Monitoring probe for groundwater flow

Apparatus for use in the ground for monitoring the flow rate and direction of groundwater, said apparatus for use with an electrical fluid having a electrical conductivity different from that of said groundwater, said apparatus comprising:

• a cylindrical membrane adapted to hold a quantity of said fluid, said membrane permeable to said fluid and having a first side and a second side, said fluid on said first side and said groundwater on said second side, said fluid permeating through said membrane from said first side to said second side to form a mixture with said groundwater, said mixture having a mixture electrical conductivity, said mixture electrical conductivity being related to the relative concentration of said groundwater in said mixture, said concentration of said groundwater in said mixture being related to said rate of flow of groundwater proximate to said membrane;
• and
• an array of sensors carried by said membrane and spaced apart from each other, each sensor of said array of measuring electrical conductivity of said mixture at a different location near said second side of said membrane and producing an output signal related thereto, said electrical conductivity of said mixture related to said groundwater flow at said different location of each of said array of sensors.

A method for monitoring the flow rate and direction of groundwater, said method for use with a fluid having an electrical conductivity different than that of said groundwater, said method comprising the steps of:

• placing said fluid on a first side of a membrane permeable to said fluid so that said fluid permeates from said first side through said membrane to an opposing second side;
• placing said membrane into the ground where groundwater is present on said second side of said membrane whereby said fluid permeates through said membrane from said first side to said second side and into said groundwater at a known rate and location, said fluid forming a mixture with said groundwater, said mixture having a mixture electrical conductivity, related to the relative concentration of said groundwater in said mixture, said concentration of said groundwater in said mixture being related to said rate of flow of groundwater proximate to said location and available for mixing said fluid.