Vaigai River Research Articles

Studies on the influence of water quality on community assemblage of immature mosquitoes in different ecosystems along the Vaigai river, Tamil Nadu, South India

BackgroundOver the last few decades, river ecosystem is highly modified through various anthropogenic activities which are resulted to alter ecosystem functions and services. This modified ecosystem rendering conducive environment to mosquitoes through various ecological links for the self-sustaining populations. However, deciphering the community assemblage of immature mosquitoes with reference to water quality at modified ecosystem is very essential to make suitable control measure to curtail mosquito populations. In order to understand how the water quality influences the larval density, habitat specificity and community assemblage of immature mosquito populations, a study was conducted at different ecosystems (urban, semi-urban and rural) along the Vaigai river. The physicochemical parameters such as pH, TDS, salinity, conductivity, turbidity, DO, were analyzed at each study site.ResultsOur results clearly revealed that Anopheline species were highly preferred to breed less polluted habitat than Culicine species. Community assemblage by Anopheline and Culicine mosquitoes were found to be higher at all the studies whilst community assemblage by Anopheline were maximum at rural and semi-urban sites. Among the Anopheline species, Anopheles subpictus able to breed at high polluted habitat, particularly higher turbid level (28.49 ± 2.18 NTU) than other Anopheles species. Cx. gelidus mostly breed at sewage disposal habitats with high salinity level (1.01 ± 0.08) whilst Cx. bitaeniorhynchus bred in only fresh water bodies particularly low turbid habitats (3.97 ± 0.40 NTU). Grouping of immature mosquitoes based on the habitat similarity, An. subpictus, Cx. vishnui, An. vagus, Cx. tritaeniorhynchus, Cx. gelidus and Cx. quinquefasciatus were able to breed in highly polluted habitats which are resulted fell in group A than group B mosquitoes. Cx. vishnui and An. subpictus have strong habitat similarity (0.96) and can able to share their habitats with more number of Anopheline and Culicine mosquitoes.ConclusionsFrom the study we concluded that, Cx. vishnui and An. subpictus were most prevalent species and strong habitats similarity along the Vaigai river basin. An. subpictus and An. vagus can adapt to breed in polluted habitats and this may be adequate to extend the vectorial capacity and disease outbreak along the Vaigai river basin.

Comprehensive river water quality monitoring using convolutional neural networks and gated recurrent units: A case study along the Vaigai River

Effective monitoring of river water quality is required for long-term water resource management. Convolutional Neural Networks and Gated Recurrent Unit-based water quality monitoring (CNGRU-WQM) were used in this investigation to develop a comprehensive monitoring system along the Vaigai River. The system was designed to collect real-time data on several crucial water quality parameters. The collected characteristics encompassed factors like water pollution levels, turbidity, pH readings, temperature, and total dissolved solids, offering a comprehensive view of river water quality. The monitoring system was methodically set up, with sensors strategically positioned at various locations along the river. This ensured that data collection would take place at regular intervals. The CNGRU-WQM model achieved a validation accuracy of 97.86%, surpassing the performance of other state-of-the-art approaches. Particularly noteworthy is the fact that the actual use of this system incorporates real-time warnings, which enable stakeholders to be instantly informed if water quality measurements surpass pre-set criteria. The study's contributions include its efficient river water quality monitoring system, which encompasses a variety of indicators, and its ability to significantly affect environmental conservation efforts by offering a helpful tool for informed decision-making and timely interventions.

Tectono‐climatic and depositional environmental controls on the Neolithic habitation sites, Vaigai River Basin, Southern India

The establishment, development and abandonment and/or destruction of ancient civilizations were catalytically controlled by geomorphic features such as lakes and rivers and the climate. This paper examined the possible influence of tectonism and climate on six habitations of the ancient Vaigai River Basin civilization in South India, using multiple proxies such as grain size, geochronology and geochemistry of the sedimentary archives. The tectonic setting of the basin changed between the active margin and passive margin; the discriminant diagrams suggested varying provenance and changing climatic conditions over the mid‐ and‐late Holocene. Tectonic activism and quiescence, base‐level change in the channel morphology led to the burial/marooning of the first habitation surface. Overall, arid conditions were punctuated with catastrophic flooding and peak discharge (flood) destroyed the second, third and fourth habitation sites. These flooding events were characterized by moderate weathering (CIA) and high values of Al, Fe and Rb/Sr and low Ca/Mg in the sediment records. The abandonment/destruction of the fifth habitation also occurred during an arid interval (droughts), possibly caused by weak monsoon. Along with the interactions between tectono‐climatic and fluvial geomorphic factors, the new results provided avenues to (a) check and recognize the archives for 8.2 and 4.2 ka‐like events in this part of the world, and (b) the utility of integrated analyses to constrain on the civilizational histories of the mankind.

Probability analysis and rainfall forecasting using ARIMA model

A 34-year rainfall data from 1976 to 2009 of ten sub-basins of the Vaigai River in Tamil Nadu were collected and analysed statistically using various probability distribution functions. The best-fit probability distributions for the annual, monthly and seasonal rainfall for the study area were found using two goodness-of-fit tests. The Box-Jenkins Autoregressive Integrated Moving Average (ARIMA) methodology has been adopted for model identification, diagnostic checking and forecasting the study area's annual rainfall. The best ARIMA models were selected for each sub-basin and the average annual precipitation for 2010, 2015, 2020 and 2025 has been forecasted. The forecasted result compared well with observed dataup to 2020, which indicates the appropriateness of the model.

Magnetic Susceptibility as Proxy for Metal Concentrations and Their Risk Levels in Vaigai River Sediment, Tamilnadu, India: Horizontal and Vertical Approach

ABSTRACT Horizontal and vertical distributions of heavy metals (Al, Fe, Mg, Cd, Cr, Cu, Ni, Pb and Zn) and magnetic susceptibility of Vaigai river sediment have been assessed to know the heavy metal toxicity and magnetic behavior of the sediment. The present study intentionally shows the magnetic susceptibility as proxy for metal concentrations and their risk levels of sediment. Univariate statistical analysis is carried out to confirm the spatial distribution of the heavy metals. The metal concentrations in present sediment are compared with iportant toxic reference values such as TEL, PEL, ERL, ERM and TRV to predict the toxicity of metals. The result shows that the frequent biological effect can be possible due to Cd, Cr, Cu, Pb and Zn in all feet sediments. Some interesting pollution factors such as PLI, PER and mPEC-Q are calculated to know the pollution status of the river. High magnetic susceptibility values in S16, S18 and S25 indicate the presence of various magnetic minerals. Principal Component Analysis (PCA) is carried out to show magnetic susceptibility as proxy for measuring heavy metals and their risk levels. Since magnetic susceptibility is strongly associated with heavy metals and their risk levels, this may be proxy for determining heavy metals and their risk levels.

Determination of Parameters for Watershed delineation using various satellite derived Digital Elevation Models and its accuracy

<p>Digital Elevation Model (DEM) is an inevitable tool for many applications, such as natural resource management. In the present scenario, it is available with various resolutions from meter to sub-meter accuracy. These data are used extensively to explore the river basin's physical features by detecting and extracting watershed boundaries, elevation points, drainage networks, flow directions, and morphological parameters. Although many researchers have used DEMs to delineate the watershed boundaries of the river basin, accuracy makes the significant distinction and usage of various DEMs. In this study, the accuracy of watershed delineation derived from various open-source DEMs such as Shuttle Radar Topographic Mission (SRTM), Advanced Spaceborne Thermal Emission, and Reflection Radiometer (ASTER), Cartosat-1, and ALOS Palsar, in the vaigai river basin have been observed. The Arc SWAT hydrological modeling tool was used to delineate the watershed boundary using the DEMs mentioned above. Eventually, the outcome is validated with the help of base data received from TN-PWD (Tamilnadu Public Work Department). The results attained from the extraction of the watershed boundary from various DEMs reveal that the watershed boundary delineated from ALOS – Palsar is closely matching with the actual boundary of vaigai river basin. The regression analysis of the watershed on area and perimeter obtained from the ALOS Palsar DEM yielded R2 as 0.97 and 0.99. This R2 exhibits the close fitness of the predicted value with data obtained from TN-PWD data. The ALOS Palsar DEM provided low vertical errors and high vertical accuracy compared to other DEMs. Overall the ALOS Palsar DEM generated outcome exhibited comparatively better results than the rest of the DEMs.</p>

A Gis-Based Parametric Analysis of Irrigational Tanks in the Oldest Civilized City in India-Madurai

The irrigational tanks being traditional Water harvesting structures designed by rulers and chieftains dating back centuries. These are constructed in such a way that they act as a major water resource in drought-prone rural communities. The main aim of this paper is to develop a GIS-based Parametric Maps of Maximum Capacity(MC), Maximum Water Level(MWL), Ayacut Area(AA), Water Spread Area(WSA), Sub-basins and Basins of irrigational Tanks which form the basic irrigation information system to assist agriculturalists, farmers, and Government organization for the proper maintenance of irrigation tanks with suitable indexing parameters, to mitigate & forecast the water and food requirements by evaluating currently available water for the given population density and irrigation lands. The study area selected is the oldest civilized city in India which is in the state of Tamilnadu-Madurai district, which is served by the Vaigai River and consists of 1338 tanks. This GIS-based information system assists the decision-makers to perform surveillance, evaluate the efficiency of the tank at any space & time and take proper managerial methods to utilize the resources economically.

Episodic habitation and abandonment of Neolithic civilization sites in the Vaigai River Basin, Southern India

Recent studies have unearthed and recovered multiple sites with evidences of past human habitations in terms of ceramic, metal, precious stone, jewel, and stone tool industries and places of varied methods of burial and worship are being unearthed at different stratigraphic levels from floodplains of the Vaigai River Basin, Southern India. In this contribution, we present high-resolution 14C chronology of the archaeological artefacts, cultural evidence and the textural characteristics of sediments collected from the excavated pits. These data along with the information on regional geology, geomorphology, sedimentary facies, texture, petrography, and mineralogy constrain the older phase of the Vaigai River Basin Civilization to be microlithic in age, followed by affirmative evidence of ca. 5511-5147 BCE (7455-7091 cal yr BP). This was followed by few more colonization/cultural/habitation sites/surfaces at ca. 2976-2961 BCE (4938-4908 cal yr BP), 1860-1489 BCE (3543-3503 cal yr BP),530-390 BCE (2435-2314 cal yr BP), 596-629 CE (1353-1321 cal yr BP) and post 1225-1312 CE (729-619 cal yr BP). These are designated as habitation sites/surfaces namely HS-1, HS-2, HS-3, HS-4, HS-5 and HS-6, respectively. Evidences of urbanism, industrial and leisure activities besides cohabitation of at least three groups that practiced mutually exclusive burial customs are documented. Microlithic tools and buried habitation stages, together with the prevalence of modern habitations, make this basin unique with human occupation at least since the mid-Holocene. Major shifts of the trunk channel of the Vaigai River, perhaps associated with flood events, marooned/buried/destroyed the ancient habitation sites that forced the inhabitants to abandon old sites and led to the reestablishment of newer ones. Inevitable dependence of the ancient societies on the riverbanks and the flood plains for settlements and livelihood compounded with the lack of knowledge on extreme climatic events possibly caused the decimation of several settlements of this important civilization from south India.

Neolithic cultural sites and extreme climate related channel avulsion: Evidence from the Vaigai River Basin, southern India

We document evidence for the role of fluvial dynamics-stream channel avulsion and flooding, tectonics and climatic conditions on the occurrence, shifting and burial of ancient cultural sites in the Vaigai River Basin in southern India. Systematic regional mapping, geophysical investigations and archaeological excavations in the flood plains of the Vaigai River led to the unearthing of an ancient culture that thrived at least since 752 BCE (2435 ± 34 BP). Evidence for early human activities include sites of ancient and now buried industries that were manufacturing steel, glass bead, dye, gold jewelry and earthenware, in addition to dwelling-habitation, sites of religious sacrificial ceremonies, and places of worship, and burial. These information together with the occurrences of microlithic age stone tools in the vicinity led to the proposition of continued habitation of the Vaigai River Basin until today. Radiometric dating shows oldest age of 2435 ± 34 BP (752 BCE) obtained at 2.5 m depth in a pit excavated at Keezhadi, a location situated far from the present day channel course whereas the youngest age of 689 ± 24 BP is obtained at Agaram, a location situated nearest to the present day channel course. The bone fragments were dated as 1115 ± 39 BP (778 CE – 1016 CE) and 1229 ± 30 BP (689 CE – 883 CE). The organic carbon/peat layers recovered between flood deposits at the upper reaches of the Vaigai River are dated as 830 ± 30 BP and 1250 ± 30 BP. The natural levee deposits show evidences of habitation-related disturbances in the internal sedimentary structure, texture and packing. In addition to occurrences of hearth etc., recurrences of overbank-channel deposits over natural levee-habitation surfaces indicate habitation-colonization over relatively highgrounds along river bank, followed by marooning/burial under overbank-channel deposit and abandonment of habitation site and/or shifting of habitat. The same sequence of events occurred again, showing two habitation surfaces that are buried under surface currently. Together with facies characteristics and other artifact occurrences, the ages obtained in our study indicate shifting of the Vaigai River from prior to 2435 BP and colonization of ancient population, which might have been affected by a catastrophic flood and stream avulsion at about 1250–830 BP. These resulted in the ancient habitation getting marooned, industries and other structural infrastructure destroyed, and were transported and deposited as interbeds in flood deposits. Following a reduction in the stream energy, the point bar-natural levee environmental setting paved way for the deposition of organic carbon layer at Agaram at about 690 BP. This was followed by lateral shifting of the channel from Agaram towards the present-day course.

Biodegradation of low-density polyethylene and polypropylene by microbes isolated from Vaigai River, Madurai, India.

The present study aimed to evaluate the microplastic degradation efficiency of bacterial isolates collected from Vaigai River, Madurai, India. The isolates were processed with proper methods and incorporated in to the UV-treated polyethylene (PE) and polypropylene (PP) degradation. Based on preliminary screening, four bacterial isolates such as Bacillus sp. (BS-1), Bacillus cereus (BC), Bacillus sp. (BS-2), and Bacillus paramycoides (BP) were proceed to further degradation experiment for 21days. The microplastics were filled with bacterial isolates which is use microplastic (PE, PP) as carbon source for their growth and proceed for shake flask experiment were carried out by two approaches with control. The microplastic degradation was confirmed through their weight loss, increasing fragmentations and changes of surface area against control experiments (microplastic without isolates) also confirms degrading efficiency of isolated bacterial strains through non-changes in their weight and surface area. The highest degradation of PP and PE were observed in BP (78.99 ± 0.005%), and BC (63.08 ± 0.009%) in single approach, while in combined approach BC & BP recorded the highest degradation in both PP (78.62 ± 2.16%), and PE (72.50 ± 20.53%). The formation of new functional groups is confirming the biofilm formation in the surface area of microplastics by isolates and proving their efficiency in degrade the microplastics. The degradation of microplastic experiments should be cost effective and zero waste which is helpful to save the environment and the present findings could reveal the way to degrade the microplastics and prevent the microplastic pollution in aquatic environment.

Quaternary Tectono Geomorphic Evolution of the Vaigai Delta as deduced from Geomorphic Mapping

The well preserved landforms of the Vaigai river delta in Tamil Nadu stand testimony to the Quaternary sea level changes, fluvial dynamics of the river and the morphotectonic movements of the region. The geomorphic mapping performed using high resolution satellite images brought out the occurrence of unique set of landforms like beachrocks, abandoned channels, deltaic lobes etc. that indicate the dynamic evolution of the Vaigai delta during the Quaternary period assisted by the palaeo sea level fluctuations, preferential migration of the river and land upliftment due to neotectonic movements. The occurrences of extensive sand dunes further suggest the strong aeolian action in the geomorphic evolution of the delta and also the Quaternary climatic changes of the region.

A case study of flood frequency analysis by intercomparison of graphical linear log-regression method and Gumbel's analytical method in the Vaigai river basin of Tamil Nadu, India

Flood Frequency Analysis (FFA) is a systematic tool used for an efficient hydraulic structures design, operation and maintenance. An effort is made to study and compare the Linear Log Regression Graphical Method (LLRGM) and Gumbel's Analytical Method (GAM) to assess the future flood magnitude for any given Return Period (RP). Twenty-four years of annual daily peak flood flow value recorded at Vaigai reservoir gauging station between the year 1995 and 2018 was used in the two methods for detailed analysis. The results indicated that the GAM predicts the maximum possible optimum future flood in comparison with the LLRGM. This conclusion was drawn based on the coefficient of determination R2 obtained as 0.8904, which is nearing 1. Based on the analytical method of Gumbel's, the magnitude of frequency factor K has been introduced based on the size of data and coveted RP. The comparative study will provide boon to regulate the storage water to the posterior areas concerning safety and optimum utilization of water for various uses.

New record of Caenis nigropuctatula Malzacher, 2015 (Ephemeroptera: Caenidae) from Southern India

Caenis nigropuctatula Malzacher, 2015, a new mayfly record of the fauna of Indian Ephemeroptera, is recorded from the Vaigai River, Tamil Nadu, India. It is known before from Thailand, Java, and Sumatra. The distribution map of C. nigropuctatula is given.

, , ,

Objective: Escherichia coli are the most common pathogenic bacteria to accountable for food and waterborne illness. Therefore, in this way the study was conducted to resolve the occurrence of E. coli bacteria from different water sources in around Tamil Nadu along with to determine their antibiotic resistance profiles. Methods: Water samples were analysed for the presence of E. coli bacteria using specific agar media Eosin Methylene Blue and McConkeys. Colony morphology, Gram staining, various biochemical tests and antibacterial tests performed by disc diffusion method were used to confirm E. coli bacteria. Results: The isolated bacteria were susceptible to Gentamycin (Mullai & Dindigul 18mm) and Tetracycline (Mullai 16mm &Vaigai 18mm) at 37°C for 24 hours. The isolate was susceptible to acetone leaves extract of Abutilon indicum, Calotropis gigantean and Solanum trilobatum in various concentrations (50µl, 75µl, & 100µl) and of A. indicum was most effective inhibition of zone formed in Mullai 24mm, Vaigai 18mm and Dindigul 23mm, triplicate value respectively. Conclusions: In this study revealed that E. coli bacteria were resistant to some antibiotics drugs. Compared to chemical antibiotic, the acetone leaves extract of A. indicum showed excellent inhibition effect (Mullai (24mm), and Dindigul drinking water (23mm) in 100µl concentrations only. But S. trilobatum was showed equal inhibition effect against Vaigai river water (18mm). Therefore, E. coli bacterium was controlled by natural antibiotics of A. indicum and it may reduce the resistance power of food and waterborne illness.

Effect of climate change on morphological characteristics of the soils of Vaigai River Basin, Alluvial Tract, Madurai District, Tamil Nadu

The pedological characterization of alluvial tract soils of Vaigai river basin, Madurai District, Tamil Nadu was taken during 2019-20. Initially a Reconnaissance Soil Survey was carried out with Toposheet as a base map. Totally nine representative pedons in Northern and Southern bank of the Vaigai river alluvial basin were selected and studied for their morphological characteristics. Along the course of Vaigai river basin, deposition of alluvial soil was evidenced by the poorly developed AC profiles in both side. The depth of the soil varied from d4 to d5 in both banks. The color of the pedons varies with hue ranging from 10YR to 7.5YR, value 2 to 6and chroma 2- 8 and in Northern bank ; from 10YR to 7.5YR,values varies by 2.5 to 6 and chroma by 1 to 6 in the Southern bank. The texture of soil varied from weak to structure less. Some yellowish brown mottles with jarosite were foundin the Northern bank and micaceous coatings found in the Southern banks. The calcium carbonate nodules were found in most of the pedons and the permeability of the soil was very rapid. Coconut, Banana and paddy are the major crops grown in this alluvial tract. Climate change, urbanization, is short of monsoon rain and industrialization had created the major impact on the shrinkage of land under cultivation and smash up the soil health. The present study on characteristics of alluvial tract of Vaigai River basin both in Northern and southern banks understood about the change due to anthropogenic activities and climate change scenario.

Open Drainages Effecting for People in their Day to Day Life and Drainage Wastage Effecting the River in Theni District

The present study is considering the drainage coming into the rivers and affecting people’s lives in Theni district, India. The Varaha (Varahanadhi) is a small river that flows through the town of Periyakulam in Theni district of the state of Tamil Nadu in India. It joins the Vaigai River near Marugalpatti. In today’s time the the Varaha river, once considered sacred, is fast becoming an open drain since the drainage water had been diverted to it. The Panchayat Union waste and Municipality waste has been directed to the river. People living along the banks complain of mosquitoes and presenting with sicknesses. They require closed drainages to prevent getting sick. Indian officials have said that to consider with an alternate drainage system to be created at the cost of about Rupees twenty-six crores. Survey and questions to the people living near this open drainage complained that the Indian officials had taken surveys, and nothing has been done so far, considering the money has been paid.

Prediction and Validation of Rainfall Classes for Vaigai River Catchment using El Nino

Extraordinary weather patterns are being observed globally during the past 30 years due to climate change resulting in variations in temperature and rainfall. Studies on long-term trend pattern of temperature and rainfall since 1980 distinctly shows a rise in mean temperature and declining rainfall trend. Due to change of climate at global level change, forecasting of rainfall with the conventional statistical analysis could not predict satisfactory results. Among the available processes, the El Niño Southern Oscillation (ENSO) cycle is considered efficient. Statistical analysis was carried out in this study so as to investigate the implication of rainfall data in seven rain gauge stations located in Vaigai River Catchment through the period from 1959 to 2016. ENSO Cycle was used also to predict rainfall for Vaigai River catchment of the Tamil Nadu State, India. Quadratic discrimination analysis (QDA) and Neural Network models are used to identify the class of rainfall classes with reference to ENSO cycle. The patterns recognized on the study area offer constructive information to administrators of water resource management, to implement the same for agriculture, water supply and power generation.

Tectono‐morphological evolution of the Cauvery, Vaigai, and Thamirabarani River basins: Implications on timing, stratigraphic markers, relative roles of intrinsic and extrinsic factors, and transience of Southern Indian landscape

Peninsular India is an amalgam of transient landscapes evolved from the interactions between tectonic and climatic forcings. In order to appraise the tectono‐geomorphic evolution of South India, it is essential to understand the relationships between intrinsic and extrinsic processes and their geomorphic expressions at a river basin scale. Seven geomorphometric parameters, namely, longitudinal profile (Lp), asymmetry factor (Af), hypsometric curve and hypsometric integral (HI), mountain front sinuosity (Smf), river sinuosity (R), stream length gradient (Sl), and shape factor (Shp) were calculated for selected drainage basins of South India. Spatial analyses of these parameters in the light of systematic field mapping were attempted in this study. The results show the occurrences of southern sub‐basins with convex hypsometric curves indicating a youth stage and significant tectonic influence. The low and moderate Smf values within the basins are indicative of mountain fronts witnessing a high level of tectonic activity. The net effects of tectonic and geomorphometric processes are inferred to have been the responses of anti‐clockwise rotation of the Indian Plate and ridge uplift‐push from west. Directional change in Thamirabarani River Basin and drainage channel reorganizations in the Cauvery and Vaigai River basins stand testimony to these, among others. Amidst these, occurrences of tectonically quiescent regions and multiple incisions by river channels and flow of modern river channels in inherited palaeovalleys but on tangent directions of ancient flows are also observed. Five stages of landscape development are envisaged: First, inheritance of river basins from palaeodrainage systems; second, reversal of river flow directions during early part of Cenozoic and inception of evolution of modern river systems; third, during Miocene–Pliocene; fourth, during Pleistocene–Early Holocene; and fifth, during the Holocene–Anthropocene. The recent resurgence of tectonics is not only reflected in the shifting of axial rivers, but is also evidenced by seismicity and landslides/faulting. Together, transient nature of the Southern Indian Plate, first‐order control of tectonics, followed by climate and lithology over landscape evolution, inheritance of river valleys, synonymy of river basin responses to intrinsic and extrinsic geomorphic processes, however with unique signatures and basin‐scale responses, are inferred. Detailed morphometric studies and supplementation with precise age data may fine‐tune the proposed model. According to the model, inheritance of Mesozoic valley/structures during Late Jurassic–Early Cretaceous, drainage reversal and initiation of Cenozoic–Recent river basin evolution, intense peneplanation during Miocene–Pliocene, intense incision during Pleistocene, periodic climatic extremes during Early Cenozoic, Palaeocene–Eocene, Oligocene and corresponding pedogenesis, and terrace formation and sedimentation have been recognized. Based on the numerical ages and documentation of basin‐scale distribution of specific types of lithologies/weathering profiles/palaeosols, provisionally we recognize the laterite/ferricrete–bauxite–calcrete 53–50 and 37–23 Ma to be the oldest weathering profiles, palaeosols (I generation palaeosols) of alluvial fans with texturally immature parent rock clasts to be of 23–9 Ma, palaeosols with intensive calcitized rootlets that are found to occur in fluvial terraces of palaeo‐floodplain/natural levee (II generation palaeosols) to be of 3.5–2.5 Ma, and relict alluvium that are documented in inland river terraces and older deltaic plains and calcareous sandstones that are documented in coastal terraces to be of ~1 Ma old and attribute them to be the results of significant climatic events and Early Cenozoic uplift of Western Ghat that proceeded from south–north and its intensive tilt toward east since 25 Ma until today at a rate of 0.1 mm/year to be tectonic events that have significantly contributed toward landscape development on basin‐regional scales and concur with the evolutionary stages proposed in our model.

An appraisal of flood events using IMD, CRU, and CCSM4-derived meteorological data sets over the Vaigai river basin, Tamil Nadu (India)

The study of the impact on climate change on water resources provides useful information for long-term trend analyses of important issues such as control of floods, management of drought, agricultural production, etc. This work is an attempt to assess the flood events in Vaigai watershed, Tamil Nadu (India). The Mann–Kendall test was performed to assess the rainfall and temperature trends on data extracted from Climatic Research Unit (CRU) and Community Climate System Model 4 (CCSM4) model for historical and future scenarios. The CCSM4 model was compared with India Meteorological Department and CRU data sets to analyze the performance and consistency of model data among the years of flood, viz., 1993, 2010, and 2015. The CCSM4 model was able to capture, in a few instances, the historical as well as future flood events over the region. The maximum rainfall (738.11 mm) was predicted for 2021 followed by 2038 and 2040, and the lowest rainfall (43.40 mm) was predicted for 2036. Besides, the temperature increased by 1 °C and rainfall was mostly maximum in September corresponding to the south-west monsoon (SWM) season. The predicted increases in rainfall can result in flash floods, which have serious implications on the agricultural sector and water resources of the basin, while the decreasing rainfall during the other seasons helps to reduce the flood severity.

Mineral and magnetic parameters as proxies for natural radioactivity level in Vaigai river sediment: Horizontal and vertical approach

The present study is aimed to show that the mineral and magnetic parameters are proxies for radioactivity level of Vaigai river sediment. In order to show the usefulness of above said parameters as proxies for radioactivity level of the river, elaborate analyses along with radioactivity level need to be analyzed in horizontal (different locations) and vertical (upper, first, second and third feet) views of the river. The radioactivity analysis shows that average concentrations of 238U, 232Th and calculated absorbed dose rate are within the recommended safety level in all depth samples. Eleven minerals have been identified and characterized by FTIR, and are confirmed by XRD techniques. Based on the calculated results of extinction co-efficient, the amount of major minerals are decreased in the order of quartz > microcline feldspar > orthoclase feldspar > kaolinite in all depth samples. The presence of ordered crystalline quartz in all depth samples have been assessed by the calculated crystallinity index values. These observations are matched with XRD results. Magnetic susceptibility measurement was carried out in horizontal and vertical views which show the presence of dia, ferri, antiferri and ferrihydrate magnetic minerals in present sediments. Studied characteristics and their distributions are almost similar in all the depths. Multivariate statistical analyses include cluster analysis (CA), Factor analysis (FA) and Principal component analysis (PCA) are effective tool to show the above said parameters as proxy and the analyses are carried out. Relevant justification is also given for explaining the parameters as proxy. In the clay mineral, high adsorption of radionuclides and magnetic minerals occurs in lattice defects or onto crystal and grain boundaries due to the high cation exchange capacity. Since, the parameters such as content of clay, magnetic susceptibility and amount of kaolinite (clay) in all depth samples are strongly associated with radioactivity variables, one can say that above said parameters may be proxies for determining the level of radioactivity in Vaigai river sediment.