The remote sensing and geospatial tools have wide applications in water resource assessment studies. Satellite images are increasingly being used in groundwater exploration because of their utility in identifying various geomorphic features. The present study has been carried out in two important river basins-the Ithikkara and the Kallada river basins, of Southern Western Ghats, Kerala, India. The groundwater potential zones are delineated from 14 thematic layers such as drainage density, geomorphology, slope, lithology, soil, land use/land cover, lineament density, topographic wetness index, rainfall distribution, roughness, curvature, dissection index, depth to water level and topographic position index using multi-criteria evaluation method. Integration of the factors has been performed in GIS platform using weighted overlay analysis. Different classes of thematic maps have been assigned weights based on influence on groundwater hydrology (through discussions with the experts in the field), and finally, factor ranks are assigned. The final map indicates the potentiality values of groundwater occurrence in the study area, which was classified into three categories-high, moderate and low. A total of 37.2% of the study area fall in low groundwater potential zone, 42.3% in moderate potential zone and 20.5% of the area in high potential zone. The groundwater potential zones delineated using the method are validated with data of springs and dug wells from field investigations, and it was found that the overlay method using GIS and remote sensing gives 95% accuracy.
The paper deals with the hydrochemical characterization and water quality assessment of springs emerging from the Archaean crystalline basements at the foothills of Western Ghat mountains in the highlands and Neogene sedimentary formations in the coastal lowlands of Kerala in south west India. A total of 19 springs from two important river basins of southern Kerala such as Ithikkara and Kallada river basins were studied for 18 physico-chemical (temperature, pH, electrical conductivity (EC), total dissolved solids (TDS), dissolved oxygen (DO), total hardness (TH), Na(+), K(+), Ca(2+), Mg(2+), CO3 (2-), HCO3 (-), Cl(-), SO4 (2-) , NO3 (-), SiO2, Fe(2+), and F(-) ) as well as bacteriological parameters. The discharge computations show that free-falling type of springs in the area discharge about 256.23 million liters of water a year. A comparative study between the spring water samples of highland and lowland regions reveal that the quality of spring water, except pH and bacteriological contents, satisfies the standards set by the Bureau of Indian Standards and World Health Organization for drinking water. Spring water samples collected from the lowlands register high value of Na(+) and Cl(-) compared with the highlands. Bicarbonate, Ca(2+), Mg(2+), and K(+) values are high in highland than lowland springs. The present study reveals that the spring water sources in the region can be developed as an alternate source for drinking water, provided pH correction and proper disinfection are done prior to its end use.
The magnitude of between-strain differences in the sensitivity of algal species to toxicants is not well known. Yet, informations obtained with a single strain are used for ecotoxicological assessment and for interspecific comparisons. Using 12 strains, we determined whether intraspecific variability occurs in the green alga Scenedesmus subspicatus. We examined growth, photosynthetic activity, and short-term sensitivity thereof to the herbicide atrazine (500 &mgr;g. L-1) as well as how these responses are affected by chronic exposure to low atrazine concentrations (0, 1, 5, and 20 &mgr;g. L-1). Independent of chronic exposure to atrazine, the strains differed in growth rate and photosynthesis rate. Yet the short-term sensitivity to atrazine was affected by the chronic treatments. All but one strain became more tolerant, their short-term sensitivity being inversely related to the applied atrazine concentration and dependent on the duration of exposure. Differences in response to increments in atrazine concentration resulted in differences in rank order of sensitivity of strains. Moreover, between-strain variability was markedly higher in the atrazine treatments than in the controls. These results can be explained by the significant role of genotype versus environment interactions in determining intraspecific differences in adaptive physiological responses of S. subspicatus to chronic exposure to atrazine.http://link.springer-ny. com/link/service/journals/00244/bibs/37n1p36.html
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