Integration of remote sensing data and the geographical information system (GIS) for the exploration of groundwater resources has become a breakthrough in the field of groundwater research, which assists in assessing, monitoring, and conserving groundwater resources. In the present paper, various groundwater potential zones for the assessment of groundwater availability in Theni district have been delineated using remote sensing and GIS techniques. Survey of India toposheets and IRS-1C satellite imageries are used to prepare various thematic layers viz. lithology, slope, land-use, lineament, drainage, soil, and rainfall were transformed to raster data using feature to raster converter tool in ArcGIS. The raster maps of these factors are allocated a fixed score and weight computed from multi influencing factor (MIF) technique. Moreover, each weighted thematic layer is statistically computed to get the groundwater potential zones. The groundwater potential zones thus obtained were divided into four categories, viz., very poor, poor, good, and very good zones. The result depicts the groundwater potential zones in the study area and found to be helpful in better planning and management of groundwater resources. ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

A morphometric analysis was carried out to describe the topography and drainage characteristics of Papanasam and Manimuthar watersheds. These watersheds are part of Western Ghats, which is an ecologically sensitive region. The drainage areas of Papanasam and Manimuthar watersheds are 163 and 211 km 2 , respectively and they show patterns of dendritic to sub-dendritic drainage. The slope of both watersheds varied from 0°to 59°and 0°to 55°, respectively. Moreover, the slope variation is chiefly controlled by the local geology and erosion cycles. Each watershed was classified as a fifth-order drainage basin. The stream order of the basin was predominantly controlled by physiographic and structural conditions. The increase in stream length ratio from lower to higher order suggests that the study area has reached a mature geomorphic stage. The development of stream segments is affected by rainfall and local lithology of the watersheds.

Groundwater is an essential and vital component of any life support system. It is not only the basic need for human existence but also a vital input for all development activities. The present hydro-geochemical study was confined to the coastal belt of Alappuzha district, which lies in the coastal lowland division of Kerala. Groundwater quality and its suitability for irrigation and domestic purpose were examined by various physico-chemical parameters such as pH, electrical conductivity, total dissolved solids, total hardness, calcium, magnesium, sodium, potassium, bicarbonate, sulfate, and chloride. These parameters were used to assess the suitability of groundwater for domestic purpose by comparing with the WHO and Indian standards. TDS, sodium adsorption ratio (SAR), and permeability index were used for irrigation suitability assessment. The sample analysis reveals that the groundwater is not entirely fit for drinking with respect to pH, EC, Ca 2? , Mg 2? , Na ? , and Cl-. In some of the collected samples, the concentrations of these parameters exceed the permissible limits of WHO and ISI standards. Based on TDS and SAR almost all samples are suitable for irrigation purpose except a few locations, which show values beyond the permissible limits. Ca-Mg-HCO 3 is the dominant water type in the study area. The sequence of the abundance of the major cations and anions is Ca [ Na [ Mg [ K = HCO 3 [ Cl [ SO 4. Based on the total hardness and TDS, 96 % of groundwater samples are found suitable for drinking purpose.

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In the present study, the geochemical characteristics of groundwater and drinking water quality has been studied. 24 groundwater samples were collected and analyzed for pH, electrical conductivity, total dissolved solids, carbonate, bicarbonate, chloride, sulphate, nitrate, calcium, magnesium, sodium, potassium and total hardness. The results were evaluated and compared with WHO and BIS water quality standards. The studied results reveal that the groundwater is fresh to brackish and moderately high to hard in nature. Na and Cl are dominant ions among cations and anions. Chloride, calcium and magnesium ions are within the allowable limit except few samples. According to Gibbs diagram, the predominant samples fall in the rock-water interaction dominance and evaporation dominance field. The piper trilinear diagram shows that groundwater samples are Na-Cl and mixed CaMgCl type. Based on the WQI results majority of the samples are falling under excellent to good category and suitable for drinking water purposes.

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A total of 20 groundwater samples were collected from both dug and bore wells of southern Tiruchirappalli district and analyzed for various hydrogeochemical parameters. The analyzed physicochemical parameters such as pH, electrical conductivity, total dissolved solids, calcium, magnesium, sodium, potassium, bicarbonate, carbonate, sulfate, chloride, nitrate, and fluoride are used to characterize the groundwater quality and its suitability for drinking and irrigational uses. The results of the chemical analysis indicates that the groundwater in the study area is slightly alkaline and mainly contains Na ? , Ca 2? , and Mg 2? cations as well as HCO 3 2-, Cl -, SO 4 2-and NO 3 -anions. The total dissolved solids mainly depend on the concentration of major ions such as Ca, Mg, Na, K, HCO 3 , Cl, and SO 4 . Based on TDS, 55 % of the samples are suitable for drinking and rest of the samples are unsuitable for drinking. The total hardness indicates that majority of the groundwater samples are found within the permissible limit of WHO. The dominant hydrochemical facies for groundwater are Ca-Mg-Cl, Ca-HCO 3 , and Ca-Cl type. The USSL graphical geochemical representation of groundwater quality suggests that majority of the water samples belongs to high medium salinity with low alkali hazards. The Gibb's plot indicates that the groundwater chemistry of the study area is mainly controlled by evaporation and rock-water interaction. Spearman's correlation and factor analysis were used to distinguish the statistical relation between different ions and contamination source in the study area.

A morphometric analysis of Bharathapuzha river basin has been carried out using geoprocessing techniques in GIS. This technique is found relevant for the extraction of river basin and its drainage networks. The extracted drainage network was classified according to Strahler's system of classification and it reveals that the terrain exhibits dendritic to sub-dendritic drainage pattern. The Bharathapuzha drainage basin is sprawled over an area of 5,988.56 km 2 . The study area was designated as seventh-order basin and lower order streams mostly dominate the basin with the drainage density value of 1.07 km/km 2 . The slope of basin varied from 0°to 70°and the slope variation is chiefly controlled by the local geology and erosion cycles. The elongation ratio of the basin is 0.57 indicating that the study area is elongated with moderate relief and steep slopes. The drainage texture of the basin is 7.78 which indicates an intermediate texture that exists over the region. Hence, from the study, it can be concluded that remote sensing data (SRTM-DEM) coupled with geoprocessing techniques prove to be a competent tool in morphometric analysis and the data can be used for basin management and other hydrological studies in future.