Monitoring temporal variations in groundwater levels in urban areas using ground penetrating radar

Abstract

Monitoring temporal variations in groundwater levels provides a key to sustainable freshwater resource utilization and management, sustainable land use, and sustainable crop acreage, yield, and production. This study used ground penetrating radar (GPR) to monitor temporal variations in groundwater levels in urban areas, and to define the factors that control these variations. The city of Ismailia, Egypt, was selected as a test site because it is experiencing a rise in groundwater levels that poses potential environmental risks, and it lacks the groundwater wells necessary for monitoring and mitigation. Three main GPR profiles were collected in summer (July 2017) and winter (March 2018) using a 100-MHz antenna. On the collected GPR data, water table was defined as a continuous linear reflector of high amplitude. The water table appeared at 8.6 m and 9.5 m (below ground surface) in the summer and the winter surveys, respectively. The depths to the water table, as extracted from GPR surveys, are identical to those measured at a nearby water supply. The higher depth to the water table in the winter is related to excessive groundwater extraction and/or exceptional drought conditions and associated baseflow recession. Results highlight the importance of using GPR in urban areas as a unique, significant, practical, comprehensive, and cost-effective tool to image the subsurface and map the temporal variations in depth to the water table.