N. J. Pawar

Evaluating pollution potential of leachate from landfill site, from the Pune metropolitan city and its impact on shallow basaltic aquifers

Leachate produced by municipal solid waste dumping site near the metropolitan city of Pune, India was examined for its pollution potential and impact on surrounding shallow basaltic aquifers. Twenty-eight physico-chemical parameters during post- and pre-monsoon seasons (Nov 2006 and May 2007) were determined to assess the seasonal variation in the leachate pollution index (LPI) as well as in the groundwater quality. The leachate demonstrated higher LPI value during pre-monsoon, comparable to those at other metropolises outside India. Potentially toxic leachates derived from the dumping site have largely influenced the adjoining basaltic aquifers through two different modes of transport. Despite high contents of heavy metals (Al, Cd, Cr, Cu, Co, Fe, Mn, Ni, Pb and Zn) in the leachate, the aquifers in the close proximity of landfill site are least polluted by metallic contaminants possibly due to redox controls. Various geoenvironmental features governing the dispersal of leachate contaminants in the basaltic aquifers under semi-arid climatic regime have been identified and discussed. Although a few remedial measures have been suggested to mitigate the impact of leachate percolation and dispersion, the present study demands for a proper solid waste management in metropolitan cities.

Nitrate pollution of ground waters from shallow basaltic aquifers, Deccan Trap Hydrologic Province, India

Analyses of groundwater samples collected from several locations in a small watershed of the Deccan Trap Hydrologic Province, indicated anomalously higher values of nitrate than the background. However, the NO3 concentrations in water from dug wells under pastureland where the subsurface material consisted of stony waste were minimum. The maximum values were reported for water from dug wells where the principal land use was agricultural. Lowering of NO3 values under shallow water-table conditions suggests denitrification. Higher concentrations of nitrate determined for samples collected from the wells with a deeper water-table indicate that denitrification process is inactive. The high values of nitrate coinciding with agricultural land use indicate fertilizers as the main source of nitrate pollution of ground-water. Decrease in Cl/NO3 ratio for agricultural land use confirms this inference.

Identifying Potential Rainwater Harvesting Sites of a Semi-arid, Basaltic Region of Western India, Using SCS-CN Method

Upper Karha watershed from semi-arid part of Deccan Volcanic Province, India was investigated to identify the potential sites to construct rainwater harvesting structures with the help of remote sensing and geographical information system. Attempt was made to understand the basaltic terrain in spatial context to find out the rainwater harvesting structures like farm ponds, percolation tank, check dams and gully plugs deriving from thematic layers, such as landuse/landcover, slope, soil, drainage and runoff from Landsat Thematic Mapper imagery and other collateral data. Subsequently, these layers were processed to derive runoff from Soil Conservation Service Curve Number (SCS-CN) method using Arc-CN runoff tool. The SCS-CN method shows that the high runoff potential is from water-body, agriculture land (including harvested land) and followed by settlement, open scrub, dense scrub and low for the open forest, dense forest area. Parameters like hydro-geomorphology, geology were considered as per Integrated Mission for Sustainable Development specifications for identification of the structures. The thematic layers overlaid using intersection based on these specifications. Derived sites were investigated for its suitability and implementation by ground truth field verification. In conclusion, the method adopted in present study deciphers the more precise, accurate and ability to process large catchment area than other methods.

Electrical resistivity imaging for aquifer mapping over Chikotra basin, Kolhapur district, Maharashtra

Electrical resistivity study assumes a special significance for mapping aquifers in hard rock areas. A two-dimensional (2D) resistivity survey of Chikotra basin, southern part of Kolhapur district in the Deccan Volcanic Province of Maharashtra was conducted. The aim of this work was to determine the aquifer zones of the study area using electrical resistivity imaging technique. The hydro-geological section derived from the available dug well/borehole lithology suggests that the top layer comprises red bole, laterite or black soil followed by weathered/fractured rock grading into compact basalts. The sources of groundwater appear to be available in weathered and fractured basalt trapped between weathered overburden and hard rock. Results from the 2D inverted models of resistivity variation with depth suggest the occurrence of aquifers mostly in weathered/fractured zones within the traps or beneath it. The resistivity models suggest that the northern part of the study area represents a promising aquifer zone with reasonable thickness of weathered basement. The models further indicate that there are several locations throughout the basin for possible groundwater exploration as it exhibited strong water-bearing potential in the subsurface rocks.

Structural mapping of Chikotra River basin in the Deccan Volcanic Province of Maharashtra, India from ground magnetic data

Ground magnetic data collected over Chikotra River in the peripheral region of Deccan Volcanic Province (DVP) of Maharashtra located in Kolhapur district was analysed to throw light on the structural pattern and distribution of magnetic sources within the basin. In order to isolate the magnetic anomalies showing varying trend and amplitude, several transformation operations including wavelength filtering, and upward continuation has been carried out on the reduced to pole anomaly map. Qualitative interpretation of these products help identify the distribution of magnetic sources, viz., the Deccan basalts, dolerite intrusives and older greenstone and schist belts in the subsurface. Present study suggests that the Chikotra basin is composed of three structural units; a NE–SW unit superposed on deeper NW–SE unit with randomly distributed trap flows on the surface. One of the major outcome of the present study is the delineation of almost 900-m thick Proterozoic Kaladgi sediments below the Deccan trap flows. The NE–SW magnetic sources may probably represent intrusives into the Kaladgi sediments, while the deeper NW–SE trends are interpreted as the northward extension of the Dharwars, underneath the Deccan lava flows, that forms the basement for the deposition of Kaladgi sediments.

Inter-annual variability of urolithiasis epidemic from semi-arid part of Deccan Volcanic Province, India: climatic and hydrogeochemical perspectives

Semi-arid Karha basin from Deccan Volcanic Province, India was investigated for inter-annual variability of urolithiasis epidemic. The number of reported urolith patient, weather station data and groundwater quality results was used to assess impact of geoenvironment on urolithiasis. Data of 7081 urolith patient were processed for epidemiological study. Gender class, age group, year-wise cases and urolith type were studied in epidemiology. Rainfall, temperature, pan evaporation and sunshine hours were used to correlate urolithiasis. Further, average values of groundwater parameters were correlated with the number of urolith episodes. A total of 52 urolith samples were collected from hospitals and analysed using FTIR technique to identify dominant urolith type in study area. Result shows that male population is more prone, age group of 20–40 is more susceptible and calcium oxalate uroliths are dominant in study area. Year-wise distribution revealed that there is steady increase in urolithiasis with inflation in drought years. In climatic parameters, hot days are significantly correlated with urolithiasis. In groundwater quality, EC, Na and F are convincingly correlated with urolith patients, which concludes the strong relation between geo-environment and urolithiasis.