Tracer release method for groundwater flow measurement

摘要

PURPOSE:To maintain the balance of water pressure with a discharged gas accurately by a method wherein a pressure gas is applied into an observing element and simultaneously onto both rear and fore-front sides of a tracer discharging element to maintain a pressure balance when the surface of underground water is formed, and thereafter a slightly larger pressure is given onto the rear side than onto the forefront side to discharge a tracer. CONSTITUTION:In the state wherein all valves 24, 26, 32 and 36 are closed, an observing element 14 is lowered to a prescribed depth in a well and set so that the lower edge of a collar 12 is positioned to be horizontal. Next, the valves 24, 32 and 36 being opened, a pressure gas from a gas cylinder 34 is supplied into the observing element 14 to expel underground water inside the element, and the gas is stored down to the lower end of the collar 12 so that the surface 46 of the underground water is formed. Then, after a diaphragm 30, an air cylinder 38, etc. are put under the same pressure so as to maintain a pressure balance, the valves 24 and 32 are closed while the valve 26 is opened, and the handle 48 of the air cylinder 38 is operated to increase the pressure gradually. Then, a tracer 40 is discharged slowly onto the water surface 46, and the movement of the tracer 40 is observed under a balance pressure by a TV camera 16 or the like, irrespective of the set depth of the observing element 14.