Method of mapping and monitoring groundwater and subsurface aqueous systems

A geophysical method using electromagnetic energy for mapping, tracking, or monitoring a subsurface aqueous system comprising:

• directly introducing an electrical current into said aqueous system to electrically energize said aqueous system;
• monitoring at a plurality of locations the primary electric and magnetic fields emanating from said aqueous system to measure magnetic and electric fields produced by said electrical current directly introduced into said aqueous system,
• wherein monitoring of said primary electric field consists of measuring:
• total horizontal electric field amplitude;
• maximum horizontal electric field amplitude;
• minimum horizontal electric field amplitude;
• vector of the surface electric field;
• direction of maximum horizontal electric field;
• direction of minimum horizontal electric field;
• and
• interpreting said measured primary electric fields and primary magnetic fields to determine extent and change in location of said aqueous system.

A geophysical method using electromagnetic energy for mapping, tracking, or monitoring a subsurface aqueous system comprising:

• directly introducing an electrical current into said aqueous system to electrically energize said aqueous system;
• monitoring at a plurality of locations the primary electric and magnetic fields emanating from said aqueous system to measure magnetic and electric fields produced by said electrical current directly introduced into said aqueous system;
• interpreting said measured primary electric fields and primary magnetic fields to determine extent and change in location of said aqueous system,
• wherein said interpreting of measured electric and magnetic fields consists of:
• a. correcting for diurnals, current drift of the transmitter, and any base intensity changes;
• b. determining a path of the aqueous system from minimum horizontal magnetic field direction or from perpendicular to maximum horizontal magnetic field;
• c. determining direction of electric current flow in the aqueous system from direction of maximum surface electrical field potential or alternatively from direction perpendicular to minimum surface electric field potential;
• d. determining width of the subsurface aqueous channel from rate of change of vertical magnetic field intensity across an anomaly;
• e. estimating depth and width of the subsurface aqueous channel from width of the measured horizontal magnetic field;
• f. resolving ambiguities of channel width and depth of said aqueous system using anomaly slope and anomaly width of vertical and horizontal magnetic field data;
• g. determining depth of said aqueous system by correlating said electric and magnetic fields;
• h. determining conductivity of the aqueous system from the measured electric field, and the measured magnetic field;
• i. determining chemical or biological activity from localized intensity increases measured in either magnetic or electric fields;
• j. comparing changes in the various components of magnetic and electric fields over time to provide information relating to fluid movement, change in chemical activity, changes of fluid in an aquifer, changes in subsurface biological activity, movement of chemical or bio-reaction fronts, leaching progress and activity relating to in situ mining, progress of subsurface chemical or biological remediation, increases or decrease in subsurface flow, changes in salinity, or any change in the groundwater that affects any of its electrical properties;
• k. mathematically normalizing electromagnetic field intensity readings for distance from the energizing electrode;
• l. evaluating electrical contrast between the channel and host rock by observing rate at which the measured magnetic and electric fields degrade;
• m. relating depth and dispersion of the ground current to the gradient of the magnetic field;
• n. relating subsurface reaction zones to crossed electric and magnetic field gradients;
• o. plotting data in profile form;
• p. plotting data as a contour map;
• q. taking account of a subsurface attached clay lens, such as a repository lining, which tends to mask the field of the conductor being tracked and could produce localized high readings in wet areas as said clay lens will act as a good conductor and concentrate current;
• r. conducting periodic surveys or sets of measurements over time, to show changes in field values which are plotted by taking the difference or ratio of measurement readings;
• s. conducting a baseline reference survey when using this method to monitor activity such as movement, chemistry changes, or bioactivity over a period of time;
• t. constructing a model of the electrical current flow in the subsurface aqueous system from the measured magnetic and electric fields.