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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]

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]

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]

Abstract: Lakes are versatile ecosystems and they are under the threat of eutrophication and siltation. The physical characteristics of a lake provide some insight into the status of the lake. Satellite imagery analysis now plays a prominent role in the quick assessment of characteristics of a lake system in a vast area. This study is an attempt to assess the water temperature, depth, and turbidity level of a lake system (Akkulam–Veli lake, Kerala, India) using IRS P6–LISS-III imagery. Field data were collected on the date of the overpass of the satellite. For the assessment of water temperature from satellite imagery, regression equation using spectral ratio (green/red bands) is found to yield superior results than the simple regression equation and multiple regression equation. For predicting the water depth, radiance in green and red bands can be used whereas that for turbidity, radiance in green and SWIR can be used. IRS P6–LISS-III imagery can be effectively used for the assessment of the physical characteristics of a lake system at a low cost. [Copyright &y& Elsevier]

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]

The study on bioaccumulation of heavy metals in a lake reveals that during the nonrainy season, accumulation of cadmium in plankton is high in the upstream of the lake where anoxic freshwater condition exists resulting from inflow of urban wastes. Stern action is required to stop the bypass of sewage from the old sewer system especially in the commercial areas of Thiruvananthapuram city, either by augmenting the sewerage system or by treating sewage at the source. During monsoon season, the accumulation of heavy metals--namely lead and nickel, followed by cadmium and chromium--is high in phytoplankton resulting from high nitrate content caused by heavy rainfall. During postmonsoon, lead and nickel accumulation is high. The study emphasizes the need for stormwater management practices for the removal of lead in urban runoff from roads caused by vehicular exhaust, tire wear, and wastes from service stations and workshops. [ABSTRACT FROM AUTHOR]

Coastal lakes are often under the threat of sea water ingress causing the depletion of fresh water bodies. Salinization due to sea water ingress causes impact on water resources especially in coastal areas. Thus there is scarcity of fresh water in this region. Climate change causes rise in sea level and this leads to increase of salinity in coastal lakes. Satellite imagery analysis now plays a prominent role in the quick assessment of water quality in a vast area. This study is an attempt to assess the extent of a lake system affected by sea water (Akkulam-Veli lake, Kerala, India) using Indian Remote Sensing Satellite, IRS P6 LISS III imagery. Field data were collected on the date of the satellite overpass. Simple regression equation using radiance in red band is found to yield superior results for the prediction of sodium content whereas polynomial equation using radiance of red band is found to yield superior results for the prediction of chloride content than the simple and multiple regression equations using spectral ratios and radiance from the individual bands from satellite imagery. The refractive index of water containing sodium chloride is more when compared with that of fresh water and this in turn results in high reflection of visible light in the red band when compared to blue and green bands. Hence the radiance of red band gives direct measure of sodium and chloride in lake water. IRS P6-LISS III imagery can be effectively used for the assessment of sea water affected area of the lake system. [ABSTRACT FROM AUTHOR]

Hydrochemical investigation of open well and river water samples of Thuthapuzha Sub-basin of Bharathapuzha, Kerala, was carried out to determine the spatial and temporal variations in the physico-chemical parameters. The suitability of water for drinking and irrigation purposes and the processes controlling the water chemistry were also assessed. The study area experiences a humid tropical climate and heavy rainfall of ~ 3830 mm/year. Thirty-five open well and nine river water samples were collected during the pre-monsoon, monsoon and post-monsoon seasons. The chemical properties of the river water samples were dominated by alkaline earths and weak acids (CaHCO3 type). Even though majority of the open well samples belonged to CaHCO3 type, few samples belonged to NaCl, mixed CaMgCl and mixed CaNaHCO3 water type. The groundwater and river water chemistry of the region was influenced by the chemistry of the host rock rather than precipitation and evaporation. Except pH and the total iron concentration, all other physico-chemical parameters of the open well samples of the study area were within the acceptable limit of drinking purposes. The physico-chemical parameters of the entire river water samples were within the acceptable limit for drinking purpose. The entire open well and river water samples were suitable for irrigation purposes. [ABSTRACT FROM AUTHOR]