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Water quality index (WQI) models are generally used in hydrochemical studies to simplify complex data into single values to reflect the overall quality. In this study, deep groundwater quality in the Chittur and Palakkad Taluks of the Bharathapuzha river basin of Kerala, India, was assessed by employing the WQI method developed by the Canadian Council of Ministers of the Environment (CCME). The assessment of overall water quality is indispensable due to the specific characteristics of the study area, such as geography, climate, over‐drafting, and prevalent agricultural practices. Forty representative samples were collected from the study area for monsoon (MON) and pre‐monsoon (PRM) seasons. The results showed a general increase of contents from MON to PRM. The major cations were spread in the order Ca2+>Na+>Mg2+>K+ and the anions HCO3−>Cl−>CO32− based on their relative abundance. Among various parameters analysed, alkalinity and bicarbonate levels during MON were comparatively high, which is indicative of carbonate weathering, and 90% of the samples failed to meet the World Health Organization (WHO, 2017)/Bureau of Indian Standards (BIS, 2012) drinking water guidelines. The CCME WQI analysis revealed that nearly 50% of the samples during each season represented good and excellent categories. The samples in the poor category comprised 10% in MON and 15% in PRM. The overall WQI exhibited 15% of poor category samples as well. The spatial depiction of CCME WQI classes helped to expose zones of degraded quality in the centre to eastward parts. The spatial and temporal variations of CCME WQI classes and different physicochemical attributes indicated the influence of common factors attributing to the deep groundwater quality. The study also revealed inland salinity at Kolluparamba and Peruvamba stations, where agricultural activities were rampant with poor surface water irrigation. [ABSTRACT FROM AUTHOR]

The study investigates the spatio-temporal variability of radon ( 222Rn) with respect to the geology and hydrogeology of the Vamanapuram River Basin (VRB), SW India. A total of 40 groundwater samples were collected during three seasons of 2019. RAD7, RAD-H2O accessory (Durridge Co. USA) was used to analyse 222Rn, and physico-chemical parameters were measured in situ by Horiba Laqua water quality analyser. The results show that the 222Rn activity was in the range of 640–79,940 Bq/m³ in pre-monsoon, 250–36,950 Bq/m3 in monsoon and 420–59,790 Bq/m³ in post-monsoon season and 18% of samples exceeded the permissible limit of USEPA (11,000 Bq/m³ ) during all seasons. Remarkably, the samples exceeding the permissible limit of 222Rn were associated with khondalitic rocks with notable amount of uranium-bearing minerals and NW-SE trending lineaments, the most active type of lineament in the study area. The study shows the considerable influence of seasons and the highest activities were found during pre-monsoon compared to the other two seasons. [ABSTRACT FROM AUTHOR]

Coastal groundwater is ubiquitously under threat due to a variety of natural and anthropogenic activities. Groundwater occurring along a stretch of the coastal tract (L = 15 km) of Thiruvananthapuram district, Kerala, India, was analyzed for hydrogeochemical characterization, identification of factors influencing water chemistry, suitability for drinking and irrigation purposes. A total of 48 water samples were collected over three sampling seasons (pre-monsoon – PRM, monsoon – MON and post-monsoon – POM) in 2012. The study area is sandwiched between two estuaries: the Akkulam–Veli estuary to the north and the Poonthura (Karamana River) estuary to the south, while a shore parallel man-made canal forms the eastern boundary on the landward side. The results of hydrogeochemical analysis showed that the parameters, such as electrical conductivity (EC), total dissolved solids (TDS) and total hardness (TH) are relatively higher in four locations towards the south due to proximity to the estuary/canal. Phosphate content exceeds the permissible limit for all samples in all sampling seasons. Water quality during POM is relatively good compared to other seasons. Hydrochemical facies of water samples suggests that groundwater samples belong to Ca-Cl type. Multivariate (R-mode) factor analysis identified a multitude of factors influencing groundwater chemistry. To assess the suitability of groundwater for irrigation use, different indices, viz., EC, percent sodium (%Na), sodium adsorption ratio (SAR), Kelley's ratio (KR), residual sodium carbonate (RSC), permeability index (PI), and magnesium hazard (MH) were computed. The study reveals that the quality of groundwater is of concern, warranting attention. It is fit for drinking purpose only after amelioratory measures, whereas, it is permissible for irrigational purposes. [ABSTRACT FROM AUTHOR]

A comprehensive study was conducted to understand the radon (222Rn) distribution and associated radiation doses to the public in a small tropical river basin partly set in the western slope of the Southern Western Ghats of Kerala, India. Radon, though detected in all the 71 monitored wells (0.17–68.3 Bq L–1), exceeded the maximum contamination level (MCL) of 11.1 Bq L–1 for drinking water recommended by United States Environmental Protection Agency (USEPA) in eight samples from isolated pockets of highland, midland and lowland of the Karamana River Basin (KRB) and found to be well within 100 Bq L–1, the parametric value suggested by the World Health Organization (WHO) and the European Union (EU). The age-wise total annual effective doses (AEDs) of groundwater radon activity ranged from 0.5–208.4 μSv a–1 for infants, 0.4–172.2 for children and 0.5–189.7 μSv a–1 for adults. The results reveal that effective doses due to groundwater radon pose no potential public health risk in the study region. Since there is no previous background information on radon-induced radiation dose in the KRB, this work is a newfangled attempt from a public health point of view. [ABSTRACT FROM AUTHOR]

Water quality modelling facilitates our better understanding of the processes taking place in a lake system, and conservation plans to address them. The water quality analysis simulation programme ( WASP) was used in this study to predict daily variations in water quality parameters, namely dissolved oxygen, nitrate, phosphate and chlorophyll-a and biochemical oxygen demand concentrations in a tropical lake system. The lake was divided into eight segments with the respective morphological, environmental and flow details being model inputs. The monthly concentration of each water quality parameter also comprised model input. The model output was daily spatiotemporal variation in these parameters over a period of 476 days. This study also indicated that the occurrence of precipitation plays a major role in defining the water quality of a tropical lake. The heavy precipitation after a long gap, especially during the summer season, results in a large quantity of organic matter entering the lake through drains, thereby increasing the organic matter and phosphate in the water body, and subsequently resulting in high chlorophyll-a concentrations in the lake. A reduced chlorophyll-a concentration was observed during the heavy rains. The water quality fluctuations are more pronounced with precipitation, especially where polluted drains enter the lake. An improved water quality can be observed downstream, including increased dissolved oxygen and nitrate concentrations. Improved water quality was observed during the postmonsoon period, with increased salinity and dissolved oxygen concentrations, a finding that confirms generalized and specific conclusions can be achieved with the use of the WASP model. [ABSTRACT FROM AUTHOR]

The long-term average annual soil loss (A) and sediment yield (SY) in a tropical monsoon- dominated river basin in the southern Western Ghats, India (Muthirapuzha River Basin, MRB; area: 271.75 km²), were predicted by coupling the Revised Universal Soil Loss Equation (RUSLE) and sediment delivery ratio (SDR) models. Moreover, the study also delineated soil erosion risk zones based on the soil erosion potential index (SEPI) using the analytic hierarchy process (AHP) technique. Mean A of the basin is 14.36 t ha-1 year-1, while mean SY is only 3.65 t ha-1 year-1. Although the land use/land cover types with human interference show relatively lower A compared to natural vegetation, their higher SDR values reflect the significance of anthropogenic activities in accelerated soil erosion. The soil erosion risk in the MRB is strongly controlled by slope, land use/land cover and relative relief, compared to geomorphology, drainage density, stream frequency and lineament frequency. [ABSTRACT FROM AUTHOR]

Seasonal monitoring of surface water was performed in Meenachil River with emphasis on heavy metal quality. Mean concentration of heavy metals such as Cu, Cr, Zn and Pb during post-monsoon are comparatively higher than that in the other seasons. As and Cd concentrations are below detectable limit in all seasons. The escalated heavy metal pollution index (HPI) and contamination degree (CD) index level at the river mouth indicate a contaminated environment. Direct application of agrochemicals in the typical catchment activities like intense plantation and widespread lowland agriculture contribute heavy metals to the riverine system. The contamination index (CI) was strongly lowered during monsoon. The study has demonstrated that the mean hazard quotient falls to a permissible level throughout pre-monsoon and monsoon while the level slightly exceeds the level during post-monsoon. HPI, CD and CI indices suggest that better agricultural management practices need to be implemented in the Meenachil River basin for maintaining ecological integrity and protecting the lotic system from further degradation. [ABSTRACT FROM AUTHOR]

Red dune sands in the southwest coast of Tamil Nadu, India, were examined to understand its chronology of formation using OSL chronometry. Degrees of weathering of these sands were deduced from field observation, clay mineral composition and geochemistry of the bulk sample. The sands were found to have been deposited in two episodes, i.e. between 16-9 ka and at 4.5 ka in the middle and lower parts of the dune field. The late Pleistocene deposition of sand in the upper terrace was associated with abundant sand supply owing to the lower sea level. The second stage of dune accretion at 4.5 ka was observed at the lower level relative to the present day coast. It was presumably associated with late Holocene higher sea level in the coasts of south India and deposition of sand in the backshore region on top of the previous indurated aeolian deposits. The elevated topography of the area acted as an obstruction to trap the sand-laden onshore winds and facilitated accumulation. Spatio-temporal variation in sand accretion was observed in terrace I at the central part of the dunes. The geochemistry and mineralogy of the sands is controlled by initial aeolian sediment sorting and chemical weathering leading to the alteration of feldspars to kaolinite and associated compositional variations in the major elements. The red colour in the sands is found to be related to the concentration of hematite in the fine fraction. [ABSTRACT FROM AUTHOR]

Many coastal lakes are under serious threats due to increased pressures associated with population growth, accelerated eutrophication, invasive species and toxic contamination. The extent of the pollution depends almost entirely on the characteristics and processes taking place in the lake basin. The objective of this study was to identify the pollution potential zones (very high, high, medium and low) in the Akkulam-Veli (A-V) Lake Basin (Thiruvananthapuram, Kerala) using GIS-enabled, multithematic overlay analysis. The primary characteristics considered were geomorphology, lithology, land use, soil, slope and population density. The results of this study indicated the major portion of the lake basin exhibits very high or high pollution potential zones, with the drains passing through the very high pollution potential zone being mainly responsible for the contamination of the lake water. High population density, predominant commercial use and settlement with mixed tree crop, level and gentle slope (low slope) are the factors responsible for the very high pollution potential. The organic pollutants in the lake system increase with the increased extent of the very high pollution potential area. This analysis approach will help authorities to identify the underlying causes of lake water quality degradation and plan and implement effective measures for protecting the lake. This process can also be utilized by scientists elsewhere to facilitate lake protection. [ABSTRACT FROM AUTHOR]

The ability to predict water quality is a major requirement for planning and execution of developmental projects. It helps entrepreneurs to effectively plan and implement pollution control measures. This study evaluates the ability of different water quality models (statistical; remote sensing; mathematical) to predict salinity in Akkulam-Veli Lake, a tropical lake system. The performance of these three water quality models was evaluated. Prediction of salinity was made accurately with the mathematical model ( WASP), compared to the other models. WASP facilitates prediction of daily water quality variations, which is not possible with the other models. A limitation of this model, however, was its ability to predict only a few water quality parameters. The statistical methods are reliable when the number of sampling sites and frequency of sample collection are high, making this method exhaustive and expensive. Remote sensing techniques proved to be less tedious, but are suitable only under specific situations, and not able to produce a high level of accuracy. Nevertheless, this method provides a continuous picture of spatial variations of different water quality parameters to a reasonable level of accuracy. The choice of the 'best' model varies on the basis of climatic and field conditions of the lake system of concern. Thus, a combination of water quality models was found to be the most ideal approach for analysing water quality data. [ABSTRACT FROM AUTHOR]

River water chemistry of Pambar River Basin (PRB), draining a rain shadow region of the southern Western Ghats, India, with granite gneiss and hornblende-biotite-gneiss lithology, was monitored for three sampling seasons, such as monsoon (MON), post-monsoon (POM) and pre-monsoon (PRM) to ascertain the spatio-temporal trends in hydrochemistry. In PRB, upstream and downstream areas have differing climate (i.e., tropical-wet–dry/humid upstream, while semi-arid downstream) and land use (plantations and farmland dominate the upstream, while pristine forest environment covers the downstream). The hydrochemical attributes, except pH and K + , exhibit distinct temporal variation mainly due to monsoon-driven climatic seasonality. Relative abundance of cations between upstream and downstream samples of PRB shows noticeable differences, in that the upstream samples follow the order of abundance: Ca 2+ > Mg 2+ > Na + > K + , while the downstream samples are in the order: Na + > Mg 2+ > Ca 2+ > K + . Ca 2+ + Mg 2+ /Na + + K + , Si/Na + + K + , Cl − /Na + and HCO 3 − /Ca 2+ ratios suggest multiple sources/processes controlling hydrochemistry, e.g., atmospheric supply, silicate weathering, dissolution of carbonate minerals and soil evaporites as well as anthropogenic inputs (domestic and farm/plantation residues). Even though weathering of silicate and carbonate minerals is the major hydrochemical driver in both upstream and downstream portions of PRB, Gibbs diagram and scatter plot of Mg 2+ /Na + vs. Mg 2+ /Ca 2+ imply the importance of evaporation in the downstream hydrochemistry. Piper diagram and partial pressure of CO 2 ( p CO 2 ) values suggest that a groundwater dominated discharge exerts a significant control on the downstream hydrochemistry, irrespective of sampling season. Although spatial variability of rainfall in PRB shows a linear downstream (decreasing) trend, the best-fit model for the dissolved load suggests that the downstream hydrochemical variability in PRB (i.e., an increasing trend) follows a power function ( f ( x ) = ax k ). This study suggests that climate has a significant role in the spatio-temporal variability of hydrochemistry in PRB. [ABSTRACT FROM AUTHOR]

Lakes are versatile ecosystems, with eutrophication being a serious problem affecting their condition and trophic status. Eutrophication can lead to an over-abundance of macrophytes in lakes, producing favourable conditions for mosquito larvae. Increased eutrophication is attributed in most to excessive phosphorus concentrations in lake water. Satellite imagery analysis now plays a prominent role for quickly assessing water quality over a large area. The present study is an attempt to illustrate the variation of phosphate and total phosphorus concentrations in Akkulam- Veli Lake, Kerala, India, using Indian Remote Sensing satellite ( IRS P6- LISS III) imagery. A multiple regression equation derived using radiance in the red and MIR bands in the imagery was found to yield superior results for predicting the phosphate concentration, whereas a simple regression equation using radiance in red band was found to yield good results for the total phosphorus concentration in lake water. Accordingly, the trophic status of the lake system can be determined easily from satellite imagery in this manner. [ABSTRACT FROM AUTHOR]

The remote sensing technique provides a rapid and relatively inexpensive means of identifying silted areas in large water bodies, in order that desilting activities can be effectively conducted. This study developed lake bathymetry for a selected lake system ( Akkulam- Veli Lake, Kerala, India) from the Indian Remote Sensing ( IRS P6- LISS III) satellite imagery, using an artificial neural network ( ANN) model. The water depth was measured for 17 months at different points in the lake on the same date of overpass of the IRS satellite. The satellite imageries obtained for 12 December 2007 and 16 February 2009 were identified as cloud-free images. ANN models were developed with the four input series of radiance values from green, red, NIR and MIR bands observed for the satellite imagery obtained on 12 December 2007 at the sampling sites, with actual water depth measurements also being taken on the same date. A three-layered feed forward neural network with back propagation training algorithm was developed for this study. To train the model, it was run several times by changing the number of neurons, learning rate and the momentum constants until the mean square error was minimum. When the number of neurons is increased to 35, and the logsig function is used as ANN transfer function, the error becomes minimum. To test the model, the developed ANN was run for a new set of input from the satellite imagery taken on 16 February 2009. Comparing the predicted and measured values for the same sites for the same day, it was found that the model is best suited for predicting water depth using ANN and the radiance values for four bands of IRS satellite imagery. The results of this study indicated that, for the shallow lake with lower depth, the difference between the actual and predicted value was considerable. In contrast, this was not the case where the lake water depth was greater, indicating an increased prediction accuracy with ANN with increasing depths for shallow lakes. A bathymetry map prepared with ANN indicated only the lake shoreline, as well as the shallow littoral zones. The approach used in this study requires further refinement, including further of the model based on using more field measurements to obtain a better bathymetry map. [ABSTRACT FROM AUTHOR]

Land use and land cover change, perhaps the most significant anthropogenic disturbance to the environment, mainly due to rapid urbanization/industrialization and large scale agricultural activities. In this paper, an attempt has been made to appraise land use/land cover changes over a century (1914-2007) in the Neyyar River Basin (L=56 km; Area = 483.4 km2) in southern Kerala - a biodiversity hot spot in Peninsular India. In this study, digital remote sensing data of the Indian Remote Sensing satellite series I-D (LISS III, 2006-2007) on 1:50,000 scale, Survey of India (SOI) toposheet of 1914 (1:63,360) and 1967 (1:50,000) have been utilized to map various land use/land cover changes. Maps of different periods have been registered and resampled to similar geographic coordinates using ERDAS Imagine 9.0. The most notable changes include decreases in areas of paddy cultivation, mixed crops, scrub lands and evergreen forests, and increases in built-up areas, rubber plantations, dense mixed forests, and water bodies. Further, large scale exploitation of flood plain mud and river sand have reached menacing proportions leading to bank caving and cut offs at channel bends. Conservation of land and water resources forms an important aspect of ecosystem management in the basin. [ABSTRACT FROM AUTHOR]