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The exploration, exploitation, and unscientific management of groundwater resources in the National Capital Territory (NCT) of Delhi, India have posed a serious threat of reduction in quantity and deterioration of quality. The objective of the study is to determine the groundwater quality and to assess the risk of groundwater pollution at Najafgarh, NCT of Delhi. The groundwater quality parameters were analyzed from the existing wells of the Najafgarh and the thematic maps were generated using geostatistical concepts. Ordinary kriging and indicator kriging methods were used as geostatistical approach for preparation of thematic maps of the groundwater quality parameters such as bicarbonate, calcium, chloride, electrical conductivity (EC), magnesium, nitrate, sodium, and sulphate with concentrations equal or greater than their respective groundwater pollution cutoff value. Experimental semivariogram values were fitted well in spherical model for the water quality parameters, such as bicarbonate, chloride, EC, magnesium, sodium, and sulphate and in exponential model for calcium and nitrate. The thematic maps of all the groundwater quality parameters exhibited an increasing trend of pollution from the northern and western part of the study area towards the southern and eastern part. The concentration was highest at the southernmost part of the study area but it could not reflect correctly the groundwater pollution status. The indicator kriging method is useful to assess the risk of groundwater pollution by giving the conditional probability of concentrations of different chemical parameters exceeding their cutoff values. Thus, risk assessment of groundwater pollution is useful for proper management of groundwater resources and minimizing the pollution threat.

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A B S T R A C TAlthough soil conservation practices are being promoted as better environmental protection technologies than traditional farmers' practice, limited information is available on how these practices affect soil water balance and root water uptake. The root water uptake (RWU) patterns of cotton grown under soil conservation practices and soil water balance in cotton (Gossypium hirsutum L.) fieldsunder a cotton-wheat (Triticum aestivum L.) cropping system were analyzed using the Hydrus-2D model. The treatments were: conventional tillage (CT), zero tillage (ZT), permanent narrow beds (PNB), permanent broad beds (PBB), ZT with residue (ZT + R), PNB with residue (PNB + R) and PBB with residue (PBB + R). Results in the third year of the cotton crop indicated that the surface (0-15 cm layer) field saturated hydraulic conductivity in both PNB and PBB plots were similar and were significantly higher than in the ZT plots. Computed potential transpiration rates (T rp ) under CT were lower than in other treatments, due to less radiation interception and lower Leaf Area Index (LAI). Both PNB and PBB plots had higher T rp and crop yields than CT plots, which were further improved by residue retention. Predicted soil water content (SWC) patterns during the simulation periods of third and fourth years showed strong correlation (R 2 = 0.88, n = 105, P < 0.001, the root mean square error (RMSE) = 0.025, and the average relative error (AVE) = 7.5% for the third year and R 2 = 0.81, n = 105, P < 0.001, RMSE = 0.021, and AVE = 9% for the fourth year) with the actual field measured SWCs. Cumulative RWU (mm) were in the order: ZT (143) < CT (157) < PNB (163) < ZT + R (174) < PBB (188) < PNB + R (198) < PBB + R (226). Thus, PBB + R and PNB + R practices could be adopted for cotton cultivation, as these enhanced root growth and improved radiation interception and LAI. The Hydrus-2D model may be adopted for managing efficient water use, as it can simulate the temporal changes in SWC and actual transpiration rates of a crop/cropping system.