Geospatial and Geophysical Approaches for Assessment of Groundwater Resources in an Alluvial Aquifer of India

Western Delhi is a peri-urban area and mainly produces cash crops like vegetables. For round the year vegetable production, the farmers in this area depend on groundwater for irrigation. Thus, widespread groundwater withdrawal for intensive vegetable cultivation is the primary cause of depletion of groundwater quantity in this part of Delhi. To understand sub-surface geologic condition and to assess groundwater availability, geophysical imaging of the sub-surface was carried out. Groundwater potential zones were found at 18–30 m below ground level, and the quality of groundwater seems to be of moderate to poor because of low resistivity values in the water potential zones. Geospatial mapping of the resistivity values of different sub-surface layers identified the geological formations like coarse fragments, clay, calcite and other formations. Longitudinal Unit Conductance (S value) and Transverse Unit Resistance (T value) and their combinations are found effective to identify groundwater potentiality. Geospatial maps prepared by ordinary kriging interpolation method indicated that 20.2% of the area has potential to get good quality groundwater. But these areas are scatteredly distributed at the east, west, and north side of west Delhi. The aquifer of the southern part of the study area showed low resistivity formation, which indicates groundwater pollution. The infiltrations of highly polluted Najafgarh drain water and fertilizer laden surface water and their subsequent movements to the aquifer are mainly responsible for this. The study will help to identify the hotspots for periodic monitoring of groundwater quality. The study also suggests the directions of future research works for scientific development and management of groundwater resources in west Delhi.