasses the tidal inlet. Classification of coastal systems in a broader view is necessary for the management of tidal inlets. There are several methods to classify tidal inlets based on different perspectives namely geo-morphological, hydrodynamic etc. In the present study, tidal inlet classification is carried out considering the hydrodynamics and morphodynamics along the Andhra Pradesh coast, considering the classification method as in Hayes (1984) and Thuy (2013). The Hayes (1984) classification considers only the tidal range and significant wave height, whereas Thuy (2013) considers discharge due to tide (∼Tidal prism /tide duration) and wave (∼ ). A total of 108 tidal inlets along Andhra Pradesh coast on the east coast of India are classified considering annual mean wave height (Hs) as well as seasonal wave heights. This paper presents the methods used and results of the coastal classification along the central east coast of India. [ABSTRACT FROM AUTHOR]

Particle size characterizations of beach sediments along Tamil Nadu coast was carried out in the present study. The main objective of this work is to identify the textural behaviour of beach sediments and how wave energy correlates with grain size distribution. To achieve this goal tri-plot analysis was performed. Grain size characteristics such as central tendency, kurtosis and skewness were estimated using an updated version of the GRADISTAT programme and discussed in this paper. The highest sediment samples having medium sand with unimodal and bimodal characters at all along the coast. The entire coastal area was characterized as well sorted, moderately well sorted and moderately sorted sediment environments. Sediments were identified as fine skewed to coarse skewed with platykurtic, mesokurtic and leptokurtic characters. Grain characteristics varied spatially and temporally along with beach orientation, foreshore slope withwave action and skewness correlates with shoreline changes. In some coastal tract having the negative skewness along the study region, but not very significant. The study depicts that the sedimentary coastal environment were influenced by the relatively medium wave action and some places were observed high wave action. From this study, it was concluded that the beach erosion, accretion, and stability of beaches are controlled by strong hydrodynamic and hydraulic process. [ABSTRACT FROM AUTHOR]

COHERENS (COupled Hydrodynamical and Ecological model for REgioNal and Shelf seas), a 3D hydrodynamic multi-purpose model, has been implemented for the coastal and shelf seas of eastern Arabian Sea to study the flow characteristics. The model has been tested and verified with one month measurements of surface and bottom currents collected off Mangalore, Ratnagiri, Mumbai and Dwarka on the west coast of India (WCI). After calibration, the model was allowed to perform under tide and wind forcings. The flow characteristics at these select locations have been well reproduced by the model. A shift in current direction from south to southeast has been observed at several occasions, and this could be attributed to shamal events. The low amplitudes of the residual currents in the measurements off Mumbai and Dwarka suggest that the influence of the West India Coastal Current is weak or negligible in the northern part of the WCI and the currents are mainly tide-dominant. Certain discrepancies are noticed especially in the southern domain, off Mangalore, where the shallow water dynamics is not only driven by the local wind forcing and tides, but also by the remotely driven currents. In order to get a comprehensive picture of the prevailing dynamics, the model domain has to be extended to the entire Indian Ocean. [ABSTRACT FROM AUTHOR]

Tides play a vital role in coastal hydrodynamics, and it is important to understand their complex characteristics in the coastal areas of creeks, bays, estuaries and gulf. In this study, the spatial variation of heterogeneous friction coefficients and their influence on the variation of different tidal constituents (K1, M2, N2, O1, P1 and S2) along Gulf of Khambhat, west coast of India, were studied. A two-dimensional finite element-based numerical model was developed and zones of different friction coefficients were identified by comparing numerically estimated tidal levels and currents with that of measured and reported by earlier studies. Based on the comparisons, the gulf was divided into five zones of different bottom friction values. The numerical model, assigned with friction coefficients, was used to map the contours of selected tidal constituents. From the results, it was observed that two constituents, M2 and K1, influence the hydrodynamics, significantly. The description of the numerical model, calibration, validation and results are presented in this paper. [ABSTRACT FROM AUTHOR]

A physically-based hillslope hydrological model with shallow overland flow and rapid subsurface stormflow components was developed and calibrated using field experiments conducted on a preferential path nested hillslope in northeast India. Virtual experiments were carried out to perform sensitivity analysis of the model using the automated parameter estimation (PEST) algorithm. Different physical parameters of the model were varied to study the resulting effects on overland flow and subsurface stormflow responses from the theoretical hillslopes. It was observed that topographical shapes had significant effects on overland flow hydrographs. The slope profiles, surface storage, relief, rainfall intensity and infiltration rates primarily controlled the overland flow response of the hillslopes. Prompt subsurface stormflow responses were mainly dominated by lateral preferential flow, as soil matrix flow rates were very slow. Rainfall intensity and soil macropore structures were the most influential parameters on subsurface stormflow. The number of connected soil macropores was a more sensitive parameter than the size of macropores. In hillslopes with highly active vertical and lateral preferential pathways, saturation excess overland flow was not evident. However, saturation excess overland flow was generated if the lateral macropores were disconnected. Under such conditions, rainfall intensity, duration and preferential flow rate governed the process of saturation excess overland flow generation from hillslopes.Editor D. Koutsoyiannis; Associate editor C. Perrin [ABSTRACT FROM PUBLISHER]

There is strong statistical evidence that solar activity influences the Indian summer monsoon rainfall. To search for a physical link between the two, we consider the coupled cloud hydrodynamic equations, and derive an equation for the rate of precipitation that is similar to the equation of a forced harmonic oscillator, with cloud and rain water mixing ratios as forcing variables. Those internal forcing variables are parameterized in terms of the combined effect of external forcing as measured by sunspot and coronal hole activities with several well known solar periods (9, 13 and 27 days; 1.3, 5, 11 and 22 years). The equation is then numerically solved and the results show that the variability of the simulated rate of precipitation captures very well the actual variability of the Indian monsoon rainfall, yielding vital clues for a physical understanding that has so far eluded analyses based on statistical correlations alone. We also solved the precipitation equation by allowing for the effects of long-term variation of aerosols. We tentatively conclude that the net effects of aerosols variation are small, when compared to the solar factors, in terms of explaining the observed rainfall variability covering the full Indian monsoonal geographical domains. [ABSTRACT FROM AUTHOR]

Summary To face the problem of groundwater depletion, the Indian Government relies on large projects of Managed Aquifer Recharge (MAR). Numerous recharge structures such as percolation tanks exist but the impact of these structures on groundwater resources remains poorly understood. Although the evaporation/infiltration ratio of percolation tanks was determined in several studies in semi-arid contexts using surface water balance methods, few studies evaluated the impact on the aquifer recharge. However, knowledge on recharge dynamics over time and space is essential for (1) the quantitative evaluation of stored water volumes, (2) the identification of beneficiaries (farmers) and (3) the estimation of percolation tanks recharge zone to the extent that is required to define proper management regulations at basin scale. These three points are of prime importance in the case of semi-arid regions where a limited number of rain events determine the water stored over the entire year. Assessment of the stored groundwater is even more difficult in crystalline aquifers due to the heterogeneous structure of flow paths. To date no methodological guidelines exist for local assessment of percolation tanks in crystalline aquifers. In this paper, we develop a method for calculating a local groundwater budget and we compare it with a computed surface balance. The method is applied to a case study in semi-arid crystalline context. From the groundwater balance we draw conclusions on (1) the limited amount of stored water in the aquifer, (2) the delayed recharge of the aquifer highlighting temporary storage/slow groundwater movement in the unsaturated zone and (3) the limited number of beneficiaries in years of medium monsoon rainfall. These results complement the understanding of the hydrodynamic functioning of percolation tanks, and their impact on the local groundwater balance. [ABSTRACT FROM AUTHOR]

Kumar, P.K.D.; Gopinath, G.; Murali, R.M., and Muraleedharan, K.R., 2014. Geospatial analysis of long-term morphological changes in Cochin estuary, SW coast of India. The Cochin estuary along the SW coast of India has undergone tremendous environmental changes due to continuous alterations. Geospatial information available since 1967 has been compiled to evaluate the long-term morphological changes. Quantification of geomorphological changes that occurred over the decades was made to have an integrated profile to ascertain the changes in the extent. Toposheet maps (1967) and satellite imageries for 2004 and 2011 have been interpreted. Quantitative comparison of inner island segments showed significant changes in island widths through time. It was found that the areas covered by the islands within the estuary during 1967, 2004, and 2011 were 81.62, 89.26, and 89.52 km2, respectively, and those covered by the water body were 130.68, 121.3, and 118.01 km2, respectively. The shrinking rate of the estuarine system was estimated to be 0.288 km2/y. About 11 km2 of island area was found to be prograded, and 3 km2 was eroded. In effect, the reduction in the aerial extent of the estuarine system was estimated to be 12.67 km2. The evolution of the western estuary margin has been characterized by a strong progradation during the past 4 decades. The results obtained conclusively show that the estuary is being inflicted with major geomorphic changes at several segments, resulting in reduction in the extent. Geomorphic differences may lead to factors in modifying estuarine flows, which ultimately affect the dynamic processes within the estuary. Observed trends of morphological changes generate concern in the background that the region may continue to remain vulnerable in the coming decades due to development pressures in the adjoining hinterlands. [ABSTRACT FROM AUTHOR]

The present study reports on a systematic procedure and maintenance plan for conducting dredging activity at the Kolkata port located in the Head Bay region, east coast of India. It is one of the oldest riverine ports in the country constructed by the British East India Company. The port comprises two docks, viz. Kolkata Dock Complex and the Haldia Dock System under the administrative control of the Kolkata Port Trust. The navigation channel located in the Hooghly River accommodates sea-going vessels with 200 GRT with pilotage assistance cruising upstream almost 145 km from Sagar Islands located in Hooghly estuary. The navigation channel experiences high rates of sedimentation being a riverine port. This study investigates the sedimentation rate throughout the navigation channel, identifying zones of high sedimentation rate. The behavioural pattern of tides and currents is analysed using the state-of-the-art ADCIRC model, and wave conditions are simulated using SWAN model. The hydrodynamic information obtained from ADCIRC and SWAN is input to the SEDTRANS model. Based on the intensity of sedimentation, the maintenance plan is proposed for three dredging seasons. On the basis of this scientific rationale and seasonal dredging maintenance procedure, it is anticipated that huge investments involved in the maintenance dredging of this channel can be minimized. [ABSTRACT FROM AUTHOR]

An in-depth analysis has been made to simulate hydrodynamic scenarios for understanding the nearshore sediment transport controls of placer mineral depletion at Manavalakurichi, India. From the analyses of topographic configuration (extracted from Hydrographic Nautical Chart No. 2048 and data generated during year 2010), we inferred that the 5-m isobaths had broadened and exhibited shallowness. Distances between the coastline and the isobaths were found to have increased significantly over the past five decades. Along with this, the 10 and 20-m contours were found to have shifted about 35-100 m horizontally landward. These changes led to severe sediment deposition in these regions due to the changed wave energy levels and refraction patterns. Numerical simulations linking bathymetry, hydrodynamics, sediment load, and significant wave heights revealed that changes in bathymetry would amplify the wave heights and convergence of wave energy. Associated removal of sand from the high-energy zones will eventually lead to sediment starvation situations and depletion of placers in the adjacent beaches. As the observed trends of depletion generate great concern, detailed oceanographic investigations should be taken up immediately in the region. Fine-resolution hydrodynamic datasets should prove useful for further evaluating the physical responses of the system to the altered geometry and for exploring remedial measures for restoring the heavy mineral content of the beach sand. [ABSTRACT FROM AUTHOR]

Hydrodynamic flow modeling is carried out using a coupled 1D and 2D hydrodynamic flow model in northern India where an industrial plant is proposed. Two flooding scenarios, one considering the flooding source at regional/catchment level and another considering all flooding sources at local level have been simulated. For simulating flooding scenario due to flooding of the upstream catchment, the probable maximum flood (PMF) in the main river is routed and its flooding impact at the plant site is studied, while at the local level flooding, in addition to PMF in the main river, the probable maximum precipitation at the plant site and breaches in the canals near the plant site have been considered. The flood extent, depth, level, duration and maximum flow velocity have been computed. Three parameters namely the flood depth, cross product of flood depth and velocity and flood duration have been used for assessing the flood hazard, and a flood hazard classification scheme has been proposed. Flood hazard assessment for flooding due to upstream catchment and study on local scale facilitates determination of plinth level for the plant site and helps in identifying the flood protection measures. [ABSTRACT FROM AUTHOR]

This study analyzes fatalities caused by rip currents in important locations along east and west coasts of India for the period 2000-2010. Results include the frequency of fatalities from rip currents, their cause, and their spatial distributions. Rip current fatalities are most common in the southeastern India, with a non-uniform spatial distribution. August and October are identified as most favorable for rip current generation. In India, rip current-related drowning is estimated as 39 per year during the last decade. East coast of India averaged 30-40 drownings, and west coast of India averaged 5-10 drownings per year. In coastal Andhra Pradesh, more than 350 people had been drowned due to rip currents and only 10 people were rescued. Visakhapatnam recorded highest drowning (293); R. K. beach is the most vulnerable potential rip current zones. From 2007 onward, rip current deaths increased at an alarming rate. The frequency of rip current drownings increased markedly during shore-normal wave incidence and mid-low tidal stages. A new empirical forecasting technique has been developed for prediction of rip current risk in India for the first time. FORTRAN-based software was developed to generate automatic rip current forecast report for any given location. The scale's performance was tested with field data and by using different statistical methods. The new predictive scale is predicting rip current occurrences reasonably well. [ABSTRACT FROM AUTHOR]

Constraining magnitudes of mechanical and thermo-mechanical parameters of rocks and shear zones are the important goals in structural geology and tectonics (Talbot in J Struct Geol 21:949-957, ). Such parameters aid dynamic scaling of analogue tectonic models (Ramberg in Gravity, deformation and the Earth's crust in theory, experiments and geological applications, 2nd edn. Academic Press, London, ), which are useful to unravel tectonics in further details (Schultz-Ela and Walsh in J Struct Geol 24:247-275, ). The channel flow extrusion of the Higher Himalayan Shear Zone (HHSZ, = Higher Himalaya) can be explained by a top-to-S/SW simple shear (i.e. the D deformation) in combination with a pressure gradient induced flow against gravity. Presuming its Newtonian incompressible rheology with parallel inclined boundaries, the viscosity (μ) of this shear zone along a part of the Himalayan chain through India, Nepal and Bhutan is estimated to vary widely between ~10 and 10 Pa s, and its Prandtl number ( P) within ~10-10. The estimates utilized ranges of known thickness (6-58 km) of the HHSZ, that of its top subzone of ductile shear of normal shear sense (STDS: 0.35-9.4 km), total rate of slip of its two boundaries (0.7-131 mm year), pressure gradient (0.02-6 kb km), density (2.2-3.1 g cm) and thermal diffusivity (0.5 × 10-2.1 × 10 m s) along the orogenic trend. Considering most of the parameters specifically for the Sutlej section (India), the calculated viscosity (μ) and the Prandtl number ( P) of the HHSZ are deduced to be μ: ~10-10 Pa s and P ~ 10-10. The upper limits of the estimated viscosity ranges are broadly in conformity with a strong Tibetan mid-crust from where a part of the HHSZ rocks extruded. On the other hand, their complete ranges match with those for its constituent main rock types and partly with those for the superstructure and the infrastructure. The estimated mechanical and thermo-mechanical parameters of the HHSZ will help to build dynamically scaled analogue models for the Himalayan deformation of the D-phase. [ABSTRACT FROM AUTHOR]

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Measurements and numerical simulations carried out off Mumbai coast for the period 22 October-22 November 2009 showed significant variations in water level and currents during cyclone Phyan. Changes in the meridional component of the current velocity were found to be highly significant during Phyan. The strong southward flow due to the cyclone resulted in a complete nullification of a flood current and continued the net flow towards south for approximately 18 h. This enhanced the ebb flow by about 0.12 m/s off Worli and 0.16 m/s off Satpati. The shift in the cyclone generated currents towards north resulted in an enhancement of flood current by 0.3 m/s off Worli and 0.2 m/s off Satpati. During the first 7 h of Phyan, a strong current system associated with an anti-cyclonic eddy was formed off Mangalore, which propagated towards north up to Ratnagiri and disappeared while the cyclone entered the land. Water level variations of 0.38 and 0.44 m were observed due to Phyan off Worli and Satpati, respectively. Positive and negative surges, that is, a fall in water level up to −20 cm and a rise up to 20 cm, were observed during Phyan and these were associated with shift in the wind direction. [ABSTRACT FROM AUTHOR]

Abstract: A 2D Hydrodynamic–Particle Analysis model was applied to the Gulf of Kachchh (GoK) to estimate the residence time of pollutants. The tidal currents in the Gulf have a strong E–W component, which prevents the material in the north being transported towards south. In the regions situated very close to the open boundary, where the GoK waters exchange freely with the northern Arabian Sea, dilution takes place rapidly with the incoming waters and hence, the residence time is on the order of 1day. Influence of eddies and a dynamic barrier across the Sikka–Mundra section on the residence time is apparent. Eastern GoK shows a relatively large residence time, on the order of 2–4days, warranting caution while releasing industrial wastes in the northeastern Gulf. The region around location-5 behaves like a bay; the dissolved matter gets trapped in this bay and the residence time increases by 3–4days. [Copyright &y& Elsevier]

Abstract: Methyl parathion (C8H10NO5PS), which is an organophosphorus pesticide that has been widely used as an agricultural insecticide in India, can result in significant water pollution due to its biorefractory nature and longer stability. In the present work, degradation of methyl parathion has been investigated using hydrodynamic cavitation reactors with possible intensification studies using different approaches. Effect of different parameters like operating pressures (1–8bar), operating temperatures (sets of intense cooling, moderate cooling and uncontrolled operation) and initial pH (2.2–8.2) has been investigated initially. Under the optimized set of operating parameters, the effect of process intensifying parameters like hydrogen peroxide (25–200mg/l), carbon tetrachloride (1–6g/l) and Fenton’s reagent (H2O2:FeSO4 ranging from 1:1 to 1:6) on the extent of degradation has been investigated. Effect of radical scavengers like sodium bicarbonate and tert-butanol on the extent of degradation was also investigated with an objective of establishing the controlling mechanism. More than 90% degradation of methyl parathion was achieved using combination of hydrodynamic cavitation with H2O2 and Fenton’s reagent. TOC analysis at optimum conditions was also performed to quantify the extent of mineralization and it has been observed that a maximum of 76% TOC reduction is obtained. The study has also focused on the determination of intermediate products formed during the degradation. It has been established that hydrodynamic cavitation in the presence of additives can be effectively used for complete removal of methyl parathion. [Copyright &y& Elsevier]

A geometrically similar model of the proposed Advanced Heavy Water Reactor being designed and built by Bhabha Atomic Research Centre has been conceived and built at Indian Institute of Technology, Bombay. The basic objective of setting up such a facility and conducting experimental studies was to simulate the thermal-hydraulic behavior during the startup and also during part or full power operation. Owing to hydrodynamic instabilities observed in natural circulation system, it is necessary to know the stability boundaries. In this paper, the details of the experimental facility, experimental studies, and numerical simulations carried out using RELAP5/MOD 3.2 are discussed. Type I and type II stability boundaries and stable two-phase operation zones have been experimentally obtained at various pressures and inlet subcooling and the results are correlated using appropriate nondimensional numbers. Further, the experimental facility is modeled using the thermal-hydraulic code RELAP5/MOD 3.2. The single-phase pressure drops measured in the loop are used to estimate the appropriate loss coefficients used in the model. The model is then used to predict stability boundaries, and the predictions are compared with the experimental findings. The details of the experimental model and simulation results are presented. The capability of RELAP5/MOD 3.2 to predict the flow oscillations during instabilities is discussed. [ABSTRACT FROM AUTHOR]

Abstract: The degradation of an aqueous solution of dichlorvos, a commonly used pesticide in India, has been systematically investigated using hydrodynamic cavitation reactor. All the experiments have been carried out using a 20ppm solution of commercially available dichlorvos. The effect of important operating parameters such as inlet pressure (over a range 3–6bar), temperature (31°C, 36°C and 39°C) and pH (natural pH=5.7 and acidic pH=3) on the extent of degradation has been investigated initially. It has been observed that an optimum value of pressure gives maximum degradation whereas low temperature and pH of 3 are favorable. Intensification studies have been carried out using different additives such as hydrogen peroxide, carbon tetrachloride, and Fenton’s reagent. Use of hydrogen peroxide and carbon tetrachloride resulted in the enhancement of the extent of degradation at optimized conditions but significant enhancement was obtained with the combined use of hydrodynamic cavitation and Fenton’s chemistry. The maximum extent of degradation as obtained by using a combination of hydrodynamic cavitation and Fenton’s chemistry was 91.5% in 1h of treatment time. The present work has conclusively established that hydrodynamic cavitation in combination with Fenton’s chemistry can be effectively used for the degradation of dichlorvos. [Copyright &y& Elsevier]

Abstract: A comprehensive knowledge of the wave climate is an essential pre-requisite for practical applications in coastal and near-shore region. In coastal areas the dominant dissipative mechanism appears to be bottom friction where the relative strength depends on bottom characteristics, sediment type and bottom ripple geometry. The present state-of-art version SWAN wave model uses three popular formulations for dissipative mechanism due to bottom interaction. The bottom friction coefficient as in SWAN cannot be a constant and needs to be tuned based on prevailing hydrodynamic conditions when applied for a tidal dominant region. A combined wave-current interaction study should take into account varying water levels, reversal of current system and associated shear on the sea-bed. The present work reports on development of a new resistance law for bottom friction under the combined action of waves and currents. This new formulation has been implemented in the SWAN model and further its implication on variability of significant wave height for the Hooghly estuary located in the Bay of Bengal, East coast of India was investigated by comparison with ENVISAT satellite measurement. Based on this study, it could be ascertained that new friction formulation has potential for wind-wave modeling studies in near-shore and coastal waters. [Copyright &y& Elsevier]

The optimal trajectory from Calcutta port to Mumbai port is charted for a tanker transshipping from the East coast to the West coast of India during rough weather. Rough weather is simulated over Indian seas using the state-of-the-art WAM numerical wave model (WAMDI Group in J Phys Oceanogr 18:1775-1810, ), assimilating satellite (IRS-P4) wind fields. These simulated wave fields and two-dimensional (2D) directional wave spectrum are an absolute representation of the irregular seaway. Hence, the same for the monsoon month of August 2000 formed the input basis for this study. Loss of ship speed due to the wave field (i.e., nonlinear motion of the tanker in waves) and associated sea-keeping characteristics in the seaway are estimated (Bhattacharya in Dynamics of marine vehicles, Wiley, New York, ). The approach adopted in this paper is unique in that it takes into account both voluntary and involuntary speed reductions of the ship. It helps in ship tracking by the optimum route using inverse velocity as the weight function for the path in an efficient way. Dijkstra's algorithm [Numer Math 1(3):269-271, ] is applied in an iterative manner for determining the optimum track. The optimum track information has broad scope for use in modern shipping industry for obtaining safe and least-time routing by avoiding schedule delays with economic fuel consumption. [ABSTRACT FROM AUTHOR]

Qualitative and quantitative evolution of the Swarna estuary, during the past 38 years (1967-2005), has been analysed by integrating the results of field surveys, satellite images, hydrodynamic modelling and topographic data in GIS context. Significant changes in erosion/accretion patterns of the estuarine banks, inlet configuration and adjacent spits, and origin, morphology, orientation and areal extent of fifteen braided islands have been estimated. Hydrodynamics of the region is studied through modelling, and probable flow pattern that is responsible for morphological changes is discussed. The simulated flow patterns indicate that current speeds are of the order of 10-20 cm/s inside the estuary and of the order of 40 cm/s at the mouth. The Right bank (Rb) of the estuary is subject to net erosion and the Left bank (Lb) is subject to net accretion. On an average, 20-30% of the area of all braided islands would be flooded, if the water level rises by 0.7 to 1.0 m. Islands of this estuary are morphologically very dynamic (migrating towards north, northeast and southwest directions) and subject to net accretion, whereas only one island (i.e., the Padu) has lost its major portion of landmass. A conceptual inverse distance weighted (IDW) interpolation model has been generated and evaluated possible flooding on the estuarine shoals and braided islands, due to heavy rainfall and/or sea-level rise. The model reveals that the possibility of flooding will be higher for those islands which are located close to the Rb than those close to the Lb. [ABSTRACT FROM AUTHOR]

A high resolution quantitative granulometric record for site Uchediya [21°43′2.22″ N, 73° 6′26.22″ E; 10 m a. s. l.] gives understanding towards accretion history of the late Holocene flood plain in the lower reaches of Narmada River. Two sediment facies (sandy and muddy) and seven subfacies (sandy subfacies: St, Sm, Sl, and St; muddy subfacies: Fm, Fm (O) and Fm (T)) are identified based on cluster analysis supplemented with sedimentary structures observed in field and other laboratory data. Changes in hydrodynamics are further deduced based on various sedimentological parameters and their ratios leading to arrive at a depositional model. [ABSTRACT FROM AUTHOR]

The December 26, 2004 tsunami left its imprints along the southern coast of India especially the coastal areas of Manakudy in Kanyakumari district of Tamil Nadu. In the study area - Manakudy estuary - the post-tsunami sediment texture is predominantly coarser as inferred from textural analysis. Granulometric analysis indicates a shift of well-sorted, coarse skewed and platykurtic nature during the pre-tsunami season, to moderately sorted, fine skewed and leptokurtic behavior, after the tsunami. Violent hydrodynamic conditions have prevailed during the post-tsunami deposition of sediments. The unimodal nature of the post-tsunami sediments as distinct from the bimodal pretsunami sediments is reflected from the frequency curves. The CM diagram and the log probability curves confirm these observations. [ABSTRACT FROM AUTHOR]

In the recent past, a number of new methods of utilizing hydrodynamic cavitation to create more intense and energy efficient liquid processes have come into existence. However, it is technically challenging to characterize these processes either quantitatively or qualitatively (Patil NM, M. chemical engineering Thesis submitted to Mumbai University, India, 2001). In this work, a hybrid device producing more energy intensive cavitation has been described, which has a blade positioned in the back pressure zone (downstream side of the orifice plate). This method of cavitation production route has been quantitatively described in the form of hydrophone measured pressure signals. Fast Fourier Transform analysis (FFT) analysis has been applied to the signal obtained at various positions of the blade, and at different inlet and outlet (back) pressures. Qualitatively analysis in terms of cavity size distribution and the total number of cavitational bubbles has been conducted, using a slightly modified technique of inverse FFT reconstruction procedure originally developed by Avvaru and Pandit to model cavity size distribution. © 2010 American Institute of Chemical Engineers AIChE J, 2011 [ABSTRACT FROM AUTHOR]

framework for dissolved oxygen (DO) modeling of the Ravi River has been developed based on a combination of laboratory measurements and field and monitoring data. Both the classical Streeter-Phelps (CSP) and the modified Streeter-Phelps (MSP) models are used for DO simulations. The MSP model considers the carbonaceous biochemical oxygen demand (CBOD) and nitrogenous biochemical oxygen demand (NBOD) separately, whereas the CSP model is evaluated considering only the CBOD and NBOD is incorporated in the overall BOD utilization rate. CBOD, NBOD and BOD rates have been determined through long-term BOD analysis of five main wastewater outfalls and two surface drains discharging into the Ravi River over a 98 km stretch. Analysis by Thomas Method manifests strong coefficient of determination 'R' between 0.72 and 0.98 for all the three types of BOD rates. Sensitivity analyses have also been carried out to find out a suitable reaeration rate formula for highly variable flows in the Ravi River. The CSP model results based on classical approach of considering only CBOD show significant difference between the model predictions and field measurements suggesting that NBOD needs to be incorporated for the model development. The dissolved oxygen values calculated using the MSP model and the CSP model based on overall BOD rate are in close agreement with field measurements and are thus suitable to model DO levels in the Ravi River. [ABSTRACT FROM AUTHOR]

Abstract: Ultrasonic attenuation due to electron–phonon interaction (EPI) has been computed in semimetallic single crystal neptunium telluride (NpTe) in low temperatures 5–80K. For the same evaluation, we have also evaluated ultrasonic velocity, electronic viscosity and second order elastic constants (SOEC). The SOEC of NpTe have been evaluated using the Born model of ionic solid. The behaviour of ultrasonic attenuation is quite similar to its inverse resistivity. The ultrasonic attenuation due to EPI is most significant at 40K. Computed results of ultrasonic parameter have been compared and discussed. [Copyright &y& Elsevier]

During the 1999 Marion Island Oceanographic Survey (MIOS 4) in late austral summer, a northbound and reciprocal southbound transect were taken along the Southwest Indian and Madagascar Ridge, between the Prince Edward Islands and 31 °S. The sections crossed a number of major fronts and smaller mesoscale features and covered a wide productivity spectrum from subtropical to subantarctic waters. Associated with the physical survey were measurements of size fractionated chlorophyll, nutrients and nitrogen (NO3, NH4 and urea) uptake rates. Subtropical waters were characterised by low concentrations (<0.27 mg m-3) of pico-phytoplankton cells (>81%) and very low f -ratios (<0.1), indicative of productivity based almost entirely on recycled ammonium and urea. Diatom growth was limited by the availability of NO3 (<1 mmol m-3) and SiO4 (<1.5 mmol m-3) through vertical stratification that prevents the upward flux of nutrients into the euphotic zone. Biomass accumulation of small cells was likely controlled by microzooplankton grazing. In subantarctic waters, total chlorophyll concentrations increased (<0.74 mg m-3) and larger cells became more prevalent, however smaller phytoplankton cells and low f -ratios (>0.15) still dominated, despite sufficient NO3 availability. The results from this study favour Si limitation, light-limited deep mixing and likely Fe deficiency as the dominant mechanisms controlling significant new production by micro-phytoplankton. Increased concentrations of micro-phytoplankton cells and and rates of new production did however occur at oceanic frontal regions (58.6% and 11.22%, respectively), and in the region of the Prince Edward archipelago (61.4% and 14.16%, respectively). Here water column stabilization and local Fe-enrichment are thought to stimulate phytoplankton growth rates, especially of diatoms. Open ocean regions such as these provide important areas for local but significant POC export and biological CO2 draw-down in an overall HNLC Southern Ocean. [ABSTRACT FROM AUTHOR]

The article presents a study that reviews issues on hydrodynamic modeling of floods at the Mahanadi River basin in India. The study used the one-dimensional (ID) hydrodynamic model in simulating the river flows as well shuttle radar topography mission digital elevation models (SRSTM DEM) in the analysis and comparison of elevations based from available topmaps and measure river cross-sections. Moreover, it has shown that SRSTM DEM was more useful to derive river cross sections.

Straight-chain N,N-dihexyloctanamide (DHOA) and branched-chain N,N-di(2-ethylhexyl)isobutyramide (D2EHIBA) have been identified as promising alternatives to tri-n-butylphosphate (TBP) for the reprocessing of spent uranium based fuels, and selective extraction of 233U from irradiated thorium fuels, respectively. The present work deals with the effects of different hydrodynamic parameters such as viscosity, density, and interfacial tension (IFT) on the phase-separation time (PST) under uranium and thorium loading conditions. The IFT values have been determined under varying experimental conditions such as the aqueous nitric acid concentration, n-dodecane purity, ligand concentration, and thorium/uranium loading conditions. These studies have suggested that the quality of n-dodecane affects the IFT values of different solutions. The IFT values of D2EHIBA changed marginally (23.3 ± 0.9 mNm-1) against THOREX feed solution for the wide range of D2EHIBA concentration (0.1-1.0 M). However, IFT, viscosity, and PST values increased with uranium loading of 1.1 M DHOA. These studies suggested that a lower phase-disengagement rate with increased uranium loading was mainly due to the increased viscosity of the loaded 1.1 M DHOA solution. [ABSTRACT FROM AUTHOR]

Summary: Environmental isotopes (2H, 18O, 3H, 13C, 14C, 34S), in conjunction with hydro-geological and hydro-chemical data, were employed to understand the groundwater recharge processes and hydrodynamics of the Tiruvadanai aquifers in the Tamilnadu State in Southern India. Hydro-chemical characterisation of the groundwater indicated that the Tertiary aquifers (depth: 50–200m, un-confined/semi-confined/confined), contain no-dominant (Ca–Mg–HCO3–Cl) to brackish (Na–Cl) type of waters and the deeper (350–500m) Cretaceous aquifer (confined) contains freshwater. The concentration of various chemical species along the general groundwater flow direction (northwest to east) showed a trend with decrease in Mg2+ and Ca2+ and an increase in Na+ and K+ in both Tertiary and Cretaceous aquifers which is also indicated by decreasing saturation index values for dolomite along the flow path. This could be attributed to ion-exchange processes. A higher pH value of Cretaceous aquifer samples (7.4–8.6) could also be responsible for the lowering of Mg2+ and Ca2+ concentrations by facilitating precipitation of carbonates in them. On the δ2H–δ18O plot, the Tertiary aquifers samples fall on an evaporation line. Their 3H values near the ephemeral rivers range from 2 to 5TU while those away from the rivers have <1TU and 14CDIC model ages range from 1 to 13kaBP. The Cretaceous aquifer samples measured 3H values <1.5TU and their 14CDIC model ages are >20kaBP, indicating palaeo-waters. Based on 14C model ages, the groundwater velocity was estimated (Tertiary aquifers: 10−2–10−3 md−1; Cretaceous aquifer: 10−3 md−1). Dissolution of carbonate bearing minerals in the Tertiary aquifer and oxidation of organic matter in the Cretaceous aquifers seems to be the dominant processes and thus resulting in the corresponding enrichment and depletion in 13CDIC along the flowpaths. The values of δ34S (aq. ) showed enrichment in the Cretaceous aquifer samples compared to that of the Tertiary aquifers samples. The δ34S (aq. ) enrichment could be due to bacterial reduction of sulphate. From the investigation, three types of recharge processes to the aquifer system are discerned, with the overall modern recharge component being low. The Cretaceous aquifer contains fossil groundwaters and hence the resources may be finite and their exploitation is mining. Deeper coastal groundwater isotopic evidence of palaeo-climatic excursions between arid and humid phases during the Holocene and Late Pleistocene in the Southern India has been obtained for the first time. [Copyright &y& Elsevier]

Tidal circulation in the Cochin Estuary, a moderately polluted estuary along the southwest coast of India, was studied using a 2D hydrodynamic model. The predicted tides and currents showed very good agreement with measured tides. Particle trajectories and residual currents computed from the model have been used to classify the study region into three zones: northern estuary, central estuary, and southern estuary. The central estuary is dynamic, whereas the other two zones are relatively weak. An amplification of measured tides in the south estuary during March indicates the presence of standing waves caused by the hydraulic barrier at Thanneermukkom. Model results suggest that the northern and southern zones are sensitive to environmental pollution. The present level of pollution in the northern estuary is due to the direct release of industrial effluents into the river Periyar, which can be minimized if they are brought down to central estuary for disposal. The concept of different zones in the estuary will be useful to planners in protecting the vulnerable regions of this productive ecosystem from human interventions. [ABSTRACT FROM AUTHOR]