Measuring Subsurface Spring Flow with Radiotracers

A hydrostatic head was imposed on Estelline Spring to prevent surface discharge and subsequent natural salt pollution of the Red River. This paper describes the use of tritiated water as a tracer to determine the rate of subsurface leakage of the Spring, the size of the Spring cavern, and the location of that area where subsurface leakage returns to the surface. Other techniques using salt and organic dyes did not prove successful, due largely to insensitivity in detection and probable losses to adsorption and degradation. The volume of the known spring chimney, including that within the dike, amounts to about 389,800 cu ft. Knowing the amount of tracer added and the initial concentration of tracer after mixing, it was determined that a volume of 493,960 cu ft existed. From these data, it is concluded that a second chamber exists below that which was previously known; and its volume amounts to about 104,000 cu ft.