Detection of Buried Water Lines and Determining the Depth of Water Tables Using Forward Modeling of Ground-Penetrating Radar Data

Ground-Penetrating Radar (GPR) is a high-resolution non-destructive geophysical method which detects buried objects and subsurface heterogeneities using transmitting high-frequency (generally in the range of 1 MHz up to 1 GHz) electromagnetic pulses and receiving reflected pulses. In the current study the possibility of employing this method to detect buried water lines and mapping groundwater for water engineering purposes was studied. To achieve this goal, the GPR response of synthetic objects corresponding to targets common in water engineering affairs containing horizontal cylinder and layered earth, was produced using numerical forward modeling by the 2-D finite-difference method modified in the frequency domain to be used for interpreting the real GPR radargrams. The GPR method was also employed to detect underground water lines in Shahin-shahr plain, Isfahan province as the case study of the present research leading to some heterogeneities in the obtained radargrams, interpreted using the results of the forward modeling as probably buried qanat semi filled by fresh water. The validity of the results was also proved through trenching on one of the surveyed profiles. Based on the results of this research, GPR method is capable of detecting all underground water lines, assessing material type (metallic or nonmetallic) of buried pipes, identification of kind of water content (fresh or saline) of nonmetallic pipes, determining depth of water table, estimating thickness of water containing layer (about waters with low conductivity) and distinguishing fresh and saline water interface.