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Sambhar Lake in Rajasthan, India is the major inland salt water lake producing salt for centuries. The present study addresses the monitoring changes in and around the lake and its consequent effect on the lake water ecology. For this, satellite images of the years 1976, 1981, 1997, and 2013 are analyzed for land use land cover classes. Significant reduction in the water body is observed in contrast with the increase in salt pan around the periphery of lake and wetland classes. Further, the extent of water body and algae in the lake are delineated as per normalized difference water index and normalized difference vegetation index. Rainfall data do not indicate any major change in the pattern, but drastic decrease in the extent of water body and significant increase in algal bloom are serious concerns for the lake's existence. This may be due to surrounding anthropogenic activities and construction of check dams and anicuts in the lake catchment which curtail the runoff into the lake and provide favorable growth of algae. Sambhar Lake, being declared as a wetland according to the Ramsar Convention, is necessary to protect and conserve the ecological importance of the lake through sustainable planning and management.

Keywords biochemical oxygen demand; coastal pollution; image segmentation; normalised difference turbidity index; object-based image analysis. AbstractThe coastal water quality of Mumbai is deteriorating by receiving partially treated effluent from wastewater treatment facilities, sewage discharges from ocean outfalls and discharges from point and non-point sources in the creek and coast. A novel approach of object-based image analysis has been used in this research study to assess the extent of sewage pollution in the coastal environment of Mumbai. For this, Indian Remote Sensing P6 Linear Imaging Self Scanning IV image was used for multiresolution segmentation and rule-based image classification as per normalised difference water index and normalised difference turbidity index. Water quality regions as per classification were strongly correlated with observed water quality parameters. Based on classified regions and water quality parameters, extent of sewage pollution in the coast was ranked from high to least polluted. The approach developed in this methodology should be tested in similarly polluted waters to ascertain its adaptability for assessing the spatial extent of sewage pollution.

Watershed prioritization is beneficial for soil, groundwater development as well as for the implementation of the artificial recharge schemes. It is a well-known scientific process of drainage network delineation and ranking of different sub-watersheds of a basin. This is the mostly adopted morphometric interpretation and assessment technique and used for prioritization of watershed. In the present study, morphometric analysis of the Deonar river sub basin has been carried out to interpret and assess its hydrological importance. The study was carried out using geospatial approach and it is reflected in morphometric parameters such as linear, areal and relief aspects of the watershed. Detailed morphometric analysis and drainage map has been prepared from ASTER DEM (digital elevation model) having 30m spatial resolution using GIS environment. The delineated and analysed morphometric parameters are helpful for planning of soil and water conservation with the PCA approach. Principal component analysis (PCA) is a well-known technique that reduces the dimensionality of the given input data set which maximizes the amount of variance information. The delineated drainage order comes 1 to 5 and the watershed comprises of 6 sub-watersheds named as SW-I to SW-VI were analyzed. Based on Deonar river sub basin morphometric analysis, the sub-watershed is categorised into three classes as high, medium and low priority zones. Watershed prioritization and correlation of morphometric parameters of the Deonar river basin illustrates and indicates the high priority due to the greater degree of erosion. The analysed result is useful for making better planning and management, to identify the artificial recharge structures of the various sub-watersheds for improving the water potentiality.

The surface and groundwater resources are depleting over time, therefore, it becomes essential to monitor and preserve these resources and also to protect their quality. Remote sensing and GIS has become an important tool of hydrological studies in recent times which helps in assessing and mapping of ground-water resources. The remote sensing and GIS approach are well known and widely used techniques to integrate contributing hydrogeological factors namely, geology, geomorphology, lineaments density, drainage density, soil type, slope and land use/ land cover. A study was conducted to delineate the groundwater potential zones in a part of Sidhi area, Madhya Pradesh using remote sensing and GIS techniques. Landsat 8 satellite data and Aster DEM is integrated with toposheets for systematic mapping. All thematic layers were integrated, overlaid and analysed using GIS software. Groundwater potential zone is delineated and to interpret thematic layer, appropriate weights assigned to topographical features for assessing the potential zone. The zones are divided into high, moderate and low groundwater potential zones. The study reveals that 21.36% of the area has high potential, 48.12% moderate and 30.51% low potential zone for groundwater occurrence. The result of this study suggests that the favourable potential zones would prove to be very helpful for better planning and management of groundwater resources in the study area.